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Sciguy

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Re: Where are we now in CO2e , which pathway are we on?
« Reply #250 on: March 26, 2021, 05:30:51 PM »
The IPCC explained their definition of pre-industrial in Chapter 1 of the report on 1.5C:

https://www.ipcc.ch/sr15/chapter/chapter-1/

Quote
What is meant by ‘the increase in global average temperature… above pre-industrial levels’ referred to in the Paris Agreement depends on the choice of pre-industrial reference period, whether 1.5°C refers to total warming or the human-induced component of that warming, and which variables and geographical coverage are used to define global average temperature change. The cumulative impact of these definitional ambiguities (e.g., Hawkins et al., 2017; Pfleiderer et al., 2018) is comparable to natural multi-decadal temperature variability on continental scales (Deser et al., 2012) and primarily affects the historical period, particularly that prior to the early 20th century when data is sparse and of less certain quality. Most practical mitigation and adaptation decisions do not depend on quantifying historical warming to this level of precision, but a consistent working definition is necessary to ensure consistency across chapters and figures. We adopt definitions that are as consistent as possible with key findings of AR5 with respect to historical warming.

This report defines ‘warming’, unless otherwise qualified, as an increase in multi-decade global mean surface temperature (GMST) above pre-industrial levels. Specifically, warming at a given point in time is defined as the global average of combined land surface air and sea surface temperatures for a 30-year period centred on that time, expressed relative to the reference period 1850–1900 (adopted for consistency with Box SPM.1 Figure 1 of IPCC (2014a) ‘as an approximation of pre-industrial levels’, excluding the impact of natural climate fluctuations within that 30-year period and assuming any secular trend continues throughout that period, extrapolating into the future if necessary. There are multiple ways of accounting for natural fluctuations and trends (e.g., Foster and Rahmstorf, 2011; Haustein et al., 2017; Medhaug et al., 2017; Folland et al., 2018; Visser et al., 2018) , but all give similar results. A major volcanic eruption might temporarily reduce observed global temperatures, but would not reduce warming as defined here (Bethke et al., 2017) . Likewise, given that the level of warming is currently increasing at 0.3°C–0.7°C per 30 years (likely range quoted in Kirtman et al., 2013
and supported by Folland et al., 2018) , the level of warming in 2017 was 0.15°C–0.35°C higher than average warming over the 30-year period 1988–2017.

In summary, this report adopts a working definition of ‘1.5°C relative to pre-industrial levels’ that corresponds to global average combined land surface air and sea surface temperatures either 1.5°C warmer than the average of the 51-year period 1850–1900, 0.87°C warmer than the 20-year period 1986–2005, or 0.63°C warmer than the decade 2006–2015. These offsets are based on all available published global datasets, combined and updated, which show that 1986–2005 was 0.63°C warmer than 1850–1900 (with a 5–95% range of 0.57°C–0.69°C based on observational uncertainties alone), and 2006–2015 was 0.87°C warmer than 1850–1900 (with a likely range of 0.75°C–0.99°C, also accounting for the possible impact of natural fluctuations). Where possible, estimates of impacts and mitigation pathways are evaluated relative to these more recent periods. Note that the 5–95% intervals often quoted in square brackets in AR5 correspond to very likely ranges, while likely ranges correspond to 17–83%, or the central two-thirds, of the distribution of uncertainty.

Quote
Any choice of reference period used to approximate ‘pre-industrial’ conditions is a compromise between data coverage and representativeness of typical pre-industrial solar and volcanic forcing conditions. This report adopts the 51-year reference period, 1850–1900 inclusive, assessed as an approximation of pre-industrial levels in AR5 (Box TS.5, Figure 1 of Field et al., 2014) . The years 1880–1900 are subject to strong but uncertain volcanic forcing, but in the HadCRUT4 dataset, average temperatures over 1850–1879, prior to the largest eruptions, are less than 0.01°C from the average for 1850–1900. Temperatures rose by 0.0°C–0.2°C from 1720–1800 to 1850–1900 (Hawkins et al., 2017) , but the anthropogenic contribution to this warming is uncertain (Abram et al., 2016; Schurer et al., 2017) . The 18th century represents a relatively cool period in the context of temperatures since the mid-Holocene (Marcott et al., 2013; Lüning and Vahrenholt, 2017; Marsicek et al., 2018) , which is indicated by the pink shaded region in Figure 1.2.

The IPCC report gives several scientific papers for each of the statements they make.  You can search for those papers in google to find out the details behind any of these statements.  For example, Hawkins et al., 2017, delves specifically into the question of the pre-industrial temperature.

https://journals.ametsoc.org/view/journals/bams/98/9/bams-d-16-0007.1.xml

Quote
Estimating Changes in Global Temperature since the Preindustrial Period
Ed Hawkins, Pablo Ortega, Emma Suckling, Andrew Schurer, Gabi Hegerl, Phil Jones, Manoj Joshi, Timothy J. Osborn, Valérie Masson-Delmotte, Juliette Mignot, Peter Thorne, and Geert Jan van Oldenborgh

Print Publication:    01 Sep 2017

DOI:    https://doi.org/10.1175/BAMS-D-16-0007.1

Abstract

The United Nations Framework Convention on Climate Change (UNFCCC) process agreed in Paris to limit global surface temperature rise to “well below 2°C above pre-industrial levels.” But what period is preindustrial? Somewhat remarkably, this is not defined within the UNFCCC’s many agreements and protocols. Nor is it defined in the IPCC’s Fifth Assessment Report (AR5) in the evaluation of when particular temperature levels might be reached because no robust definition of the period exists. Here we discuss the important factors to consider when defining a preindustrial period, based on estimates of historical radiative forcings and the availability of climate observations. There is no perfect period, but we suggest that 1720–1800 is the most suitable choice when discussing global temperature limits. We then estimate the change in global average temperature since preindustrial using a range of approaches based on observations, radiative forcings, global climate model simulations, and proxy evidence. Our assessment is that this preindustrial period was likely 0.55°–0.80°C cooler than 1986–2005 and that 2015 was likely the first year in which global average temperature was more than 1°C above preindustrial levels. We provide some recommendations for how this assessment might be improved in the future and suggest that reframing temperature limits with a modern baseline would be inherently less uncertain and more policy relevant.

So that is how the IPCC concluded that 2015 was the first year in which the global temperature was 1C above pre-industrial.

Why do you think that definition of pre-industrial is incorrect?  Please provide links to the peer-reviewed science that shows it's incorrect.


vox_mundi

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“There are three classes of people: those who see. Those who see when they are shown. Those who do not see.” ― Leonardo da Vinci

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Tom_Mazanec

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Re: Where are we now in CO2e , which pathway are we on?
« Reply #252 on: March 29, 2021, 11:26:05 AM »
Reply #251 on: March 28, 2021, 09:55:04 PM »

Interesting that it starts rising c6000 BC, then takes off with Industrial Revolution.
Agriculture raising it slowly, perhaps?
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kassy

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Re: Where are we now in CO2e , which pathway are we on?
« Reply #253 on: March 29, 2021, 04:39:17 PM »
Yes agriculture and deforestation played a role.

The Ruddiman Hypothesis: A Debated Theory Progresses Along Interdisciplinary Lines

...snip...

https://www.globalpolicyjournal.com/blog/24/02/2021/ruddiman-hypothesis-debated-theory-progresses-along-interdisciplinary-lines

See linked post or the article for details.
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Stephan

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Re: Where are we now in CO2e , which pathway are we on?
« Reply #254 on: March 29, 2021, 05:39:39 PM »
A classic hockey stick pattern.
It is too late just to be concerned about Climate Change

kassy

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Re: Where are we now in CO2e , which pathway are we on?
« Reply #255 on: April 04, 2021, 11:40:17 AM »
The IPCC explained their definition of pre-industrial in Chapter 1 of the report on 1.5C:

https://www.ipcc.ch/sr15/chapter/chapter-1/
...

So that is how the IPCC concluded that 2015 was the first year in which the global temperature was 1C above pre-industrial.

Why do you think that definition of pre-industrial is incorrect?  Please provide links to the peer-reviewed science that shows it's incorrect.

The argument made on the blog is simple enough. Why use 1850 as a baseline when we could use a different one.

Now that would not really matter is we had good definition of the lines we should not cross but we do not have those either. They paint scenarios with a really broad brush. Combine this with lobbying interests from oil producing countries and the usual kick the can down the road approach and we end up in 2020 with people talking about a bit of reductions by 2050.

Basically their reporting claims we still have time to solve this while we are very much running out.

Some further temperature constraints:

Threshold for Dangerous Climate Warming Will Likely Be Crossed Between 2027–2042
https://phys.org/news/2020-12-threshold-dangerous-climate.html

The threshold for dangerous global warming will likely be crossed between 2027 and 2042—a much narrower window than the Intergovernmental Panel on Climate Change's estimate of between now and 2052. In a study published in Climate Dynamics, researchers from McGill University introduce a new and more precise way to project the Earth's temperature. Based on historical data, it considerably reduces uncertainties compared to previous approaches.

... Until now, wide ranges in overall temperature projections have made it difficult to pinpoint outcomes in different mitigation scenarios. For instance, if atmospheric CO2 concentrations are doubled, the General Circulation Models (GCMs) used by the Intergovernmental Panel on Climate Change (IPCC), predict a very likely global average temperature increase between 1.9 and 4.5C—a vast range covering moderate climate changes on the lower end, and catastrophic ones on the other.

"Our new approach to projecting the Earth's temperature is based on historical climate data, rather than the theoretical relationships that are imperfectly captured by the GCMs. Our approach allows climate sensitivity and its uncertainty to be estimated from direct observations with few assumptions," says co-author Raphael Hebert, a former graduate researcher at McGill University, now working at the Alfred-Wegener-Institut in Potsdam, Germany.

In a study for Climate Dynamics, the researchers introduced the new Scaling Climate Response Function (SCRF) model to project the Earth's temperature to 2100. Grounded on historical data, it reduces prediction uncertainties by about half, compared to the approach currently used by the IPCC. In analyzing the results, the researchers found that the threshold for dangerous warming (+1.5C) will likely be crossed between 2027 and 2042. This is a much narrower window than GCMs estimates of between now and 2052. On average, the researchers also found that expected warming was a little lower, by about 10 to 15 percent. They also found, however, that the "very likely warming ranges" of the SCRF were within those of the GCMs, giving the latter support.

Raphaël Hébert et al, An observation-based scaling model for climate sensitivity estimates and global projections to 2100, Climate Dynamics (2020)
https://link.springer.com/article/10.1007/s00382-020-05521-x

Abstract: ... Projecting to 2100, we find that to keep the warming below 1.5 K, future emissions must undergo cuts similar to RCP 2.6 for which the probability to remain under 1.5 K is 48 %. RCP 4.5 and RCP 8.5-like futures overshoot with very high probability

Now if the world had started some concerted effort to work together to stop climate change 5 or 10 or more years ago i would feel better but we have not really started. Yes renewables are gaining ground but we also need worldwide standards on plastics and we have to totally change the food cycle.

Also this ignores the amount of trouble we are already in. Do we really have time for decades more of forest fires, ocean acidification? How many coral reefs will we lose in the meantime?

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Stephan

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Re: Where are we now in CO2e , which pathway are we on?
« Reply #256 on: May 05, 2021, 09:13:08 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 January 2021 than in January 2020 and in December 2020. This should not be surprising as most of the increase rates are higher than average or even record-breaking.

The values [W/m²], change to Dec 2020, change to Jan 2020 and change to Jan 2011:
CO2 2.147    (+ 0.016)    (+ 0.027)    (+ 0.318)
CH4 0.527    (+ 0.001)    (+ 0.008)    (+ 0.034)
N2O 0.208   (+ 0.000)     (+ 0.004)    (+ 0.031)
SF6  0.0054 (+ 0.0000)   (+ 0.0001)   (+ 0.0017)
sum  2.887  (+ 0.017)   (+ 0.038)   (+ 0.384)  (rounding differences)

The relative annual increase is 1.33 %, higher than in January 2020 (+ 1.28%).

This recalculates to a CO2eq of 476.8 ppm (annual increase of 3.4 ppm).

Compared with 1980 [average was 1.578 W/m²] the increase since then sums up to 83.0 %.
« Last Edit: May 05, 2021, 09:35:48 PM by Stephan »
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Sciguy

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Re: Where are we now in CO2e , which pathway are we on?
« Reply #257 on: May 05, 2021, 11:30:33 PM »
The preliminary annual numbers are in on the NOAA site too.  Here's how they stack up to the RCP scenario assumptions:


                             Observed   RCP 2.5   RCP 4.5   RCP 6.0   RCP 8.5

CO2 PPM              412.46       412.1       411.1      409.4      415.8

CH4 PPB             1879.1            1731     1801        1786        1924

N2O PPB               333.2              329        330       330        332

SF6 PPT               10.27              8.9         8.7        10.3         9.9


If Stephan can plug these numbers into his spreadsheet and see what it means in terms of radiative forcing, we can see which RCP pathway we were on in the 2010s.

oren

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Re: Where are we now in CO2e , which pathway are we on?
« Reply #258 on: May 05, 2021, 11:47:54 PM »
While CO2 concentration is lower than RCP8.5, the other gases mostly resemble that RCP and much more different from the other pathways.
I also wonder at the expected annual growth rates in each RCP for 2019 to 2020, compared to the actual annual growth rate. This way we can find out if differences were accumulated in the past or if they are still being accumulated.

Sciguy

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Re: Where are we now in CO2e , which pathway are we on?
« Reply #259 on: Today at 12:23:52 AM »
CO2 is responsible for about two-thirds of the global warming.

https://www.climate.gov/news-features/understanding-climate/climate-change-atmospheric-carbon-dioxide

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Carbon dioxide is the most important of Earth’s long-lived greenhouse gases. It absorbs less heat per molecule than the greenhouse gases methane or nitrous oxide, but it’s more abundant and it stays in the atmosphere much longer. And while carbon dioxide is less abundant and less powerful than water vapor on a molecule per molecule basis, it absorbs wavelengths of thermal energy that water vapor does not, which means it adds to the greenhouse effect in a unique way. Increases in atmospheric carbon dioxide are responsible for about two-thirds of the total energy imbalance that is causing Earth's temperature to rise.


oren

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Re: Where are we now in CO2e , which pathway are we on?
« Reply #260 on: Today at 02:39:21 AM »
The preliminary annual numbers are in on the NOAA site too.  Here's how they stack up to the RCP scenario assumptions:


                             Observed   RCP 2.5   RCP 4.5   RCP 6.0   RCP 8.5

CO2 PPM              412.46       412.1       411.1      409.4      415.8

CH4 PPB             1879.1            1731     1801        1786        1924

N2O PPB               333.2              329        330       330        332

SF6 PPT               10.27              8.9         8.7        10.3         9.9
This probably belongs in the stupid questions thread but browsing the NOAA site for a while does not produce obvious results, though I found quite a few CSVs each containing different numbers. Can some kind soul provide the link for the annual observed data (this year + history) for each gas? And another link for the RCP scenario assumptions for each year?

Simon

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Re: Where are we now in CO2e , which pathway are we on?
« Reply #261 on: Today at 08:19:05 AM »
Is this what you need?

Bottom of page

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

As RCP is the radiative forcing of all greenhouse gases bar water vapour at the year 2100, you can see we are already tracking rcp6.0, possibly more.


oren

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Re: Where are we now in CO2e , which pathway are we on?
« Reply #262 on: Today at 11:04:19 AM »
Is this what you need?

Bottom of page

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

As RCP is the radiative forcing of all greenhouse gases bar water vapour at the year 2100, you can see we are already tracking rcp6.0, possibly more.
No, I am looking for the numbers posted by Sciguy, for 2020 as well as for previous years.

Sciguy

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Re: Where are we now in CO2e , which pathway are we on?
« Reply #263 on: Today at 05:53:08 PM »
Is this what you need?

Bottom of page

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

As RCP is the radiative forcing of all greenhouse gases bar water vapour at the year 2100, you can see we are already tracking rcp6.0, possibly more.
No, I am looking for the numbers posted by Sciguy, for 2020 as well as for previous years.

For CO2: go to global, click on the data tab and then on the link for globally averaged marine surface annual mean data:  https://www.esrl.noaa.gov/gmd/webdata/ccgg/trends/co2/co2_annmean_gl.txt

For CH4: click on the trends in CH4 button and scroll to the bottom.  Then click on the link for globally averaged marine surface annual mean data: https://www.esrl.noaa.gov/gmd/webdata/ccgg/trends/ch4/ch4_annmean_gl.txt

N2O (https://www.esrl.noaa.gov/gmd/webdata/ccgg/trends/n2o/n2o_annmean_gl.txt) and SF6 (https://www.esrl.noaa.gov/gmd/webdata/ccgg/trends/sf6/sf6_annmean_gl.txt) are the same as the methane instructions once you click on the tab to go their pages.

jai mitchell

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Re: Where are we now in CO2e , which pathway are we on?
« Reply #264 on: Today at 06:38:48 PM »
Yes agriculture and deforestation played a role.

The Ruddiman Hypothesis: A Debated Theory Progresses Along Interdisciplinary Lines

...snip...

https://www.globalpolicyjournal.com/blog/24/02/2021/ruddiman-hypothesis-debated-theory-progresses-along-interdisciplinary-lines

See linked post or the article for details.

Here is the referenced paper from the article:  https://www.nature.com/articles/s41598-018-28419-5



Quote
In summary, both our model simulations and proxy evidence suggest currently suitable conditions for incipient glaciation, in the absence of anthropogenic carbon emissions, due to the same favorable orbital and greenhouse forcing that triggered the cessation of interglacial warmth at the end of MIS19. Present-day orbital forcing is virtually the same as in MIS19, and contemporary GHG forcing would be virtually equivalent to MIS19’s if the Holocene climate had followed the expected late-interglacial GHG decline33. In that case, our present-day natural climate should be approximately the same as MIS19’s, including glacial inception. If the upward GHG trends during the late Holocene were caused by early agricultural carbon emissions, then ancient farming was apparently sufficient to avert a contemporary glacial inception.

bonus: a blast from the past. . .

https://forum.arctic-sea-ice.net/index.php/topic,1920.msg109831.html#msg109831
« Last Edit: Today at 06:48:17 PM by jai mitchell »
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oren

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Re: Where are we now in CO2e , which pathway are we on?
« Reply #265 on: Today at 06:47:48 PM »
Thanks Sciguy. And where do you get the RCP scenario assumptions for each gas for a given year?