Arctic Sea Ice : Forum

AGW in general => Science => Topic started by: kassy on January 24, 2020, 11:45:57 PM

Title: Where are we now in CO2e , which pathway are we on?
Post by: kassy on January 24, 2020, 11:45:57 PM
Recently there was a request in the Moana Loa CO2 thread for a CO2e calculation and it looks like it can be done.

Basically it combines the updates from the CO2, NH4 and other greenhouse gas threads.

We can use this number and then maybe also use it to check which RCP we are following.

It might be interesting to include other metrics like the carbon clock.

*

First data post comes tomorrow.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Ken Feldman on January 25, 2020, 01:09:16 AM
Details of the RCPs are included in the technical annex to the IPCC Working Group I Report for AR5 published in 2013 available at this link:

 https://www.ipcc.ch/site/assets/uploads/2017/09/WG1AR5_AnnexII_FINAL.pdf (https://www.ipcc.ch/site/assets/uploads/2017/09/WG1AR5_AnnexII_FINAL.pdf)

Tables for concentrations start on page 1422.

For CO2, the RCP 2.6 concentration in 2020 is 412.1 ppm and the RCP 8.5 concentration is 415.8 ppm.

According to NOAA, the global (which is what should be used, not the Mauna Loa which isn't comparable to global concentrations) CO2 concentration in January 2020 is about 411 ppm. 

(https://www.esrl.noaa.gov/gmd/webdata/ccgg/trends/co2_trend_gl.png)

So CO2, which is almost 2/3 of the radiative forcing, is under the RCP 2.6 concentration.  Unfortunately, methane, the next highest contributor to the greenhouse effect at 16%, isn't doing as well.

For RCP 2.6 the 2020 concentration of CH4 is 1731 ppb and the RCP 8.5 number is 1924 ppb.  According to NOAA, we're about 1870 ppb.

(https://www.esrl.noaa.gov/gmd/webdata/ccgg/trends/ch4_trend_gl.png)

For N2O (about 6% of the GHG forcing)  the concentrations at RCP 2.6 and 8.5 are 323 and 332 ppb respectively.  NOAA shows us just above 332 ppb.

That's roughly 90% of the GHG forcings summarized.  The big one, CO2 is less than RCP 2.6 and is projected to decrease relatively rapidly compared to the RCPs due to the decline of coal.  CH4 is between RCP 2.6 and 8.5 and will also decrease rapidly as coal mining declines and natural gas and oil are phased out over the next three decades.  Since the lifetime of CH4 is about 12 years, when emissions decrease concentrations will quickly follow.  N2O is tied to agricultural fertilizers and isn't projected to stabilize until global populations level out (at 344 ppb in the later half of this century under RCP 2.6, it keeps growing under the other RCPs).
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: wdmn on January 25, 2020, 06:09:44 AM
<snip, no need for this at all, don't do it again, please; N.>

You know Jan concentrations are not reflective of what the year average will be.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: sidd on January 25, 2020, 07:42:55 AM
Re: RCP 2.6 concentration in 2020 is 412.1 ppm and the RCP 8.5 concentration is 415.8 ppm.

We will not be able to tell which CO2 path we are on for a decade or so.
all RCPs are very close to each other, difference comparable to noise.

and i see no reason to denigrate Mr Feldman. nowhere does he say that january numbers are the ones to compare.

sidd
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: blumenkraft on January 25, 2020, 07:57:55 AM
and i see no reason to denigrate Mr Feldman. nowhere does he say that january numbers are the ones to compare.

This!

Is Ken overly optimistic? Imho yes. But is that a reason to be so harsh? Of course not. His arguments are mostly sound.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: El Cid on January 25, 2020, 08:36:31 AM
I think there is reason to be optimistic. During the past 10-15 years solar and wind became economically sound proposals and this shows up in the quickly changing expectations - noone expected such a strong change so quickly (the below chart is telling me that Co2emissions are likely topping out in the 2020s to start going down thereafter:
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Stephan on January 25, 2020, 08:43:57 AM
Re-posted from the 2020 Mauna Loa CO2 thread:
Thank you Stephan. Since you are regularly updating several GHG readings, would it be possible to add a CO2e figure?
In that way we'll have the cumulative GHG effect updated. I know it depends on assumptions but you can put those in.
nanning,
I will do it in the next time. I have the monthly reading of four gas concentrations (CO2, CH4, N2O and SF6) on my PC, in different files, and I can put them together.
I did it, but the sum differs from what I saw from gerontocrat's posting further upthread where he provides NOAA's annual table.
I took the monthly concentrations (beginning from 2000 on, before that date I do not have all the four gases) and multiplied CH4 with the factors 85 (20 years) and 28 (100 years), N2O with 264 (20 & 100 years), and finally SF6 with 17500 (20 years) and 23500 (100 years), using the conversion factors from the later IPCC report. Then I looked up the definition of these CO2 equivalents, which are not given in moles, but in kg and converted the numbers by taking their molecular weight.
I end up with the latest data (Sep 2019) with the following values (100 years equivalent):
CO2: 408.54
CH4:   19.05
N2O:   87.65
SF6    0.78
sum: 516.01
This sum is higher than the CO2 eq given further upthread. Also the proportions of the ratio CH4 to N2O differs completely from NOAA's table. Where is the error?
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Tom_Mazanec on January 25, 2020, 11:19:20 AM
I think there is reason to be optimistic. During the past 10-15 years solar and wind became economically sound proposals and this shows up in the quickly changing expectations - noone expected such a strong change so quickly (the below chart is telling me that Co2emissions are likely topping out in the 2020s to start going down thereafter:
The danger is that we may hit tipping points and feedbacks in this decade.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: wdmn on January 25, 2020, 01:33:57 PM
...

and i see no reason to denigrate Mr Feldman. nowhere does he say that january numbers are the ones to compare.

sidd

He stated twice that we are below RCP 2.6 based on 411ppm
That is an inaccurate statement, and he knows it. How is it harsh to call him out on that? Ken's a smart guy, he knows what he's doing.

At this time of year the honest thing to do would be to report 2019 numbers, which would of course show that we are above RCP 2.6. I will call out such bullshit every time, and I would hope people would call me out for my bullshit too.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: nanning on January 25, 2020, 02:26:57 PM
^^
I agree with wdmn.
But I don't like "... shit".
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: nanning on January 25, 2020, 02:47:16 PM
Stephan, could you please post your calculation and the numbers you used?

You mention different factors for GHG's but there is only 1 column in your table. I would have expected several CO2e numbers based on those factors.

Your CH4 seems much too low.
I have done it like this:

https://www.esrl.noaa.gov/gmd/ccgg/trends/monthly.html
dec2020 CO₂ 412 ppm                 =   412    ppm

https://www.esrl.noaa.gov/gmd/ccgg/trends_ch4/
sep2019 CH4    1.8705 ppm * 85 =  158.99 ppm (85)
                          1.8705 ppm * 28 =    52.37 ppm (20)

https://www.esrl.noaa.gov/gmd/hats/combined/N2O.html
dec2020 N₂O      0.332 ppm * 264 =   87.6 ppm

Total CO2e  equivalent                        -------- +
                                                      658.6  ppm CO2e (85)
                                                      552.0  ppm          (20)
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: AbruptSLR on January 25, 2020, 03:37:22 PM
...

and i see no reason to denigrate Mr Feldman. nowhere does he say that january numbers are the ones to compare.

sidd

He stated twice that we are below RCP 2.6 based on 411ppm
That is an inaccurate statement, and he knows it. How is it harsh to call him out on that? Ken's a smart guy, he knows what he's doing.

At this time of year the honest thing to do would be to report 2019 numbers, which would of course show that we are above RCP 2.6. I will call out such bullshit every time, and I would hope people would call me out for my bullshit too.

As far as I remember, the annual values for well mixed GHG atmospheric concentrations given in the RCP scenarios is for mid-year (i.e. the end of June not January), thus wdmn has a valid point as there is a clear trendline for WMGHG concentrations, so on average these concentrations will be higher in June than in January regardless of variability.  Thus going forward I would recommend that this thread evaluation values for June if it wants to compare with RCP values.

Edit:  With a hat tip to gerontocrat, the UK MetOffice has project the comparable Mauna Loa CO2 concentration value for 2020, see the red * on the attached image on the trendline at the end of June, from the linked website:

The complete MetOffice forecast is at
https://www.metoffice.gov.uk/research/climate/seasonal-to-decadal/long-range/forecasts/co2-forecast

Extract: "We forecast the annual average CO2 concentration at Mauna Loa to be 2.74 ± 0.57 parts per million (ppm) higher in 2020 than in 2019 (Figure 1). This will continue the rising trend in CO2 seen in the long-term record of measurements from the Mauna Loa observatory in Hawaii that date back to 1958 and are a good guide to global CO2 levels. As a result, we forecast the 2020 annual average CO2 concentration at Mauna Loa to be 414.2 ± 0.6 ppm. For the first time, monthly CO2 levels will exceed 415 ppm (during spring and summer) and will remain above 410 ppm for the entire year."
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: kassy on January 25, 2020, 08:59:05 PM
Thus going forward I would recommend that this thread evaluation values for June if it wants to compare with RCP values.

Thanks , good point.

*

And on a general note please attack the arguments not the posters since that detracts from the discussion.

Trash the argument.

Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Stephan on January 25, 2020, 09:26:33 PM
Stephan, could you please post your calculation and the numbers you used?
I re-calculate for June 2019 (recommended by ASLR)
CO2
concentration 413.92 ppm
factor 1
resulting 413.92 ppm CO2 eq

CH4
concentration 1.8596 ppm
factors 84 (20 y) and 28 (100 y)
resulting 156.21 or 52.07 ppm CO2 eq
adjusting mole weight 56.80 or 18.93 ppm CO2 eq.
→ this was one of my questions whether this has to be done or is it already implemented in the GHG factor? This makes my CH4 value so low

N2O
concentration 0.3318 ppm
factor 264 (I didn't use factor 265 for 100 y, so I used 264 for both times)
resulting 87.60 ppm CO2 eq
no adjust of mole weight necessary

SF6
concentration 0.00093 ppm
factors 17,500 (20 y) or 23,500 (100 y)
resulting 0.17 or 0.23 CO2 eq
adjusting mole weight 0.58 or 0.77 ppm CO2 eq
(same question as above, makes SF6 value much higher because it is so heavy)

The sum of the bold written black lines gives me the same value as yours, nanning (apart from the different month used) 657.90 ppm CO2 eq (20 y) or 553.82 ppm CO2 eq (100 y)
Including the mole weights the values are lower: 558.89 ppm CO2 eq (20 y) or 521.22 ppm CO2 eq (100 y)
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Stephan on January 25, 2020, 09:49:10 PM
While writing these lines a further question came into my mind:
Is a simple addition right at all? Maybe the IR spectra of the molecules (especially CO2 and N2O) overlap and reduce each other by some interference?
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: gerontocrat on January 25, 2020, 10:13:25 PM

adjusting mole weight 56.80 or 18.93 ppm CO2 eq.
→ this was one of my questions whether this has to be done or is it already implemented in the GHG factor? This makes my CH4 value so low

The link seems to say the GWP ratio is based on WEIGHT
_____________________________________
https://climatechangeconnection.org/emissions/co2-equivalents/
The three main greenhouse gases (along with water vapour) and their 100-year global warming potential (GWP) compared to carbon dioxide are: (1)

1 x – carbon dioxide (CO2)
25 x – methane (CH4) – I.e. Releasing 1 kg of CH4 into the atmosphere is about equivalent to releasing 25 kg of CO2
298 x – nitrous oxide (N2O) – I.e. Releasing 1 kg of N2O into the atmosphere is about equivalent to releasing 298 kg of  CO2
__________________________________________

So I think this is the correct (?) result from your calculation
Including the mole weights the values are lower:
558.89 ppm CO2 eq (20 y) or 521.22 ppm CO2 eq (100 y)


ps: I have to go back to my spreadsheets to ciorrect them,

pps: The NOAA calculation of CO2e /AGGI does not include SF6 which is becoming significant,

ppps: CFC 11 & 12 that are in the NOAA CO2e /AGGI calculation and together as significant as N20. But how they do that I do not know.
https://www.esrl.noaa.gov/gmd/aggi/ & https://www.esrl.noaa.gov/gmd/aggi/aggi.html


Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Tom_Mazanec on January 25, 2020, 10:24:38 PM
Don’t forget the halocarbons.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Stephan on January 25, 2020, 10:31:13 PM
Don’t forget the halocarbons.
I didn't mention them because I only took the four "NOAA gases" that are reported on https://www.esrl.noaa.gov/gmd/ccgg/trends/index.html in a regular way. Of course the halocarbons are relevant and must be included into any realistic calculation of the GHG in Earth's atmosphere.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: RoxTheGeologist on January 25, 2020, 11:53:48 PM
While writing these lines a further question came into my mind:
Is a simple addition right at all? Maybe the IR spectra of the molecules (especially CO2 and N2O) overlap and reduce each other by some interference?

The overlapping (or not) of spectra is already built into the GWP.

One think I am not sure of is if aviation emissions are counted correctly, as they are largely in the stratosphere.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: AbruptSLR on January 26, 2020, 12:15:21 AM
Don’t forget the halocarbons.

The total radiative forcings, RFs, from the linked ORNL website article by Blasing, T.J. (that updates such RF values reported in April 2016, see the attached table) are used in the linked Wikipedia article to calculate a CO2e value of 526.6ppm.  This relatively high value of for CO2e appears to be associated with RF associated with tropospheric ozone and its chemical interaction in the atmosphere with GHGs like methane.

https://en.wikipedia.org/wiki/Carbon_dioxide_equivalent


Extract: "To calculate the CO2e of the additional radiative forcing calculated from April 2016's updated data: ∑ RF(GHGs) = 3.3793, thus CO2e = 280 e3.3793/5.35 ppmv = 526.6 ppmv."

Title: "Recent Greenhouse Gas Concentrations" by Blasing, T.J., 2016, DOI: 10.3334/CDIAC/atg.032

http://cdiac.ornl.gov/pns/current_ghg.html
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Stephan on January 26, 2020, 08:00:26 AM
If I use the radiative forcing from the table and compare that to the concentration of each GHG for 2016 I calculated the following factors with which the concentration has to be multiplied to achieve that radiative forcing:
CO2 = 1 (per definition)
CH4 = 57
N2O = 128
SF6 = 116,000
Using these factors one can adjust the concentration table to the radiative forcing of each gas.
_____________

Question: In the ORNL table there is the line: "increased radiative forcing". If I take this seriously, I subtracted the pre-industrial values from the actual values and receive new, modified factors:
CO2 = 1 (per definition)
CH4 = 28
N2O = 213
SF6 = 34,100
Is this a better way to calculate the CO2 eq?
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: nanning on January 26, 2020, 10:50:22 AM
From: https://en.wikipedia.org/wiki/Carbon_dioxide_equivalent
    Carbon dioxide equivalent

Global warming potential

Carbon dioxide equivalency is a quantity that describes, for a given mixture and amount of greenhouse gas, the amount of CO
2 that would have the same global warming potential (GWP), when measured over a specified timescale (typically 100 years). Carbon dioxide equivalency thus reflects the time-integrated radiative forcing of a quantity of emissions or rate of greenhouse gas emission—a flow into the atmosphere—rather than the instantaneous value of the radiative forcing of the stock (concentration) of greenhouse gases in the atmosphere described by CO2e.

The carbon dioxide equivalency for a gas is obtained by multiplying the mass and the GWP of the gas
For example, the GWP for methane over 100 years is 34,[3] and for nitrous oxide, 298. This means that emissions of 1 million tonnes of methane or nitrous oxide are equivalent to emissions of 34 or 298 million tonnes of carbon dioxide, respectively.


Equivalent carbon dioxide

Equivalent CO2 (CO2e) is the concentration of CO2 that would cause the same level of radiative forcing as a given type and concentration of greenhouse gas. Examples of such greenhouse gases are methane, perfluorocarbons, and nitrous oxide. CO2e is expressed as parts per million by volume, ppmv.

    CO2e calculation examples:

The radiative forcing for pure CO2 is approximated by R F = α ln(C/C0) where C is the present concentration, α is a constant, 5.35, and C0 is the pre-industrial concentration, 280 ppm. Hence the value of CO2e for an arbitrary gas mixture with a known radiative forcing is given by C0 exp(R F/ α) in ppmv.

To calculate the radiative forcing for a 1998 gas mixture, IPCC 2001 gives the radiative forcing (relative to 1750) of various gases as: CO2=1.46 (corresponding to a concentration of 365 ppmv), CH4=0.48, N2O=0.15 and other minor gases =0.01 W/m2. The sum of these is 2.10 W/m2. Inserting this to the above formula, we obtain CO2e = 412 ppmv.

To calculate the CO2e of the additional radiative forcing calculated from April 2016's updated data:[5] ∑ RF(GHGs) = 3.3793, thus CO2e = 280 exp(3.3793/5.35) ppmv = 526.6 ppmv.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Aporia_filia on January 26, 2020, 12:15:52 PM
Here you have another unexpected parameter in the equation: HFC-23 the most potent greenhouse that should have been controlled under actual legislation.

https://www.nature.com/articles/s41467-019-13899-4

"Starting in 2015, India and China, thought to be the main emitters of HFC-23, announced ambitious plans to abate emissions in factories that produce the gas. As a result, they reported that they had almost completely eliminated HFC-23 emissions by 2017.

In response to these measures, scientists were expecting to see global emissions drop by almost 90 percent between 2015 and 2017, which should have seen growth in atmospheric levels grind to a halt.

Now, an international team of researchers have shown, in a paper published today in the journal Nature Communications, that concentrations were increasing at an all-time record by 2018.

Dr Matt Rigby, who co-authored the study, is a Reader in Atmospheric Chemistry at the University of Bristol and a member of the Advanced Global Atmospheric Gases Experiment (AGAGE), which measures the concentration of greenhouse gases around the world, said: "When we saw the reports of enormous emissions reductions from India and China, we were excited to take a close look at the atmospheric data.

"This potent greenhouse gas has been growing rapidly in the atmosphere for decades now, and these reports suggested that the rise should have almost completely stopped in the space of two or three years. This would have been a big win for climate.""
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: AbruptSLR on January 26, 2020, 06:58:17 PM
If I use the radiative forcing from the table and compare that to the concentration of each GHG for 2016 I calculated the following factors with which the concentration has to be multiplied to achieve that radiative forcing:
CO2 = 1 (per definition)
CH4 = 57
N2O = 128
SF6 = 116,000
Using these factors one can adjust the concentration table to the radiative forcing of each gas.
_____________

Question: In the ORNL table there is the line: "increased radiative forcing". If I take this seriously, I subtracted the pre-industrial values from the actual values and receive new, modified factors:
CO2 = 1 (per definition)
CH4 = 28
N2O = 213
SF6 = 34,100
Is this a better way to calculate the CO2 eq?

In the Wikipedia approximation for the data published on April 2016 (but for 2015, from January 2015 through December 2015),  CO2e = 280 exp(3.3793/5.35) ppmv = 526.6 ppmv, the value of 280ppmv correlates the modern value of radiative forcing to the pre-industrial condition.  Thus to determine CO2e for 2019 one can wait until April 2020 when NOAA publishes their radiative forcing values for well mixed GHG and add in the radiative forcing for tropospheric ozone into this formula and you will have a value for 2019 to compare with the RCP values
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: AbruptSLR on January 26, 2020, 08:18:26 PM
….
In the Wikipedia approximation for the data published on April 2016 (but for 2015, from January 2015 through December 2015),  CO2e = 280 exp(3.3793/5.35) ppmv = 526.6 ppmv, the value of 280ppmv correlates the modern value of radiative forcing to the pre-industrial condition.  Thus to determine CO2e for 2019 one can wait until April 2020 when NOAA publishes their radiative forcing values for well mixed GHG and add in the radiative forcing for tropospheric ozone into this formula and you will have a value for 2019 to compare with the RCP values

For example, the attached NOAA table gives the radiative forcing for well mixed GHG in 2018 as 3.101 and adding the radiative forcing for tropospheric ozone as 0.4 gives 3.5101, which per the equation gives CO2e, in 2018, an approximate value of 538.7 ppmv
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: oren on January 26, 2020, 10:08:16 PM
Quote
Carbon dioxide equivalency is a quantity that describes, for a given mixture and amount of greenhouse gas, the amount of CO
2 that would have the same global warming potential (GWP), when measured over a specified timescale (typically 100 years). Carbon dioxide equivalency thus reflects the time-integrated radiative forcing of a quantity of emissions or rate of greenhouse gas emission—a flow into the atmosphere—rather than the instantaneous value of the radiative forcing of the stock (concentration) of greenhouse gases in the atmosphere described by CO2e.
I normally don't question established science but I think this 100-yr approach is wrong. As we track GHG concentrations, none of them has been faliing. We are obviously on a path where new emissions (both anthropogenic and natural feedbacks) are sufficient to maintain and even increase concentrations, regardless of sinks and destructive processes in the atmosphere. Thus the proper calculation should be the "instantaneous value of the radiative forcing of the stock (concentration) of greenhouse gases in the atmosphere". Assume this level is maintained going forward, to understand our current situation.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Stephan on January 26, 2020, 10:46:39 PM
oren,
I strongly support your opinion about the "instantaneous" GHG effect as all GHG concentrations (not sure whether this is true for all the halocarbons) increase for many decades now.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Tor Bejnar on January 27, 2020, 05:21:20 AM
I, too, agree, Oren.  Half-life (or equivalent) calculations are useful when 'exposure' will decline at known rates but when 'exposure' (e.g., continued release of methane and other greenhouse (GH) gasses by industry, etc.) is expected to go up or stay somewhat steady, half-life calculations don't make much sense ... unless the calculations include both expected new releases (all sources) and half-life attributes of those GH gasses.  However, our handle on future emissions of the various greenhouse gasses is probably not very clear (1.5 to 4 ppm or whatever CO2 levels?).

Remember those algebra problems about the bathtub with the open drain and turned-on faucets, only with ACC we don't know how the inflows will change over time, and some outflows get less efficient the warmer the ocean gets.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: wolfpack513 on January 27, 2020, 01:43:02 PM
Instantaneous CO₂ equivalent is basically why NOAA/ESRL created AGGI.  The AGGI is made up of all the major GHGs and even the 15 minor GHGs.

2019 data hasn't been added yet but through 2018, radiative forcing is currently 3.1 Watts/m² above pre-industrial.  https://www.esrl.noaa.gov/gmd/aggi/aggi.html (https://www.esrl.noaa.gov/gmd/aggi/aggi.html)
 
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Tom_Mazanec on January 27, 2020, 03:59:40 PM
So we added as much forcing in the last 40 years as in the entire previous history.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: wdmn on January 27, 2020, 04:37:04 PM
Well all of these measures are helpful I think it's important to consider the CO2e assuming a higher multiplier.

RF is a great measure (and reminds us to account for negative forcings), but most people have been trained to think in terms of a doubling of CO2 concentration, and all the modelling is done around ECS and TCR. We need to know how close we are to doubling, (or how long ago we doubled) to start making sense of how much risk we've already exposed ourselves too, I think... Otherwise why do we keep looking at CO2 concentration? We should just be looking at RF.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: oren on January 27, 2020, 05:03:48 PM
Thing is, while we haven't doubled CO2 (yet) we have greatly increase methane concentration and are busy maintaining it in the face of atmospheric destruction processes. The big question in calculating CO2eq is and has always been the methane question. So a higher multiplier is in order, but what should the multiplier be?
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Tom_Mazanec on January 27, 2020, 05:08:44 PM
I doubt this is taken into account here, but as the air warms it can hold more water vapor, which is itself a GHG, right?
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: nanning on January 27, 2020, 05:21:18 PM
Thanks wdmn, very good observation in my view.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: AbruptSLR on January 27, 2020, 05:48:08 PM
Well all of these measures are helpful I think it's important to consider the CO2e assuming a higher multiplier.

RF is a great measure (and reminds us to account for negative forcings), but most people have been trained to think in terms of a doubling of CO2 concentration, and all the modelling is done around ECS and TCR. We need to know how close we are to doubling, (or how long ago we doubled) to start making sense of how much risk we've already exposed ourselves too, I think... Otherwise why do we keep looking at CO2 concentration? We should just be looking at RF.

First, while it may be the case that this thread was created to focus on CO2e as calculated as a well mixed gas, and on the increasing emissions of methane and nitrous oxide; I note that CMIP6 models do consider scenarios with increasing methane and nitrous oxide emissions (such as SSP5) which provide projections of GMSTA that are relatively high in the coming decades (see the first attached image).

Second, the CMIP6 projections significantly underestimate the RF from ice-climate feedback mechanisms (say from a release of relatively warm & fresh water from the Beaufort Gyre in the next decade, or so, triggering a collapse of significant portions of the WAIS via the bipolar seesaw mechanisms) as indicated by the second attached image (see the gold curve assuming a 5-year doubling time).  Which this indicated increase in RF from such large freshwater hosing events might only last for a few decades, that period of time might be sufficient to push the NH atmosphere into an equable pattern before 2100.

I plan to stop posting in this thread after this post (so as not to highjack the main focus) but I think that it is important to realize that RF threat from ice-climate feedback is real (the already large amount warm fresh water still accumulating in the Beaufort Gyre will be released before too long) and is not fully accounted for by any consensus climate model projection.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Ken Feldman on January 27, 2020, 06:23:35 PM
...

and i see no reason to denigrate Mr Feldman. nowhere does he say that january numbers are the ones to compare.

sidd

He stated twice that we are below RCP 2.6 based on 411ppm
That is an inaccurate statement, and he knows it. How is it harsh to call him out on that? Ken's a smart guy, he knows what he's doing.

At this time of year the honest thing to do would be to report 2019 numbers, which would of course show that we are above RCP 2.6. I will call out such bullshit every time, and I would hope people would call me out for my bullshit too.

As the point of this exercise it to attempt to get a more current estimate of total forcings, I thought I would use the most current data available.  On NOAA's website, the most recent annual data is from 2018 (which is a global average of 407.38 ppm).

Mauna Loa is in the northern hemisphere which has the largest GHG emitters.  The Southern Ocean, which is one of the largest CO2 sinks, is in the Southern Hemisphere.  And the difference between the annual global average at Mauna Loa and the global average reported by  NOAA is evident from the data.

Year   Mauna Loa Avg (ppm)  Global Avg (ppm)
2019             411.44             Not yet available
2018             408.52                       407.38 
2017             406.55                       405.00
2016             404.24                       402.85
2015             400.83                       399.41

You can see that the Mauna Loa average is consistently higher than the global average, but that the amount differs from year to year.  So if you want to use the Mauna Loa data, you'd have to correct to get the global forcings.  However, the correction factor wouldn't be available until the global average is reported in spring of the following year.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Ken Feldman on January 27, 2020, 06:29:55 PM
Either I missed this before or NOAA just added it, but there's a new feature on their website for Trends in CO2 covering the daily Global CO2.  It shows the global average as well as readings from several observation sites.

https://www.esrl.noaa.gov/gmd/ccgg/trends/gl_trend.html (https://www.esrl.noaa.gov/gmd/ccgg/trends/gl_trend.html)

(https://www.esrl.noaa.gov/gmd/webdata/ccgg/trends/global_trend.png)
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: kassy on January 27, 2020, 07:52:30 PM
I plan to stop posting in this thread after this post (so as not to highjack the main focus) but I think that it is important to realize that RF threat from ice-climate feedback is real

Thanks for some key remarks (#11). Do post here if something pertinent comes up.

I am really interested in the difference between our scenarios and the actual earth systems but more of that on the other thread. Nice timing on the Beaufort Gyre reposts btw.  :)

You can see that the Mauna Loa average is consistently higher than the global average, but that the amount differs from year to year.  So if you want to use the Mauna Loa data, you'd have to correct to get the global forcings.  However, the correction factor wouldn't be available until the global average is reported in spring of the following year.

Basically the comparison is yearly.

All the non CO2 updates were monthly and they do not vary that much.

Technically that looks like less work (or a whole lot more if you really want to dive into it).

I normally don't question established science but I think this 100-yr approach is wrong. As we track GHG concentrations, none of them has been faliing. We are obviously on a path where new emissions (both anthropogenic and natural feedbacks) are sufficient to maintain and even increase concentrations, regardless of sinks and destructive processes in the atmosphere. Thus the proper calculation should be the "instantaneous value of the radiative forcing of the stock (concentration) of greenhouse gases in the atmosphere". Assume this level is maintained going forward, to understand our current situation.

It would be interesting to see the difference between using the two values.


 

Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Stephan on January 27, 2020, 09:49:29 PM
Either I missed this before or NOAA just added it, but there's a new feature on their website for Trends in CO2 covering the daily Global CO2.  It shows the global average as well as readings from several observation sites.
I do not see a fundamental difference in these readings. Barrow has a much larger intra-year fluctuation than the very smooth South Pole data. But in the end the slope of all these graphs is identical. I do not think that we should discuss whether the global average is 408.53 or 407.92 or 406.05 ppm. It is the annual increase (and the positive 2nd derivative of it) that must worry us all.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Neven on January 27, 2020, 11:05:37 PM
And on a general note please attack the arguments not the posters since that detracts from the discussion.

Trash the argument.

+1
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: TerryM on January 28, 2020, 07:36:19 PM
oren
I fully concur.


100 year numbers can only apply if we expect CH4 emissions to suddenly end & the atmospheric concentrations fall over that time period.
Since we're currently replacing each molecule as rapidly as one fails, the "instantaneous" value is the only one of concern.
The PPM numbers represent the CH4 present at this instant, not the CH4 that will have survived over a 100 year period.


If our blanket were being devoured by moths, we'd measure the heat radiated today rather than fretting over the fact that in 100 years it would be a thin rag, providing very little comfort. Nor would we be concerned about calculating the average heat radiated back over that period.


In 20 years, or 100 we could again measure the blanket's remaining efficiency - at that particular instant.
Today we're adding more wool than the moths are devouring. The longer, lower numbers are simply pulling wool over the sheep's eyes. ::)
Terry
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: bluice on January 28, 2020, 09:39:50 PM
Same applies for biomass burning. If we fell a tree, or a forest, and burned it as firewood it would take 50 years or so for the trees to grow back.

All this time the co2, although slowly diminishing, would stay in the atmosphere warming the planet.

And who knows, maybe the forest won’t grow back at all.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: edmountain on January 28, 2020, 10:46:50 PM
It seems to me that discarding the 100-year time horizons neglects the fact that there are (at least) two different problems to be solved. Each problem has their own metrics that work well within the domain of that problem but which are problematic when applied out of context.

The first problem is that of modelling the response of the climate system to future radiative forcing from GHGs and feedbacks. The solution to this problem requires (among other things) an estimate of the time evolution of GHG concentrations from initial conditions; this is what the RCPs are designed to serve.

The second problem is to provide a metric for use by policy makers to estimate and account for the cumulative future effect of their current actions. Implicit in any solution to this problem is the need to integrate an effect over time: it is a cumulative result that is being estimated. This is the problem that GWPs are intended to help with and why, by definition, they require a time horizon to serve as the limits on the integral.

So GWPs are not intended as a tool to project future concentrations with. They are simply an accounting mechanism to quantify and compare from one jurisdiction to the next behaviour that’s happening today.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Ken Feldman on January 31, 2020, 07:38:06 PM
One way to track which pathway we are on is to look at the annual change in the concentrations of each greenhouse gas and compare them to the RCPs.  This will capture both the anthropogenic and natural emissions, so would include feedbacks from climate change (such as increased ghg emissions from wetlands drying or permafrost thaw).

Here's the link to the RCPs:

https://www.ipcc.ch/site/assets/uploads/2017/09/WG1AR5_AnnexII_FINAL.pdf (https://www.ipcc.ch/site/assets/uploads/2017/09/WG1AR5_AnnexII_FINAL.pdf)

For CO2, the concentrations are projected to be:

Year    RCP 2.6    RCP 8.5
2010     389.3       389.3
2020     412.1       415.8
2030     430.8       448.8

The average annual change from 2010 to 2020 was projected as 2.28 ppm under RCP 2.6 and 2.65 ppm under RCP 8.5.  The actual average annual (using the global avg annual data from NOAA) change was (411.44 - 389.9)/10 = 2.15 ppm.

Data available here.

https://www.esrl.noaa.gov/gmd/ccgg/trends/data.html (https://www.esrl.noaa.gov/gmd/ccgg/trends/data.html)

While all of the RCPs are very close up to the 2020s, in the future, the projections really start to differ.  For the next decade, RCP 2.6 projections average annual increases in CO2 of 1.87 ppm while RCP 8.5 projects annual changes of 3.3 ppm.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Ken Feldman on January 31, 2020, 08:00:28 PM
The linked commentary in the January 29, 2020 issue of Nature makes it clear that the RCP8.5 scenario (updated to SSP5-8.5 for the upcoming AR6 report) is unrealistic.

https://www.nature.com/articles/d41586-020-00177-3 (https://www.nature.com/articles/d41586-020-00177-3)

Quote
COMMENT 29 January 2020
Emissions – the ‘business as usual’ story is misleading
Stop using the worst-case scenario for climate warming as the most likely outcome — more-realistic baselines make for better policy.
Zeke Hausfather & Glen P. Peters

More than a decade ago, climate scientists and energy modellers made a choice about how to describe the effects of emissions on Earth’s future climate. That choice has had unintended consequences which today are hotly debated. With the Sixth Assessment Report (AR6) from the Intergovernmental Panel on Climate Change (IPCC) moving into its final stages in 2020, there is now a rare opportunity to reboot.

In the lead-up to the 2014 IPCC Fifth Assessment Report (AR5), researchers developed four scenarios for what might happen to greenhouse-gas emissions and climate warming by 2100. They gave these scenarios a catchy title: Representative Concentration Pathways (RCPs)1. One describes a world in which global warming is kept well below 2 °C relative to pre-industrial temperatures (as nations later pledged to do under the Paris climate agreement in 2015); it is called RCP2.6. Another paints a dystopian future that is fossil-fuel intensive and excludes any climate mitigation policies, leading to nearly 5 °C of warming by the end of the century2,3. That one is named RCP8.5.

Quote
Assessment of current policies suggests that the world is on course for around 3 °C of warming above pre-industrial levels by the end of the century — still a catastrophic outcome, but a long way from 5 °C7,8. We cannot settle for 3 °C; nor should we dismiss progress.
Plan for progress

Some researchers argue that RCP8.5 could be more likely than was originally proposed. This is because some important feedback effects — such as the release of greenhouse gases from thawing permafrost9,10 — might be much larger than has been estimated by current climate models. These researchers point out that current emissions are in line with such a worst-case scenario11. Yet, in our view, reports of emissions over the past decade suggest that they are actually closer to those in the median scenarios7. We contend that these critics are looking at the extremes and assuming that all the dice are loaded with the worst outcomes.

Quote
For policymakers, mitigation policies that depend on the assumptions underlying high-emission baseline scenarios such as RCP8.5 will seem exorbitant, because they do not incorporate the plummeting costs of many low-carbon technologies over the past decade. The marginal investments required to move from 3 °C of warming to well below 2 °C (the main Paris goal) will be much less than moving from 5 °C to well below 2 °C. A narrative of progress and opportunity can make the Paris targets seem feasible, rather than seemingly impossible.

(https://media.nature.com/lw800/magazine-assets/d41586-020-00177-3/d41586-020-00177-3_17600472.jpg)

Quote
Finally, we suggest that climate-impact studies using models developed for AR6 should include scenarios that reflect more-plausible outcomes, such as SSP2-4.5, SSP4-6.0 and SSP3-7.0 (see ’Possible futures’). When RCP8.5 or its successor SSP5-8.5 are deployed, they should be clearly labelled as unlikely worst cases rather than as business as usual.

Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: wdmn on January 31, 2020, 08:28:15 PM
One way to track which pathway we are on is to look at the annual change in the concentrations of each greenhouse gas and compare them to the RCPs.  This will capture both the anthropogenic and natural emissions, so would include feedbacks from climate change (such as increased ghg emissions from wetlands drying or permafrost thaw).

Ken, while it's a good idea, it's actually not true since those feedbacks are not included in CMIP5 models.

This is exactly what the debate over the article you shared from Glen Peters and Zeke Hausfather is about: Glen and Zeke are confident antrho emissions won't follow RCP 8.5; scientists like Michael Mann and Gavin Schmidt have pointed out (and Glen and Zeke concede) that without RCP 8.5 there's nothing capturing higher emissions scenarios from non-anthro sources unaccounted for in the models.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: oren on January 31, 2020, 10:58:32 PM
Quote
The average annual change from 2010 to 2020 was projected as 2.28 ppm under RCP 2.6 and 2.65 ppm under RCP 8.5.  The actual average annual (using the global avg annual data from NOAA) change was (411.44 - 389.9)/10 = 2.15 ppm.
Silly me is having trouble understanding how the actual 2020 value was 411.44 if 2020 hasn't finished yet.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Ken Feldman on January 31, 2020, 11:00:04 PM
One way to track which pathway we are on is to look at the annual change in the concentrations of each greenhouse gas and compare them to the RCPs.  This will capture both the anthropogenic and natural emissions, so would include feedbacks from climate change (such as increased ghg emissions from wetlands drying or permafrost thaw).

Ken, while it's a good idea, it's actually not true since those feedbacks are not included in CMIP5 models.

This is exactly what the debate over the article you shared from Glen Peters and Zeke Hausfather is about: Glen and Zeke are confident antrho emissions won't follow RCP 8.5; scientists like Michael Mann and Gavin Schmidt have pointed out (and Glen and Zeke concede) that without RCP 8.5 there's nothing capturing higher emissions scenarios from non-anthro sources unaccounted for in the models.

The observed concentrations include all emissions (as well as all sinks).  There is no need to rely on climate model assumptions for the observations. 

And if you compare the actual observations to the projected concentrations for each RCP, you also avoid the problem.  You're just looking at how much of each greenhouse gas is needed to get to the radiative forcing assumed by the RCP, it doesn't matter whether the emissions are from fossil fuels or burning forests. 
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Ken Feldman on January 31, 2020, 11:01:59 PM
Quote
The average annual change from 2010 to 2020 was projected as 2.28 ppm under RCP 2.6 and 2.65 ppm under RCP 8.5.  The actual average annual (using the global avg annual data from NOAA) change was (411.44 - 389.9)/10 = 2.15 ppm.
Silly me is having trouble understanding how the actual 2020 value was 411.44 if 2020 hasn't finished yet.

I took the 10 years from 2010 through 2019 for Mauna Loa data (the global number for 2019 isn't reported yet). If you went to the link I posted, you would've known that.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: oren on January 31, 2020, 11:17:30 PM
I did click on the link, but these numbers were not immediately apparent while browsing it. I did not download any data files though.
Be that as it may, average of 2010 to average of 2019 sounds like 9 years to me, rather than 10. What am I missing?
Why not take the last actual available annual global average (2019? 2018?), compare it to the annual global average of 2010, and compare these numbers and their diffs to what the RCPs had to say about the same timespan (2018-2010 or 2019-2010)? Sounds liks a more proper comparison to me.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Tom_Mazanec on January 31, 2020, 11:21:25 PM
Quote
Be that as it may, average of 2010 to average of 2019 sounds like 9 years to me, rather than 10. What am I missing?

First 2010
Second 2011
Third 2012
Fourth 2013
Fifth 2014
Sixth 2015
Seventh 2016
Eighth 2017
Ninth 2018
Tenth 2019
 
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Ken Feldman on January 31, 2020, 11:57:41 PM
I did click on the link, but these numbers were not immediately apparent while browsing it. I did not download any data files though.
Be that as it may, average of 2010 to average of 2019 sounds like 9 years to me, rather than 10. What am I missing?
Why not take the last actual available annual global average (2019? 2018?), compare it to the annual global average of 2010, and compare these numbers and their diffs to what the RCPs had to say about the same timespan (2018-2010 or 2019-2010)? Sounds liks a more proper comparison to me.

The RCP tables in the IPCC report go by the decade, so 2010, 2020, 2030, 2040, …

We can wait a year and go with your approach, I was offering up something we can do now.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: wdmn on February 01, 2020, 02:33:45 AM
Sorry Ken, I misunderstood, and it's because I am a bit mixed up as to the point of this thread.

The title asks, which pathway are we on? I believe that means, which CO2eq pathway are we on, rather than CO2, and the reason that we originally wanted to calculate CO2eq is because there are a bunch of us on this board who think that the RF from CO2eq using GWP10 is an important figure to have, and we can't find it anywhere.

But I shouldn't speak for others, I've just heard that expressed by a few people.

Personally, the reason I'm interested in CO2eq is that a recent study suggested RF from anthro aerosols in 2008 was ~ -2W/m^2. If we looked at RF from CO2eq using GWP10 instead of GWP100 could it be that we're actually masking ~1.5C of warming? That we've actually passed CO2 doubling and TCR is ~2.7C and ECS>5C? I know some of the CMIP6 models had values of ECS and TCR that are similar.

I realize this is unlikely, but I'd like to know how long ago CO2eq passed (assuming it has) a doubling of pre-industrial.

We can't use any of the IPCC models for this assuming that none of them use the GWP10 numbers when thinking about CH4 or NO2.

Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: kassy on February 01, 2020, 04:08:20 PM
I am a bit mixed up as to the point of this thread.


1) Looking at the numbers to see which RCP we were closest too.

There was a recent discussion in the ASLR thread about which RCP scenario we were on and that interested me. So one goal was moving that discussion out of that thread because it has a steady stream of updates so the discussion would be buried soon and it is too interesting.

2) Possibly using the Co2e for that

(and moving related discusssion out of ML CO2 thread)

3) At some point see how the Carbon Clock data on the budget matches up to the numbers.

4) RCPs change to SCP or whatever so we could track that change if needed.

Basically lets play with numbers and see if we can learn from that.

I realize this is unlikely, but I'd like to know how long ago CO2eq passed (assuming it has) a doubling of pre-industrial.


And to check things like that.

I would like to see the comparison using "instantaneous value of the radiative forcing of the stock (concentration) of greenhouse gases in the atmosphere" see #25 for details.



Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: wdmn on February 03, 2020, 08:27:31 AM
I don't believe the below graph has been posted yet and seems essential to the topic of this thread.

Assuming I'm reading this graph right we are well above RCP 8.5 at this point for CO2eq, as we are already above 450ppm CO2eq according to all of the numbers presented in this thread...

Also, I still haven't figured out how you get from ppb in CH4 to ppm in CO2eq if it's not using the GWP multiplier (some posters in this thread have claimed that GWP is not for atmospheric CO2 concentrations).
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: wolfpack513 on February 03, 2020, 04:56:20 PM
I'm not 100% sure but I believe RCPs use a 20-year running average/smooth and include anthropogenic aerosols(negative forcing).  Therefore endpoints or single years will have much higher CO2e than the 20 year average.  Lower pathways have less aerosols and less cooling.  Higher end RCPs: 6 & 8.5 have more cooling from aerosols.  Since all pathways begin at 2000 it takes a while for separation especially with inverse negative forcing/cooling in emission mitigation.

I don't believe the below graph has been posted yet and seems essential to the topic of this thread.

Assuming I'm reading this graph right we are well above RCP 8.5 at this point for CO2eq, as we are already above 450ppm CO2eq according to all of the numbers presented in this thread...

Also, I still haven't figured out how you get from ppb in CH4 to ppm in CO2eq if it's not using the GWP multiplier (some posters in this thread have claimed that GWP is not for atmospheric CO2 concentrations).
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: gerontocrat on February 03, 2020, 05:36:59 PM
I'm not 100% sure but I believe RCPs use a 20-year running average/smooth and include anthropogenic aerosols(negative forcing).

Given the speed of change using a 20 year running average seems a bit out-of-date, and downright misleading. It reminds me of once a decade producing a new 30 year average of temperature, even though the climate in year 30 is now so much different from what it was in year 1.

The WMO in its recent report to the IPCC of THE GLOBAL CLIMATE 2015–2019 ,showed how much the average of 2015-2019 had changed from the average 2010-2014. i.e. the WMO used the change in 5 years to highlight what a rotten state the climate is and how quickly it is changing.

Executive summary
Quote
Compared to the previous five-year assessment period 2011–2015, the current five-year period 2015–2019 has seen a continued increase in carbon dioxide (CO2) emissions and an accelerated increase in the atmospheric concentration of major greenhouse gases (GHGs), with growth rates nearly 20% higher. The increase in the oceanic CO2 concentration has increased the ocean’s acidity.

The five-year period 2015–20191 is likely to be the warmest of any equivalent period on record globally, with a 1.1 °C global temperature increase since the pre-industrial period and a 0.2 °C increase compared to the previous five-year period.

Continuing and accelerated trends have also predominated among other key climate
indicators, including an acceleration of rising sea levels, a continued decline in the Arctic sea-ice extent, an abrupt decrease in Antarctic sea ice, continued ice mass loss in the glaciers and the Greenland and Antarctic ice sheets, and the clear downward trend in the northern hemisphere spring snow cover.

More heat is being trapped in the ocean; 2018 had the largest ocean heat content values on
record measured over the upper 700 meters.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: wdmn on February 03, 2020, 07:27:54 PM
Thanks.

Not sure about the 20 year running average; as gerontocrat says it would be very misleading. I know that aerosols are included. They are also included in the numbers posted here from external sources. For example the 454ppm number in 2017.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Ken Feldman on February 03, 2020, 09:15:04 PM
I don't believe the below graph has been posted yet and seems essential to the topic of this thread.

Assuming I'm reading this graph right we are well above RCP 8.5 at this point for CO2eq, as we are already above 450ppm CO2eq according to all of the numbers presented in this thread...

Also, I still haven't figured out how you get from ppb in CH4 to ppm in CO2eq if it's not using the GWP multiplier (some posters in this thread have claimed that GWP is not for atmospheric CO2 concentrations).

Keep in mind that the RCPs also include aerosols and land use (albedo) changes which have a cooling effect.  We've only been comparing the greenhouse gases on this thread. 

To get to a CO2eq you can take the measured concentration of a greenhouse gas in the atmosphere and calculate it's radiative forcing.  Then you can convert to CO2eq by finding the amount of CO2 that would have the same radiative forcing.  So you can get around the whole GWP 20 vs GWP 100 argument.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: wdmn on February 03, 2020, 10:02:55 PM
Thanks for the explanation re. GWP Ken.

As for the cooling effect of aerosols please see my last post ^^

Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: mitch on February 03, 2020, 11:37:32 PM
You don't actually get around the GWP20 vs GWP100 issue using Co2 equivalents.  Here is the NOAA website explaining how they calculate them:
https://www.esrl.noaa.gov/gmd/aggi/aggi.html

The CO2e depends on a calculation of forcing. 
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: wolfpack513 on February 04, 2020, 01:09:55 AM
I’m not a fan of 5-year averages gerontocrat.  2015-2019 was dominated by +ENSO.  2010-2014 which was weighted more -ENSO.  There has been some acceleration the last 40 years but majority of the last 5 years bump was internal variability.  The 20-year and 30-year trend are identical.  You can hardly see the red line overlaid the green line. 
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: wdmn on February 04, 2020, 02:33:46 AM
You don't actually get around the GWP20 vs GWP100 issue using Co2 equivalents.  Here is the NOAA website explaining how they calculate them:
https://www.esrl.noaa.gov/gmd/aggi/aggi.html

The CO2e depends on a calculation of forcing.

Thanks, that had been my understanding.

I feel like a dog chasing his tail with this one, but I also feel that those of us making a clamour here are on to something.

Here's how I look at it: there's uncertainty attached to almost all of the numbers we're interested in. If we use RF there's a large uncertainty around aerosols.

So let's start with the things we can actually measure directly. To me that is atmospheric concentration. Yes, we have to find a way to make the different concentrations comparable and that is a problem... We can also measure GMSTA. Using those measurements we could potentially get clues about some of the areas where we lack certainty.

That's my reasoning.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: edmountain on February 04, 2020, 05:30:51 PM
I don’t think there’s any way to get around using time horizons when discussing CO2 equivalents. This is because the very definition of GWP is based on integration over time. From the IPCC AR5 report:

Quote
The Global Warming Potential (GWP) is defined as the time-integrated RF due to a pulse emission of a given component, relative to a pulse emission of an equal mass of CO2 (Figure 8.28a and formula).
Source: https://www.ipcc.ch/site/assets/uploads/2018/02/WG1AR5_all_final.pdf

The absolute GWPs (AGWP) of hypothetical gases are the areas under the curves red and green curves in Figure 8.28a from the same report as shown below. The AGWP for CO2 is the area under the blue curve. GWP for a gas is the AGWP for that gas divided by the AGWP for CO2.
(https://i.imgur.com/IBcrNzN.png)

CO2 equivalents are essentially a unit of measure of GWP (analogous to how meters are a measure of distance). As such, time horizons are inseparable from the definition of CO2 equivalents. I’m not sure how to interpret the instantaneous ratio of RF that Ken refers to other than being some measure of relative fluxes.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: wolfpack513 on February 04, 2020, 05:31:40 PM
CMIP5 data in the IPCC 5th AR uses RCPs in 20-year centered periods: "Twenty-year AR5 climatologies and climatological anomalies are calculated for the averaging periods 2016-2035, 2046-2065, 2081-2100 for the CMIP5 scenario experiments rcp26, rcp45, rcp60 and rcp85."  So not exactly 20-year running averages. 

The 1998-2012 hiatus period is highlighted for issues with timescales of 15 years or less. Heat uptake is still occurring but internal variability may briefly slow GMST trends.  20-year period are long enough to average out most of this internal variability.  https://www.ipcc.ch/site/assets/uploads/2018/02/WG1AR5_Chapter09_FINAL.pdf (https://www.ipcc.ch/site/assets/uploads/2018/02/WG1AR5_Chapter09_FINAL.pdf)


Thanks.

Not sure about the 20 year running average; as gerontocrat says it would be very misleading. I know that aerosols are included. They are also included in the numbers posted here from external sources. For example the 454ppm number in 2017.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: nanning on February 04, 2020, 07:27:41 PM
[rant]
"Where are we now in CO2e , which pathway are we on? "

I am fed up with these 'pathways'.
We are clearly on the pathway to catastrophy, to the end of life as we know it. Please talk to 'aware' children about that.

Forget those stupid budgets (a faraway point that 'the can' can be kicked to, and re-kicked) and 'informing decision makers' because nobody is listening (see COP25) and if anything is being done by some, it is far too little and far too late. How much more do you need to know to be certain of catastrophy? U.N.: Essential: Fundamental changes to our production/consumption systems.
Well, green BAU isn't it
.

People may wanna know precisely when 'it''ll happen to them? Well, it's already happening to millions of people elsewhere on this planet, i.e. the global poor south. It is here! People are dying!

I ask myself: Why study your own destruction in such detail? Putting all focus on analysis and modelling meanwhile the Earth is burning, drowing and sterilising and more and more humans (far away) are dying from it. Please see the big picture. It includes Africa. Africans are as much human as you and me.
[/rant]
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: sark on February 07, 2020, 08:10:42 AM
Have we doubled the greenhouse effect?
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: wdmn on February 07, 2020, 08:52:14 AM
Have we doubled the greenhouse effect?

The best answer comes from here: https://www.esrl.noaa.gov/gmd/aggi/aggi.html

and seems to be "no." The NOAA (IPCC) method gives us 496 ppm CO2e for 2018, so I guess somewhere around 500ppm for 2019. Growing at a rate of ~3.7 ppm/yr over the last six years, if that were to continue we would double in something like 20 years.

To understand how RF is calculated (i.e. how the constants used in table 1 above were derived), and so how the CO2eq is calculated, you would need to tackle the following:

Radiative Forcing of Climate Change, Chapter 6 in Climate Change 2001: The Scientific Basis

available here: https://www.ipcc.ch/site/assets/uploads/2018/03/TAR-06.pdf


Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Tom_Mazanec on February 07, 2020, 11:42:23 AM
Quote
Growing at a rate of ~3.7 ppm/yr over the last six years, if that were to continue we would double in something like 20 years.
But that rate of increase is itself slowly increasing, so more like 18 or 19 years.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: rboyd on February 07, 2020, 11:13:59 PM
The NOAA CO2e calculation uses the 100-year CO2 equivalent for CH4.

CH4 is degraded out of the atmosphere over a 14 years period, with a 20-year CO2e of about 100, vs 34 for 100 years. Given that we are more than replacing the degraded CH4 every year (the atmospheric concentration keeps going up) we should be using at least the 20-year, if not the continuous, CO2e for CH4. Using the 20-year we are at about 620ppm CO2e - that is an accurate view of the current energy imbalance of the Earth System.

So we already doubled CO2e from pre-industrial (not taking into account climate dimming aerosols) and its only Earth System delayed responses (plus aerosols) which have stopped us from hitting the 2 degrees C increase already. The IPCC scientists assume that the CH4 will be reduced as NG use reduces, but thats not happening given the ongoing coal to NG switching and there is also the problem of natural CH4 emissions increasing as temperatures increase.

Thats how we get to be on the RCP8.5 scenario without the required level of anthropogenic CO2 emissions, the short-term effects of CH4 plus feedbacks fill the gap. If the Arctic Sea Ice goes then we will need a new scenario - RCP10 or perhaps RCP WAF (as in "we are f....").
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: wdmn on February 08, 2020, 04:28:14 AM
Rboyd,

Does it say that somewhere on the NOAA site?

My understanding from reading the site was that they're first calculating RF for each GHG using numbers from lab experiments/models, and then they convert RF to CO2eq? They are able to do this because they have ppm CO2 and RF, so going from RF to ppm COe would be pretty simple. It seems to me they don't use a GWP multiplier at all, as Ken suggested earlier...
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Stephan on February 08, 2020, 11:10:51 PM
With the actual values of CO2, CH4, N2O and SF6 for October 2019 (see the individual threads) there is an annual increase (Oct 2019 vs. Oct 2018) of 3.08 ppm CO2 eq (20 y) or 2.87 ppm CO2 eq (100 y).
October 2019 vs. Sept. 2019 delivers an increase of 0.20 ppm CO2 eq (20 y) or 0.08 ppm CO2 eq (100 y)
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: rboyd on February 11, 2020, 01:10:55 AM
Rboyd,

Does it say that somewhere on the NOAA site?

My understanding from reading the site was that they're first calculating RF for each GHG using numbers from lab experiments/models, and then they convert RF to CO2eq? They are able to do this because they have ppm CO2 and RF, so going from RF to ppm COe would be pretty simple. It seems to me they don't use a GWP multiplier at all, as Ken suggested earlier...

2017 to 2018 rise for CO2 was 2.39ppm, which produced an increase in radiative forcing of 0.031
- 0.031 / 2.39 = radiative forcing per CO2 ppm = 0.01297


2017 to 2018 rise for NH4 was 8.27ppb = 0.00827ppm, which produced an increase in radiative forcing of 0.003
- 0.003 / 0.00827 - radiative forcing per NH4 ppm = 0.36276

An NH4 ppm produces a radiative forcing approximately 28 times that of a CO2 ppm, the 100-year equivalent amount according to the UN IPCC in 2011. The more recent 100-year value is 36. The 20-year value is 86 (direct forcing only).
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: oren on February 11, 2020, 08:15:24 AM
Thanks for the calculation rboyd. (NH4 should be CH4).
I note it does not include a timeframe (integration period) so I will take it as the instantaneous value I was looking for, which I would expect to be higher than 100-yr and 20-yr values as those include an assumption of CH4 concentration decay.
What I find weird is that the value of 28 is close to the 100-yr value and much lower than the 20-yr value. Are you sure there isn't some error in the calculation?
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: rboyd on February 11, 2020, 06:23:49 PM
Oren, thanks for the correction, Ammonia is a very different thing!

I remember reading that NOAA was still using the outdated 28 multiplier for the CO2e of CH4, looked around a lot but couldn't find the reference. Neither any simple statement about the GPWP that NOAA. Thats why I did the calculation.

I really do think that they are using the 28 multiplier as a measure of RF, not even the GWP100 of CH4 which is more up to date. I did get a confirmation of this from AbruptSLR, but would definitely welcome information from somebody more in the know.

This is from the official NOAA website, they never mention the GWP20:

Quote
Methane plays an important role in the chemistry and radiative properties of the atmosphere. With a global warming potential of 28 over a 100-year horizon, methane is a potent greenhouse gas (IPCC, AR5). Atmospheric methane has a lifetime of about a decade, and it is ultimately oxidized to CO2. It is one of the greenhouse gases targeted by the Kyoto Protocol, and may well be regulated by the United States in the future. Controlling methane emissions also has implications for air quality, since oxidation of CH4 leads to tropospheric ozone formation in polluted environments.

https://www.esrl.noaa.gov/gmd/ccgg/carbontracker-ch4/ (https://www.esrl.noaa.gov/gmd/ccgg/carbontracker-ch4/)
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Ken Feldman on February 11, 2020, 10:56:01 PM
The linked article discusses the global warming potential of SF6 and shows why reductions in CO2 and CH4 should be prioritized, even if it means slight increases in SF6 emissions in the next few decades.

http://theconversation.com/why-sf-emissions-from-the-renewable-energy-sector-should-not-be-considered-a-dirty-secret-130734 (http://theconversation.com/why-sf-emissions-from-the-renewable-energy-sector-should-not-be-considered-a-dirty-secret-130734)

Quote
Why SF₆ emissions from the renewable energy sector should not be considered a ‘dirty secret’
February 10, 2020

How much does generating electricity using renewables boost global warming? You’d probably think not at all, but according to a BBC article published in September 2019, emissions of sulfur hexafluoride (SF₆), “the most powerful greenhouse gas known to humanity”, have been rising rapidly in recent years, and the likely culprit is “the green energy boom”.

SF₆ gas is used to insulate electrical installations like wind turbines and was quoted as the industry’s “dirty secret” in the BBC article. The article also claimed that SF₆ emissions to the atmosphere in 2017 had the same warming effect as adding an extra 1.3 million cars to roads across the UK and the EU.

Quote
The most important sentence in the BBC’s article is this:

    Concentrations in the atmosphere [of SF₆] are very small right now, just a fraction of the amount of CO₂ in the air.

Unfortunately, this critical point isn’t developed.

The global concentration of atmospheric CO₂ today is about 410 parts per million, whereas the global concentration of SF₆ is only about 10 parts per trillion. In other words, there is 41 million times more CO₂ in the atmosphere than SF₆.

But since SF₆ is 23,500 times stronger at trapping heat than CO₂, doesn’t this still mean it’s a bigger problem than CO₂ for the climate?

CO₂ is actually a very weak greenhouse gas and is much less efficient at trapping heat compared to other greenhouse gases, such as methane (CH₄) and nitrous oxide (N₂O). The reason why CO₂ has the largest impact on the climate is partly because, like SF₆, it is very long-lived. But mostly, it is because there is so much more CO₂ in the atmosphere than other greenhouse gases (except for water vapour, which is not the main driver of anthropogenic climate change because it is so short-lived).

(https://images.theconversation.com/files/313499/original/file-20200204-41554-148bamv.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip)

(https://images.theconversation.com/files/312281/original/file-20200128-81411-w37q6l.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=473&fit=crop&dpr=1)

Note that the article refers to Methane's GWP(200) as 28.  It has been updated to 34 as explained in the following reference.

https://ui.adsabs.harvard.edu/abs/2017AGUFM.A51N..08H/abstract (https://ui.adsabs.harvard.edu/abs/2017AGUFM.A51N..08H/abstract)

Quote
The global warming potential of methane reassessed with combined stratosphere and troposphere chemistry

    Holmes, C. D.; Archibald, A. T.; Eastham, S. D.; Søvde, O. A.

Abstract

Methane is a direct and indirect greenhouse gas. The direct greenhouse effect comes from the radiation absorbed and emitted by methane itself. The indirect greenhouse effect comes from radiatively active gases that are produced during methane oxidation: principally O3, H2O, and CO2. Methane also suppresses tropospheric OH, which indirectly affects numerous greenhouses gases and aerosols. Traditionally, the methane global warming potential (GWP) has included the indirect effects on tropospheric O3 and OH and stratospheric H2O, with these effects estimated independently from unrelated tropospheric and stratospheric chemistry models and observations. Using this approach the CH4 is about 28 over 100 yr (without carbon cycle feedbacks, IPCC, 2013). Here we present a comprehensive analysis of the CH4 GWP in several 3-D global atmospheric models capable of simulating both tropospheric and stratospheric chemistry (GEOS-Chem, Oslo CTM3, UKCA). This enables us to include, for the first time, the indirect effects of CH4 on stratospheric O3 and stratosphere-troposphere coupling. We diagnose the GWP from paired simulations with and without a 5% perturbation to tropospheric CH4 concentrations. Including stratospheric chemistry nearly doubles the O3 contribution to CH4 GWP because of O3 production in the lower stratosphere and because CH4 inhibits Cl-catalyzed O3 loss in the upper stratosphere. In addition, stratosphere-troposphere coupling strengthens the chemical feedback on its own lifetime. In the stratosphere, this feedback operates by a CH4 perturbation thickening the stratospheric O3 layer, which impedes UV-driven OH production in the troposphere and prolongs the CH4 lifetime. We also quantify the impact of CH4-derived H2O on the stratospheric HOx cycles but these effects are small. Combining all of the above, these models suggest that the 100-yr GWP of CH4 is over 33.5, a 20% increase over the latest IPCC assessment.


Publication:
    American Geophysical Union, Fall Meeting 2017

Also note that the Methane GWP already includes its impact on Ozone and Stratospheric Water Vapor, so it would be double-counting to include separate factors for those gases.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: rboyd on February 17, 2020, 08:11:56 PM
Looks like there are alternatives for SF6 in medium voltage uses, but not in high voltage ones. Looks like more research money needs to be spent on the HV applications. But definitely less of a issue that CO2 and CH4.

Quote
The rationale for this was that there was no viable alternative. However, as has been made clear this in this paper, this is no longer the case, at least not in the case of MV switchgear. There are alternatives which are technically and commercially viable. With EU regulation No 517/2014 due to be reviewed in 2020, policy makers should campaign for further legislation with the final aim of phasing out SF6. This will further invigorate the research and development of SF6 -free technologies, not only for MV switchgear, but also for HV applications. These measures will represent a significant step in the fight against climate change and also help reestablish Europe as a leader in cleantech

https://energypost.eu/why-the-eu-should-ban-sf6/ (https://energypost.eu/why-the-eu-should-ban-sf6/)
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: wdmn on February 17, 2020, 10:35:15 PM
In response to Ken Feldman's post ^^

Impacts of CH4 over 100 years are 24% of warming. This confirms my suspicion that considering a shorter timeframe CH4 could be responsible for most of the warming we see now.

This might sound crazy, but if cooling from anthro aerosols really is closer to -2W/m2 as a recent study suggests (or even if it is closer to -1.45 W/m2), then almost all of the warming from CO2 is being masked. Might this explain the hiatus? Didn't it occur during a time of flat methane emissions?

This is crazy speculation, which is why I've not said it before. But heck, here we go.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: blumenkraft on February 18, 2020, 10:22:19 AM
OMG  :-[
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Ken Feldman on February 18, 2020, 06:18:33 PM
In response to Ken Feldman's post ^^

Impacts of CH4 over 100 years are 24% of warming. This confirms my suspicion that considering a shorter timeframe CH4 could be responsible for most of the warming we see now.

This might sound crazy, but if cooling from anthro aerosols really is closer to -2W/m2 as a recent study suggests (or even if it is closer to -1.45 W/m2), then almost all of the warming from CO2 is being masked. Might this explain the hiatus? Didn't it occur during a time of flat methane emissions?

This is crazy speculation, which is why I've not said it before. But heck, here we go.

There was no hiatus.  While temperatures vary from year to year, almost 93% of the extra heat in the climate winds up in the oceans.  Keep an eye on ocean heat content.

https://www.nodc.noaa.gov/OC5/3M_HEAT_CONTENT/ (https://www.nodc.noaa.gov/OC5/3M_HEAT_CONTENT/)

(https://www.nodc.noaa.gov/OC5/3M_HEAT_CONTENT/heat_content2000m.png)
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: rboyd on February 18, 2020, 07:28:43 PM
One of the reasons considered as causing the observed "hiatus" is that there were more La Nina events (with cold ocean surface), which pulled more heat from the atmosphere into the oceans. Also, atmospheric levels of CH4 flat-lined from 2000 to 2007 and China ramped up their coal production (the aerosol cooling is immediate while the CO2 effects take years to offset the aerosol cooling).

With the drive for clean air in China, now intensified by the actions taken to combat the virus, less aerosols to cool China.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Stephan on March 06, 2020, 09:02:59 PM
With the actual values of CO2, CH4, N2O and SF6 for November 2019 (see the posts in the individual threads) there is an annual increase (Nov 2019 vs. Nov 2018) of 2.81 ppm CO2 eq (20 y) or 2.60 ppm CO2 eq (100 y). Both values are in the lower end of what has been observed in the last year.

I plotted the annual increases of both (20 y / 100 y) CO2 eq. in a graph (see attached). The linear trend lines are increasing (= acceleration).
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: AbruptSLR on March 06, 2020, 09:55:25 PM
With the actual values of CO2, CH4, N2O and SF6 for November 2019 (see the posts in the individual threads) there is an annual increase (Nov 2019 vs. Nov 2018) of 2.81 ppm CO2 eq (20 y) or 2.60 ppm CO2 eq (100 y). Both values are in the lower end of what has been observed in the last year.

I plotted the annual increases of both (20 y / 100 y) CO2 eq. in a graph (see attached). The linear trend lines are increasing (= acceleration).

With a hat tip to rboyd, why is it that the mean global annual rate of growth of atmospheric CO2 in 2019 of 3.08 +/- 0.08 ppm (see attached images from the linked NOAA website) is higher than your calculation for the difference of CO2-e for 2018 and 2019?

https://www.esrl.noaa.gov/gmd/ccgg/trends/gl_gr.html
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Stephan on March 06, 2020, 10:14:31 PM
With the actual values of CO2, CH4, N2O and SF6 for November 2019 (see the posts in the individual threads) there is an annual increase (Nov 2019 vs. Nov 2018) of 2.81 ppm CO2 eq (20 y) or 2.60 ppm CO2 eq (100 y). Both values are in the lower end of what has been observed in the last year.

With a hat tip to rboyd, why is it that the mean global annual rate of growth of atmospheric CO2 in 2019 of 3.08 +/- 0.08 ppm (see attached images from the linked NOAA website) is higher than your calculation for the difference of CO2-e for 2018 and 2019?

Because I used the November 2019-November 2018 difference, which is the lowest individual difference observed in 2019. If I take all 12 values from Dec 2018 up to Nov 2019 I receive an average annual increase in CO2 eq of 3.47 ppm (20 y) or 3.29 ppm (100 y).
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: AbruptSLR on March 06, 2020, 11:01:36 PM
With the actual values of CO2, CH4, N2O and SF6 for November 2019 (see the posts in the individual threads) there is an annual increase (Nov 2019 vs. Nov 2018) of 2.81 ppm CO2 eq (20 y) or 2.60 ppm CO2 eq (100 y). Both values are in the lower end of what has been observed in the last year.

With a hat tip to rboyd, why is it that the mean global annual rate of growth of atmospheric CO2 in 2019 of 3.08 +/- 0.08 ppm (see attached images from the linked NOAA website) is higher than your calculation for the difference of CO2-e for 2018 and 2019?

Because I used the November 2019-November 2018 difference, which is the lowest individual difference observed in 2019. If I take all 12 values from Dec 2018 up to Nov 2019 I receive an average annual increase in CO2 eq of 3.47 ppm (20 y) or 3.29 ppm (100 y).

Thanks
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Stephan on March 06, 2020, 11:08:33 PM
You're welcome.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Stephan on April 06, 2020, 09:07:26 PM
With the actual values of CO2, CH4, N2O and SF6 for December 2019 (see the posts in the individual threads) there is an annual increase (Dec 2019 vs. Dec 2018) of 3.16 ppm CO2 eq (20 y) or 2.99 ppm CO2 eq (100 y).
This increase is mainly driven (2.69 ppm) by CO2 itself.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: kassy on April 21, 2020, 06:52:56 PM
New Study Says The North Pole Will Be Completely Ice-Free In Summer Before 2050, Even If We Curb Carbon Emissions

A new study in the journal Geophysical Research Letters forecasts a massive reduction in Arctic sea ice over the next three decades, predicting that the North Pole will experience its first ice-free summer before 2050. What’s particularly disquieting is that this eventuality appears likely for all climate models, including those that factor in rapid reductions in carbon dioxide emissions.

...

It is estimated that the world has a remaining carbon budget of around 1,000 gigatonnes of carbon dioxide, meaning that this is the absolute limit to our future emissions if we want to prevent a 2°C rise in global temperatures compared to pre-industrial levels. Yet after analyzing more than 40 different climate models, the study authors found that the Arctic will sometimes be ice-free in summer even if we stick to this budget.

https://www.iflscience.com/environment/new-study-says-north-pole-completely-ice-free-summer-before-2050-even-curb-carbon-emissions/

So if you do not reject this study this basically tells you we are on an unsafe trajectory.

It should have been 1C. This also means that not being on rcp 8.5 projections is not going to help and we can´t just let the markets do their thing.

PS: Another hint was permafrost becoming a source instead of a sink:

Arctic Shifts To a Carbon Source Due to Winter Soil Emissions

...

The earlier 2020 date (from some other research see link for details, k) triggered me because one of the goals always was to prevent things like this from happening and now it is already here.

Eyeballing Mauna Loa CO2 anything over 370 is bad. So that is an interesting challenge.


 
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Phoenix on April 21, 2020, 07:47:23 PM
New Study Says The North Pole Will Be Completely Ice-Free In Summer Before 2050, Even If We Curb Carbon Emissions


The title is a tad sensational.

1) The study points to a likelihood, while the title implies certainty.

2) The study indicates the likelihood declines in lower emission scenarios, while the title implies its the outcome is out of human control.

3) The study is indicating the likelihood of BOE level loss (1M km2 at minimum) while the title indicates complete loss.

It would be more responsible for the journalists and the study authors to better highlight the correlation between emission scenarios and likelihood of BOE 2050.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: The Walrus on April 21, 2020, 09:40:05 PM
New Study Says The North Pole Will Be Completely Ice-Free In Summer Before 2050, Even If We Curb Carbon Emissions


The title is a tad sensational.

1) The study points to a likelihood, while the title implies certainty.

2) The study indicates the likelihood declines in lower emission scenarios, while the title implies its the outcome is out of human control.

3) The study is indicating the likelihood of BOE level loss (1M km2 at minimum) while the title indicates complete loss.

It would be more responsible for the journalists and the study authors to better highlight the correlation between emission scenarios and likelihood of BOE 2050.

I guess that is what happens when people read a pseudoscience website that publishes unproven and misleading information. 
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: kassy on April 22, 2020, 12:16:01 AM
The title is a tad sensational.

We agreed to the Paris 2C thing to keep us safe. To prevent real world effects like losing the ice.

To point 1) do you like these odds? Do you have children? Etc.

If we aim for 2C we will overshoot that because that is how we roll. So you can safely assume the worse inputs

2) It is not out of our control we just don´t really do anything. This gap can be closed.

3) Editors always sort of botch headlines which is why you read the article and the science article it is about if it looks interesting.

Why do you focus on article formatting?

I guess that is what happens when people read a pseudoscience website that publishes unproven and misleading information.

Arctic Sea Ice in CMIP6

This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as doi: 10.1029/2019GL086749

The whole point in preventing climate change was stopping the loss of Arctic ice (fail), permafrost feedbacks (fail) and keeping Iceland and Antarctica somewhat intact (guess).

There always was this tension between the carbon budget and the time lines people talked about and the time lines people actually commit too.




Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: The Walrus on April 22, 2020, 01:16:28 AM
I think you misplaced the target of my post.  The article itself is fine.  I was referring to the website, which misrepresented an otherwise valid scientific paper.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Phoenix on April 22, 2020, 01:54:14 AM
I am opposed to inaccurate messaging that induces people to give up hope.

For the benefit of people who might just be grazing in the thread, I thought it would be useful to explain that a superficial glance at the post is not necessarily reflecting the substance of the study.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Juan C. García on April 22, 2020, 02:08:59 AM
New Study Says The North Pole Will Be Completely Ice-Free In Summer Before 2050, Even If We Curb Carbon Emissions


The title is a tad sensational.

1) The study points to a likelihood, while the title implies certainty.

2) The study indicates the likelihood declines in lower emission scenarios, while the title implies its the outcome is out of human control.

3) The study is indicating the likelihood of BOE level loss (1M km2 at minimum) while the title indicates complete loss.

It would be more responsible for the journalists and the study authors to better highlight the correlation between emission scenarios and likelihood of BOE 2050.
I don't have access to the study, but Dr. Dirk Notz is from Universität Hamburg, and they have also an internet page saying that:
Quote
"If we reduce global emissions rapidly and substantially, and thus keep global warming below 2 °C relative to preindustrial levels, Arctic sea ice will nevertheless likely disappear occasionally in summer even before 2050. This really surprised us" said Dirk Notz, who leads the sea-ice research group at University of Hamburg, Germany.
https://www.cen.uni-hamburg.de/en/about-cen/news/11-news-2020/2020-04-20-sea-ice-notz.html (https://www.cen.uni-hamburg.de/en/about-cen/news/11-news-2020/2020-04-20-sea-ice-notz.html)
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Bruce Steele on April 22, 2020, 02:18:38 AM
https://www.eurekalert.org/pub_releases/2020-04/uoh-nps042020.php
Says the low emissions pathways they used were IPCC 1-1.9 and IPCC 1-2.6 scenarios .
I thought we had already missed the bus on those two options.
 Maybe if the current Covid-19 lockdowns extended for decades we could still meet the IPCC 2.6
pathway ?
 Hard to find good news in the options remaining.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Juan C. García on April 22, 2020, 05:29:22 AM
https://www.eurekalert.org/pub_releases/2020-04/uoh-nps042020.php
Says the low emissions pathways they used were IPCC 1-1.9 and IPCC 1-2.6 scenarios .
I thought we had already missed the bus on those two options.
And very important, even in these low emissions pathways:
Quote
"If we reduce global emissions rapidly and substantially, and thus keep global warming below 2 °C relative to preindustrial levels, Arctic sea ice will nevertheless likely disappear occasionally in summer even before 2050. This really surprised us" said Dirk Notz, who leads the sea-ice research group at University of Hamburg, Germany.
https://www.cen.uni-hamburg.de/en/about-cen/news/11-news-2020/2020-04-20-sea-ice-notz.html (https://www.cen.uni-hamburg.de/en/about-cen/news/11-news-2020/2020-04-20-sea-ice-notz.html)
they are finally acknowledging what we knew several years ago.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: S.Pansa on April 22, 2020, 10:05:54 AM
New Study Says The North Pole Will Be Completely Ice-Free In Summer Before 2050, Even If We Curb Carbon Emissions


The title is a tad sensational.

1) The study points to a likelihood, while the title implies certainty.

2) The study indicates the likelihood declines in lower emission scenarios, while the title implies its the outcome is out of human control.

3) The study is indicating the likelihood of BOE level loss (1M km2 at minimum) while the title indicates complete loss.

It would be more responsible for the journalists and the study authors to better highlight the correlation between emission scenarios and likelihood of BOE 2050.
I don't have access to the study, but Dr. Dirk Notz is from Universität Hamburg, and they have also an internet page saying that:
Quote
"If we reduce global emissions rapidly and substantially, and thus keep global warming below 2 °C relative to preindustrial levels, Arctic sea ice will nevertheless likely disappear occasionally in summer even before 2050. This really surprised us" said Dirk Notz, who leads the sea-ice research group at University of Hamburg, Germany.
https://www.cen.uni-hamburg.de/en/about-cen/news/11-news-2020/2020-04-20-sea-ice-notz.html (https://www.cen.uni-hamburg.de/en/about-cen/news/11-news-2020/2020-04-20-sea-ice-notz.html)
Here  (https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2019GL086749)is a link to a freely available draft of the full paper. If anyone has use for it.
And below a pic of Table S4 from the supporting information (https://agupubs.onlinelibrary.wiley.com/action/downloadSupplement?doi=10.1029%2F2019GL086749&file=grl60504-sup-0001-2019GL086749-SI.pdf).
And another one - figure 2 -  from the paper itself.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: kassy on April 22, 2020, 02:30:26 PM
I am opposed to inaccurate messaging that induces people to give up hope.

For the benefit of people who might just be grazing in the thread, I thought it would be useful to explain that a superficial glance at the post is not necessarily reflecting the substance of the study.

In this case false hope is much more dangerous.

And the question is what are we hoping for?

the objective of the IPCC is to provide governments at all levels with scientific information that they can use to develop climate policies. IPCC reports are also a key input into international climate change negotiations.

Very early on in the process the target was shifted from 1 to 1,5C for pure economic reasons. Then we slid to 2C because we did nothing in the meantime.

So you already see that the targets are not underpinned by science but politics.

As were the choices about the type of presentation made. Theoretically it would make sense to have a number of lines we should not cross (kickstarting irreversible melt in Arctic, Waking Antarctica, the permafrost, avoid losing mountain glaciers which quench our thirst etc) and let the best science on those produce constraints on the budget.

But no they cobbled together a bunch of scenarios in which the near term did not really matter. This choice in itself was once again political which you can clearly see if you read up on all the earth responses in the different categories.

And on that note...

For the benefit of people who might just be grazing in the thread

This is a specialist forum which means that if people graze a thread they are probably checking to see if new posts contain an interesting new article or just the running discussion or something like that.

If an article is interesting i will often read the science attached if it´s not paywalled. Then you think about it in relation to all the things you have already read.

When you discover ASIF the first time there is so much to delve into. How much and what people delve into varies.

An on topic response addressing a specific point in the study or something like that would arguably be of more benefit for people grazing the thread.

Hope is fine but we need action too. Whatever our state of despair we have only one (1) planet and nowhere else to go. Any long term problem we do not prevent will be harder and more costly to solve later on. We are acting irresponsibly and we should stop that.

Quote
It might be interesting to include other metrics like the carbon clock.

We only have a tiny real budget. Even if things are looking good for solar that does not mean it will happen fast enough. Plans are announced to be carbon neutral in 2050 (slow clap here) while the budget runs out in 2030. EVs and solar are only part of the carbon mix.

You can hope you brake in time before you go over the cliff or not drive towards that with your foot on the accelerator. We are still doing the latter while it is 2020.

Or a free variation on Curt & Kurt: Who needs action when you´ve got numbers?
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: The Walrus on April 22, 2020, 04:14:00 PM
Thank you kassy for that data and graph.  From their graph, Arctic sea ice area appears to fall below 1 km2 around 2075 under scenario SSP2-4.5.  Using their data, I calculated an average value of 2054 +/- 55 years.  I used average values, when they posted a range, and I suspect they treated those ranges differently.  Interestingly, in scenario SSP1-2.6, the sea ice reaches a minimum, and never falls below 1 km2.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: kassy on April 23, 2020, 06:02:58 PM
Probably not good for that scenario.

Assuming they know more about what they are doing then someone plotting averages i would still go with their numbers.

Basically 2099 would stil be horrific. / -55 would yield 1999. We had other worries then.  ::)

Playing with numbers is nice but it is not going to help the planet. The extremely cynical way to read the research is that you have a decade left to argue data fits and then the 8 legged gompertz is going to win.

As a bonus:

In the linked 2017 RealClimate article Rahmstorf and Levermann make the case the global GHG emissions must peak by 2020.  I guess that we will all find out in a few years whether the global socio-economic system manages to meet/sustain that target/date:

Title: " Why global emissions must peak by 2020" by Stefan Rahmstorf and Anders Levermann

http://www.realclimate.org/index.php/archives/2017/06/why-global-emissions-must-peak-by-2020/comment-page-4/




Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: kassy on April 27, 2020, 09:54:22 PM
The world is on lockdown. So where are all the carbon emissions coming from?

...
global CO2 emissions are on-track to drop by … about 5.5 percent.

...

A 5.5-percent drop in carbon dioxide emissions would still be the largest yearly change on record, beating out the financial crisis of 2008 and World War II. But it’s worth wondering: Where do all of those emissions come from? And if stopping most travel and transport isn’t enough to slow down climate change, what will be?

Transportation makes up a little over 20 percent of global carbon dioxide emissions, according to the International Energy Agency. (In the United States, it makes up around 28 percent.) That’s a significant chunk, but it also means that even if all travel were completely carbon-free (imagine a renewable-powered, electrified train system, combined with personal EVs and battery-powered airplanes), there’d still be another 80 percent of fossil fuel emissions billowing into the skies.

So where are all those emissions coming from? For one thing, utilities are still generating roughly the same amount of electricity — even if more of it’s going to houses instead of workplaces. Electricity and heating combined account for over 40 percent of global emissions. Many people around the world rely on wood, coal, and natural gas to keep their homes warm and cook their food — and in most places, electricity isn’t so green either.

Manufacturing, construction, and other types of industry account for approximately 20 percent of CO2 emissions. Certain industrial processes like steel production and aluminum smelting use huge amounts of fossil fuels — and so far, Schmidt says, that type of production has mostly continued despite the pandemic.

The reality is that emissions need to be cut by 7.6 percent every year to keep global warming from surpassing 1.5 degrees Celsius above pre-industrial levels


https://grist.org/climate/the-world-is-on-lockdown-so-where-are-all-the-carbon-emissions-coming-from/
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: blumenkraft on April 28, 2020, 01:51:08 PM
Beautiful and scary visualisation:

A Brief History of CO2 Emissions

Link >> https://www.reddit.com/r/VisualChemistry/comments/g8v5fs/a_brief_history_of_co2_emissions/
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: kassy on April 28, 2020, 03:00:56 PM
Below some excerpts from Why ‘Carbon-Cycle Feedbacks’ Could Drive Temperatures Even Higher. It is a nice summary so do read it.

https://e360.yale.edu/features/why-carbon-cycle-feedbacks-could-drive-temperatures-even-higher


1

last September at the National Institute for Space Research in the Brazilian research city of Sao Jose dos Campos. Atmospheric chemist Luciana Gatti was rushing to tell her colleagues the result of her latest analysis of carbon dioxide emissions from the Amazon rainforest, which she had completed that morning.

For a decade, her team had been sampling the air from sensors on aircraft flying over the world’s largest rainforest. Their collating of recent results showed that, perhaps for the first time in thousands of years, a large part of the Amazon had switched from absorbing CO2 from the air, damping down global warming, to being a “source” of the greenhouse gas and thus speeding up warming.

“We have hit a tipping point,” Gatti almost shouted, caught between elation at her discovery and anguish at the consequences. ... But now it no longer mattered if it was a wet or a dry year, or how many fires there were, the sink had become a source.

...

The scientists are warning that past climate models used by the UN’s Intergovernmental Panel on Climate Change (IPCC) have not fully reflected the scale of the warming that lies ahead as carbon sinks die. These revelations are coming from three areas of research:

1 Studies such as Gatti’s in the Amazon, showing forests turning from sinks to sources of CO2;

2 A new generation of climate models that incorporate these findings into future projections of climate change, and whose early outputs are just emerging;

3 Recent revelations that ecosystems are releasing rising volumes of methane, the second most important greenhouse gas and of vital importance for temperatures in the next couple of decades.

The extra emissions, known as carbon-cycle feedbacks, could already be making the prospect of keeping warming below 2 degrees Celsius — the target agreed to in the Paris climate accord in 2015 — all but impossible.

...

Non-tropical forests remain largely in carbon “sink” mode. But other tropical rainforests appear to be following the Amazon in moving toward becoming carbon sources. Wannes Hubau, now at the Royal Museum of Central Africa in Belgium, reported recently that “overall, the uptake of carbon into Earth’s intact tropical forests peaked in the 1990s” and has been declining since. The jungles of tropical Africa began showing increased carbon losses around 2010, he found.

Another big concern is the impact of thawing permafrost. ... One recent study in northern Canada found thawing had reached depths “already exceeding those projected to occur by 2090.”


2

The risks of such rapid runaway carbon releases to the atmosphere have been worrying ecologists for a while. That worry is now being reinforced by the projections of a new generation of climate models designed to factor in how ecosystems respond to climate change.

Until now, most climate models have largely confined themselves to assessing how our CO2 emissions warm the air, and how that warming interacts with physical feedbacks such as reduced ice cover, elevated atmospheric water vapor, and changes to clouds. This remains a work in progress. I wrote here on Yale Environment 360 in February how new field research suggests that the ability of clouds to keep us cool could be drastically reduced as the world warms, pushing global heating into overdrive.

When ecological feedbacks have been included in the models, it has mostly been in a very simplistic way. But new models being developed for the next IPCC assessment of climate science are changing that.

...

Even a scenario that is “reasonably consistent with currently enacted climate policies” could deliver up to 5 degrees C of warming rather than the current estimate of 3 degrees. This, Betts says, is “because the upper end of possible feedbacks results in 40 percent more CO2 in the air than previously supposed: 936 parts per million [ppm] by 2100, compared to a prediction without the carbon-cycle feedbacks of 670 ppm.” (Current levels are 415 ppm, and pre-industrial levels were around 280 ppm.)

3

The growing concern about CO2 feedbacks comes on top of alarm about trends in atmospheric levels of the second most important greenhouse gas, methane. These are more than twice pre-industrial levels, and after a decade of stability until 2007 they have been rising again sharply. The National Oceanic and Space Administration (NOAA) estimated this month that methane levels in the atmosphere reached a record 1,875 parts per billion in 2019, after the second largest year-on-year leap ever recorded.

How come? Euan Nisbet of Royal Holloway, University of London, says isotopic analysis shows industrial emissions such as those from fracking remain important sources of methane. But the major reason for the recent upsurge is microbial emissions, mostly from the tropics.

...

None of this methane increase is built into even the new climate models with carbon-cycle feedbacks. These models mostly assume that methane levels in the air will remain stable. But the concern is growing that, even if technology can reduce industrial emissions, a warmer world will drive a continuing surge in methane levels — and more warming as a consequence.

Methane typically lasts in the atmosphere for only a decade – much less than CO2. But while it is there, it packs a big warming punch. Measured over 20 years, each molecule of methane emitted has 84 times more warming effect than each molecule of CO2.

Climate models conventionally assess the warming impacts of greenhouse gases over a century. This effectively tunes them to emphasize the importance of C02, and relegates methane to an also-ran. But if they were tuned to the shorter timeframe, methane would appear almost three times more important.

It seems odd that this shorter timeframe is rarely adopted, given that the world risks exceeding its two-degree warming limit by 2050.
As Nisbet puts it, if natural ecosystems keep pumping out more methane as the world warms, “it may become very difficult to meet the Paris goals.”

*

Bottom line: we need lots of real carbon and methane reductions this decade.

In fact you can already argue that we have passed the tipping points. If we stopped emitting today we would still be in a world that keeps warming thus pushing up the methane emissions from the tropics and northern sources.

We would still have the amazon and northern permafrost as carbon sources.

We would still have ocean acidification get worse for decades etc.

So we cannot rely on markets to fix it, or technology to fix it.
We need real action which also includes sacrifices. Especially the historical big emitters (see vid above) should invest in going zero first and export those technologies but most won´t because they are captured by the carbon economy.

Hope is important but we have only 1 planet so we are going to have to live here anyway.

So we can´t give up hope anyway...but we need real action and then we have to hope for the best effects from that. 

We already gave the younger generation a huge set of problems to solve and i hope we make the AGW problem as small as we can this decade.

(Just imagine being born now or say 2010 and at age 20 figuring out how we got in this mess. It would piss me off.)
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Stephan on May 05, 2020, 10:34:27 PM
With the actual values of CO2, CH4, N2O and SF6 for January 2020 (see the posts in the individual threads) there is an annual increase (Jan 2020 vs. Jan 2019) of 2.83 ppm CO2 eq (20 y) or 2.67 ppm CO2 eq (100 y).
This increase is mainly driven (2.37 ppm) by CO2 itself.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Stephan on May 05, 2020, 10:57:04 PM
I add the graph for the NOAA gases (20y and 100y CO2 equivalents) from 2000 to 2020.
Please note that the linear fit does not perfectly match the data. The increase is of exponential nature (see my post in the CO2 thread from today).
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: nanning on May 06, 2020, 04:57:13 AM
Thank you for that Stephan. Would it be possible to extend your graph to pre-industrial years, when CO2 ppm was 280?
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Stephan on May 06, 2020, 07:21:35 AM
I do not have the resources for that at the moment. My spreadsheet starts (apart from CO2) around 2000, using the NOAA data. I am not sure whether I would be able (as a layman) to find reliable and comparable data for earlier years, especially before Keeling started his experiments in 1958...
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Steven on May 09, 2020, 11:23:10 AM
I add the graph for the NOAA gases (20y and 100y CO2 equivalents) from 2000 to 2020.
(https://i.imgur.com/aj5gTYD.jpg)

That graph doesn't make sense.

I suspect you've been using GWP multipliers in your calculations.  But those can only be used in the context of emissions, not in the context of concentrations.  The GWP approach can not be used to calculate the CO2 equivalent for the entire atmospheric amount of CO2/methane/N2O etc.  The only meaningful way to do that is to calculate radiative forcing and use a logarithmic transform, e.g. see here (https://www.esrl.noaa.gov/gmd/aggi/aggi.html).

There seems to be a lot of confusion about this topic on this forum.  I think the source of confusion is a poorly written wikipedia page (https://en.wikipedia.org/wiki/Carbon_dioxide_equivalent) that discusses two very different definitions of "CO2 equivalent": one definition for emissions and another one for concentrations.  Discussions on GWP and 20-year timescales etc are only relevant to the former definition but are not related to the latter definition.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Stephan on May 09, 2020, 08:28:41 PM
Steven,
I know that and I am aware of that. There has been already a lengthy discussion about this topic maybe two pages above in this thread.
Anyway, if there would be a formula (but as far as I can remember there is none) to add concentrations of greenhouse gases into a "global GHG CO2 equivalent" I would recalculate my spreadsheet and present it again. If not, I will keep it for myself from now on. The smart thing about this formula would be that the easily available concentrations of the different gases could be directly converted into one CO2 equivalent.
If there is anybody to help me out - you're welcome.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Steven on May 10, 2020, 12:33:20 PM
Anyway, if there would be a formula (but as far as I can remember there is none) to add concentrations of greenhouse gases into a "global GHG CO2 equivalent" I would recalculate my spreadsheet and present it again. If not, I will keep it for myself from now on. The smart thing about this formula would be that the easily available concentrations of the different gases could be directly converted into one CO2 equivalent.
If there is anybody to help me out - you're welcome.

There are formulas in the NOAA link I posted:

https://www.esrl.noaa.gov/gmd/aggi/aggi.html

see especially Table 1.  The CO2 equivalent concentration (in parts per million) can be calculated by using this formula:

CO2equivalent = 278 exp( RF / 5.35)   

where RF = radiative forcing.  For example, for the year 2018 that gives the following values for CO2 equivalent concentration:

• CO2 only:  407 ppm  (RF = 2.044)
• CO2 + CH4 + N2O:  465 ppm (RF = 2.755)
• CO2 + CH4 + N2O + halogenated gases:  496 ppm (RF = 3.101)
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Stephan on May 10, 2020, 01:15:52 PM
Thank you Steven. I saw that calculation and the formula (thank you for that link), but I thought it could be simpler than that.
Anyway, I will introduce these formulae into my spreadsheet and I hopefully will end up with the same results (excluding CFC etc.) as presented in Table 2 of that link.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Stephan on May 10, 2020, 09:36:57 PM
Said and done.
I recalculated the data, now turning from CO2 equivalents into Delta radiative forcing. I checked my calculations with the NOAA table. It worked well for CO2, CH4 and N2O. I didn't find any conversion formula for SF6, therefore I used a factor from the fourth IPCC assessment report https://archive.ipcc.ch/publications_and_data/ar4/wg1/en/ch2s2-10-2.html where I found the factor 0.52 (*10-3) with which the SF6 concentration shall be multiplied to give its additional warming potential. As SF6 has a very low in concentration it does not really matter. The distribution among the gases are:
CO2 74 %
CH4 18 %
N2O  7 %
SF6   0.2 %
In addition I could add the years 1979-2001 for all four "NOAA gases" to my spread sheet. :)

I hope you are satisfied with the attached graph:
(linear fit again doesn't work perfectly due to the acceleration of the concentration)
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Ken Feldman on May 15, 2020, 10:27:09 PM
NOAA has updated the Annual Greenhouse Gas Index through the end of 2019.

https://www.esrl.noaa.gov/gmd/aggi/ (https://www.esrl.noaa.gov/gmd/aggi/)

(https://www.esrl.noaa.gov/gmd/aggi/aggi.fig4.png)

Quote
AGGI2019 = 1.45
CO2 equivalent = 500 ppm

Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Stephan on June 05, 2020, 09:47:27 PM
More radiative forcing of the "NOAA gases" (CO2, CH4, N2O, SF6) in Feb 2020 than in Jan 2020 or in Feb 2019.
The values [W/m²], change to Jan 2020 and change to Feb 2019:
CO2 2.132   (+ 0.012)    (+ 0.031)   
CH4 0.519   (± 0.000)    (+ 0.003)
N2O 0.204   (± 0.000)    (+ 0.002)
SF6  0.0053 (± 0.0000)  (+ 0.0002)
sum 2.861   (+ 0.012)    (+ 0.036)
The relative annual increase is 1.27 %
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: nanning on June 06, 2020, 03:58:47 AM
Thanks for the updates Stephan.

Please note: ±0.000 = 0  ,  so your e.g. N₂O 0.204 is stated as an absolute analytical value with no error margin. That is incorrect.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Stephan on June 06, 2020, 08:16:59 AM
nanning,
I do not want to put too many digits to that value, therefore the "interpretation" shall read as follows: The increase is (much) smaller than 0.0005 W/m², which means that this small change is irrelevant to the total of 2.861 W/m². The same "interpretation" applies to CH4.
In addition, my spread sheet calculates the sum including all (hidden) digits. Therefore the total sum contains all these little changes of the individual values.
Title: Re: 2020 Mauna Loa CO2 levels
Post by: Ken Feldman on June 22, 2020, 08:15:59 PM
But at first it dropped. Why is that?

Collapse of the Soviet Union and their allies.
Future looked so bright when the wall fell (no more cold war!) and this was a bonus. And then we went BAU for dollars or something.

Also there was a leveling off of methane concentrations from around 1997 to 2007.  Methane concentrations have increased again since 2007, when fracking tight shale for oil and natural gas really took off.

It will be interesting to see if methane concentrations decrease later this year since much of the US and Canadian fracking decreased in May and looks to be reduced through 2021 with the oil oversupply and Covid recession demand destruction.
Title: Re: Re: 2020 Mauna Loa CO2 levels
Post by: Sebastian Jones on June 23, 2020, 09:12:30 PM
It will be interesting to see if methane concentrations decrease later this year since much of the US and Canadian fracking decreased in May and looks to be reduced through 2021 with the oil oversupply and Covid recession demand destruction.

Considering methane leaks are a feature of fracked wells, and considering that the frackers have even less free cash than usual for properly abandoning their wells, I  do not expect methane pollution to drop appreciably.
Title: Re: Re: 2020 Mauna Loa CO2 levels
Post by: Ken Feldman on June 24, 2020, 12:45:27 AM
It will be interesting to see if methane concentrations decrease later this year since much of the US and Canadian fracking decreased in May and looks to be reduced through 2021 with the oil oversupply and Covid recession demand destruction.

Considering methane leaks are a feature of fracked wells, and considering that the frackers have even less free cash than usual for properly abandoning their wells, I  do not expect methane pollution to drop appreciably.

Abandoned wells leak less methane then wells that are actively venting and flaring the cheap gas because it's in the way of the oil that the producers can sell.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Stephan on July 06, 2020, 09:47:28 PM
More radiative forcing of the "NOAA gases" (CO2, CH4, N2O, SF6) in Mar 2020 than in Feb 2020 or in Mar 2019.
The values [W/m²], change to Feb 2020 and change to Mar 2019:
CO2 2.137   (+ 0.005)    (+ 0.033)   
CH4 0.520   (+ 0.001)    (+ 0.003)
N2O 0.204   (+ 0.001)    (+ 0.003)
SF6  0.0053 (+ 0.0000)  (+ 0.0002)
sum 2.868  (+ 0.007)   (+ 0.040)
The relative annual increase is 1.41 %
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: kassy on July 08, 2020, 11:02:56 AM
Delayed emergence of a global temperature response after emission mitigation

A major step towards achieving the goals of the Paris agreement would be a measurable change in the evolution of global warming in response to mitigation of anthropogenic emissions. The inertia and internal variability of the climate system, however, will delay the emergence of a discernible response even to strong, sustained mitigation. Here, we investigate when we could expect a significant change in the evolution of global mean surface temperature after strong mitigation of individual climate forcers. Anthropogenic CO2 has the highest potential for a rapidly measurable influence, combined with long term benefits, but the required mitigation is very strong. Black Carbon (BC) mitigation could be rapidly discernible, but has a low net gain in the longer term. Methane mitigation combines rapid effects on surface temperature with long term effects. For other gases or aerosols, even fully removing anthropogenic emissions is unlikely to have a discernible impact before mid-century.

https://www.nature.com/articles/s41467-020-17001-1

Interesting paper. Open access.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: kassy on July 08, 2020, 08:09:18 PM
Quote
Previously, Tebaldi and Friedlingstein7 (hereafter TF13) have quantified the expected delayed detection of climate mitigation benefits due to climate inertia and variability. They found that for global mean surface temperature, emergence would occur ~25–30 years after a heavily mitigated emission pathway (RCP2.6) departs from the higher ones (RCP8.5 or RCP4.5). At the time of writing, that translated into 2035–2045, where the delay was mostly due to the impacts of the around 0.2 °C of natural, interannual variability of global mean surface air temperature (GSAT, see “Methods”), and the general inertia of a climate system out of equilibrium. They also showed that for smaller (but more policy and societally relevant) regions, where natural variability is intrinsically higher, the detection time occurs a decade or more later.

More recently, Marotzke8 (hereafter M18) investigated the range of near-term warming rates under very strong climate mitigation (RCP2.6), and found that in over a third of 100 realizations (members of an initial condition ensemble, i.e. identically forced simulations differing only by internal variability), the world would still warm faster until 2035 than it has done for the past two decades (i.e. a higher 15-year trend for 2021–2035 than for 2006–2020). He warns that we might face what they term a hiatus debate in reverse, where the most well-known indicator of climate change (global mean surface temperature, or GMST; see methods for the distinction between GSAT and GMST) continues to rise even after massive, international efforts to mitigate emissions. This might, in turn, present a substantial challenge for communication and science-policy interactions.

Lots of articles use RCP 8.5 and there is the claim that we are not on that pathway. I wonder about 2.6. That does not look to feasible either.

But even if we would do the max we would still have a 15 year lag of effects in which the damage to the arctic north and glaciers worldwide compound.

And many goals aim for 2050 or so which is way beyond that date.

So maybe we are stuck with 4.5ish territory.

I am interested in both the claim that 8.5 is of the table (might be just emission projection?) and whatever exists on 2.6 vs 4.5.

RCPs:
https://link.springer.com/article/10.1007/s10584-011-0148-z


 

Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: nanning on July 09, 2020, 05:37:52 AM
kassy, are the rising permafrost emissions, possible subsea methane bursts, rising lake emissions and lost forest-sinks etc. included in our radiative forcing path?
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: kassy on July 09, 2020, 03:45:16 PM
They are about our human emissions so basically those are not in there (there is something for land cover change but have not looked into that , they probably don´t have much simulation runs with a dead Amazon and knock on effects).

It is one reason not to dismiss any RCP8.5 based papers out of hand. Our contribution + feedbacks might mean they are closer to the true situation anyway.

The one thing that is problematic is that they never defined dangerous criteria or points we should not cross.

Last century i always thought of it as simply maintaining a climate which saved the Arctic Ice and Greenland and prevented the permafrost from flipping because those were the big concerns.

I think a 1C target would have worked (and it is such a simple number) but that would cost too much or so they thought.



 

Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Ken Feldman on July 09, 2020, 08:45:23 PM
The energy mixes assumed in the RCPs were extremely pessimistic on renewables.  The RCPs were drafted in the early 2000s when renewables were much more expensive than fossil fuels.  Now renewables are cheaper than both new build and operating coal, and new natural gas.  As a result, more money is being invested in renewables then in fossil fuel plants.  Some fossil fuel plants are being shut down and being replaced with renewables at a savings to the rate payers.

Skepticalscience has a great article on the RCPs:

https://skepticalscience.com/rcp.php?t=3 (https://skepticalscience.com/rcp.php?t=3)

Quote
The Beginner's Guide to Representative Concentration Pathways

By G. P. Wayne

Welcome to the Beginner's Guide to Representative Concentration Pathways. Arranged in three parts, you can access each part by clicking on the tabs below. Part 1 provides background to the scenarios used by climate scientists. Part 2 describes the development of RCPs, and Part 3 provides a quick reference to many of the key parameters and data (there’s also a further reading list at the end). The guide is also available as a PDF.

Here are some images from that article related to energy trends:

(https://static.skepticalscience.com/pics/energy-oil.PNG)

Quote
Figure 13: Development of primary energy consumption (direct equivalent) and oil consumption for the different RCPs (van Vuuren et.al. 2011). The grey area indicates the 98th and 90th percentiles (light/dark grey) (AR4 database (Hanaoka et al. 2006) and more recent literature (Clarke et al. 2010; Edenhofer et al. 2010). The dotted lines indicate four of the SRES marker scenarios

    “For energy use, the scenarios underlying the RCPs are consistent with the literature— with the RCP2.6, RCP4.5 and RCP6 again being representative of intermediate scenarios in the literature (resulting in a primary energy use of 750 to 900 EJ in 2100, or about double the level of today).

    “The RCP8.5, in contrast, is a highly energy-intensive scenario as a result of high  population growth and a lower rate of technology development”. (van Vuuren et.al. 2011).

(https://static.skepticalscience.com/pics/energy-sources-2100.PNG)

Quote
Figure 14: Energy sources by sector (van Vuuren et.al. 2011)

    “In terms of the mix of energy carriers, there is a clear distinction across the RCPs given the influence of the climate target. Total fossil- fuel use basically follows the radiative forcing level of the scenarios; however, due to the use of carbon capture and storage (CCS) technologies (in particular in the power sector), all scenarios, by 2100, still use a greater amount of coal and/or natural gas than in the year 2000. The use of oil stays fairly constant in most scenarios, but declines in the RCP2.6 (as a result of depletion and climate policy).

    The use of non-fossil fuels increases in all scenarios, especially renewable resources (e.g. wind, solar), bio-energy and nuclear power. The main driving forces are increasing energy demand, rising fossil-fuel prices and climate policy. An important element of the RCP2.6 is the use of bio-energy and CCS, resulting in negative emissions (and allowing some fossil fuel without CCS by the end of the century)”. (van Vuuren et.al. 2011).

While we are currently somewhere between 2.6 and 8.5, current investments in energy infrastructure that will dictate future energy trends are much closer to the RCP2.6 scenario, even though the mix is much more weighted to renewables than bioenergy with CCS.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Ken Feldman on July 09, 2020, 08:58:42 PM
kassy, are the rising permafrost emissions, possible subsea methane bursts, rising lake emissions and lost forest-sinks etc. included in our radiative forcing path?

Many of the projects about emissions from permafrost, methane bursts, etc... are based on RCP8.5 model runs.  Reading the papers, you see that the projections of increased emissions are much lower for RCP 4.5 or RCP 2.6.  And the amount of methane from the Arctic is much less than what's emitted in the tropics, much of it coming from fossil fuel extraction and agriculture.

Here's today's view of methane emissions from Copernicus, the North Pole view.  Note that many parts of the Arctic Ocean over the ESAS are free of sea ice now, Siberia is burning up, etc...  Yet those areas are below the global average methane concentration.

https://atmosphere.copernicus.eu/charts/cams/methane-forecasts?facets=undefined&time=2020070800,3,2020070803&projection=classical_north_pole&layer_name=composition_ch4_totalcolumn (https://atmosphere.copernicus.eu/charts/cams/methane-forecasts?facets=undefined&time=2020070800,3,2020070803&projection=classical_north_pole&layer_name=composition_ch4_totalcolumn)

(https://stream.ecmwf.int/data/gorax-blue-007/data/scratch/20200708-2110/43/render-gorax-blue-007-6fe5cac1a363ec1525f54343b6cc9fd8-NV5LTV.png)
(https://stream.ecmwf.int/data/gorax-blue-003/data/scratch/20200708-1850/d6/legend-gorax-blue-003-6fe5cac1a363ec1525f54343b6cc9fd8-Wt1kpP.png)

(https://www.esrl.noaa.gov/gmd/webdata/ccgg/trends/ch4_trend_gl.png)
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: kassy on July 10, 2020, 02:56:08 PM
Thanks Ken! Table 4 from the Skeptical science link seems like a good starting point.
Will get back to this later.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: kassy on July 15, 2020, 03:27:48 PM
Well that was an interesting read and it also gave me a slight headache.

First i went to look around RCP2.6.

https://link.springer.com/content/pdf/10.1007/s10584-006-9172-9.pdf

Quote
Abstract

On the basis of the IPCC B2, A1b and B1 baseline scenarios, mitigation scenarios
were developed that stabilize greenhouse gas concentrations at 650, 550 and 450 and –
subject to specific assumptions – 400 ppm CO2-eq. The analysis takes into account a large
number of reduction options, such as reductions of non-CO2 gases, carbon plantations and
measures in the energy system. The study shows stabilization as low as 450 ppm CO2-eq. to
be technically feasible, even given relatively high baseline scenarios. To achieve these lower
concentration levels, global emissions need to peak within the first two decades. The net
present value of abatement costs for the B2 baseline scenario (a medium scenario) increases
from 0.2% of cumulative GDP to 1.1% as the shift is made from 650 to 450 ppm. On the other
hand, the probability of meeting a two-degree target increases from 0% –10% to 20% –70%.

And chopped the rest.

Bolded.

1) We need to do it this decade. If all the countries in the world had united for a real concerted push that would help. Real reductions not pledges. But we do not really see that and many are not on board.

2) The GPD vs the target shift. And general discussions of GPD % costs. This would be so much more honest if somewhere in the process they actually calculated the costs of the knock on damage. So going for 450 costs more on the short term but we would gain so much by actually hitting the 2C target instead of way overshooting it.

Economics has been used to kick the can down the road. Yeas in some scenarios a little later mitigation is cheaper. But then we are not sure if it works or how well it works or if we cross some important treshhold in between that is not something to bank on.

Of the 4 scenarios this is the one we should aim for and next decade will tell if we do.

Next up 8.6 but i will put that in a different post.

Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: kassy on July 15, 2020, 03:59:25 PM
RCP 8.6

Mostly using quotes from. Probably better to read the whole thing on the link.
https://www.carbonbrief.org/explainer-the-high-emissions-rcp8-5-global-warming-scenario

Explainer: The high-emissions ‘RCP8.5’ global warming scenario

In this article, Carbon Brief examines how the emissions scenario underlying RCP8.5 was developed and how it has subsequently been used in the academic literature and media. According to the researchers who developed it, RCP8.5 was intended to be a “very high baseline emission scenario” representing the 90th percentile of no-policy baseline scenarios available at the time.

The creators of RCP8.5 had not intended it to represent the most likely “business as usual” outcome, emphasising that “no likelihood or preference is attached” to any of the specific scenarios. Its subsequent use as such represents something of a breakdown in communication between energy systems modellers and the climate modelling community.

...

Rather than starting with detailed socioeconomic storylines to generate emissions and climate scenarios, as had been the case with the SRES scenarios, the energy systems modeling community decided to start by creating scenarios of future “radiative forcing” for climate modelling not associated with any particular unique socioeconomic or emissions scenario. Radiative forcing is a measure of the combined effect of greenhouse gases, aerosols, and other factors that can influence climate to trap additional heat.

Each RCP provides only one of many possible pathways to that level of radiative forcing. The researchers developing the RCPs also stressed that they were not intended to be “the final new, fully integrated scenarios” but rather would simply focus on future concentrations of greenhouse gases and other radiative forcings used as inputs into climate models.

Four pathways were developed based on their end-of-century radiative forcing: RCP2.6 (indicating a 2.6 watts per metre squared – W/m2 – forcing increase relative to pre-industrial conditions), RCP4.5, RCP6.0, and RCP8.5.

The selection of these four pathways was a result of a number of different priorities. These included having scenarios that spanned the range of future emissions and concentrations projected in scientific literature, but also being sufficiently distinct from one another.

Unfortunately, the development of the socioeconomic pathways took much longer than originally foreseen, and the RCPs were never turned into fully integrated scenarios in time for the publication of the AR5.

This left them as useful tools for modelling different potential climate outcomes, but lacking any consistent socioeconomic assumptions that would allow researchers to examine the likelihood of different no-policy baseline and mitigation scenarios. For example, Moss and colleagues specifically state that “RCP8.5 cannot be used as a no-climate-policy reference scenario for the other RCPs because RCP8.5’s socioeconomic, technology and biophysical assumptions differ from those of the other RCPs.”

...

In their paper outlining the development of the RCP scenarios, Prof Detlef van Vuuren and colleagues explained that they include “one mitigation scenario leading to a very low forcing level (RCP2.6), two medium stabilisation scenarios (RCP4.5/RCP6.0) and one very high baseline emission scenarios (RCP8.5).”

They suggest that “RCP8.5 should be seen as a high emission scenario” while “RCP6.0 can be interpreted as either a medium baseline or a high mitigation case”. This suggests that the authors say no reason to consider RCP8.5 a more likely “business as usual” outcome than, say, RCP6.0.

RCP8.5 was specifically selected as a high-end baseline scenario, and was not intended to be portrayed as the most likely “business as usual” no-policy outcome. The researchers emphasise this point in their paper, showing how the emissions in each scenario compared to the range found in the energy modelling literature at the time.

...

As van Vuuren tells Carbon Brief:

“RCP8.5 was never meant to be a business-as-usual scenario, but as a high-end scenario, consistent with the highest emissions scenarios in the literature.

“Clearly, RCP8.5 is a possible no-climate policy world. But it is surely not the only one, and in terms of the level of GHG emissions, it is not the most likely. One can only get that high by a combination of factors, e.g. high population growth and a lot of coal use (as in the original RCP8.5 scenario) or high economic growth and strong reliance on fossil fuels (in the current SSP5 version). But an emission level leading to a forcing level of around 6-7 W/m2 can be achieved by many more scenarios, not only by medium assumptions for many factors (RCP6.0) but also by high population growth and low economic growth or the exact opposite.

“In other words, even if the specific RCP6.0 scenario is not necessarily more likely than any other scenario, a forcing level in that order-of-magnitude might be more likely based on the central limit theorem.”

...

Kassy: Then this is cute:

As Peters tells Carbon Brief:

“All scenarios will look like they are on track in the early years, as they are always set to the same base year. I don’t think it is possible to say, with aggregated CO2, if we are on track with any scenario in particular.”

https://www.carbonbrief.org/explainer-the-high-emissions-rcp8-5-global-warming-scenario

One more post coming.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: kassy on July 15, 2020, 04:46:06 PM
From the 2.6 link 2 posts above:

Quote
4 Stabilizing GHG concentration at 650, 550, 450 ppm: central scenarios
4.1 Emission pathways and reductions
Under the central baseline, B2, worldwide primary energy use nearly doubles between
2000 and 2050 and increases by another 35% between 2050 and 2100. Most of this growth
occurs in non-annex I regions (about 80%). Oil continues to be the most important energy
carrier in the first half of the century, with demand being mainly driven by the transport sector.
Natural gas dominates new capacity in electric power in the first decades, but starts to be
replaced by coal from 2030 onwards due to increasing gas prices. As a result, coal becomes
the dominant energy carrier in the second half of the twenty-first century.
Energy-sector CO2
emissions continue to rise for most of the century, peaking at 18 GtC in 2080. Total GHG
emissions12 also increase, i.e., from about 10 GtC-eq. today to 23 GtC-eq. in 2100 (Fig. 3).
Figure 3 also shows that compared to existing scenario literature; this baseline is a medium-high emission baseline. As a result of decreasing deforestation rates, CO2 emissions
from land use decrease. At the same time, CH4 emissions, mostly from agriculture, increase. The GHG concentration reaches a level of 925 ppm CO2-eq., leading to an increase
in the global mean temperature of 3 °C in 2100 (for a climate sensitivity of 2.5 °C).

That bolded part of the scenario looks very unlikely with current developments. And this
is only the 2.6 scenario.

So that leaves us with the 2 others.

One question is how to rate the 8.6 research. Ideally if you had enough computing power you could calculate anything for all four and see where the thing you were researching was not an issue or emerging as a problem.

I think i will just go back to my simple version.

1 Given the fact the IPCC experts forgot to actually define dangerous the public aka me is going to do that.

2 Back in the last century we figured we should prevent the Arctic ice from collapsing so we would not get into trouble with Greenland or feedbacks from the permafrost. Antarctica would not come into play ever.

But we have Arctic ice which will have a hard time surviving the next decade. Lets ignore Greenland. Permafrost is a source not a sink and Antarctica is looking iffy.

This all in the time frame where our RCPs can´t distinguish themselves from their brethren.





Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Simon on July 15, 2020, 09:12:58 PM
Given that the RCP values refer to radiative forcing of all greenhouse gases in 2100, and given that the rf value now is 3.2 And assuming a steady increase as seen in recent years, the nearest pathway is RCP6.0.

RCP8.5 was imagined as a very high end scenario but one which is not actually impossible but one that would depend upon increasing greenhouse gas emissions and a huge failure of our main CO2 sinks, namely biomass and oceans.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Ken Feldman on July 16, 2020, 06:57:37 PM
Keep in mind that RCP 2.6 is a scenario with a peak above 3.0 w/m2 and then a decrease in the later half of the century back down to 2.6 w/m2.  Given the rate at which renewables are replacing coal and natural gas plants and the coming transition from gas to electric vehicles, RCP 2.6 is still very possible.

Also, RCP 4.5 is currently possible too.  This article was written before the Covid recession and the oil and natural gas gluts that are currently stifling further investment in fossil fuel infrastructure.  (It also uses the new SSP scenarios, which are an update over the RCPs).

https://thebreakthrough.org/issues/energy/3c-world (https://thebreakthrough.org/issues/energy/3c-world)

Quote
Our business-as-usual projection of 3C of warming — rather than 4 or 5C — is a testament to the progress in global decarbonization over the last few decades. It also reflects the fact that rapid growth in coal use during the 2000s was not necessarily characteristic of longer-term energy use trends. The world has taken concrete steps to move away from coal in the past decade, and this progress should be reflected in our assessment of likely emissions pathways — and their resulting climate impacts — going forward.

The worst case outcomes of ten years ago appear far less likely today. But there is also a risk of overenthusiasm about progress; there is still an ever-growing gap between current emissions and what would be needed to limit warming below 2C. With every year of continued emissions growth and increased deployment of clean energy, we make both low warming (<2C) and high warming (>4C) increasingly unlikely.

Quote
IEA CPS emissions in 2040 are in-between the SSP4-6.0 and SSP2-4.5 scenarios, and are in the bottom 15% of all the baseline scenarios in the SSP database. The SPS scenario is a bit below SSP2-4.5, and lower than any baseline scenarios — though this is not necessarily unexpected, as baseline scenarios exclude current commitments that have not yet been translated into policy.

Quote
The recent UNEP Emissions Gap report provided an estimate of combined emissions from all greenhouse gases — including land use change — in the year 2030 under both current policy and under a scenario where countries meet their Paris Agreement nationally determined contributions (NDCs). UNEP’s current policies scenario has 2030 GHG emissions of 60 GtCO2e. This falls between SSP2-4.5 (57 GtCO2e) and SSP3-6.0 (62 GtCO2e), and is well below SSP3-7.0 (69 GtCO2e) and the worst-case SSP5-8.5 (71GtCO2e). UNEP projects 2030 emissions of 54 GtCO2e if all Paris Agreement NDCs are met.

(https://thebreakthrough.imgix.net/Figure-2.png)

Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Simon on July 16, 2020, 08:17:17 PM
Thanks for that. I am pessimistic however that governments will institute the policies necessary even for a RCP4.5 scenario.

We have to close down all use of gas, oil and coal in a very short timeframe, twenty years or so. The zero carbon emitting alternatives exist and are plentiful. No problem now with the technology. It’s just government who stand in our way.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Tom_Mazanec on July 17, 2020, 12:17:42 AM
Ken:
Do those studies saying >4C is very unlikely take into account the feedbacks and tipping points 3° warming is likely to kick in?
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: bluice on July 17, 2020, 01:02:26 PM
Keep in mind that RCP 2.6 is a scenario with a peak above 3.0 w/m2 and then a decrease in the later half of the century back down to 2.6 w/m2.  Given the rate at which renewables are replacing coal and natural gas plants and the coming transition from gas to electric vehicles, RCP 2.6 is still very possible.
The first step to recovery is to acknowledge there is a problem. Renewables are not replacing fossil fuels. They haven't even stabilized global CO2 emissions.

Only the economic crash after Covid-19 pandemic has stopped emission growth. Unless structural changes are made globally, emissions will continue to grow once economy recovers.

Then there are emissions from land use, agriculture, collapsing carbon sinks...

--
GLOBAL ENERGY GROWTH IS OUTPACING DECARBONIZATION

After a three-year hiatus with stable global emissions
from 2014 to 2016 (Jackson et al. 2016, Le Quéré
et al. 2018, IEA 2018), CO2 emissions grew by
1.4% in 2017 and 2.1% in 2018 to 37 Gt (billion
tonnes), and are expected to continue to grow in 2019


...growth in energy use
from fossil fuel sources is still outpacing the rise of
low-carbon sources and activities

--

https://www.globalcarbonproject.org/global/pdf/GCP_2019_Global%20energy%20growth%20outpace%20decarbonization_UN%20Climate%20Summit_HR.pdf
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: oren on July 17, 2020, 01:13:18 PM
Indeed. Renewables are partially replacing fossil fuel additions, and just in the electricity sector. It's a good thing, but so very far from decarbonization. A long way ahead.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: bluice on July 17, 2020, 01:38:28 PM
Exactly, while we need a steady drop in global emissions year after year to avoid the worst outcomes.

It's easy for us to get distracted from the big picture because in the US and EU emissions have been falling.

Globally, emissionwise, developed countries lose their relative importance as their emissions fall and global emissions rise.  This makes it ever more important to focus on the developing world.

Picture from the report linked to my earlier post

Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Ken Feldman on July 17, 2020, 08:27:20 PM
Renewables only became cheaper than fossil fuels in some areas starting in 2018.  With costs of renewables continuing to decline, they are becoming cheaper than fossil fuels in more areas.  And given that it can take two years for a new wind or solar farm to come online, and five to ten years for a fossil fuel plant, it will take some time for the full impact of the cost reductions in renewables to be seen.

We're already seeing it in new investments.  Investments in renewables are now outpacing investment in fossil fuel infrastructure.

https://markets.businessinsider.com/news/stocks/renewable-energy-trillion-investment-opportunity-surpass-oil-first-time-goldman-2020-6-1029318482?utm_source=energy+news+network+daily+email+digests&utm_campaign=cefb1504a8-email_campaign_2020_05_11_11_46_copy_01&utm_medium=email&utm_term=0_724b1f01f5-cefb1504a8-89260815# (https://markets.businessinsider.com/news/stocks/renewable-energy-trillion-investment-opportunity-surpass-oil-first-time-goldman-2020-6-1029318482?utm_source=energy+news+network+daily+email+digests&utm_campaign=cefb1504a8-email_campaign_2020_05_11_11_46_copy_01&utm_medium=email&utm_term=0_724b1f01f5-cefb1504a8-89260815#)

Quote
Goldman Sachs says renewable-energy spending will surpass oil and gas for the first time ever in 2021 — and sees total investment spiking to $16 trillion over the next decade
Ben Winck
Jun. 17, 2020

Green-energy investing will account for 25% of all energy spending in 2021 and, for the first time ever, surpass spending on traditional fuel sources like oil and gas, Goldman Sachs said in a Tuesday note.
Should the US aim to hold global warming within 2 degrees Celsius, the pivot to renewable energy sources will create between $1 trillion and $2 trillion in yearly infrastructure spending, the team of analysts added, or an investment opportunity as big as $16 trillion through 2030.
While past economic downturns halted efforts to lift clean energy initiatives, the coronavirus recession "will be different," the firm said.
Green technologies "are now mature enough to be deployed at scale," and the transition can benefit massively from cheap capital and "an attractive regulatory framework," according to Goldman.

In the US, electric utilities are retiring coal plants early and replacing them with renewables.  Becuase they can save lots and lots of money.  It's cheaper to build new renewable power plants than to operate existing coal fired power plants.  And that trend is spreading around the world.  It's estimated that $141 billion can be saved by replacing coal with clean energy by 2025.

https://energy.economictimes.indiatimes.com/news/renewable/replacing-coal-with-clean-energy-can-save-up-to-141-billion-by-2025/76886624 (https://energy.economictimes.indiatimes.com/news/renewable/replacing-coal-with-clean-energy-can-save-up-to-141-billion-by-2025/76886624)

Quote
Replacing coal with clean energy can save up to $141 billion by 2025

Out of 2,500 coal plants, the share of uncompetitive coal plants worldwide will increase rapidly to 60 per cent in 2022 and to 73 per cent in 2025

ETEnergyWorld July 10, 2020

New Delhi: Replacing coal with clean energy can potentially save electricity customers around the world $141 billion by 2025, according to a report by US-based Rocky Mountain Institute launched in collaboration with Carbon Tracker Initiative and the US-based environmental organisation Sierra Club.

Utilities are increasingly skip the "bridge" of replacing coal with natural gas and just jumping strait to solar or wind.

https://pv-magazine-usa.com/2020/07/02/more-utilities-bypassing-natural-gas-bridge-and-going-straight-to-renewables/ (https://pv-magazine-usa.com/2020/07/02/more-utilities-bypassing-natural-gas-bridge-and-going-straight-to-renewables/)

Quote
More utilities bypassing natural gas bridge and going straight to renewables

Utilities that are transitioning away from coal are starting to view the creation of a natural gas “bridge” to renewable energy as an unnecessary step.
July 2, 2020 Jean Haggerty

Utilities that are transitioning away from coal are starting to view the creation of a natural gas “bridge” to renewable energy as an unnecessary step. Last week utilities in Arizona, Colorado and Florida announced plans to close one or more of their coal plants and build renewables without adding any new gas-fired generation.

There are many more examples I could post of renewables replacing operating fossil fuel plants.  And the trend will accelerate in the future as the costs of renewables continue to decrease.

Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: GoSouthYoungins on July 17, 2020, 08:56:50 PM
Wind farms can't make wind farms. A drilled oil field can provide enough energy to drill a new field (or make a wind farm). Basically the energy comes from fossil fuels originally. If the energy is used to build a solar panel rather than spin a turbine, maybe it is more efficient, but the foundation is always fossil fuel energy.

Industry relies are fossil fuels. Manufacturing, mining, and practically everything else can't be run on wind or solar. These renewables are great at providing addition electricity to a grid that has a base load maintained on fossil fuels. This is the lowest of the low hanging fruit. And we are barely succeeding at that.

The transition will always seem to be at hand in the next decade or two. But it will never happen (until society collapses). It is impossible.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: wili on July 18, 2020, 04:45:03 AM
Ah, another fact free post
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: gerontocrat on July 19, 2020, 12:08:52 AM
These renewables are great at providing addition electricity to a grid that has a base load maintained on fossil fuels. This is the lowest of the low hanging fruit. And we are barely succeeding at that.

The transition will always seem to be at hand in the next decade or two. But it will never happen (until society collapses). It is impossible.
The UK National Electricity Grid is due to be capable of running entirely on renewable energy by 2025. The bosses are happy with this target.

Now if you had said that it is unlikely that the world will reduce CO2 emissions by 7% a year every year from now to 2030 you might have had some people agree with you.

And that is definitely all I'm going to say about that
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: vox_mundi on August 04, 2020, 12:41:45 AM
'Worst-Case' CO2 Emissions Scenario Is Best for Assessing Climate Risk and Impacts to 2050
https://phys.org/news/2020-08-worst-case-co2-emissions-scenario-climate.html

The RCP 8.5 CO2 emissions pathway, long considered a "worst case scenario" by the international science community, is the most appropriate for conducting assessments of climate change impacts by 2050, according to a new article published today in the Proceedings of the National Academy of Sciences.

Long dismissed as alarmist or misleading, the paper argues that is actually the closest approximation of both historical emissions and anticipated outcomes of current global climate policies, tracking within 1% of actual emissions.

"Not only are the emissions consistent with RCP 8.5 in close agreement with historical total cumulative CO2 emissions (within 1%), but RCP8.5 is also the best match out to mid-century under current and stated policies with still highly plausible levels of CO2 emissions in 2100," the authors wrote. "... Not using RCP8.5 to describe the previous 15 years assumes a level of mitigation that did not occur, thereby skewing subsequent assessments by lessening the severity of warming and associated physical climate risk."

The commentary also emphasizes that while there are signs of progress on bending the global emissions curve and that our emissions picture may change significantly by 2100, focusing on the unknowable, distant future may distort the current debate on these issues. "For purposes of informing societal decisions, shorter time horizons are highly relevant, and it is important to have scenarios which are useful on those horizons. Looking at mid-century and sooner, RCP8.5 is clearly the most useful choice," they wrote.

The article also notes that RCP 8.5 would not be significantly impacted by the COVID-19 pandemic, adding that "we note that the usefulness of RCP 8.5 is not changed due to the ongoing COVID-19 pandemic. Assuming pandemic restrictions remain in place until the end of 2020 would entail a reduction in emissions of -4.7 Gt CO2. This represents less than 1% of total cumulative CO2 emissions since 2005 for all RCPs and observations."

Christopher R. Schwalm el al., "RCP8.5 tracks cumulative CO2 emissions," PNAS (2020)
https://www.pnas.org/content/early/2020/07/30/2007117117

----------------------------------
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Ken Feldman on August 05, 2020, 12:24:09 AM
'Worst-Case' CO2 Emissions Scenario Is Best for Assessing Climate Risk and Impacts to 2050
https://phys.org/news/2020-08-worst-case-co2-emissions-scenario-climate.html

The RCP 8.5 CO2 emissions pathway, long considered a "worst case scenario" by the international science community, is the most appropriate for conducting assessments of climate change impacts by 2050, according to a new article published today in the Proceedings of the National Academy of Sciences.

Long dismissed as alarmist or misleading, the paper argues that is actually the closest approximation of both historical emissions and anticipated outcomes of current global climate policies, tracking within 1% of actual emissions.

"Not only are the emissions consistent with RCP 8.5 in close agreement with historical total cumulative CO2 emissions (within 1%), but RCP8.5 is also the best match out to mid-century under current and stated policies with still highly plausible levels of CO2 emissions in 2100," the authors wrote. "... Not using RCP8.5 to describe the previous 15 years assumes a level of mitigation that did not occur, thereby skewing subsequent assessments by lessening the severity of warming and associated physical climate risk."

The commentary also emphasizes that while there are signs of progress on bending the global emissions curve and that our emissions picture may change significantly by 2100, focusing on the unknowable, distant future may distort the current debate on these issues. "For purposes of informing societal decisions, shorter time horizons are highly relevant, and it is important to have scenarios which are useful on those horizons. Looking at mid-century and sooner, RCP8.5 is clearly the most useful choice," they wrote.

The article also notes that RCP 8.5 would not be significantly impacted by the COVID-19 pandemic, adding that "we note that the usefulness of RCP 8.5 is not changed due to the ongoing COVID-19 pandemic. Assuming pandemic restrictions remain in place until the end of 2020 would entail a reduction in emissions of -4.7 Gt CO2. This represents less than 1% of total cumulative CO2 emissions since 2005 for all RCPs and observations."

Christopher R. Schwalm el al., "RCP8.5 tracks cumulative CO2 emissions," PNAS (2020)
https://www.pnas.org/content/early/2020/07/30/2007117117

----------------------------------

A close read of the study shows that it didn't take into account economic considerations, such as the fact that renewables are now cheaper than fossil fuels.  And it's also missing the point that emissions up through the 2020s are very close in all scenarios.  Here's a figure from the paper that shows that fact:

(https://www.pnas.org/content/pnas/early/2020/07/30/2007117117/F1.medium.gif)

For future projections, they rely on the IEA assessment of Government policy decisions, ignoring the impacts of the energy transition underway.  And let's not forget how badly the IEA has been at forecasting the pace of the energy transition.

(https://onclimatechangepolicydotorg.files.wordpress.com/2019/01/screen-shot-2019-01-18-at-17.02.16.png?w=768&h=630)
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: kassy on August 05, 2020, 03:33:51 PM
See the picture attached to this post to see that current emissions are much more close to 8.5:

The attached image is just a reminder that thru 2019 our CO2 emissions were still closely tracking the RCP 8.5 emissions scenario.

or as they said: Long dismissed as alarmist or misleading, the paper argues that is actually the closest approximation of both historical emissions and anticipated outcomes of current global climate policies, tracking within 1% of actual emissions.

and

The article also notes that RCP 8.5 would not be significantly impacted by the COVID-19 pandemic, adding that "we note that the usefulness of RCP 8.5 is not changed due to the ongoing COVID-19 pandemic. Assuming pandemic restrictions remain in place until the end of 2020 would entail a reduction in emissions of -4.7 Gt CO2. This represents less than 1% of total cumulative CO2 emissions since 2005 for all RCPs and observations."


Eyeballing the graph i am not sure you can claim that it's also missing the point that emissions up through the 2020s are very close in all scenarios.

This is more evidence that we are not doing enough.

Of course the energy transition will knock a big fat part of the tail of 8.5 but that does not mean we are actually in the clear.

It would of course really help if we actually defined safe limits , or our actual goals for limiting the damage by AGW.

Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: kassy on August 06, 2020, 03:55:33 PM
Losing the remaining Arctic sea ice and its ability to reflect incoming solar energy back to space would be equivalent to adding one trillion tons of CO2 to the atmosphere, on top of the 2.4 trillion tons emitted since the Industrial Age, according to current and former researchers from Scripps Institution of Oceanography at the University of California San Diego.

At current rates, this roughly equates to 25 years of global CO2 emissions.

https://scripps.ucsd.edu/news/research-highlight-loss-arctics-reflective-sea-ice-will-advance-global-warming-25-years

So this exactly the sort of thing we try to avoid. And the effect should build as we lose ice along the way.

Can we avert this at our current rate? With actual realized global reductions because that is how the planet counts? I doubt it.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Richard Rathbone on August 06, 2020, 05:51:57 PM
Losing the remaining Arctic sea ice and its ability to reflect incoming solar energy back to space would be equivalent to adding one trillion tons of CO2 to the atmosphere, on top of the 2.4 trillion tons emitted since the Industrial Age, according to current and former researchers from Scripps Institution of Oceanography at the University of California San Diego.

At current rates, this roughly equates to 25 years of global CO2 emissions.

https://scripps.ucsd.edu/news/research-highlight-loss-arctics-reflective-sea-ice-will-advance-global-warming-25-years

So this exactly the sort of thing we try to avoid. And the effect should build as we lose ice along the way.

Can we avert this at our current rate? With actual realized global reductions because that is how the planet counts? I doubt it.

Posted to wrong thread? Its an old story and a bad paper.

They've only looked at the summer and ignored the winter and generalised from the summer to a year round effect. Loss of ice in winter is cooling, not heating and its a dominant effect not a trivial one. This is a number for what would happen if the ice were removed in April, kept in a cold store in Svalbard over the summer, and then replaced at the end of September.

This is a common mistake and a common alarmist cherry pick. Ice insulates and when it goes missing the effects are opposite in winter to what they are in summer.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Stephan on August 06, 2020, 07:45:33 PM
More radiative forcing of the "NOAA gases" (CO2, CH4, N2O, SF6) in Apr 2020 than in Mar 2020 or in Apr 2019.
The values [W/m²], change to Mar 2020 and change to Apr 2019:
CO2 2.159   (+ 0.022)    (+ 0.035)   
CH4 0.520   (+ 0.000)    (+ 0.004)
N2O 0.205   (+ 0.000)    (+ 0.004)
SF6  0.0053 (+ 0.0000)  (+ 0.0002)
sum 2.889  (+ 0.021)   (+ 0.045) (rounding difference)
The relative annual increase is 1.58 %
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Simon on August 06, 2020, 09:42:30 PM
But isn’t the total greater than that, about 3.2W/m2 ?

https://www.esrl.noaa.gov/gmd/aggi/aggi.html

Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Stephan on August 07, 2020, 06:48:09 AM
Yes, you're absolutely right.
As I only monitor the four gases whose concentration NOAA regularly publishes (CO2, CH4, N2O, SF6) their sum is smaller than the sum of all greenhouse gases. Therefore I talk about the "NOAA gases" in my first sentence.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Simon on August 07, 2020, 08:09:29 AM
The rcip pathways are based on the total greenhouse gas radiative forcings which now stand at about 3.2W/m2 or so. I think I am right in saying this.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Tom_Mazanec on August 07, 2020, 11:51:53 AM
So every square meter of the planet has the equivalent of a 3.2?watt bulb burning on it.
What is the wattage of a small penlight bulb?
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: nanning on August 07, 2020, 01:48:33 PM
Tom, I think that the 3.2W is from the extra GHG in the atmosphere since pre-industrial. It is not the total incoming power and it is not the same for all places on Earth. You could say that the cumulative radiative forcing is a force that changes the pre-industrial climate equilibrium. In our case to much higher temperatures because of a positive force (and a high climate sensitivity).
So the light bulb is much stronger than 3.2W and uses no batteries :).
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Tom_Mazanec on August 07, 2020, 01:59:31 PM
Yes, I know there is a lot of illumination. I meant the extra illumination.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Hefaistos on August 07, 2020, 02:04:42 PM
Tom, I think that the 3.2W is from the extra GHG in the atmosphere since pre-industrial. It is not the total incoming power and it is not the same for all places on Earth. You could say that the cumulative radiative forcing is a force that changes the pre-industrial climate equilibrium. In our case to much higher temperatures because of a positive force (and a high climate sensitivity).
So the light bulb is much stronger than 3.2W and uses no batteries :).

The radiative forcing from the GHG is 3.2 W/sq.m, which corresponds to 1.2 K or so in average increased temperatures. The other effect you talk about is not a forcing per se, but are various feedback processes.

https://scienceofdoom.com/2014/06/26/the-greenhouse-effect-explained-in-simple-terms/#comment-153310
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: kassy on August 12, 2020, 01:43:25 PM
Losing the remaining Arctic sea ice and its ability to reflect incoming solar energy back to space would be equivalent to adding one trillion tons of CO2 to the atmosphere, on top of the 2.4 trillion tons emitted since the Industrial Age, according to current and former researchers from Scripps Institution of Oceanography at the University of California San Diego.

At current rates, this roughly equates to 25 years of global CO2 emissions.

https://scripps.ucsd.edu/news/research-highlight-loss-arctics-reflective-sea-ice-will-advance-global-warming-25-years

So this exactly the sort of thing we try to avoid. And the effect should build as we lose ice along the way.

Can we avert this at our current rate? With actual realized global reductions because that is how the planet counts? I doubt it.

Posted to wrong thread? Its an old story and a bad paper.

They've only looked at the summer and ignored the winter and generalised from the summer to a year round effect. Loss of ice in winter is cooling, not heating and its a dominant effect not a trivial one. This is a number for what would happen if the ice were removed in April, kept in a cold store in Svalbard over the summer, and then replaced at the end of September.

This is a common mistake and a common alarmist cherry pick. Ice insulates and when it goes missing the effects are opposite in winter to what they are in summer.

Lets start with another paper:

Summary
The Arctic Ocean will become ice free during summer before mid-century unless greenhouse gas emissions are rapidly reduced.

Notz and Stroeve 2018
https://link.springer.com/article/10.1007/s40641-018-0113-2

This is the abstract of the actual paper:

Abstract
During recent decades, there has been dramatic Arctic sea ice retreat. This has reduced the top‐of‐atmosphere albedo, adding more solar energy to the climate system. There is substantial uncertainty regarding how much ice retreat and associated solar heating will occur in the future. This is relevant to future climate projections, including the timescale for reaching global warming stabilization targets. Here we use satellite observations to estimate the amount of solar energy that would be added in the worst‐case scenario of a complete disappearance of Arctic sea ice throughout the sunlit part of the year. Assuming constant cloudiness, we calculate a global radiative heating of 0.71 W/m2 relative to the 1979 baseline state. This is equivalent to the effect of one trillion tons of CO2 emissions. These results suggest that the additional heating due to complete Arctic sea ice loss would hasten global warming by an estimated 25 years.

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019GL082914

I don´t think they actually extrapolate. It is just the effect they calculate.

And that is why we should tried to avoid this although at our current rate that is going to be hard.

*

There is a bit of a problem with the pathways. They are not really useful.
This is also because they forgot to define dangerous.

We know that we want to avoid certain feedbacks like:
Loss of arctic sea ice (failing in the thirties)
Permafrost becoming a source (already done)
Triggering Iceland and Antarctica

So if we just take the Arctic ice as a safe point it is clear that collectively we should have done a lot more.

Combine this with the knowledge that we wont slow that fast because we are not planning to and the fact that the effect lingers even if we go zero overnight then saving the ice looks really iffy.



Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Tom_Mazanec on August 12, 2020, 03:47:02 PM
Quote
Triggering Iceland and Antarctica
And Greenland.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: kassy on August 12, 2020, 08:21:41 PM
Yes Greenland not Iceland.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Simon on August 12, 2020, 08:43:56 PM
May not be the right thread but as Arctic summer sea ice is being referred to, the latest modelling indicates circa 2035 for its first disappearance.

https://www.sciencedaily.com/releases/2020/08/200810113216.htm

Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: mitch on August 12, 2020, 09:39:45 PM
The Guarino et al (2020) study that gave 2035 for BOE used CMIP6 models, which tend to have higher equilibrium climate sensitivity, and added the melt pond physics.  While it appears that 2035 is plausible, I will wait for more confirmation.  Or, we can all wait 15 years and see for ourselves. 
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: kassy on August 12, 2020, 10:40:20 PM
Adding physics that actually happen will improve the forecast. 15 years is quite short climate wise.

I am quite happy to wait but i maintain that the planet does not have that luxury because when we know it happened it is too late. And we know it is happening although we much like to ignore it.

You can draw lines and extrapolate some time number in the future but we must also weigh that vs what is already locked in.

And think about the consequences that actually brings.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: ArcTickTock on August 14, 2020, 06:22:08 AM
May not be the right thread but as Arctic summer sea ice is being referred to, the latest modelling indicates circa 2035 for its first disappearance.

https://www.sciencedaily.com/releases/2020/08/200810113216.htm

2035 seems about right, right around there is when the trend line for arctic sea ice volume at minimum reaches 0.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Tom_Mazanec on August 14, 2020, 12:50:24 PM
May not be the right thread but as Arctic summer sea ice is being referred to, the latest modelling indicates circa 2035 for its first disappearance.

https://www.sciencedaily.com/releases/2020/08/200810113216.htm

2035 seems about right, right around there is when the trend line for arctic sea ice volume at minimum reaches 0.

Of course that assumes we don't have a fluke event like 2012, which would bring it about sooner.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: kassy on August 15, 2020, 09:50:11 PM
Warming Greenland Ice Sheet Passes Point of No Return
https://phys.org/news/2020-08-greenland-ice-sheet.html

Nearly 40 years of satellite data from Greenland shows that glaciers on the island have shrunk so much that even if global warming were to stop today, the ice sheet would continue shrinking.

See the link for the details but this is another one we can add. We are on overtime on this one too.

If you had asked me about 25 years ago what scenes i would imagine when this news broke i could not have come up with this.

Since this fact of Greenland melt is true today it also demonstrates that 1,5 C is not a safe goal.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: kassy on August 15, 2020, 10:56:25 PM
May not be the right thread but as Arctic summer sea ice is being referred to, the latest modelling indicates circa 2035 for its first disappearance.

https://www.sciencedaily.com/releases/2020/08/200810113216.htm

2035 seems about right, right around there is when the trend line for arctic sea ice volume at minimum reaches 0.

Of course that assumes we don't have a fluke event like 2012, which would bring it about sooner.

If we go back through the historical record all the recent conditions are from icy conditions. ESAS has been melting for 12k years or so and it is only going to get worse.

We are heading into territory we know less well. Yes we have historical analogues but the data points are less scarce at that end. And you can combine that with the things we cannot model well.

We do not know where we are going to end up but we could have used some points of no return. Things we should have avoided. But those where glossed over for economic gains and bs discounting on those measures.

Even if we would hit the Paris goals we would still be in a world were the Arctic ice is doomed, Greenland too. And probably Antarctica is already in play too.

That is our world today.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: liefde on August 31, 2020, 11:38:51 PM
Yes Greenland not Iceland.
Eeh.. remember the Ok glacier in Iceland? Declared "dead" in 2014..
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Stephan on September 10, 2020, 08:45:34 PM
To finalize my update on greenhouse gases here is the summary of the four postings in the individual gas concentration threads.

More radiative forcing of the "NOAA gases" (CO2, CH4, N2O, SF6) in May 2020 than in Apr 2020 or in May 2019.

The values [W/m²], change to Apr 2020 and change to May 2019:
CO2 2.170   (+ 0.011)    (+ 0.031)   
CH4 0.520   (+ 0.000)    (+ 0.005)
N2O 0.205   (+ 0.000)    (+ 0.004)
SF6  0.0053 (+ 0.0000)  (+ 0.0002)
sum  2.900  (+ 0.011)   (+ 0.040)

The relative annual increase is 1.36 %.
It also means never before since we measure these gases has their radiative forcing been so strong.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: kassy on September 12, 2020, 06:27:48 PM
Where does the heat go?

This study calculates that the amount of CO2 in the atmosphere must be reduced from the present concentration of nearly 410 ppm to approximately 350 ppm to bring the Earth back towards energy balance.

https://public.wmo.int/en/media/news/where-does-heat-go

See the article for details but hey look another piece of evidence that we are well into overshoot.

Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: nanning on September 12, 2020, 07:08:27 PM
280 ppm is the pre-industrial level. Reaching that means returning to nature's original track. That should be the goal. To undo the damage we've done.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: wdmn on September 12, 2020, 07:35:37 PM
280 ppm is the pre-industrial level. Reaching that means returning to nature's original track. That should be the goal. To undo the damage we've done.

Back on this old nonsense eh nanning? It would have been better had humans never evolved! But then that would mean blaming... nature?

At 280ppm we were heading into a glacial period.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Stephan on September 12, 2020, 08:42:21 PM
A short explanation of this plot would be helpful, wdmn, including the designation of x and y axes.
I guess it is worldwide temperature the last 10,000 years?
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: wili on September 12, 2020, 10:20:10 PM
wdmn, I know nanning can seem tiresomely simplistic and repetitive sometimes, but the fact of the matter is that somehow we have managed in quite a short time to turn the earth from a 'goldilocks' climate into something more and more resembling a fiery hell.

It is at least as important, and arguably much more, to try to figure out how we got here so we can figure out exactly what we have to stop doing (and thinking), as it is to understand the nuances of the science that tells us what is happening to sea ice on a day by day basis.

Humans 'evolved' to have thousands of different cultures around the world. Arguably, it is only one of those, modern industrial culture and society (at first Western, now global), that has pushed the world to and probably past the point that it will be readily habitable by future generations.

So questioning where we went wrong is not the same as being against all human evolution, lol.

Maybe we have to look further back than the industrial revolution. Maybe it was the particular way the industrial revolution developed that holds the key. In any case, the issue is not one that should, imo, be lightly tossed under the rug.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: wdmn on September 12, 2020, 11:19:00 PM
@Stephen

My apologies.

The graph comes from: https://twitter.com/alxrdk/status/1295016785180270594

The time period (x-axis) is 12,000 years, 9980 BC - 2020 AD.
Baseline is 20th century mean. Minimum temperature shown = -1.37°C, Max T = 0.99°C (2020).

Sources for the data are provided in the above linked twitter thread.

The graph shows the end of the last glacial period, the Holocene and the Anthropocene (if you are so inclined to use the latter designation). The Holocene is the period in which agriculture and settled human civilization was born. Humans of course lived during the last glacial period, but were not present in large parts of currently inhabited land, as that land was under thick ice sheets.

I used this graph, because it very clearly shows the slow arc down from the Holocene maximum temperature. That arc had us on the trajectory to another glacial period, which would be -- one could argue -- at least as devastating to human civilization as global heating now threatens to be.

@wili

I of course agree that we are in a dire situation regarding climate change, as is unanimously stated by the most reputable climate scientists. The 350 ppm target was set by one of those same scientists, James Hansen.

While the consequences of industrialization are now threatening human civilization, I think it is ridiculous to dismiss the whole period as a cancer that should be done away with. I simply want to point out that the pre-industrial target would also condemn human civilization.

I also question the 280ppm target as arbitrary; it already includes human activity throughout the Holocene, so why is that "nature's track" as it was intended?. Why not "put it back as it was" before the Holocene? Before humans? What is "undoing the harm?" What is nature's track, if not the one that we're on? That of course includes the possibility that we address global heating before it does as much damage as it might (i.e. that we might completely overhaul our culture, including learning from those non-industrialized cultures that still exist).

Nanning's logic -- as has been discussed elsewhere ad nauseam -- presumes that humans have no right to take actions that affect nature's path, while at the same time declaring that we should make a decision to go back to one specific point in nature's path (i.e. making the human decision as to what nature's path should be; i.e. doing the same thing he condemns when we set the target at 350 ppm). He also seems to condemn human beings to either being passive animals that accept whatever fate is handed to us by "nature" (we should allow a glacial period or an astroid to hit us, even if we could avoid it, for example; which condemns nature for giving us a survival instinct and the ability to practice climate science or astronomy, etc.), or to eliminate us completely from nature (which, as pointed out, condemns nature, which gave rise to our species).
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: nanning on September 13, 2020, 07:39:08 AM
Quote from: wdmn
Back on this old nonsense eh nanning?
Nanning's logic -- as has been discussed elsewhere ad nauseam -- presumes

That's not my logic you describe wdmn. That's your logic projected onto me.
I won't react further to your unkind words and charges.
Main point is: high technology comes with high responsibility and we are not alone on this planet and this planet is not ours to spoil.

edit: added quotes
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: wili on September 13, 2020, 02:27:30 PM
I don't presume to speak for nanning.

But again I would point out that humans have devised thousands of different ways to live in the world without destroying it, and presumably there are countless more ways.

Global civilization seems to have hit on the one way to live in the world that destroys most other forms of life as well as disrupting the systems that support said life.

Our most desperate need is to rediscover a culture/way of life that fosters rather than obliterates the rest of the living community.

Any ideas? :)
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Tom_Mazanec on September 13, 2020, 02:49:33 PM
I am sure mammoths, saber tooth tigers, mastodons, teratorns et al would dispute that global industrial civilization is the only one that exterminates other species.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: wili on September 13, 2020, 04:09:56 PM
Yes, as humans left their original homelands in Africa, we probably wiped out a number of large species, being basically an invasive species ourselves. There is still some debate about which ones were wiped out by us and which failed to adapt to changing climates.

But those extinctions pale compared to the global mass extinctions and destruction of ecosystems going on today.

And once humans did settle in any particular area, they tended to fairly quickly develop a set of taboos to avoid wiping out crucial local and fauna. If they didn't they would generally not last very long.

Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: nanning on September 13, 2020, 06:25:22 PM
Thank you wili. Beautiful. :)
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: kassy on September 13, 2020, 08:44:03 PM
And also off topic.

280 is moot if we cannot even get close to 350.
And extinctions belong in another thread.

Also to taboos:
I think that is wrong.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: nanning on September 14, 2020, 05:06:52 AM
Thank you for letting it stand, moderator kassy.

"280 is moot if we cannot even get close to 350."
Indeed. It's completely academic.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Ken Feldman on September 28, 2020, 08:47:29 PM
I found the data for the RCP scenario assumptions on the IPCC website.

https://www.ipcc-data.org/observ/index.html (https://www.ipcc-data.org/observ/index.html)

At that webpage, click on the top link, "Climate System Scenario Tables (Annex II of IPCC 5th Assessment Report, WG1 -- as Excel workbook"

This will open a large Excel spreadsheet with many tabs.  The tabs showing greenhouse gas concentrations by year are 4-1 (CO2), 4-2 (CH4), etc...

Here is the table for CO2:
Quote
Table AII.4.1 | CO2 abundance (ppm)                                 
Year   Observed   RCP2.6   RCP4.5   RCP6.0   RCP8.5   A2   B1   IS92a   Min   RCP8.5&   Max
PI   278 ± 2   278   278   278   278   278   278   278         
2011 obs   390.5 ± 0.3                              
2000      368.9   368.9   368.9   368.9   368   368   368         
2005      378.8   378.8   378.8   378.8               378.8   
2010      389.3   389.1   389.1   389.3   388   387   388   366   394   413
2020      412.1   411.1   409.4   415.8   416   411   414   386   425   449
2030      430.8   435.0   428.9   448.8   448   434   442   412   461   496
2040      440.2   460.8   450.7   489.4   486   460   472   443   504   555
2050      442.7   486.5   477.7   540.5   527   485   504   482   559   627
2060      441.7   508.9   510.6   603.5   574   506   538   530   625   713
2070      437.5   524.3   549.8   677.1   628   522   575   588   703   810
2080      431.6   531.1   594.3   758.2   690   534   615   651   790   914
2090      426.0   533.7   635.6   844.8   762   542   662   722   885   1026
2100      420.9   538.4   669.7   935.9   846   544   713   794   985 ± 97   1142

Here is the table for CH4:

Quote
Table AII.4.2 | CH4 abundance (ppb)                                                         
Year   RCP2.6   RCP4.5   RCP6.0   RCP8.5   A2   B1   IS92a      RCP2.6&         RCP4.5&         RCP6.0&         RCP8.5&   
PI   720   720   720   720            722   ±   25   722   ±   25   722   ±   25   722   ±   25
2011 obs                        1803   ±   4   1803   ±   4   1803   ±   4   1803   ±   4
2000   1751   1751   1751   1751   1760   1760   1760                                    
2010   1773   1767   1769   1779   1861   1827   1855   1795   ±   18   1795   ±   18   1795   ±   18   1795   ±   18
2020   1731   1801   1786   1924   1997   1891   1979   1716   ±   23   1847   ±   21   1811   ±   22   1915   ±   25
2030   1600   1830   1796   2132   2163   1927   2129   1562   ±   38   1886   ±   28   1827   ±   28   2121   ±   44
2040   1527   1842   1841   2399   2357   1919   2306   1463   ±   50   1903   ±   37   1880   ±   36   2412   ±   74
2050   1452   1833   1895   2740   2562   1881   2497   1353   ±   60   1899   ±   47   1941   ±   48   2784   ±   116
2060   1365   1801   1939   3076   2779   1836   2663   1230   ±   71   1872   ±   59   1994   ±   61   3152   ±   163
2070   1311   1745   1962   3322   3011   1797   2791   1153   ±   78   1824   ±   72   2035   ±   77   3428   ±   208
2080   1285   1672   1940   3490   3252   1741   2905   1137   ±   88   1756   ±   87   2033   ±   94   3624   ±   250
2090   1268   1614   1819   3639   3493   1663   3019   1135   ±   98   1690   ±   100   1908   ±   111   3805   ±   293
2100   1254   1576   1649   3751   3731   1574   3136   1127   ±   106   1633   ±   110   1734   ±   124   3938   ±   334
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: SimonF92 on September 28, 2020, 11:12:34 PM
I plotted that data;
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Tor Bejnar on September 28, 2020, 11:14:59 PM
From the 2020 Mauna Loa CO2 levels (https://forum.arctic-sea-ice.net/index.php/topic,2983.msg288103.html#msg288103) thread, Steven posted
Quote
Sunday evening [Sept. 27, 2020]- an update from Mauna Loa CO2:
Week beginning on September 20, 2020:     411.00 ppm
Now, are those IPCC numbers Ken just posted "Mauna Loa equivalent"? Or some other "average global number?  I looked it up (thanks for the guidance, Ken!): They are "global mean values".

So, what is the relationship between "global mean CO2" and Moana Loa values? 
(I guess we will have to wait for January 2021 to know the actual 2020 global mean CO2 value ...)
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: SimonF92 on September 28, 2020, 11:19:36 PM
Methane too;

Oh my, i have just realised these plots have axes the wrong way round, please imagine the labels reversed- I havent used matplotlib for a while
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Ken Feldman on September 29, 2020, 02:38:47 AM
From the 2020 Mauna Loa CO2 levels (https://forum.arctic-sea-ice.net/index.php/topic,2983.msg288103.html#msg288103) thread, Steven posted
Quote
Sunday evening [Sept. 27, 2020]- an update from Mauna Loa CO2:
Week beginning on September 20, 2020:     411.00 ppm
Now, are those IPCC numbers Ken just posted "Mauna Loa equivalent"? Or some other "average global number?  I looked it up (thanks for the guidance, Ken!): They are "global mean values".

So, what is the relationship between "global mean CO2" and Moana Loa values? 
(I guess we will have to wait for January 2021 to know the actual 2020 global mean CO2 value ...)

For 2019, NOAA reported an annual average of 411.43 ppm at Mauna Loa and 409.85 ppm for the global average.  So in 2019, Mauna Loa was about 1.6 ppm higher than the global average.  In 2018 Mauna Loa was 1.13 ppm higher and in 2017 Mauna Loa was 1.55 ppm higher. 

However, since this forum tracks Mauna Loa weekly averages, it's more complicated.

The NOAA Global Monitoring Laboratory publishes both the Mauna Loa and the Global values.  The Mauna Loa values are updated weekly but often change over time as the quality control process needs data from the other observatories that collect the same data.  The global value is updated monthly and lags by several months.  Currently, they are reporting the global measurement data from June 2020 (412.62 ppm) while Mauna Loa is reporting the August 2020 monthly average measurement (412.55 ppm).  While they're pretty close now, at other times of the year they differ.

To further complicate the issue, the RCPs are based on annual average concentrations.  These aren't available on the NOAA website until April or May of the next year, and they can be updated later in the year as more quality control is done. 

Link to the global data:

https://www.esrl.noaa.gov/gmd/ccgg/trends/gl_data.html (https://www.esrl.noaa.gov/gmd/ccgg/trends/gl_data.html)

Link to Mauna Loa data:

https://www.esrl.noaa.gov/gmd/ccgg/trends/data.html (https://www.esrl.noaa.gov/gmd/ccgg/trends/data.html)
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: so_whats_happening on September 29, 2020, 06:03:21 AM
I found the data for the RCP scenario assumptions on the IPCC website.

https://www.ipcc-data.org/observ/index.html (https://www.ipcc-data.org/observ/index.html)

At that webpage, click on the top link, "Climate System Scenario Tables (Annex II of IPCC 5th Assessment Report, WG1 -- as Excel workbook"

This will open a large Excel spreadsheet with many tabs.  The tabs showing greenhouse gas concentrations by year are 4-1 (CO2), 4-2 (CH4), etc...

Here is the table for CO2:
Quote
Table AII.4.1 | CO2 abundance (ppm)                                 
Year   Observed   RCP2.6   RCP4.5   RCP6.0   RCP8.5   A2   B1   IS92a   Min   RCP8.5&   Max
PI   278 ± 2   278   278   278   278   278   278   278         
2011 obs   390.5 ± 0.3                              
2000      368.9   368.9   368.9   368.9   368   368   368         
2005      378.8   378.8   378.8   378.8               378.8   
2010      389.3   389.1   389.1   389.3   388   387   388   366   394   413
2020      412.1   411.1   409.4   415.8   416   411   414   386   425   449
2030      430.8   435.0   428.9   448.8   448   434   442   412   461   496
2040      440.2   460.8   450.7   489.4   486   460   472   443   504   555
2050      442.7   486.5   477.7   540.5   527   485   504   482   559   627
2060      441.7   508.9   510.6   603.5   574   506   538   530   625   713
2070      437.5   524.3   549.8   677.1   628   522   575   588   703   810
2080      431.6   531.1   594.3   758.2   690   534   615   651   790   914
2090      426.0   533.7   635.6   844.8   762   542   662   722   885   1026
2100      420.9   538.4   669.7   935.9   846   544   713   794   985 ± 97   1142

Here is the table for CH4:

Quote
Table AII.4.2 | CH4 abundance (ppb)                                                         
Year   RCP2.6   RCP4.5   RCP6.0   RCP8.5   A2   B1   IS92a      RCP2.6&         RCP4.5&         RCP6.0&         RCP8.5&   
PI   720   720   720   720            722   ±   25   722   ±   25   722   ±   25   722   ±   25
2011 obs                        1803   ±   4   1803   ±   4   1803   ±   4   1803   ±   4
2000   1751   1751   1751   1751   1760   1760   1760                                    
2010   1773   1767   1769   1779   1861   1827   1855   1795   ±   18   1795   ±   18   1795   ±   18   1795   ±   18
2020   1731   1801   1786   1924   1997   1891   1979   1716   ±   23   1847   ±   21   1811   ±   22   1915   ±   25
2030   1600   1830   1796   2132   2163   1927   2129   1562   ±   38   1886   ±   28   1827   ±   28   2121   ±   44
2040   1527   1842   1841   2399   2357   1919   2306   1463   ±   50   1903   ±   37   1880   ±   36   2412   ±   74
2050   1452   1833   1895   2740   2562   1881   2497   1353   ±   60   1899   ±   47   1941   ±   48   2784   ±   116
2060   1365   1801   1939   3076   2779   1836   2663   1230   ±   71   1872   ±   59   1994   ±   61   3152   ±   163
2070   1311   1745   1962   3322   3011   1797   2791   1153   ±   78   1824   ±   72   2035   ±   77   3428   ±   208
2080   1285   1672   1940   3490   3252   1741   2905   1137   ±   88   1756   ±   87   2033   ±   94   3624   ±   250
2090   1268   1614   1819   3639   3493   1663   3019   1135   ±   98   1690   ±   100   1908   ±   111   3805   ±   293
2100   1254   1576   1649   3751   3731   1574   3136   1127   ±   106   1633   ±   110   1734   ±   124   3938   ±   334

Hi sorry new to the forum. Long time lurker but had a question. The data presented in the 2.6 column it is as if we continued on the path of the current amount emissions of CO2 and Methane and then each sequential line to the right is if we were to increase in amounts being thrown into the atmosphere or is there some type of mitigation process in there i'm not seeing in 2.6 and 4.5? Clearly 8.5 is the most ambitious of them.

Thanks,
Tylor
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: kassy on September 29, 2020, 01:44:12 PM
Welcome Tylor.

Not sure if i would call 8.6 the most ambitious. It is the one where we emit most carbon.

You can read more in post #124 (and some below that):
Skepticalscience has a great article on the RCPs:

https://skepticalscience.com/rcp.php?t=3 (https://skepticalscience.com/rcp.php?t=3)

Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: SimonF92 on September 29, 2020, 01:51:48 PM
If your ambition was to destroy the Arctic as it currently exists, then RCP 8.5 would be the best
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Ken Feldman on September 29, 2020, 06:37:46 PM

Hi sorry new to the forum. Long time lurker but had a question. The data presented in the 2.6 column it is as if we continued on the path of the current amount emissions of CO2 and Methane and then each sequential line to the right is if we were to increase in amounts being thrown into the atmosphere or is there some type of mitigation process in there i'm not seeing in 2.6 and 4.5? Clearly 8.5 is the most ambitious of them.

Thanks,
Tylor

Tylor,

The RCPs are "representative concentration pathways" and each present a series of inputs for running climate simulations in models.  They're meant to represent a pattern of climate forcings, not really a forecast of future emissions.  So we'll never be entirely on one path or another.

The number at the end of the RCP is the radiative forcing in the year 2100.  So RCP 2.6 would see 2.6 watts per meter of forcing while RCP would have 8.5 watts per meter in 2100.

The pattern of forcings over the years is broadly described in each of the scenario descriptions.  RCP 8.5 assumes continued growth in fossil fuel emissions, including burning coal at an increasing rate, for the rest of the century.  RCP 2.6 assumes we began reducing non-CO2 greenhouse gas emissions, especially methane, in 2011 (which we haven't), we reach a peak in CO2 emissions around 2040 and then decline and use Negative Emissions Technologies to reduce CO2 concentrations from 2050 through 2100.  RCPs 4.5 and 6.0 assume a peak of CO2 emissions in the second half of the century and then stabilization of concentrations toward the end of the century.

A good summary in easy to read format is available at skepticalscience.org at this link:

https://www.skepticalscience.com/rcp.php (https://www.skepticalscience.com/rcp.php)

That website has some very useful graphics that show the assumed emission trajectories in each of the scenarios:

(https://skepticalscience.com/pics/emissions-graph-rpc.PNG)

The assumed atmospheric concentrations:

(https://static.skepticalscience.com/pics/ghg-concentrations-small.gif)

One of the interesting features of all of the RCPs, which were developed about 15 years ago, is that they assumed that renewable energy would be too expensive to deploy extensively.  This is shown in another image at the skeptical science article:

(https://static.skepticalscience.com/pics/energy-sources-2100.PNG)

Of course, wind and solar are now cheaper than coal and competitive with natural gas, so these assumptions are way too pessimistic.  By 2030, almost all new energy investment will be wind and solar (about 67% is now, with coal seeing almost no new investment the past two years), so by 2050, almost no fossil fuel power plants will be operating. 

Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: so_whats_happening on September 30, 2020, 05:47:43 AM

Hi sorry new to the forum. Long time lurker but had a question. The data presented in the 2.6 column it is as if we continued on the path of the current amount emissions of CO2 and Methane and then each sequential line to the right is if we were to increase in amounts being thrown into the atmosphere or is there some type of mitigation process in there i'm not seeing in 2.6 and 4.5? Clearly 8.5 is the most ambitious of them.

Thanks,
Tylor

Tylor,

The RCPs are "representative concentration pathways" and each present a series of inputs for running climate simulations in models.  They're meant to represent a pattern of climate forcings, not really a forecast of future emissions.  So we'll never be entirely on one path or another.

The number at the end of the RCP is the radiative forcing in the year 2100.  So RCP 2.6 would see 2.6 watts per meter of forcing while RCP would have 8.5 watts per meter in 2100.

The pattern of forcings over the years is broadly described in each of the scenario descriptions.  RCP 8.5 assumes continued growth in fossil fuel emissions, including burning coal at an increasing rate, for the rest of the century.  RCP 2.6 assumes we began reducing non-CO2 greenhouse gas emissions, especially methane, in 2011 (which we haven't), we reach a peak in CO2 emissions around 2040 and then decline and use Negative Emissions Technologies to reduce CO2 concentrations from 2050 through 2100.  RCPs 4.5 and 6.0 assume a peak of CO2 emissions in the second half of the century and then stabilization of concentrations toward the end of the century.

A good summary in easy to read format is available at skepticalscience.org at this link:

https://www.skepticalscience.com/rcp.php (https://www.skepticalscience.com/rcp.php)

That website has some very useful graphics that show the assumed emission trajectories in each of the scenarios:

(https://skepticalscience.com/pics/emissions-graph-rpc.PNG)

The assumed atmospheric concentrations:

(https://static.skepticalscience.com/pics/ghg-concentrations-small.gif)

One of the interesting features of all of the RCPs, which were developed about 15 years ago, is that they assumed that renewable energy would be too expensive to deploy extensively.  This is shown in another image at the skeptical science article:

(https://static.skepticalscience.com/pics/energy-sources-2100.PNG)

Of course, wind and solar are now cheaper than coal and competitive with natural gas, so these assumptions are way too pessimistic.  By 2030, almost all new energy investment will be wind and solar (about 67% is now, with coal seeing almost no new investment the past two years), so by 2050, almost no fossil fuel power plants will be operating.

I appreciate the amazing response to this my wording may not have been the best to use but this truly helped me understand and I thank you for that. I see there may be a few who may dislike my approach to speaking about these things, unfortunately that is on them. Ill remove myself at this point from the conversation and going back to lurking.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Stephan on October 06, 2020, 08:41:14 PM
To finalize my update on greenhouse gases here is the summary of the four postings in the individual gas concentration threads.

More radiative forcing of the "NOAA gases" (CO2, CH4, N2O, SF6) in June 2020 than in June 2019, but less than in May 2020, because CO2 and CH4 reach their seasonal maximum in May.

The values [W/m²], change to May 2020 and change to June 2019:
CO2 2.161    (- 0.009)    (+ 0.031)   
CH4 0.519    (- 0.001)    (+ 0.005)
N2O 0.205   (+ 0.000)    (+ 0.003)
SF6  0.0053 (+ 0.0000)  (+ 0.0001)
sum  2.891  (- 0.009)   (+ 0.040) (rounding differences)

The relative annual increase is 1.43 %, a little bit higher than May 2020.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Juan C. García on October 07, 2020, 12:27:07 AM
To finalize my update on greenhouse gases here is the summary of the four postings in the individual gas concentration threads.

More radiative forcing of the "NOAA gases" (CO2, CH4, N2O, SF6) in June 2020 than in June 2019, but less than in May 2020, because CO2 and CH4 reach their seasonal maximum in May.

The values [W/m²], change to May 2020 and change to June 2019:
CO2 2.161    (- 0.009)    (+ 0.031)   
CH4 0.519    (- 0.001)    (+ 0.005)
N2O 0.205   (+ 0.000)    (+ 0.003)
SF6  0.0053 (+ 0.0000)  (+ 0.0001)
sum  2.891  (- 0.009)   (+ 0.040) (rounding differences)

The relative annual increase is 1.43 %, a little bit higher than May 2020.
Thanks for your posts, Stephan.  :)
Is there a way to change the final value to CO2e, in ppm?
And a way to compare the sum of them with what we have, by example, versus 1980?
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: wolfpack513 on October 07, 2020, 02:46:28 PM
Using ESRL AGGI you can extrapolate the annual CO2 equivalent down to a monthly value.
With the seasonal cycle in GHGs, I would only use year over year monthly changes.

A radiative forcing increase of 0.05 Watts/m2 is worth ~5 ppm of CO2 equivalent.
https://www.esrl.noaa.gov/gmd/aggi/aggi.html
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: nanning on October 08, 2020, 06:34:28 AM
Thanks wolfpack513.
Do you know what methane CO₂e factor is used? It can differ hugely (ca. 20-100) and is therefore a bit arbitrary. It would be good to post that number also for clarity.
Aerosols are not included because they are spatially heterogeneous and short-lived. But it's constantly being replenished with new aerosols. I understand that a global figure is impossible, but it sure is part of integrated radiative forcing. Can a global map be made?
At what height in the atmosphere is the radiative forcing valid? Top of troposphere or at sea level?
Perhaps I've misunderstood.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Ken Feldman on October 09, 2020, 12:30:08 AM
Thanks wolfpack513.
Do you know what methane CO₂e factor is used? It can differ hugely (ca. 20-100) and is therefore a bit arbitrary. It would be good to post that number also for clarity.
Aerosols are not included because they are spatially heterogeneous and short-lived. But it's constantly being replenished with new aerosols. I understand that a global figure is impossible, but it sure is part of integrated radiative forcing. Can a global map be made?
At what height in the atmosphere is the radiative forcing valid? Top of troposphere or at sea level?
Perhaps I've misunderstood.
 

Since the RCPs show the concentrations of greenhouse gases that were used to define the forcings, we can directly compare measured concentrations to the concentrations used to build the RCPs.  We can ignore the global warming potentials and assumed timeframes.


Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: nanning on October 09, 2020, 07:51:00 AM
Thanks Ken (I am not very familiar with RCP), but where do they measure the radiative forcing? Does it include aerosols (especially in the NH)?
Furthermore you seem to say that knowing the CO₂e is not important? I think actually it is for defining GHG budgets for certain climate/GMST outcomes.
And I don't understand "concentrations of greenhouse gases that were used to define the forcings". The forcings are defined?
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: oren on October 09, 2020, 11:09:45 AM
Nanning, if you wish to learn more about Radiative Forcing, Global Warming Potential and other related issues, you will be smarter (and much more confused) if you read this old thread here (https://forum.arctic-sea-ice.net/index.php/topic,2383.msg168462.html#msg168462).
You will discover the difference between concentration-based calculations (=Radiative Forcing) and emission-based calculations (=GWP). But the confusion will stem from the big argument between Ned W and ASLR. Ned W was out to prove at all costs that methane is not important using narrowly defined science (I think he was wrong and tried to explain why, as you'll see if you read to the end). ASLR was out to prove the opposite at all costs but used very widely defined science and thus they talked past each other to no avail. Still I learned a lot from that thread.

In essence:
* RF is derived from a given concentration compared to a baseline concentration. For example CO2 today vs. CO2 one year ago.
* GWP is derived by assessing what would happen given an x amount of emissions, some of which would be absorbed or decayed over time. For example, a pulse of 1GT of methane.
* And my position was that to discuss RF properly one must calculate a baseline RF - concentration now compared to concentration if humanity ceased all emissions, thus taking into account the emission and decay rates separately, rather than lumping them together.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: nanning on October 09, 2020, 06:05:35 PM
Thanks oren. I haven't read anything I didn't know (RF can be expressed in other units as well imo). Perhaps I have problems in connecting them to my questions.
Am I right in thinking that GWP is not only from emissions but also from loss of albedo?
I have read many times about the multiple of radiative forcing effect that methane gives compared to carbon dioxide. I've read numbers from 20-100 depending on the time-frame.
I have no 'agenda'.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Ken Feldman on October 09, 2020, 07:18:23 PM
Nanning,

I was responding in the context of this thread, which uses the weekly or monthly observations of greenhouse gas concentrations and then tries to determine which of the RCPs we are closest too.

The thread got a bit confusing because they refer to CO2e in the title.  As Oren pointed out, CO2e is a way to compare the global warming potential of different greenhouse gases as they are emitted.  It doesn't really work for concentrations, because of the different lifetimes of the greenhouse gases.

As you note, methane has a short lifetime compared to CO2 (11 to 12 years versus 100+).  So the calculation for it's CO2e can range from 25 (which I think is implied by the calculations used in NOAA's greenhouse gas index) if you're looking at climate change over a century, to 80 for it's warming over 20 years.  The long term global warming for methane has been revised up to 34 in the past few years because of the feedbacks methane causes in atmospheric chemistry as it decays.

One of the shortcomings of converting a short term greenhouse gas to a CO2e is that it doesn't accurately portray the warming effects of the short term gas over time.  So a new method to calculate global warming potential, GWP*, has been proposed.  This article explains it better.

https://www.carbonbrief.org/guest-post-a-new-way-to-assess-global-warming-potential-of-short-lived-pollutants (https://www.carbonbrief.org/guest-post-a-new-way-to-assess-global-warming-potential-of-short-lived-pollutants)

Quote
7 June 2018
Guest post: A new way to assess ‘global warming potential’ of short-lived pollutants
Dr Michelle Cain

Quote
At the moment, it is not obvious how this will be done. In a new paper published in npj Climate and Atmospheric Science, my co-authors and I address one of the stocktake’s key stumbling blocks – the treatment of all greenhouse gases as “CO2-equivalent”, using a metric known as “global warming potential” (GWP). This misrepresents the impact of short-lived climate pollutants, such as methane, on future warming.

We show that modifying the use of GWP, so that it accounts for the differences between short- and long-lived gases, can better link emissions to warming. This means that the true impact of an emission pathway on global temperature can be easily assessed. For countries with high methane emissions – due to, say, agriculture – this can make a huge difference to how their progress in emission reductions is judged.

Greenhouse gas emissions are commonly presented in units of billion tonnes of carbon dioxide equivalent (Gt CO2e). The de facto way of converting non-CO2 emissions to CO2e is to multiply the gas by its GWP100 (global warming potential over 100 years). The value of GWP100 for methane (CH4) from the last IPCC assessment report is 28. This means that methane has 28 times as much “global warming potential” as CO2, so 1Gt CH4 equates to 28 GtCO2e.

This masks the fact that 1 GtCH4 has a strong warming influence when it is first emitted, which then diminishes rapidly over a few decades. This is because chemical reactions cause it to be removed from the atmosphere, with a half life of about a decade. So, at the end of that 100 years, that methane is no longer causing strong warming, because it has almost all been destroyed.

By comparison, a 28Gt “equivalent” emission of CO2 would effectively persist in the atmosphere for centuries or longer, continuing to cause warming at almost the same rate as when it was first released. This shows how the two emissions are not really equivalent, which has important consequences if GWP100 is applied to future emissions scenarios inappropriately.

For example, the figure below shows some simplified emissions scenarios for CO2 and methane, with the resulting temperature responses. If methane is held constant (middle panel), temperature will remain constant. This is because the short lifetime of methane means atmospheric concentrations will remain constant with constant sources, assuming constant sinks. (Note that this is a simplification to demonstrate the direct warming from methane. Secondary effects from carbon cycle feedbacks following a methane emission can also cause smaller amounts of additional warming.)

However, a stable CO2 emission pathway leads to year-on-year increases in warming, because the CO2 accumulates in the atmosphere. If methane emissions are simply multiplied by GWP100 to generate CO2e, this would look like a warming pathway, when it should lead to stable temperatures.

(https://www.carbonbrief.org/wp-content/uploads/2018/06/Screen-Shot-2018-06-06-at-16.38.28-1024x573.png)

Quote
Even more pronounced is the impact when emissions are falling (right panel). For methane, falling emissions leads to cooling. Converting to CO2e would imply warming until the emissions hit zero. Ambitious mitigation scenarios could, therefore, give the impression of giving rise to warming instead of cooling from methane, if expressed using GWP100.

Quote
By using GWP*, emissions of methane expressed as CO2e relate much more closely to temperature response. This can be seen in the figure below. The top panels use GWP100, while the lower panels use GWP*. The left panels show annual emissions of CO2e (upper left) and CO2e* (lower left). In the right panels, temperature is shown in the dashed lines alongside the cumulative CO2e/CO2e* emissions in the solid lines.

Quote
Consider a power station and a herd of cows. A power station emits CO2 by burning fossil fuels. This CO2 is taxed. When it shuts down permanently, it emits no more CO2, so is no longer taxed. However, the CO2 already emitted continues to affect the climate for hundreds, or potentially, thousands of years. So even after closing down, that power station still contributes to holding up global temperatures because of the CO2 that remains in the atmosphere.

Now to the cows. A herd of cows emits methane, so the farmer is taxed for those emissions. If the herd remains the same size with the same methane emissions every year, it will maintain the same amount of additional methane in the atmosphere year on year. In terms of its contribution to warming, this is equivalent to the closed power station.

The power station pushed up global temperatures when it was running in the past, just as the farmer’s great-grandparent pushed up global temperatures when they were building up the herd of cattle. But neither a steady herd of cattle nor a defunct power station is pushing up global temperatures any more.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: nanning on October 10, 2020, 10:02:41 AM
Thank you Ken for explaining and providing the linked article. I understand better now :).
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: oren on October 10, 2020, 10:41:55 AM
The only problem is that the planet is not in energy balance, and the herd of cows helps maintain methane levels that lead to further warming until the new balance is reached.
While the GWP of methane assume a pulse of methane being absorbed and decayed rather quickly, in truth the level of methane has been stable or rising. As humanity's problem is short-term and not just long-term, it should be realized that methane will help push the planet above 2C and into huge positive feedbacks, and then it will not help much that the methane decayed at some point when we stopped maintaining (and even increasing) its atmospheric level.
Thus the downplaying of methane using RF and GWP justifications is IMHO very wrong. IMHO Co2eq of methane should be calculated by the short-term warming it induces. I think this is what Stephan does.
However, emission of methane should be evaluated in comparison not to the resulting growth in methane concentrations over a year, but compared to the baseline where methane should have decayed from a year ago. I think this is where some posters are missing the issue. However the emission part is probably off-topic here, so I'll avoid further discussion.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Stephan on October 10, 2020, 10:00:51 PM
Is there a way to change the final value to CO2e, in ppm?
And a way to compare the sum of them with what we have, by example, versus 1980?

Here you go, Juan:

I converted the radiative forcing back into CO2 equivalents. Please find the values for each January of the following years. Please also keep in mind that these numbers only represent the four "NOAA gases" CO2, CH4, N2O and SF6. Therefore the "true" value is higher than that.

Jan 1980 372.2 ppm
Jan 1990 394.8 ppm (+22.6 ppm or +6.1%)
Jan 2000 415.7 ppm (+20.9 ppm or +5.3%)
Jan 2010 440.4 ppm (+24.7 ppm or +5.9%)
Jan 2020 473.4 ppm (+33.0 ppm or +7.5%)

The latest value (June 2020) represents a CO2 equivalent of 477.1 ppm (annual increase of 3.6 ppm). I will report this equivalent in future, once a month, when NOAA adds the latest monthly averages to its website.

It is obvious that we are on an exponential track. The smaller increase during the 1990s is a consequence of the breakdown of the Soviet Union's and its allies' economy after the revolutions of 1989/90. 
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: kassy on October 11, 2020, 01:34:03 AM
That is quite the progression.

Now there were always two ways of looking at it. OK so 1 you have got a number for  the CO2eq but what does it actually mean.

What does it mean for the actual world?

For this you can look to graphs and theories or alternatively you look out of the window and see what is already happening.

We will lose the arctic ice some time the next decade , we have already comittted to a whole lot of sea level rise. Somewhere out there we are comitting to a protocol to stop some dangerous undefined future climate change while ignoring where we already are.

And we are on the edge of going from ice house to hot house earth. So much things will change so drastically before we do anything meaningful.

Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: nanning on October 11, 2020, 09:48:10 AM
Thanks for that, Stephan.
What CO₂e factor do you use for methane?
I would expect the total to be more than a bit above 500ppm, using a short-term factor of 80.

--

I agree with kassy and oren.
But 'we' do meaningful stuff, we aren't doing nothing. But it is not mitigation but the opposite; worsening the problem even more. Year in year out. We can't even stop deforestation. Governments have no power over large international companies and these companies WILL NOT STOP WITH DESTRUCTION because their investors want more profit of them. Nice system eh? Out of control, just like the climate and biosphere destruction.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Stephan on October 11, 2020, 06:59:19 PM
I do not use a factor for methane, but I convert the actual concentration into radiative forcing (values listed in my posting). I sum up all the radiative forcings of the four "NOAA gases" and re-convert them into CO2 equivalents using the same formula I use to convert CO2 concentrations into radiative forcing.

There has been a lengthy discussion how to do it some months ago in this thread, because before that I had used the factors 28 and 80. But this is scientifically not correct as I was told.
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Stephan on November 06, 2020, 07:42:33 PM
To finalize my update on greenhouse gases here is the summary of the four postings in the individual gas concentration threads.

More radiative forcing of the "NOAA gases" (CO2, CH4, N2O, SF6) in July 2020 than in July 2019, but less than in June 2020, because CO2 and CH4 reach their seasonal maximum in May.

The values [W/m²], change to June 2020 and change to July 2019:
CO2 2.136    (- 0.025)    (+ 0.034)   
CH4 0.519    (- 0.000)    (+ 0.005)
N2O 0.206   (+ 0.001)    (+ 0.004)
SF6  0.0054 (+ 0.0001)  (+ 0.0002)
sum  2.865  (- 0.026)    (+ 0.043) (rounding differences)

The relative annual increase is 1.49 %, a little bit higher than June 2020.

This recalculates to a CO2eq of 474.8 ppm (annual increase of 3.7 ppm).
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Tom_Mazanec on November 06, 2020, 10:45:00 PM
But aren't there other GHGs, Stephan, like CFCs and HFCs?
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Stephan on November 06, 2020, 10:50:22 PM
Yes, of course. See my posting Oct 10, where I state that the true value is higher than that I had just posted. I only take care of these four "NOAA gases" because their concentration is followed on a daily (CO2) or monthly basis (CH4, N2O, SF6) by NOAA.
In the end I think that the absolute value itself is not too interesting. So I focus on the increase which I think is concerning, and please do not forget the slightly exponential development of all of these four gases, where we all should have taken a U-turn decades ago...
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: Ken Feldman on November 09, 2020, 06:46:12 PM
But aren't there other GHGs, Stephan, like CFCs and HFCs?

SF6 represents the "15-Minor" greenhouse gases that NOAA tracks.  As you can see by the image below,  CO2 represent the bulk of the warming and CH4 most of the rest.  The 15 minor, with the CFCs that have been reduced due to the Montreal Protocol to protect the ozone layer, combined with N2O roughly equal the forcing from CH4.

(https://www.esrl.noaa.gov/gmd/aggi/aggi.fig4.png)
Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: kassy on November 13, 2020, 05:37:56 PM
So i ran into this article:

Quote
Science journal U-turns on claim that global warming cannot be stopped after British experts cry foul

Richard Betts, a professor of climate impacts at the University of Exeter:
 'While the press release suggests that global warming may now be unstoppable for centuries, the model result in this paper is not convincing as support for that message.

Andrew Watson, a Royal Society research professor at the University of Exeter, said that he did not agree with the press release describing global warming as potentially catastrophic, 'given that it occurs over 500 years'.

Some scientists hailed Scientific Reports' findings as significant. 'This study provides evidence for what we don't want to hear: that global heating may have already become self-reinforcing, and that we have therefore passed the point of no return for halting long-term climate change,' Phillip Williamson of the University of East Anglia said.

https://www.dailymail.co.uk/sciencetech/article-8942619/Ending-greenhouse-gas-emissions-not-stop-global-warming.html

The actual article:
An earth system model shows self-sustained melting of permafrost even if all man-made GHG emissions stop in 2020

https://www.nature.com/articles/s41598-020-75481-z

The model they use is fairly simple to put it mildly:
Abstract. We have made a simple system dynamics model, ESCIMO (Earth System Climate Interpretable Model), which runs on a desktop computer in seconds and is able to reproduce the main output from more complex climate models. ESCIMO represents the main causal mechanisms at work in the Earth system and is able to reproduce the broad outline of climate history from 1850 to 2015.

https://esd.copernicus.org/articles/7/831/2016/


What did they find? Some background:

Quote
Method
We used ESCIMO to simulate the development of the global climate system from 1850 to 2500 under different assumptions concerning the emission of man-made GHGes. ESCIMO is a system dynamics model that includes representations of the world’s atmosphere, oceans, forests (and other land types), biomass—and their interactions. It is described here5. The source code with documentation is available online6.

In the first simulation reported here, “Scenario 1”, we assume that humanity reduces man-made GHG emissions to zero by 2100. In the second simulation, “Scenario 2”, we assume that emissions are cut much faster—to zero in 2020. In both cases man-made emissions remain zero thereafter.

Results
The result is shown in Fig. 1. In both scenarios the global temperature keeps rising for hundreds of years—to around + 3 °C in 2500—after a temporary decline in this century in conjunction with the decline in man-made emissions (Fig. 1c).

So where does effect come from:


Scenario 1
Scenario 1 describes the result when we assume that man-made emissions peak in the 2030s and decline to zero in 2100 (see Fig. 1, solid lines). This is the “most likely” scenario as described here7.

Quote
The historical part of the simulation (1850–2015) and the ensuing 60 years (2015–2075) are intuitive and understandable. Rising emissions of man-made GHGes lead to an increase in the concentration of GHGes in the atmosphere (Fig. 1b,d). This, in turn, leads to a rise in the global average surface temperature because GHG molecules block outgoing long-wave (heat) radiation from the surface. The warming is enhanced by the increased amount of water vapour which accumulates in a warmer atmosphere because H2O is a strong greenhouse gas which blocks other frequencies (Fig. 1f). The warming leads to rising sea levels because of thermal expansion and glacier run-off. Difficult to detect, but of great significance for the years beyond 2150, surface albedo starts a slow and smooth decline as the ice and snow cover melts, making the planet darker and leading to more absorption of short-wave (SW) radiation in the surface (Fig. 1h).

So what happens in the realistic scenario:

Quote
In Scenario 1 the temperature passes a temporary peak around 2075 at + 2.3 °C above pre-industrial times. The temperature then falls for 75 years (2075–2150) to + 2 °C. There are two reasons: (a) the concentration of GHGs in the atmosphere declines, and (b) heat is used to melt on-land glaciers and Arctic ice.

Furthermore, the concentration of CO2 declines (from its all-time peak of 450 ppm in 2050) through two processes: (a) CO2 is gradually absorbed in the ocean surface (and later transported into the deep ocean), and (b) CO2 is gradually absorbed in the biosphere. CO2 in the atmosphere is converted through photosynthesis into biomass in living matter and soils at a rate that is determined by the temperature and the amount of CO2 in the atmosphere. By 2150 all on-land snow and ice are gone in ESCIMO Scenario 1 (except in Greenland and Antarctica, which require thousands of years to melt).

While the developments to 2150 are understandable, developments in ESCIMO beyond 2150 are more surprising (counter-intuitive). As shown in Fig. 1 the temperature once more starts rising. The surprising fact is that this rise takes place 50 years after man-made emissions have ceased, and after the concentration of CO2 in the atmosphere has been significantly reduced through absorption in oceans and biomass.

The explanation (in ESCIMO) is as follows. While GHG concentrations—and thus their forcings—fall from 2070 to 2150, the effect of surface albedo continues on its smooth upward path throughout this period. Its time development is much slower than that of GHGes. It is the result of mainly Arctic ice melting—but it has enough ‘momentum’ to push the climate system back onto a path of rising temperatures, with its secondary effects of raising humidity and permafrost melting, which then in turn help the system become warmer and warmer, even if man-made GHG emissions are zero. A cycle of self-reinforcing processes is established. See Fig. 2a.

So the model is really simple but is there anything in the IPCC models to counter these effects? Or to put it more simply what do they show for the same trajectories?

Essentially this a very simple general model that shows us we are already in dangerous territory because we overshot whatever the goal was to keep the permafrost stabile.

Title: Re: Where are we now in CO2e , which pathway are we on?
Post by: wehappyfew on November 13, 2020, 05:51:14 PM
Assuming we retain any kind of technology, we're going to end up doing some kind of solar radiation blocking, either stratospheric aerosols, or space based shades.

What will be the consequences? Who knows.

The chief source of problems is solutions to previous problems.