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Ned W

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Re: Global Surface Air Temperatures
« Reply #1550 on: August 28, 2017, 01:59:08 AM »
Jai, no.  Start with the basics.  You need to learn how to walk before you can run.

The first question is, do you understand the meaning of "radiative forcing"?

Try to calculate it for some easy case.  A good one to start with is the Myhre et al (1998) approximation for CO2.  Go to the wikipedia page for "radiative forcing" and scroll down to the section on "forcing due to atmospheric gas".

For the baseline CO2 concentration, use preindustrial (278 ppm).  For 2017 CO2 concentration, use 402 or 404 or whatever ppm. 

The number you are calculating, dF, represents the change in forcing by CO2 in 2017 relative to 1750.

Now, look up the CO2 concentration for some other year, and use that as C-sub-0 in the formula.  For example, the year 2000. 

When you use the concentration for the year 2000 as C-sub-0 and the concentration for 2017 as C ...

... what does dF represent?

Answering that question will help you understand this.

jai mitchell

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Re: Global Surface Air Temperatures
« Reply #1551 on: August 28, 2017, 02:34:32 AM »
Instead of your attempts to calculate the total anthropogenic forcing, I recommend you use the free data that is provided by PIK Potsdam and used by the IPCC.  The value of total CH4 forcing quoted in the Etminan (2016) of 0.48036474 W/m^s can be found there.  That is the value he used and the value that you can then easily adjust to see what the effect is on the Total Anthropogenic forcing value (which is slightly more than the GHG forcing value even though Total Aerosols are extracted from the total).

you can access the data here:  http://www.pik-potsdam.de/~mmalte/rcps/20c3m.htm

I fully understand what you are trying to say and I agree, under the RCP 8.5 projections through 2035 the series with CH4 adjustments that fit the Etminan (2016) analysis are only increased by 0.05 W/m^2 over the increase in the non-adjusted column. 

However, the TOTAL ADDITIONAL forcing over the non-adjusted column at 2035 is 0.177 W/m^2  or 118,000 Hiroshima bombs per day of extra absorbed radiation.
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Ned W

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Re: Global Surface Air Temperatures
« Reply #1552 on: August 28, 2017, 02:46:02 AM »
You can lead a horse to water but you can't make him drink.  Well, I led Jai to the edge of the water, anyway.

Seriously, Jai.  Go back, read my previous post, and try doing the calculations for yourself.  Don't tell me about hiroshima bombs or RCP whatever.  Just calculate dF for CO2 from 1750-2017, and then from 2000-2017.  Then, when you've done the math, you can try to put it into words.

That's the beginning.  There's more later.

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Re: Global Surface Air Temperatures
« Reply #1553 on: August 28, 2017, 06:37:15 AM »
You can lead a horse to water but you can't make him drink.  Well, I led Jai to the edge of the water, anyway.

Seriously, Jai.  Go back, read my previous post, and try doing the calculations for yourself.  Don't tell me about hiroshima bombs or RCP whatever.  Just calculate dF for CO2 from 1750-2017, and then from 2000-2017.  Then, when you've done the math, you can try to put it into words.

That's the beginning.  There's more later.


Ned,

You are attempting (poorly) to reproduce work that has already been done by people much more talented (and qualified) than you are.

Do yourself a favor and download the spreadsheets that include EVERY greenhouse gas that is being released through human activity.

http://www.pik-potsdam.de/~mmalte/rcps/

When you understand how top-of-atmosphere radiation balances are determined, and their components, then you will understand why the revision upward of CH4 RF is so troubling.  It means that the NEGATIVE forcing values in TOA are stronger than has been previously accounted for and indicates much greater long-term warming potential AT CURRENT GHG abundances, once those negative forcing values are removed through fossil fuel consumption declines. 

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Ned W

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Re: Global Surface Air Temperatures
« Reply #1554 on: August 28, 2017, 02:47:39 PM »
Yesterday, I wrote:

: Ned W
I did the calculations in a hurry, and need to check them over.  But it seems to be possible that over the next couple of decades, the new methods for calculating radiative forcing could well lead to a result that is actually lower than the old methods. 


I re-checked my work, found a minor error that didn't significantly alter the results.  Sure enough, as we'll see below, the Etminan (2016) updated forcings have a pretty small effect over the next few decades, and there are plausible scenarios in which they actually lower the magnitude of the sum of the three forcings (CO2, CH4, N2O) relative to current concentrations.

Yesterday I was working with observed concentrations from CSIRO/Cape Grim.  It is probably better to use NOAA's global concentrations, though the annual averages only run through 2016.

As a reminder, what I'm doing is directly calculating the radiative forcing for the three molecules included in Etminan (2016), using both the "old" (Myhre 1998/IPCC) and "new" (Etminan 2016) versions of the forcing equations. 

+++++++++++++++++++++++++++++++++

First, the historical period (forcing in 2016 relative to pre-industrial).  Concentration data are from IPCC (for pre-industrial) and NOAA ESRL (1979-2016).  The new forcing calculations increase/decrease the previous results as follows:

CO2:  +0.616%   
CH4: +23.236%
N2O: -3.429%   
Total: +4.626%

Looking specifically at the forcing over a shorter time period, the effects of the Etminan adjustment on the 2000-2016 forcing are:

CO2:  -0.624%%   
CH4: +22.896%
N2O: -1.635%   
Total: -0.408%

So Etminan (2016) increased the forcing over the entire historical period by 4.6%, but decreased the "recent" forcing (2016 relative to 2000) by 0.4%

+++++++++++++++++++++++++++++++++

Next, let's look at the future, using the IPCC RCP 6.0 and 8.5 concentration models.  Here's RCP 6.0 for various time periods into the future, all with forcings relative to 2017 (we're looking at future warming here):

CO2, 2035:  -0.653%
CH4, 2035:  +23.036%
N2O, 2035:  -1.753%
Total, 2035:  -0.237%

CO2, 2100:  +2.011%
CH4, 2100:  +22.429%
N2O, 2100:  -2.075%
Total, 2100:  +1.013%

Under RCP 6.0, Etimnan reduces the future forcing at 2035 by 0.2%, but increases it at 2100 by 1.0%

+++++++++++++++++++++++++++++++++

And here's RCP 8.5, again looking at the forcings in 2035 and 2100 relative to now:

CO2, 2035:  -0.340%
CH4, 2035:  +22.108%
N2O, 2035:  -2.760%
Total, 2035:  +2.653%

CO2, 2100:  +4.550%
CH4, 2100:  +18.335%
N2O, 2100:  -7.702%
Total, 2100:  +5.304%

So in RCP 8.5, Etimnan increases the future forcing (relative to now) at 2035 by 2.7%, and at 2100 by 5.3%

+++++++++++++++++++++++++++++++++

Here are the "old" (IPCC/Myhre 1998) and "new" (Etminan 2016) forcings (sum of CO2, CH4, N2O) relative to 2017 concentrations:



PS to Jai:  I've been working with CMIP5 concentrations and outputs for years, thanks. 
----------------------------------
Methodological notes:
Historical data (1979-2016) here (via here)
RCP 6.0 and 8.5 concentrations here
Equations for RF from Myhre/IPCC here
Equations for RF from Etminan here
« Last Edit: August 28, 2017, 03:25:50 PM by Ned W »

Ned W

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Re: Global Surface Air Temperatures
« Reply #1555 on: August 28, 2017, 04:31:14 PM »
See Graph of the Actual Forcing Series with Etminan Revision, The same historic forcing values were used for AR4 and AR5 (as far as I remember).


Just curious, Jai -- where did you find that graph?

I'm asking because the "Etminan" lines don't actually seem to be based on the equations given in Etminan (2016).  They appear to be slightly too high. 

I used your graph as background, and plotted my calculated values for RF relative to 1765 on top of it (as dots).  Note that the non-Etminan versions line up fine, but the Etminan ones don't match up.  That seems odd.



-----------------------------------------
Methodological note:
I used as input the concentrations from here.  I have not tried to calculate "total anthropogenic forcing" since I'm only looking at the three forcings included in Etminan 2016; so for the total I used PIK's value for TAF, subtracted the non-Etminan versions of the CO2/CH4/N2O forcings, and added back the Etminan versions. 

jai mitchell

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Re: Global Surface Air Temperatures
« Reply #1556 on: August 28, 2017, 08:17:39 PM »
See Graph of the Actual Forcing Series with Etminan Revision, The same historic forcing values were used for AR4 and AR5 (as far as I remember).


Just curious, Jai -- where did you find that graph?

I'm asking because the "Etminan" lines don't actually seem to be based on the equations given in Etminan (2016).  They appear to be slightly too high. 

I used your graph as background, and plotted my calculated values for RF relative to 1765 on top of it (as dots).  Note that the non-Etminan versions line up fine, but the Etminan ones don't match up.  That seems odd.



-----------------------------------------
Methodological note:
I used as input the concentrations from here.  I have not tried to calculate "total anthropogenic forcing" since I'm only looking at the three forcings included in Etminan 2016; so for the total I used PIK's value for TAF, subtracted the non-Etminan versions of the CO2/CH4/N2O forcings, and added back the Etminan versions. 



I took the historic 20th century data at PIK Potsdam for 2005 and adjusted the CH4 component according to Etminan.  I then added this adjustment to the Anthropogenic total.  I then applied this adjustment as a function of total CH4 abundance to the RCP 8.5 concentration values and again added to the difference to the anthropogenic forcing total values.

Methane is currently 1834 ppbv (actually slightly higher this value is 2016:  http://cdiac.ornl.gov/pns/current_ghg.html

RCP 8.5 abundance for 2016 is 1853 ppbv so the values I used for the graph are slightly higher than current totals (several year's worth of growth at current rates).
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jai mitchell

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Re: Global Surface Air Temperatures
« Reply #1557 on: August 28, 2017, 08:21:35 PM »
I think you should check your calculations.  The first value in the graph is the 2005 value that is specifically mentioned in the Etminan paper and the adjustment made there is the exact value that the paper calls for. 

So it is not low.
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Ned W

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Re: Global Surface Air Temperatures
« Reply #1558 on: August 28, 2017, 08:35:58 PM »
I took the historic 20th century data at PIK Potsdam for 2005 and adjusted the CH4 component according to Etminan.

"adjusted the CH4 component according to Etminan" meaning how?  Do you mean you used the equations in Etminan's Table 1 to calculate RF for CH4?  I'm puzzled about why your graph doesn't match my calculated values of RF, but don't see any obvious errors.

I then added this adjustment to the Anthropogenic total.

If you actually are calculating a new Etminan-style RF for CH4 and then adding it to the Total Anthro Forcing (TAF) I hope you're remembering to first subtract the "old" (non-Etminan) RF for CH4 from the TAF before adding your new one in.  Otherwise, you'll end up with double the CH4 forcing.

I then applied this adjustment as a function of total CH4 abundance to the RCP 8.5 concentration values and again added to the difference to the anthropogenic forcing total values.

OK, now you've really lost me.  I have no idea what you just said.

The normal way to make this graph would be to

(1) Plot the existing ("old") lines for CH4 forcing and TAF.

(2) Use Etminan Table 1 to calculate the updated CO2, CH4, and N2O forcings using the concentration values available from the same site you've been using (PIK).

(3) Subtract the "old" CO2, CH4, and N2O forcings from the TAF (conveniently, the PIK website you're using includes a separate column for the CO2/CH4/N2O total).  Then add your new versions of the three forcings back.  Plot the new version of this TAF, and the new version of the CH4 series on the graph, along with the "old" versions from (1).

If that's not what you're doing, I would gently suggest that you're doing it wrong.

Ned W

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Re: Global Surface Air Temperatures
« Reply #1559 on: August 28, 2017, 08:39:55 PM »
I think you should check your calculations.  The first value in the graph is the 2005 value that is specifically mentioned in the Etminan paper and the adjustment made there is the exact value that the paper calls for. 

So it is not low.

What "first value in the graph"?  The graph begins in 1987, not 2005.  What value from the paper?  The only occurrences of "2005" in the paper are in the years of references.

It's really hard to follow your work when you're so unclear about explaining what you've done.

jai mitchell

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Re: Global Surface Air Temperatures
« Reply #1560 on: August 28, 2017, 08:42:48 PM »
Yesterday, I wrote:

: Ned W
I did the calculations in a hurry, and need to check them over.  But it seems to be possible that over the next couple of decades, the new methods for calculating radiative forcing could well lead to a result that is actually lower than the old methods. 

I re-checked my work, found a minor error that didn't significantly alter the results. 
+++++++++++++++++++++++++++++++++

And here's RCP 8.5, again looking at the forcings in 2035 and 2100 relative to now:

CO2, 2035:  -0.340%
CH4, 2035:  +22.108%
N2O, 2035:  -2.760%
Total, 2035:  +2.653%

CO2, 2100:  +4.550%
CH4, 2100:  +18.335%
N2O, 2100:  -7.702%
Total, 2100:  +5.304%

So in RCP 8.5, Etimnan increases the future forcing (relative to now) at 2035 by 2.7%, and at 2100 by 5.3%

+++++++++++++++++++++++++++++++++

Quick note:

The RCP 8.5 value difference in 2016 between total GHG forcing and CO2 CH4 & N2O forcing is +.355 W/m^2 due to the contribution of trace gasses.
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Re: Global Surface Air Temperatures
« Reply #1561 on: August 28, 2017, 08:49:37 PM »
Sorry, I meant the Last value (2005) which is the value that is quoted in the Entminan paper abstract.

I meant to post this one.
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Ned W

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Re: Global Surface Air Temperatures
« Reply #1562 on: August 28, 2017, 09:00:36 PM »
Sorry, I meant the Last value (2005) which is the value that is quoted in the Entminan paper abstract.

I meant to post this one.

The number "2005" appears nowhere in the Etminan abstract.  The number "2005" appears nowhere in the entire Etminan paper except in references to two papers (Lean et al. 2005 and Forster et al 2005).

I still have no idea what you are doing.

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Re: Global Surface Air Temperatures
« Reply #1563 on: August 28, 2017, 09:40:42 PM »
Table S2 in the SI for Etminan (2016) contains a whole bunch of examples of calculations of dF for various combinations of CO2, CH4, and N2O.  It provided a handy way for me to check my calculations.  I copied the first 20 rows of Table S2, used them as inputs to my calculator, and compared my output to theirs.  The results were virtually identical, with only minor differences due to rounding:



So I can declare pretty confidently that my setup is working correctly.

Now, Jai Mitchell posted another graph.  I overlaid my calculations on it, and once again the non-Etminan ones line up exactly, while the Etminan ones are all offset:



In other words, on Jai's graphs, the lines where Jai could just copy data from PIK work fine, but the lines where Jai needed to calculate something are all screwed up.

At this point, I'm pretty much convinced that Jai has no idea what is going on here.  Jai's numbers don't work out and Jai's attempts to explain it don't make any sense.

More importantly, Jai doesn't seem to understand the question I'm trying to address in this thread, or the necessity of doing a certain type of calculation in order to answer it.

The question is: what is the impact of the new calculations for radiative forcing (RF) for CO2, CH4, and N2O on the expected radiative forcing from now to 2035, and from now to 2100?  That's the question I'm trying to answer (and have answered, actually):

Under RCP 6.0, Etminan reduces the future forcing at 2035 by 0.2%, but increases it at 2100 by 1.0%

Under RCP 8.5, Etminan increases the future forcing at 2035 by 2.7%, and at 2100 by 5.3%


for forcings relative to 2017. 



So, bottom line:  the revisions in Etminan 2016 have a pretty small impact on future radiative forcings from CO2, CH4, and N2O.  I think it's a great paper and I will be working with it further, but clearly we should not drastically change our expectations of future warming based on these new RF calculations.

« Last Edit: August 28, 2017, 09:53:58 PM by Ned W »

jai mitchell

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Re: Global Surface Air Temperatures
« Reply #1564 on: August 28, 2017, 09:55:31 PM »
Ned,

If you had any kind of reading comprehension you would know that my adjustments were for CH4 only.  If you have a different Ch4 adjustment then yours is off. 

In addition, your projections going forward on likely emissions scenarios contain the same bias inherent in the dataset that you used.  These do not include carbon cycle feedbacks, nor do they contain the potential hazards of CH4 emissions from expansion of fracking and natural gas consumption.

Finally, forcing on a long-term potential must include oxidation products and water vapor feedbacks which, again, your calculation neglects to include.  While the N2O adjustment is negative, a larger than projected increase in methane in future years will easily overcome this.  As will the feedbacks that you neglect to include in your long-term graph, though, of course this is inherent in the RCPs and not your fault.

Congratulations on being able to successfully reproduce someone else's work.  When you come up with something new and valid, I am sure I will see it.  For example, your expression of the combined CH4 N2O and CO2 combination forcing going down in future potential emissions scenarios is completely misguided since you don't include the long-term increase in forcing that the entire adjustment is really all about.

To neglect an equivalent increase in absorbed energy from current methane abundances found in Etminan that is equivalent to 118,000 hiroshima bombs per day being absorbed in the biosphere, ABOVE PREVIOUS PROJECTIONS, is short-sighted at best and this short-sightedness makes it quite obvious why you think 1 billion human deaths from climate catastrophe (and related conflict-induced and migration-induced) mortality is an overestimate.

You are a luke-warmer with a spreadsheet, congrats.

I will remind you that the values in Etminan are clearly stated in the abstract of the paper.

http://onlinelibrary.wiley.com/doi/10.1002/2016GL071930/pdf

RF is about 25% higher (increasing from 0.48Wm−2 to 0.61Wm−2


Since this is the increase value for CH4 forcing on my graph, they are indeed correct.  It is very telling that you think the values Entminan put in his abstract are wrong (according to YOUR calculations of his methodology).   
« Last Edit: August 28, 2017, 10:14:18 PM by jai mitchell »
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Re: Global Surface Air Temperatures
« Reply #1565 on: August 29, 2017, 12:57:56 AM »
A. Ned and Jai, I suggest a deep breath, cool down, we are talking science here.
B. Ned, I cannot follow your calculations nor Jai's references, but I have what feels like a stupid question which I'll risk asking:
It seems you are focused on the relative change of forcing from 2017 to 2035. So if the value of 2017 has been increased by 5% and so has the value for 2035, the relative change is 0%. However, in layman terms and as we are currently not in equilibrium, radiative forcing drives the speed of warming and not the actual temp. So if 2017 and 2035 are 5% higher we will get a faster rate of warming from 2017 onward, even if the relative change from 2017 to 2035 is 0%. If I press the gas pedal harder now and continue to do so with no change, my car will accelerate faster. Am I getting this wrong? Or am I misunderstanding what you are trying to say?

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Re: Global Surface Air Temperatures
« Reply #1566 on: August 29, 2017, 02:24:30 AM »
A. Ned and Jai, I suggest a deep breath, cool down, we are talking science here.
B. Ned, I cannot follow your calculations nor Jai's references, but I have what feels like a stupid question which I'll risk asking:
It seems you are focused on the relative change of forcing from 2017 to 2035. So if the value of 2017 has been increased by 5% and so has the value for 2035, the relative change is 0%. However, in layman terms and as we are currently not in equilibrium, radiative forcing drives the speed of warming and not the actual temp. So if 2017 and 2035 are 5% higher we will get a faster rate of warming from 2017 onward, even if the relative change from 2017 to 2035 is 0%. If I press the gas pedal harder now and continue to do so with no change, my car will accelerate faster. Am I getting this wrong? Or am I misunderstanding what you are trying to say?

Thanks for the comment, Oren.  That is not a stupid question at all.  Let's see how cleanly I can explain this first without using math, and if that's not clear enough I'll use the math.

(1) What I'm ultimately calculating is the difference between two methods of estimating radiative forcing for the three most important noncondensing greenhouse gases. 

(2) One method was described by Myhre et al (1998) and then adopted by the IPCC.  The other is a refinement of the first one, described last year by Etminan et al (with Myhre as the second author).  Both methods are very close approximations of the results for radiative forcing that would be given by computationally intensive line-by-line radiative transfer algorithms.

(3) The way I compare the two is to calculate the forcing dF for each of the three molecules, using both the old and new methods, for a given time period (or, alternatively, for a given change in atmospheric concentration for one or more of the molecules).  Then I report the percentage difference between the old vs new versions. 

(4) I report this difference for each of the three molecules and for their total, because typically the new version has N2O going in one direction while CH4 goes in the other direction, and CO2 may go either way (relative to the old version).

(5) For calculating RF values in the past, I use the annual global mean values of CO2, CH4, and N2O from NOAA ESRL, which go back to 1979.  For longer terms, I use the IPCC/CMIP5 concentrations, which go back to 1765 ("pre-industrial")

(6) The most common usage of the term "radiative forcing" (dF)  in climate science is the change in radiant flux density between two conditions or two points in time.  We are used to the starting point for dF being some representation of "preindustrial" conditions, but one can use any starting or ending point depending on the question one wants to ask.

(7) Using 1765 as the starting point is useful for answering the question "how much has the radiant flux density changed since 1765?"  The IPCC wants to know that because they want to use it in models of the multicentury process of anthropogenic global warming.

(8) I am more interested in how dF will evolve over the next few decades.  To calculate the radiative forcing between now and 2035, I use 2017 concentrations as the starting point and 2035 as the end point.  I do the same for 2100 concentrations as well. 

(9) Since I am uncertain how concentrations of CO2, CH4, and N2O will evolve in the future, I use the CMIP5 standard concentration time series for RCP 6 and 8.5 pathways.  I should probably use RCP 4.5 as well but haven't yet done so.

(10) There is nothing wrong with using a non-1765 year as the starting point for calculating dF.  In fact, in table S2 of their paper's Supplementary Information, Etminan et al. do something very similar to what I'm doing.  They use 2011 concentrations as the baseline and then calculate dF using both the "old" and "new" methods, for a large number of combinations of values of CO2, CH4, and N2O.

(11) Much of the potential confusion over this seems to revolve around not matching up the mathematics to the specific question that is being asked.  For example, if one were to do this old-vs-new comparison using forcings from 1765 to 2035, the results would be a very poor answer to the question of how radiative forcing will evolve from 2017 to 2035, because the absolute and relative values of the three species' concentrations will be very different in the 2020s than in the 1920s or 1820s.

(12) Oren's question goes beyond radiative forcing to ask about issues of equilibrium, temperature change, etc.  Those are interesting and we could talk about them, but they're not directly relevant to the simple question I'm asking, which is strictly limited to the method of calculation of radiative forcing.

I hope this helps explain it.  I can only reiterate what I told Jai earlier -- actually doing the math is probably the best way to understand this, because it forces one to be absolutely clear about what one is doing.

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Re: Global Surface Air Temperatures
« Reply #1567 on: August 29, 2017, 02:34:53 PM »
I'd like to make a more general point about this. 

Increasing the estimated value of the (past) climate forcing doesn't necessarily increase the expected magnitude of future warming.  In fact, it may decrease our expectation of future warming. 

The rate of warming is determined by the forcing and the climate sensitivity.  For the past, the rate of warming is fixed -- so if our estimated value of the forcing goes up, it suggests that climate sensitivity is actually lower than previously believed.  That in turn suggests less warming in the future.

An alternative, of course, is to assume that some other forcing must go down to counteract the increased forcing.  This allows the total forcing to stay the same, and thus keeps climate sensitivity the same.  So whenever we, e.g., recalculate a higher forcing from CH4, we can also assume that we must have been underestimating the magnitude of some negative forcing like volcanic or anthropogenic aerosols.

But modelers need to work with actual numbers.  And unless they actually do revise downward some other forcing, increasing the past CH4 forcing (or whatever) will have the effect of making models with higher climate sensitivity perform less well, and models with lower climate sensitivity perform better.

In this case (the adjustments proposed by Etminan 2016) the effect is pretty small.  From pre-industrial to 2017 it increases the estimate of forcing from the "big 3" greenhouse gases by only 4% or so.  But when people argue for things that would increase the estimate of past climate forcing -- like more drastic changes to how the CH4 forcing is calculated -- it's hard not to see that leading to a lower estimate of climate sensitivity, or at least of the transient climate response (TCR).

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Re: Global Surface Air Temperatures
« Reply #1568 on: August 29, 2017, 04:57:32 PM »
Increasing the estimated value of the (past) climate forcing doesn't necessarily increase the expected magnitude of future warming.  In fact, it may decrease our expectation of future warming. 

The rate of warming is determined by the forcing and the climate sensitivity.  For the past, the rate of warming is fixed -- so if our estimated value of the forcing goes up, it suggests that climate sensitivity is actually lower than previously believed.  That in turn suggests less warming in the future.

It does suggest it, but it is not necessarily the case, as climate sensitivity generally refers to equilibrium climate sensitivity, which is not actually a measured value at any given point in time. It could be that the ocean heat uptake is higher than previously thought, for example. In that case, we might expect greater warming in the future.

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Re: Global Surface Air Temperatures
« Reply #1569 on: August 29, 2017, 05:23:42 PM »
Increasing the estimated value of the (past) climate forcing doesn't necessarily increase the expected magnitude of future warming.  In fact, it may decrease our expectation of future warming. 

The rate of warming is determined by the forcing and the climate sensitivity.  For the past, the rate of warming is fixed -- so if our estimated value of the forcing goes up, it suggests that climate sensitivity is actually lower than previously believed.  That in turn suggests less warming in the future.


It does suggest it, but it is not necessarily the case, as climate sensitivity generally refers to equilibrium climate sensitivity, which is not actually a measured value at any given point in time. It could be that the ocean heat uptake is higher than previously thought, for example. In that case, we might expect greater warming in the future.


Additionally, to BenB's point:

First, both anthropogenic and natural aerosols are radiative forcings that are normally net negative.  So for example, if the radiative forcing for methane is higher, then if modeler's underestimated the historical/paleo negative forcing from aerosol then climate sensitivity may be higher than AR5 assumes.  This point is well illustrated by Shrivastava et al (2017) which states:

"Several SOA processes highlighted in this review are complex and interdependent, and have non-linear effects on the properties, formation and evolution of SOA.  Current global models neglect this complexity and non-linearity, and thus are less likely to accurately predict the climate forcing of SOA, and project future climate sensitivity to greenhouse gases."

Shrivastava M, Kappa CD, Fan J, et al. (2017), "Recent Advances in Understanding Secondary Organic Aerosol: Implications for global climate forcing", Reviews of Geophysics, DOI: 10.1002/2016RG000540

http://onlinelibrary.wiley.com/doi/10.1002/2016RG000540/full

Abstract: "Anthropogenic emissions and land-use changes have modified atmospheric aerosol concentrations and size distributions over time. Understanding pre-industrial conditions and changes in organic aerosol due to anthropogenic activities is important because these features 1) influence estimates of aerosol radiative forcing and 2) can confound estimates of the historical response of climate to increases in greenhouse gases. Secondary organic aerosol (SOA), formed in the atmosphere by oxidation of organic gases, represents a major fraction of global submicron-sized atmospheric organic aerosol. Over the past decade, significant advances in understanding SOA properties and formation mechanisms have occurred through measurements, yet current climate models typically do not comprehensively include all important processes. This review summarizes some of the important developments during the past decade in understanding SOA formation. We highlight the importance of some processes that influence the growth of SOA particles to sizes relevant for clouds and radiative forcing, including: formation of extremely low-volatility organics in the gas phase; acid-catalyzed multi-phase chemistry of isoprene epoxydiols (IEPOX); particle-phase oligomerization; and physical properties such as volatility and viscosity. Several SOA processes highlighted in this review are complex and interdependent, and have non-linear effects on the properties, formation and evolution of SOA. Current global models neglect this complexity and non-linearity, and thus are less likely to accurately predict the climate forcing of SOA, and project future climate sensitivity to greenhouse gases. Efforts are also needed to rank the most influential processes and non-linear process-related interactions, so that these processes can be accurately represented in atmospheric chemistry-climate models."

Second, mounting evidence indicates a nonlinear climatic sensitivity to GHG, as indicated by Li Lo et. al. (2017); which indicates that with increasing levels of GHG concentration the ENSO climate attractor can abruptly and dramatically increase:

Li Lo et. al. (2017), "Nonlinear climatic sensitivity to greenhouse gases over past 4 glacial/interglacial cycles", Scientific Reports 7, Article number: 4626, doi:10.1038/s41598-017-04031-x

https://www.nature.com/articles/s41598-017-04031-x.

Abstract: "The paleoclimatic sensitivity to atmospheric greenhouse gases (GHGs) has recently been suggested to be nonlinear, however a GHG threshold value associated with deglaciation remains uncertain. Here, we combine a new sea surface temperature record spanning the last 360,000 years from the southern Western Pacific Warm Pool with records from five previous studies in the equatorial Pacific to document the nonlinear relationship between climatic sensitivity and GHG levels over the past four glacial/interglacial cycles. The sensitivity of the responses to GHG concentrations rises dramatically by a factor of 2–4 at atmospheric CO2 levels of >220 ppm. Our results suggest that the equatorial Pacific acts as a nonlinear amplifier that allows global climate to transition from deglacial to full interglacial conditions once atmospheric CO2 levels reach threshold levels."

Also, N. J. Burls and A. V. Fedorov, (2014) notes that if we approach Pliocene conditions, there may be an abrupt/nonlinear change in the Equatorial Pacific into near continuous El Nino-like conditions:

N. J. Burls and A. V. Fedorov, (2014), "Simulating Pliocene warmth and a permanent El Niño-like state: the role of cloud albedo", Paleoceanography, DOI: 10.1002/2014PA00264

http://onlinelibrary.wiley.com/doi/10.1002/2014PA002644/abstract

Also, Praetorius & Mix (2014) provide paleo-evidence of the importance of the synchronization of the North Pacific, and the North Atlantic, Oceans on Artic amplification: Summer K. Praetorius, Alan C. Mix, (2014), "Synchronization of North Pacific and Greenland climates preceded abrupt deglacial warming", Science 25 July 2014: Vol. 345 no. 6195 pp. 444-448 DOI: 10.1126/science.1252000

There are numerous other reason that masking could be hiding both high current GHG radiative forcing (I note that if Etminan et al (2016) is correct that the GWP100 of methane is 25% higher than in AR5 then CO2e is was above 548ppm after 2016); and high current ECS; so that if these masking factors are reduced (say by deforestation reducing SOA concentrations) then temperatures could increase rapidly.
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Re: Global Surface Air Temperatures
« Reply #1570 on: August 29, 2017, 06:36:22 PM »
Increasing the estimated value of the (past) climate forcing doesn't necessarily increase the expected magnitude of future warming.  In fact, it may decrease our expectation of future warming. 

The rate of warming is determined by the forcing and the climate sensitivity.  For the past, the rate of warming is fixed -- so if our estimated value of the forcing goes up, it suggests that climate sensitivity is actually lower than previously believed.  That in turn suggests less warming in the future.

It does suggest it, but it is not necessarily the case, as climate sensitivity generally refers to equilibrium climate sensitivity, which is not actually a measured value at any given point in time. It could be that the ocean heat uptake is higher than previously thought, for example. In that case, we might expect greater warming in the future.

Yes, that was what I was referring to with the reference to TCR in the final sentence of my post. 

Basically, if you believe that some forcing has been greatly underestimated in the past, something else has to adjust.  It probably won't be our estimate of the historical rate of warming, because that's been studied six ways to Sunday by now.  So it means that something else has to give way:

* There is another forcing that is also in error but in the opposite direction
* ECS is lower than previously expected
* TCR is lower than previously expected and the timescale for ECS will be longer than expected

In terms of inferences about future warming rates ...

* In the first case, future warming won't change unless and until that other mystery forcing goes away.
* In the second case, future warming won't change.
* In the third case, near-future rates of warming might not change much but over the long term the warming will continue longer than previously expected and end up at a higher temperature than previously expected.

There might be other possibilities as well, I suppose.  In any case, my point is that people should not assume that a change in our estimates of past forcings must obviously lead to a big change in our estimates of future warming.  It is possible that even a much larger change than, say, that from Etminan et al would lead to relatively little change in how much warming is expected over the next few decades.

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Re: Global Surface Air Temperatures
« Reply #1571 on: August 29, 2017, 06:52:03 PM »
ASLR Says (with references)

if the radiative forcing for methane is higher, then if modeler's underestimated the historical/paleo negative forcing from aerosol then climate sensitivity may be higher than AR5 assumes.  This point is well illustrated by Shrivastava et al (2017) which states:

Ned says, (without references)

So it means that something else has to give way:

* There is another forcing that is also in error but in the opposite direction
* ECS is lower than previously expected
* TCR is lower than previously expected and the timescale for ECS will be longer than expected

Ned,

you are out of your element here and I suggest you do some more listening and less talking if you want to understand climate sensitivity, how global energy balances are measured and what their implications are on current methodologies when a change like Etminan (2016) comes along.

Otherwise you start to appear less than ignorant and more like intentionally deceiving self (and others).

The fact is that if the total GHG forcing is revised higher then the Aerosol forcing component is underestimated, suppressing previous warming.  Previous warming is used to determine TCR and there is no Aerosol component in ECS.  This means that an underestimate of the (negative) forcing of aerosols in the historic and paleo models produces a significant revision UPWARDS of ECS (and TCR).
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Re: Global Surface Air Temperatures
« Reply #1572 on: August 29, 2017, 07:05:59 PM »
Basically, if you believe that some forcing has been greatly underestimated in the past, something else has to adjust.  It probably won't be our estimate of the historical rate of warming, because that's been studied six ways to Sunday by now.  So it means that something else has to give way:

* There is another forcing that is also in error but in the opposite direction
* ECS is lower than previously expected
* TCR is lower than previously expected and the timescale for ECS will be longer than expected

In terms of inferences about future warming rates ...

* In the first case, future warming won't change unless and until that other mystery forcing goes away.
* In the second case, future warming won't change.
* In the third case, near-future rates of warming might not change much but over the long term the warming will continue longer than previously expected and end up at a higher temperature than previously expected.

There might be other possibilities as well, I suppose.  In any case, my point is that people should not assume that a change in our estimates of past forcings must obviously lead to a big change in our estimates of future warming.  It is possible that even a much larger change than, say, that from Etminan et al would lead to relatively little change in how much warming is expected over the next few decades.


First, negative forcings could go away for a large number of reasons in the next few decades, including: reductions in anthropogenic aerosols as air pollution is cleaned-up rapidly and reductions in natural aerosols due to fires, pests (see below) and land use change (say farming).

The linked article discusses how boreal forest are under assault from pests due to rising temperatures:

Title: "Tree-Killing Beetles Spread into Northern U.S. Forests as Temperatures Rise"

https://insideclimatenews.org/news/28082017/southern-pine-beetles-spreading-climate-change-northern-canada-new-jersey-maine

Extract: "A study finds strong links between climate change and the spread of southern pine beetles, whose damage increases the risk of ecosystem harm and forest fires."

See also:

http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate3375.html?foxtrotcallback=true

Second, you totally ignore nonlinear increases in climate sensitivity with continued warming due to such matters as increases in El Ninos (see my last post), activation of polar amplifications, and future negative impacts of climate change on vegetation.
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Re: Global Surface Air Temperatures
« Reply #1573 on: August 29, 2017, 07:10:41 PM »
I note that if Etminan et al (2016) is correct that the GWP100 of methane is 25% higher than in AR5 then CO2e is was above 548ppm after 2016

I am mildly curious how you calculate that. 

Based on the NOAA ESRL data here (Table 2), CO2eq in 2016 was 489.  By subtracting their forcings for CO2,CH4,N2O and substituting the correctly calculated Etminan versions, I get a revised CO2eq for 2016 of 499.9

That seems like a big difference from 548 ppm - it's more than a decade's worth of difference, actually.

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Re: Global Surface Air Temperatures
« Reply #1574 on: August 29, 2017, 07:18:02 PM »
The linked reference (with an open access preprint) provides a discussion of a new framework for understanding climate sensitivity using adjustments that are responses to forcings that are not controlled by global mean warming.  This new approach offers the promise of reducing some of the uncertainties associated with the range of climate sensitivity and is particularly well suited for clarifying the uncertainties associated with aerosols:

Sherwood, S. C., S. Bony, O. Boucher, C. Bretherton, P. M. Forster, J. M. Gregory and B. Stevens, (2014), "Adjustments in the forcing-feedback framework for understanding climate change", Bull. Amer. Meteorol. Soc., doi: http://dx.doi.org/10.1175/BAMS-D-13-00167.1

http://journals.ametsoc.org/doi/abs/10.1175/BAMS-D-13-00167.1

For an open access pre-print:

http://web.science.unsw.edu.au/~stevensherwood/forcefeed_v2.2.1.pdf

Abstract: "The traditional forcing-feedback framework has provided an indispensable basis for discussing global climate changes. However, as analysis of model behavior has become more detailed, shortcomings and ambiguities in the framework have become more evident and physical effects unaccounted for by the traditional framework have become interesting. In particular, the new concept of adjustments, which are responses to forcings that are not mediated by the global mean temperature, has emerged. This concept, related to the older ones of climate efficacy and stratospheric adjustment, is a more physical way of capturing unique responses to specific forcings. We present a pedagogical review of the adjustment concept, why it is important, and how it can be used. The concept is particularly useful for aerosols, where it helps to organize what has become a complex array of forcing mechanisms.  It also helps clarify issues around cloud and hydrological response, transient vs. equilibrium climate change, and geoengineering."

In this regards, the Sherwood (2015) presentation focuses on the influence of aerosols on the radiative forcing over the Southern Ocean, which were not previously recognized.

Steven Sherwood (2015) "Radiosonde trends and a (perhaps) unexpected aerosol forcing mechanism", Ringberg workshop:

http://www.mpimet.mpg.de/fileadmin/atmosphaere/WCRP_Grand_Challenge_Workshop/Ringberg_2015/Talks/Sherwood_24032015.pdf

Extract:
"- We should not assume aerosol effects can only be in the northern hemisphere.

- Possible that greenhouse forcing in SH-extratropics has been negated by aerosol (or sea-ice) increases for some time. Deserves further attention?

- Would help to explain both (a) sluggish recent warming and (b) weird SH-NH contrast since 1979.

- Ozone depletion is the most likely culprit for the wind increase—would make this a rapid adjustment to ozone forcing."
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Re: Global Surface Air Temperatures
« Reply #1575 on: August 29, 2017, 07:23:53 PM »
To be more specific -- for 2016

From NOAA/ESRL:
RF(CO2) = 1.985
RF(CH4) = 0.507   
RF(N2O) = 0.193   
RF(Total, incl other gases) = 3.027   
CO2eq = 489

From equations in Etminan et al. 2016:
Recalculated RF(CO2) = 1.996
Recalculated RF(CH4) = 0.624
Recalculated RF(N2O) = 0.176

Subtract big 3 from NOAA total and add them from Etminan:
Recalculated RF(Total, incl other gases) = 3.139
Recalculated CO2eq = 499.9

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Re: Global Surface Air Temperatures
« Reply #1576 on: August 29, 2017, 07:28:08 PM »
To be more specific -- for 2016

From NOAA/ESRL:
RF(CO2) = 1.985
RF(CH4) = 0.507   
RF(N2O) = 0.193   
RF(Total, incl other gases) = 3.027   
CO2eq = 489

From equations in Etminan et al. 2016:
Recalculated RF(CO2) = 1.996
Recalculated RF(CH4) = 0.624
Recalculated RF(N2O) = 0.176

Subtract big 3 from NOAA total and add them from Etminan:
Recalculated RF(Total, incl other gases) = 3.139
Recalculated CO2eq = 499.9

Etminan et al does not consider feedbacks cited in AR5 (see image), so per NOAA's notes they assume a GWP100 of 25 for methane, so using the linked values for 2016, I took the cited radiative forcing contribution of 0.507 for methane in 2016 divided it by 25 and multiplied by 35 time 1.25 (per Etminan et al), and I ignored NO2 & CO2 changes.

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

 Global Radiative Forcing, CO2-equivalent mixing ratio, and the AGGI
                         Global Radiative Forcing (W m-2)           CO2-eq
                                                                                     (ppm)        AGGI
Year     CO2     CH4    N2O   CFC12 CFC11 15-minor  Total Total   1990 = 1   %change

2013   1.882  0.496   0.184   0.167   0.059   0.114  2.901   478      1.340        2.0
2014   1.908  0.499   0.187   0.166   0.058   0.116  2.935   481      1.356        1.6
2015   1.939  0.504   0.190   0.165   0.058   0.118  2.974   485      1.374        1.8
2016   1.985  0.507   0.193   0.164   0.057   0.121  3.027   489      1.399        2.5

CH4   ΔF = β(M½ - Mo½) - [f(M,No) - f(Mo,No)]   β = 0.036

Note, the attached image of Table 8.7 of AR5 has this footnote for methane: "These values do not include CO2 from methane oxidation. Values for fossil methane are higher by 1 and 2 for the 20 and 100 year metrics, respectively (Table 8.A.1)"  Thus, when you consider methane from fossil fuel and when you consider the GWP from the CO2 from methane oxidation, the resulting GWP values are higher than in Table 8.7 (i.e. the GWP100 for fossil fuel methane is 36 so when averaged with natural methane gives 35.)  Also AR5 asserts a -50 and +75% uncertainty in their GWP values for CH4 (on the 100 year timeline); which means that this confidence range has a fat right-tail.
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Re: Global Surface Air Temperatures
« Reply #1577 on: August 29, 2017, 08:02:15 PM »
ASLR,

Those are warming potentials not forcing,  a much more important value IMO

but by looking only at the 100 year projections we are falsely asserting CH4 power generation is a 'bridge fuel'. 

Have you considered the RF impact of Etminan on the 20 year projection of GWP, knowing that CH4 atmospheric residency is only about 12 years?

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Re: Global Surface Air Temperatures
« Reply #1578 on: August 29, 2017, 09:00:12 PM »
Etminan et al does not consider feedbacks cited in AR5 (see image), so per NOAA's notes they assume a GWP100 of 25 for methane, so using the linked values for 2016, I took the cited radiative forcing contribution of 0.507 for methane in 2016 divided it by 25 and multiplied by 35 time 1.25 (per Etminan et al), and I ignored NO2 & CO2 changes.

OK.  Let's take that a piece at a time.  The first problem is that even doing it that way, your math is wrong.

( 0.507 / 25 ) * 35 * 1.25 = 0.88725

NOAA total minus NOAA CH4: 3.027 - 0.507 = 2.52
Add back in adjusted CH4: 2.52 + 0.88725 = 3.40725
Convert to CO2eq:  EXP(3.40725/5.35) * 278 = 525.6 ppmv

That's still a long way from 548 ppmv ... and it's already too high.

Normally when people calculate CO2eq they are calculating it from the summed radiative forcings, which include stratospheric temperature adjustment but not slower feedbacks such as the carbon cycle.  The material in AR5 Table 8.7 is for calculation of GWP, not RF, and it's not appropriate to use that to calculate some kind of hybrid RF that incorporates feedbacks. 

The "25%" figure in the abstract of Etminan 2016 is just an approximation in 2011; the actual value in 2016 is 23%, but more importantly, it is inappropriate to apply Etminan's upward adjustment of CH4 without also applying their adjustments to CO2 and N2O -- otherwise you're cherry-picking an upward revision (CH4) while ignoring a downward revision (N2O).

Taking all that into account, we end up with the 2016 CO2eq of 499.9 ppmv, as I stated earlier.

FWIW, while it's not directly relevant to this calculation, you might be interested to know that Etminan 2016 recalculates GWP for methane as 32, not 25.  See page 12,622.

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Re: Global Surface Air Temperatures
« Reply #1579 on: August 29, 2017, 09:58:19 PM »
Ned says, (without references)

So it means that something else has to give way:

* There is another forcing that is also in error but in the opposite direction
* ECS is lower than previously expected
* TCR is lower than previously expected and the timescale for ECS will be longer than expected


Ned,

you are out of your element here and I suggest you do some more listening and less talking if you want to understand climate sensitivity, how global energy balances are measured and what their implications are on current methodologies when a change like Etminan (2016) comes along.


I thought it was so basic and obvious that no reference was necessary.  But here you go:



Kiehl, J. T. (1992) "Atmospheric General Circulation Modeling."  Chapter 10 in Trenberth, K. (ed), Climate System Modeling.  Cambridge University Press.

Of course there are older references but I liked the opportunity to drag that ol' tome off my bookshelf.  Ah, for the happy days of youth.

dT = lambda * G

If G increases and dT stays the same (it's in the past!) then lambda must decrease.




Of course, there are the other two possible scenarios that I listed above, but this one is perfectly defensible, and arguably the most likely.

Hey, I just noticed the stamp on the inside cover.  Apparently I paid only $49.95 at the time for this massive hardcover textbook!  Nowadays some poor student would need to take out a loan to buy a book like that.
« Last Edit: August 29, 2017, 10:06:06 PM by Ned W »

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Re: Global Surface Air Temperatures
« Reply #1580 on: August 30, 2017, 12:59:24 AM »
The first problem is that even doing it that way, your math is wrong.

( 0.507 / 25 ) * 35 * 1.25 = 0.88725

NOAA total minus NOAA CH4: 3.027 - 0.507 = 2.52
Add back in adjusted CH4: 2.52 + 0.88725 = 3.40725
Convert to CO2eq:  EXP(3.40725/5.35) * 278 = 525.6 ppmv

That's still a long way from 548 ppmv ... and it's already too high.

Normally when people calculate CO2eq they are calculating it from the summed radiative forcings, which include stratospheric temperature adjustment but not slower feedbacks such as the carbon cycle.  The material in AR5 Table 8.7 is for calculation of GWP, not RF, and it's not appropriate to use that to calculate some kind of hybrid RF that incorporates feedbacks. 


I have very little time available at the moment, so I may have made a math error, & the 525.6ppm may be correct.  In any case it appears that CO2e is based on GWP and not RF, which is what I am concerned about at the moment. Regarding, the nature and time frame of the feedbacks for the GWP100 for methane you can get the details from Shindell at al 2009:

Drew T. Shindell, Greg Faluvegi, Dorothy M. Koch, Gavin A. Schmidt, Nadine Unger & Susanne E. Bauer (Oct 30, 2009)"Improved Attribution of Climate Forcing to Emissions", Science  Vol. 326, Issue 5953, pp. 716-718, DOI: 10.1126/science.1174760

http://isites.harvard.edu/fs/docs/icb.topic1325972.files/SLCPs/Science-2009-Shindell-716-8.pdf


See also:

W. J. Collins, M. M. Fry, H. Yu, J. S. Fuglestvedt, D. T. Shindell, and J. J. West (2013), "Global and regional temperature-change potentials for near-term climate forcers", Atmos. Chem. Phys., 13, 2471–2485, doi:10.5194/acp-13-2471-2013

https://www.atmos-chem-phys.net/13/2471/2013/acp-13-2471-2013.pdf
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Re: Global Surface Air Temperatures
« Reply #1581 on: August 30, 2017, 01:17:21 AM »
ASLR,

Those are warming potentials not forcing,  a much more important value IMO

but by looking only at the 100 year projections we are falsely asserting CH4 power generation is a 'bridge fuel'. 

Have you considered the RF impact of Etminan on the 20 year projection of GWP, knowing that CH4 atmospheric residency is only about 12 years?

I believe that the carbon cycle feedbacks that Shindell et al (2009) cite may take more than 12 years to be fully realized; so until I know better I am referring to GWP100 when calculating CO2e.
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Re: Global Surface Air Temperatures
« Reply #1582 on: August 30, 2017, 03:17:47 AM »
ASLR,

Those are warming potentials not forcing,  a much more important value IMO

but by looking only at the 100 year projections we are falsely asserting CH4 power generation is a 'bridge fuel'. 

Have you considered the RF impact of Etminan on the 20 year projection of GWP, knowing that CH4 atmospheric residency is only about 12 years?

I believe that the carbon cycle feedbacks that Shindell et al (2009) cite may take more than 12 years to be fully realized; so until I know better I am referring to GWP100 when calculating CO2e.

I recommend that you do a 20 year calculation nonetheless to see the difference in warming potentials from their respective components.  If you include the Etminan adjustments of shortwave forcing of CH4 it goes up considerably, leading to an even higher fraction of the total warming potential (I estimate it to be an increase of 35% above the Shindell Schmidt value of 105.

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Re: Global Surface Air Temperatures
« Reply #1583 on: August 30, 2017, 03:20:37 AM »
The first problem is that even doing it that way, your math is wrong.

( 0.507 / 25 ) * 35 * 1.25 = 0.88725

NOAA total minus NOAA CH4: 3.027 - 0.507 = 2.52
Add back in adjusted CH4: 2.52 + 0.88725 = 3.40725
Convert to CO2eq:  EXP(3.40725/5.35) * 278 = 525.6 ppmv

That's still a long way from 548 ppmv ... and it's already too high.

Normally when people calculate CO2eq they are calculating it from the summed radiative forcings, which include stratospheric temperature adjustment but not slower feedbacks such as the carbon cycle.  The material in AR5 Table 8.7 is for calculation of GWP, not RF, and it's not appropriate to use that to calculate some kind of hybrid RF that incorporates feedbacks. 

I have very little time available at the moment, so I may have made a math error, & the 525.6ppm may be correct.  In any case it appears that CO2e is based on GWP and not RF, which is what I am concerned about at the moment.
There are several different quantities referred to as "CO2 equivalent".  The one that is based on GWP is for emissions by mass (units in tonnes) not for atmospheric concentration (units in ppmv).  The latter, which is what you are actually using, is based on RF not GWP. 

For the CO2eq you are using, you want this:

EXP(Ftot/5.35) * 278

where Ftot is the sum of the GHG forcings.  For 2016, it is 499.9 ppmv as shown in the calculations above.

The NOAA ESRL table that you linked to above includes columns for Total GHG forcing and CO2eq.  You can use that to test the formula above, if you want confirmation.
« Last Edit: August 30, 2017, 03:52:04 AM by Ned W »

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Re: Global Surface Air Temperatures
« Reply #1584 on: August 30, 2017, 04:07:26 AM »
The first problem is that even doing it that way, your math is wrong.

( 0.507 / 25 ) * 35 * 1.25 = 0.88725

NOAA total minus NOAA CH4: 3.027 - 0.507 = 2.52
Add back in adjusted CH4: 2.52 + 0.88725 = 3.40725
Convert to CO2eq:  EXP(3.40725/5.35) * 278 = 525.6 ppmv

That's still a long way from 548 ppmv ... and it's already too high.

Normally when people calculate CO2eq they are calculating it from the summed radiative forcings, which include stratospheric temperature adjustment but not slower feedbacks such as the carbon cycle.  The material in AR5 Table 8.7 is for calculation of GWP, not RF, and it's not appropriate to use that to calculate some kind of hybrid RF that incorporates feedbacks. 


I have very little time available at the moment, so I may have made a math error, & the 525.6ppm may be correct.  In any case it appears that CO2e is based on GWP and not RF, which is what I am concerned about at the moment.

There are several different quantities referred to as "CO2 equivalent".  The one that is based on GWP is for emissions by mass (units in tonnes) not for atmospheric concentration (units in ppmv).  The latter, which is what you are actually using, is based on RF not GWP. 

For the CO2eq you are using, you want this:

EXP(Ftot/5.35) * 278

where Ftot is the sum of the GHG forcings.  For 2016, it is 499.9 ppmv as shown in the calculations above.

The NOAA ESRL table that you linked to above includes columns for Total GHG forcing and CO2eq.  You can use that to test the formula above, if you want confirmation.


Ned W,

Per you linked Wikipedia article you are wrong and the value of CO2e from the April 2016 updated
Blasing, T.J. (April 2016), Current Greenhouse Gas Concentrations, doi:10.3334/CDIAC/atg.032 is 526.6ppm.  The calculations are given below:

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."

Edit: Thus if one assumes CO2e is currently increasing about 3.5ppm per that would give about 530ppm for an April 2017 update.

Edit 2: Is it a coincidence that Rick Perry is shutting down ORNL's CO2e updates at the end of September, or is it part of Trump's assault on science?

Title: "Recent Greenhouse Gas Concentrations"

http://cdiac.ornl.gov/pns/current_ghg.html

Extract: "NOTICE (July 2017): CDIAC will cease operations on September 30, 2017. Data will continue to be available through this portal until that time. A new DOE data archive is now at Lawrence Berkeley National Laboratory and is named ESS-DIVE. Data stored at CDIAC is being transitioned to ESS-DIVE and will be available from ESS-DIVE by September 30, 2017. If you have any questions regarding the new archive or the data transition, please contact ess-dive-support@lbl.gov."
« Last Edit: August 30, 2017, 04:28:50 AM by AbruptSLR »
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Ned W

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Re: Global Surface Air Temperatures
« Reply #1585 on: August 30, 2017, 11:35:39 AM »
The first problem is that even doing it that way, your math is wrong.

( 0.507 / 25 ) * 35 * 1.25 = 0.88725

NOAA total minus NOAA CH4: 3.027 - 0.507 = 2.52
Add back in adjusted CH4: 2.52 + 0.88725 = 3.40725
Convert to CO2eq:  EXP(3.40725/5.35) * 278 = 525.6 ppmv

That's still a long way from 548 ppmv ... and it's already too high.

Normally when people calculate CO2eq they are calculating it from the summed radiative forcings, which include stratospheric temperature adjustment but not slower feedbacks such as the carbon cycle.  The material in AR5 Table 8.7 is for calculation of GWP, not RF, and it's not appropriate to use that to calculate some kind of hybrid RF that incorporates feedbacks. 

I have very little time available at the moment, so I may have made a math error, & the 525.6ppm may be correct.  In any case it appears that CO2e is based on GWP and not RF, which is what I am concerned about at the moment.
There are several different quantities referred to as "CO2 equivalent".  The one that is based on GWP is for emissions by mass (units in tonnes) not for atmospheric concentration (units in ppmv).  The latter, which is what you are actually using, is based on RF not GWP. 

For the CO2eq you are using, you want this:

EXP(Ftot/5.35) * 278

where Ftot is the sum of the GHG forcings.  For 2016, it is 499.9 ppmv as shown in the calculations above.

The NOAA ESRL table that you linked to above includes columns for Total GHG forcing and CO2eq.  You can use that to test the formula above, if you want confirmation.

Ned W,

Per [the] linked Wikipedia article you are wrong and the value of CO2e from the April 2016 updated
Blasing, T.J. (April 2016), Current Greenhouse Gas Concentrations, doi:10.3334/CDIAC/atg.032 is 526.6ppm.  The calculations are given below:

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."

Feel like I'm playing whack-a-mole here.

Did you notice that the formula for CO2e you just cited on wikipedia is exactly the same as what I gave you?  It's based on RF, not GWP.  For the sense of "CO2e" that you are using (atmospheric concentration in ppmv, not emission in tonnes) CO2e is simply a log transformed version of the total RF from well-mixed greenhouse gases.

Next ... did you notice that the values calculated for CO2e on your wikipedia page are oddly inconsistent with the NOAA ESRL AGGI data you linked to as the basis for your 548 ppm a few posts back? 

* On the wikipedia page, the 1998 CO2e is 412, while in NOAA AGGI it's 436.  In that case, it's because the RF value for "other minor gases" on the wikipedia page doesn't adequately represent the RF from halocarbons, which wasn't fully understood at the time of the TAR.

* But then comes the real surprise.  On the wikipedia page, the 2016 CO2e is 526, while in NOAA AGGI (which, again, you cited as your source) it's 489. Can you figure out the reason for this inconsistency?  Hint: fixing it brings the wikipedia version down to 489, the same as NOAA's.

« Last Edit: August 30, 2017, 11:43:25 AM by Ned W »

Ned W

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Re: Global Surface Air Temperatures
« Reply #1586 on: August 30, 2017, 02:00:59 PM »
: ASLR
Edit 2: Is it a coincidence that Rick Perry is shutting down ORNL's CO2e updates at the end of September, or is it part of Trump's assault on science?

DOE's Office of Science made the decision to close CDIAC a year ago, under the previous administration.  I haven't heard an explanation for why their funding was yanked, but neither Perry nor Trump had anything to do with it.


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Re: Global Surface Air Temperatures
« Reply #1587 on: August 30, 2017, 06:20:45 PM »

* But then comes the real surprise.  On the wikipedia page, the 2016 CO2e is 526, while in NOAA AGGI (which, again, you cited as your source) it's 489. Can you figure out the reason for this inconsistency?  Hint: fixing it brings the wikipedia version down to 489, the same as NOAA's.

Perhaps, as ORNL is contributing to the ACME project they may have found that RF from Tropospheric ozone needs to be included in calculating CO2e while NOAA may not account for the atmospheric chemistry between O3 and key GHGs as pointed out by Shindell et al 2009.  Thus NOAA's values (that I was saying needed to be updated to account for Shindell's research) are an example of scientists clinging to the training they received in college and not using the latest research thus resulting in erring on their side of least drama.
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AbruptSLR

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Re: Global Surface Air Temperatures
« Reply #1588 on: August 30, 2017, 07:06:59 PM »
For ease of reference I provide Figure 2 from Shindell et al 2009, and their abstract confirming that the higher RF of key GHG like methane is associated with atmospheric chemistry including ozone and aerosols:

Shindell, D.T., Faluvegi, G., Koch, D.M., Schmidt, G.A., Unger, N., and Bauer S.E. (2009), "Improved Attribution of Climate Forcing to Emissions" Science, Vol. 326 no. 5953 pp. 716-718, DOI: 10.1126/science.1174760.

http://saive.com/911/DOCS/AAAS-Aerosols-not-CO2-Cause-Global-Warming.pdf

Abstract: "Evaluating multicomponent climate change mitigation strategies requires knowledge of the diverse direct and indirect effects of emissions. Methane, ozone, and aerosols are linked through atmospheric chemistry so that emissions of a single pollutant can affect several species. We calculated atmospheric composition changes, historical radiative forcing, and forcing per unit of emission due to aerosol and tropospheric ozone precursor emissions in a coupled composition climate model.  We found that gas-aerosol interactions substantially alter the relative importance of the various emissions. In particular, methane emissions have a larger impact than that used in current carbon-trading schemes or in the Kyoto Protocol. Thus, assessments of multigas mitigation policies, as well as any separate efforts to mitigate warming from short-lived pollutants, should include gas-aerosol interactions."
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AbruptSLR

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Re: Global Surface Air Temperatures
« Reply #1589 on: August 30, 2017, 07:39:49 PM »
Along those lines -- at least to a degree. There's some fresh doubt over the stability of the entire AMOC as well. I'll find that paper.

The linked reference confirms that the AMOC will likely slowdown in coming decades; however, I imagine that Hansen would warn that this likely is related to his ice-climate feedback:

Olson, R., An, SI., Fan, Y. et al. (2017), " North Atlantic observations sharpen meridional overturning projections", Clim Dyn,  https://doi.org/10.1007/s00382-017-3867-7

https://rd.springer.com/article/10.1007%2Fs00382-017-3867-7

Abstract: "Atlantic Meridional Overturning Circulation (AMOC) projections are uncertain due to both model errors, as well as internal climate variability. An AMOC slowdown projected by many climate models is likely to have considerable effects on many aspects of global and North Atlantic climate. Previous studies to make probabilistic AMOC projections have broken new ground. However, they do not drift-correct or cross-validate the projections, and do not fully account for internal variability. Furthermore, they consider a limited subset of models, and ignore the skill of models at representing the temporal North Atlantic dynamics. We improve on previous work by applying Bayesian Model Averaging to weight 13 Coupled Model Intercomparison Project phase 5 models by their skill at modeling the AMOC strength, and its temporal dynamics, as approximated by the northern North-Atlantic temperature-based AMOC Index. We make drift-corrected projections accounting for structural model errors, and for the internal variability. Cross-validation experiments give approximately correct empirical coverage probabilities, which validates our method. Our results present more evidence that AMOC likely already started slowing down. While weighting considerably moderates and sharpens our projections, our results are at low end of previously published estimates. We project mean AMOC changes between periods 1960–1999 and 2060–2099 of −4.0 Sv and −6.8 Sv for RCP4.5 and RCP8.5 emissions scenarios respectively. The corresponding average 90% credible intervals for our weighted experiments are [−7.2, −1.2] and [−10.5, −3.7] Sv respectively for the two scenarios."
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Ned W

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Re: Global Surface Air Temperatures
« Reply #1590 on: August 30, 2017, 07:43:17 PM »

* But then comes the real surprise.  On the wikipedia page, the 2016 CO2e is 526, while in NOAA AGGI (which, again, you cited as your source) it's 489. Can you figure out the reason for this inconsistency?  Hint: fixing it brings the wikipedia version down to 489, the same as NOAA's.

Perhaps, as ORNL is contributing to the ACME project they may have found that RF from Tropospheric ozone needs to be included in calculating CO2e while NOAA may not account for the atmospheric chemistry between O3 and key GHGs as pointed out by Shindell et al 2009.  Thus NOAA's values (that I was saying needed to be updated to account for Shindell's research) are an example of scientists clinging to the training they received in college and not using the latest research thus resulting in erring on their side of least drama.

Let's keep in mind that the CO2e number you've moved on to comes from an anonymous user at Wikipedia.  It's not an ORNL product.  The only connection to ORNL is that the example on Wikipedia makes use of RF data from an ORNL web page.

And Shindell (2009) is a red herring.  Not in the sense of its role in the climate science literature, but it has zero bearing on the specific issue at hand, which is the fact that the thing you are referring to as "CO2e" -- the log-transformed version of the sum of radiative forcings from well-mixed greenhouse gases -- does not ever involve an adjustment for carbon-cycle feedbacks or "GWP". 

Look at the NOAA ESRL page you originally linked to.  Look at the Wikipedia page you're relying on now.  Look at the PIK web page that Jai linked to.  All of them show you how to calculate CO2e, and none of them use any adjustment for GWP or carbon-cycle feedbacks. 

I think the point is clear, and I'm pretty much done with this. 
« Last Edit: August 30, 2017, 08:14:42 PM by Ned W »

AbruptSLR

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Re: Global Surface Air Temperatures
« Reply #1591 on: August 30, 2017, 10:50:42 PM »
I think the point is clear, and I'm pretty much done with this.

Soft denialism frequently hides behind definitions, without acknowledging the physics that goes on in the atmosphere (and models of that physics such as the linked reference on ACCMIP models).  Thus it is disingenuous to say that NOAA's definition of RF and associated values for CO2e, which does not include the influence of ozone is the appropriate measure of our current situation.  The linked references clearly discuss the complete chemical interactions between ozone and GHGs like methane, etc; and it is irrelevant whether one attributes the changes RF to either ozone of the interacting GHG, but rather the total RF that ORNL gives (see the attached table).  Thus my point that CO2e currently exceeds 530ppm is valid:

Stevenson et al (2013), "Tropospheric ozone changes, radiative forcing and attribution to emissions in the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP),"Atmos. Chem. Phys., 13, 3063–3085, doi:10.5194/acp-13-3063-2013

https://core.ac.uk/download/pdf/9666974.pdf

Abstract. Ozone (O3) from 17 atmospheric chemistry models taking part in the Atmospheric Chemistry and Climate
Model Intercomparison Project (ACCMIP) has been used to calculate tropospheric ozone radiative forcings (RFs). All models applied a common set of anthropogenic emissions, which are better constrained for the present-day than the past. Future anthropogenic emissions follow the four Representative Concentration Pathway (RCP) scenarios, which define a relatively narrow range of possible air pollution emissions. We calculate a value for the pre-industrial (1750) to present-day (2010) tropospheric ozone RF of 410mWm−2. The model range of pre-industrial to present-day changes in O3 produces a spread (±1 standard deviation) in RFs of ±17 %. Three different radiation schemes were used – we find differences in RFs between schemes (for the same ozone fields) of ±10 %. Applying two different tropopause definitions gives differences in RFs of ±3 %. Given additional (unquantified) uncertainties associated with emissions, climate-chemistry interactions and land-use change, we estimate an overall uncertainty of ±30% for the tropospheric ozone RF. Experiments carried out by a subset of six models attribute tropospheric ozone RF to increased emissions of methane (44±12 %), nitrogen oxides (31±9 %), carbon monoxide (15±3 %) and non-methane volatile organic compounds (9±2 %); earlier studies attributed more of the tropospheric ozone RF to methane and less to nitrogen oxides. Normalising RFs to changes in tropospheric column ozone, we find a global mean normalised RF of 42mWm−2 DU−1, a value similar to previous work. Using normalised RFs and future tropospheric column ozone projections we calculate future tropospheric ozone RFs (mWm−2; relative to 1750) for the four future scenarios (RCP2.6, RCP4.5, RCP6.0 and RCP8.5) of 350, 420, 370 and 460 (in 2030), and 200, 300, 280 and 600 (in 2100). Models show some coherent responses of ozone to climate change: decreases in the tropical lower troposphere, associated with increases in water vapour; and increases in the sub-tropical to mid-latitude upper troposphere, associated with increases in lightning and stratosphere-to-troposphere transport. Climate change has relatively small impacts on global mean tropospheric ozone RF."


See also:

https://tes.jpl.nasa.gov/mission/climateO3/

Extract: "Tropospheric O3 is also the source of the hydroxyl radical (OH), which controls the abundance and distribution of many atmospheric constituents (including greenhouse gases such as methane and hydrochlorofluorocarbons). Ozone makes a significant contribution to the radiative balance of the upper troposphere and lower stratosphere, such that changes in the distribution of O3 in these atmospheric regions affect the radiative forcing of climate.

Climate Feedback and Forcing for Tropospheric Ozone

Climate forcing by O3 remains uncertain because O3 change as a function of altitude has been under-measured. In order to better understand the role of tropospheric O3 in climate, accurate temperature measurements are needed along with co-located O3 and CO profiles."
« Last Edit: August 31, 2017, 01:33:47 AM by AbruptSLR »
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jai mitchell

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Re: Global Surface Air Temperatures
« Reply #1592 on: August 31, 2017, 12:32:35 AM »
with regard to the calculation of CO2e and Global Warming Potential

https://www.theguardian.com/environment/2011/apr/27/co2e-global-warming-potential

Standard ratios are used to convert the various gases into equivalent amounts of CO2. These ratios are based on the so-called global warming potential (GWP) of each gas, which describes its total warming impact relative to CO2 over a set period – usually a hundred years. Over this time frame, according to the standard data, methane scores 25 (meaning that one tonne of methane will cause the same amount of warming as 25 tonnes of CO2), nitrous oxide comes in at 298 and some of the super-potent F-gases score more than 10,000.

The only wrinkle with all this is that 100 years is a fairly arbitrary time frame, and the ratios change significantly if a shorter or longer period is chosen. That's because some gases last much longer in the atmosphere than others. For instance, a tonne of CO2 emissions may warm the planet gently but over many centuries. A tonne of methane emissions, by contrast, creates a strong burst of warming over a much shorter period.

Relatively speaking, therefore, the impact of methane – and the strategic importance of tackling its sources, such as agriculture and landfill sites – depends on whether you're more interested in the next few decades or the next few centuries. Over a period of 20 years, methane's GWP rises to 72; over a period of 500 years, it falls to just 7.6.
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Re: Global Surface Air Temperatures
« Reply #1593 on: August 31, 2017, 06:10:28 AM »
https://twitter.com/SoonerTom/status/903089795345338376

This seems alarming to me. Is it possible to estimate how deep the water column was upwelled during the storm, or will people be going out to measure it?

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Re: Global Surface Air Temperatures
« Reply #1594 on: August 31, 2017, 05:19:19 PM »
https://twitter.com/SoonerTom/status/903089795345338376

This seems alarming to me. Is it possible to estimate how deep the water column was upwelled during the storm, or will people be going out to measure it?


Look up Ekman Pumping, happens with cyclonic systems and moves huge amounts of water.
Terry

Niall Dollard

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Re: Global Surface Air Temperatures
« Reply #1595 on: September 05, 2017, 01:14:31 AM »

AbruptSLR

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Re: Global Surface Air Temperatures
« Reply #1596 on: September 06, 2017, 04:42:17 PM »
Per the attached Stokes information, the NCEP/NCAR monthly anom for August 2017 was 0.337C, and that Sept 2017 is starting out only slightly cooler:
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Re: Global Surface Air Temperatures
« Reply #1597 on: September 17, 2017, 09:37:20 PM »
Quick check of #NCEI #global #temperature #records set in 2017.  #Ratio of #daily #highs to #lows is 3.15 to 1.
 ...
https://twitter.com/climateguyw/status/909204434886037504
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Re: Global Surface Air Temperatures
« Reply #1598 on: September 18, 2017, 03:58:50 PM »
Just read through the Ned W/Jai discussion and I feel like a Yanomami tribesman from the Amazon rainforest who has just found himself at Wimbledon watching a tennis match without knowing the rules.

Abrupt SLR: Sorry about discounting your contribution but you're more like a line judge, sitting high on a chair and inexplicably shouting while frantically pointing and waving your arms.
« Last Edit: September 18, 2017, 04:09:58 PM by Shared Humanity »

Shared Humanity

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Re: Global Surface Air Temperatures
« Reply #1599 on: September 18, 2017, 04:00:09 PM »
Meanwhile, global mean surface temperatures continue on an exponential growth pattern.
« Last Edit: September 18, 2017, 04:07:25 PM by Shared Humanity »