With This Decade’s Climate Policy, Expect More Warming Than if Nothing Was Done at All

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The fundamental climate change policy question today is not how much we should reduce carbon dioxide emissions by when, but what will currently proposed carbon dioxide emissions reductions do to our climate in the near-term? In addition, what are the ramifications of short-lived climate pollutants that are discounted by the traditional long-term 100-year climate policy time frame?

Our current policy has changed little from the dawning of the Kyoto Protocol era. This era dates back to the Rio Earth Summit in 1992, and embodied the roots of current climate policy extending back to the first Intergovernmental Panel on Climate Change report (IPCC) in 1988.

Currently proposed (June 2014) EPA regulations on carbon dioxide emissions reductions are only 13 percent more stringent than Kyoto’s goals and do not address short-lived climate pollutants or the short-term climate time frame. (1)

Since the inception of the Kyoto era, we have emitted as much carbon dioxide as was emitted in the prior 236 years. (2) This rapid increase in greenhouse gas emissions is not the only thing that has changed. The science has changed dramatically as well.

What is important now is near-term increases in temperature from short-lived climate pollutants and the global cooling component of coal emissions.

Science Background: Fundamental Principles of Our New Climate Policy

The traditional 100-year climate projection time frame discounts short-term changes from short-lived climate pollutants.

Cooling aerosols, that are mostly sulfate emissions from burning coal, have masked up to 57 percent of warming that should have already occurred.

Increased warming earlier means future warming will be greater than it would have otherwise been because of feedbacks, and greater warming means an increased risk of abrupt change.

Frequent, geologically recent, abrupt changes that are 10 to 100 times more powerful than anything current modeling projects are robustly supported in the literature by highly accurate evidence preserved in ice cores.

These things have created a new climate policy paradigm where the most important consideration is not carbon dioxide. Of course, carbon dioxide is still the king of all warming pollutants and we must not neglect 25 years of valid climate pollution policy work, but there is more to the story now that climate science has progressed to the place it is today.

As important as carbon dioxide is, current policy today is so out of date that it could literally cause more warming in the most critical short-term time frames than if nothing was done at all.

The Underestimating Consensus Opinion

Why is this fundamental knowledge on short-lived climate pollutants, the short-term time frame and abrupt climate changes not significantly represented in the IPCC consensus opinion? It is because a consensus opinion is conservative by nature. In the case of climate science, the IPCC underestimates the impacts of climate change and discounts the most recent research. (3) Whether this is because climate change is worse than expected, emissions have grown faster than expected or because we have yet to act on reducing emissions (or all three) is not important.

What must be acknowledged is that the IPCC underestimates, and the magnitude of this fundamental trait of a consensus process can best be described through example: The 2007 IPCC said Antarctic ice loss would not begin until after 2100. The 2013 IPCC said that Antarctic ice loss has now begun and it has almost caught up with Greenland. This is not because Antarctica suddenly began losing ice. In the late 1990s, the academic literature was quantifying Antarctic ice loss similarly to what the 2013 IPCC report says. It has taken the IPCC 15 years for these research findings to be incorporated into the IPCC consensus. (4)

Climate policy today must look deeply into the science and not rely solely on the consensus opinion. Knowledge gained in the last half-dozen years about short-lived climate pollutants, atmospheric interactions of climate pollutants and even earlier findings about abrupt climate changes are not well assimilated into the consensus opinion. The times have changed, and the consensus is behind.

Traditional 100-Year Climate Policy Underestimates Short-Term Warming

Yet to be included significantly in consensus opinions is new knowledge that tells us short-term warming is discounted in traditional climate pollution policy. This discounting is caused by widespread use of global warming potential (GWP) based on the 100-year time frame.

Methane is one of several important short-lived warming pollutants that include black carbon, hydrogenated fluorocarbons (HFCs) and ozone. Based on which research is cited, methane (natural gas) has a GWP that is 21 or 25 times more than carbon dioxide in the 100-year time frame, but in the 20-year time frame this GWP is 105 times that of carbon dioxide. (5)

Researchers from the Massachusetts Institute of Technology (MIT) tell us: “Static measures, such as the GWP, give a false sense of the gases’ impacts, and could lead to unintended climate outcomes when used as the basis for policies and planning.” (6)

An example of the unintended consequences of not including short-lived climate pollutants in policy and planning is, after 12 years half of methane emissions disappear and after another 12 half to three-quarters of what remains is gone. After 100 years, the load of methane emissions remaining in our sky is relatively constant at about 10 to 20 years’ worth given a constant emission rate, but the amount of carbon dioxide keeps increasing because its half-life is about 300 years. (7)

In the 100-year time frame, current policy only credits methane with 10 to 20 percent of the warming that it is responsible for in the short-term time frame. This traditional policy characteristic creates a short-term world where warming is more than what the 100-year projections state.

More Warming Than if We Did Nothing at All

How can it warm “more” if we reduce carbon dioxide emissions? This is a fundamental policy problem that just five or six years ago did not exist because we did not know enough about short-lived warming and cooling pollutants and things like indirect atmospheric effects, black carbon and low elevation ozone to guide policy making for the short-term.

We now have the knowledge to create an “accounting” of warming from short and long-term climate pollutants that shows there is the distinct possibility that current policy will create more warming in the short-term (and thus the long-term through feedbacks) than if we did nothing at all. (8)

The National Center for Atmospheric Research (NCAR) has done this accounting with methane because the hydraulic fracturing boom has radically increased the penetration of natural gas in the energy generating market leading to a significant shutdown of coal generating facilities. This is widely thought to be a very good thing as natural gas produces only about half the carbon dioxide when burned compared to coal.

Hydraulic fracturing, or fracking, however, greatly increases the fugitive emissions from natural gas production and, being a short-lived climate pollutant, the short-term warming from natural gas is discounted. It is also very important to understand that the 2013 IPCC says methane is responsible for 42 percent of current warming. (9)

The NCAR researchers found that if we replaced half of all coal burning with natural gas we experience additional warming (not less warming because of less carbon dioxide) out to 2140 if the leakage rate is as high as 10 percent. But, relative to traditional 100-year climate policy, there was a big surprise. They found additional warming out to 2050 if the leakage rate is zero (0) percent. In other words, methane creates more warming in the short-term time frame as compared to the 100-year time frame even if we swapped no coal for natural gas. It’s the short-term nature of short-lived climate pollutants that matters. (10)

But it is not just methane that is a problem with current climate policy. Research out of NASA, the University of Illinois, Environmental Defense Fund and Berkeley shows oil is responsible for 2.5 times more warming than coal in the 20-year time frame. Yes, I wrote that correctly. This is the opposite of what we have known for 30 or more years. The traditional 100-year time frame, test tube laboratory evaluation does not take into account the short-term, other pollutants emitted from burning coal such as black carbon, indirect atmospheric effects and most importantly, global cooling from aerosols that are mostly sulfates in coal emissions. (11)

Global Cooling Pollutants

What, global cooling still lives? Didn’t that go away in the 1970s? The answer is both yes and no. The “global cooling” in the 1970s that a few papers discussed back then was not caused by the first stages of Earth’s 100,000 year-long ice age cycle. Our climate did stop warming between World War II and the late 1970s, but it was because of air pollution from postwar industrial expansion and global cooling sulfate emissions from burning fossil fuels, mostly in the United States and Europe. (12)

The Clean Air Act in 1970 and similar regulations in Europe put air pollution controls into effect that basically cleaned up the sulfate (acid rain) pollution through the use of power plant sulfate emission regulations and catalytic converters on automobiles. With the global cooling pollutants cleaned up, warming resumed by the end of the 1970s.

These global cooling pollutants created a “pause” in warming very similar to what we have seen since the turn of the 20th century because of many things that are led by rapidly increasing industrialization in Asia with almost no controls on global cooling sulfate emissions.

Verification that these global cooling emissions are a leading contributor to the “pause” comes from the 2013 IPCC report. They say that up to 57 percent of all warming could have been masked (mostly) by these global cooling sulfate aerosols. (13) This number does represent the high end of the IPCC range, but considering the underestimating capacity of the IPCC, this high end of the scenario is more likely than not.

Why Is the Short-Term So Important?

As we have already seen, greater warming in the short-term increases long-term warming even more. But there is a sleeper out there that is far more worrisome than a little extra warming in the short or long-term. (8)

This sleeper is abrupt climate change. In the last 100,000 years, highly accurate evidence from ice cores shows Earth has experienced 20 or more abrupt temperature changes of 9 to 15 degrees Fahrenheit globally, and 25 to 35 degrees in Greenland. Astonishingly, these changes happened in mere decades to as little as a few years. (14)

The reason they are not prevalent in the consensus opinion is, once again, the underestimating nature of the consensus process. Like Antarctic ice loss over the last 15 years, we simply do not have enough evidence of why these abrupt changes happened to include them in modeling of future changes.

Supercomputer climate models are actually quite good at recreating the relatively slow climate changes in prehistory. We know this because the scientists calibrate their models by starting them in the ancient past and seeing how well they recreate the history of our climate.

But modeling the abrupt changes is another matter entirely. A decent body of academic literature has been published showing why these abrupt changes have taken place, and we know for sure that they did take place with temperature jumps that make today’s 100-year worst-case warming scenarios pale in comparison. We also know that today’s carbon dioxide concentrations are increasing 14,000 times faster than anything normal in the last 610,000 years and possibly the last 64 million years, but the models still do not reproduce these abrupt changes well. (15)

So the underestimating consensus caveats their work heavily to keep from ignoring abrupt climate change. The IPCC reports are riddled with exceptions that state that warming could be more and it could be faster. But there is simply no way to model these changes so they are significantly understated in the consensus opinion.

The Big Picture

Because of the long-term bias of consensus climate policy, there is the distinct possibility of more warming in the critical short-term time frame than if nothing is done at all. Emissions reductions timing must be taken into consideration to minimize warming in the short, as well as the long-term. Decreasing coal use results in decreasing emissions of global cooling sulfates, which creates more warming in the short and long-term. Swapping natural gas for coal increases, not decreases warming in all but the longest time frames.

Because of the non-linear way that climate change happens, the future will likely see a proportionately radical change in the need for more robust policy than this article represents over the climate policy of the Kyoto era.

It is worth saying again that we will inevitably gain control over carbon dioxide pollution in the long-term, but the risk of abrupt changes makes extra warming in the short-term even more important than the long-term.

Footnotes

1. Thirteen percent more stringent . . . Kyoto’s US 2012 requirements were 7 percent below 1990 levels or 4,754 Gt C. The June 2014 EPA regulations require carbon dioxide emissions reductions that are 30 percent below 2005 levels or 4,124 Gt C., a 13.3-percent increase of reductions over Kyoto. It is important to note that in 2012 the only countries that had not ratified the Kyoto Protocol were the United States, Afghanistan, Andorra and South Sudan. In 2012, Canada renounced and in 2013 Afghanistan ratified.
https://unfccc.int/kyoto_protocol/status_of_ratification/items/2613.php

2. Since 1986 carbon dioxide emissions have been as much as were emitted in the prior 236 years . . . 1750 to 2013 (2012 and 2013 estimated) global emissions equal 1,443 G carbon dioxide, 1750 to 1986 global emissions equal 717 Gt carbon dioxide.
Boden et al., Global carbon dioxide Emissions from Fossil-Fuel Burning, Carbon dioxide Information Analysis Center, Oak Ridge National Laboratory, June 2011.
https://cdiac.ornl.gov/ftp/ndp030/global.1751_2008.ems

3. Underestimating IPCC Climate Consensus . . . Climate Science Predictions Prove Too Conservative, Scientific American, December 6, 2012, first sentence.
“Checking 20 years’ worth of projections shows that the Intergovernmental Panel on Climate Change has consistently underestimated the pace and impacts of global warming”
https://www.scientificamerican.com/article.cfm?id=climate-science-predictions-prove-too-conservative

The climate science consensus is likely conservative and does not reflect the magnitude of the problem . . . Freudenburg and Muselli, Global Warming estimates, media expectations and the asymmetry of scientific challenge, Global Environmental Change, August 2010. (This paper is backed up with 75 references.)

Top of the abstract: “Mass media in the US continue to suggest that scientific consensus estimates of global climate disruption, such as those from the Intergovernmental Panel on Climate Change (IPCC), are ‘exaggerated’ and overly pessimistic. By contrast, work on the Asymmetry of Scientific Challenge (ASC) suggests that such consensus assessments are likely to understate climate disruptions.”

Last part of the abstract: “…new scientific findings were more than twenty times as likely to support the ASC perspective than the usual framing of the issue in the US mass media. The findings indicate that supposed challenges to the scientific consensus on global warming need to be subjected to greater scrutiny, as well as showing that, if reporters wish to discuss “both sides” of the climate issue, the scientifically legitimate “other side” is that, if anything, global climate disruption may prove to be significantly worse than has been suggested in scientific consensus estimates to date.”

From the bottom of the second paragraph of the Introduction on page 1: “Precisely because of the ongoing pattern of criticisms toward climate science in general, and the IPCC in particular, work on the Asymmetry of Scientific Challenge (ASC) predicts that the overall effect on science will be precisely the opposite of the usual charges in the US mass media – that is, that scientific consensus estimates such as those from the IPCC should be expected to underestimate the severity of climate disruption taking place.”
https://gpwayne.files.wordpress.com/2010/09/freudenburg_2010_asc.pdf

The Copenhagen Diagnosis: Consensus process underestimates climate change . . . Brysse et al., Climate change prediction: Erring on the side of least drama?, Global Environmental Change, February 2013. (This paper is backed up by 113 references.)

From the abstract: “Over the past two decades, skeptics of the reality and significance of anthropogenic climate change have frequently accused climate scientists of “alarmism” . . . However, the available evidence suggests that scientists have in fact been conservative in their projections of the impacts of climate change. . . . We suggest, therefore, that scientists are biased not toward alarmism but rather the reverse: toward cautious estimates, where we define caution as erring on the side of less rather than more alarming predictions.”

Another quote from the paper definitively spells out the authors findings on page 330, section 3.0, first sentence: “Our analysis of the available studies suggests that if a bias is operative in the work of climate scientists, it is in the direction of under-predicting, rather than over-predicting, the rate and extent of anthropogenic climate change.”

Sea level rise underestimated . . . From page 328, section 2.1, first paragraph: “In a 2007 article, Rahmstorf and colleagues compared projections of global mean temperature change, sea level rise, and atmospheric carbon dioxide concentration from IPCC’s Third Assessment Report (TAR) with observations made since 1973 and concluded: “Overall, these observational data underscore the concerns about global climate change. Previous projections, as summarized by IPCC, have not exaggerated but may in some respects even have underestimated the change, in particular for sea level” (p. 709). In the TAR, released in 2001, the IPCC predicted an average sea level rise of less than 2 mm/yr, but from 1993 to 2006, sea level actually rose 3.3 mm/yr. – more than 50 percent above the IPCC prediction.”

From the 2009 National Research Council report prepared by the Committee on Strategic Advice on the US Climate Change Science Program, Bryssa and team reports in section 2.3: “IPCC projections have systematically underestimated key climate change drivers and impacts. This committee found that ‘The Intergovernmental Panel on Climate Change (IPCC) projections may have been too conservative’ in several areas, including carbon dioxide emissions by various countries, increases in surface temperatures, and sea level rise. The key climate metrics of global mean temperature and sea level rise are biased toward underestimation, so far as the evidence in this analysis shows.

From the Copenhagen Diagnosis (Allison et al., 2009), page 328, section 2.4: “[The Copenhagen Diagnosis] reviewed “hundreds of papers . . . on a suite of topics related to human-induced climate change” since the drafting of AR4, and, like the NRC report, found that key changes were happening either at the same rate as, or more quickly than, anticipated. Among their key findings were that global temperature increases over the past 25 years have been consistent with model predictions of 0.19 C per decade, virtually the same rate as for the 16 years mentioned in Rahmstorf et al., 2007), while other important impacts are proceeding faster than expected, including carbon dioxide emissions, increased rainfall in already rainy areas, continental ice-sheet melting, arctic sea-ice decline, and sea level rise. The data examined here overlap substantially with those analyzed by the Rahmstorf team, and it is noteworthy that an independent analysis by a different group of scientists comes to much the same judgment.”

Key Findings of the Copenhagen Diagnosis:

Rainfall has become more intense in already rainy areas, and “recent changes have occurred faster than predicted” (Allison et al., 2009, p. 15; see also Wentz et al., 2007; Allan and Soden, 2008; Liu et al., 2009).

Sea level rise has far exceeded predictions: “satellites show recent global average sea level rise (3.4 mm/yr. over the past 15 years) – to be “80 percent above past IPCC predictions” (Allison et al., 2009, p. 7).

Surface ocean heat uptake between 1963 and 2003 was 50 percent higher than expected based on previous calculations. This difference helps explain why sea level rise (from thermal expansion) is also greater than expected (Allison et al., 2009, p. 35; see also Domingues et al., 2008; Bindoff et al., 2007).

Studies also show that deep ocean warming is more widespread than previously thought (Allison et al., 2009, p. 35; see also Johnson et al., 2008a,b).

Summertime melting of Arctic sea ice has “accelerated far beyond the expectations of climate models” (Allison et al., 2009, p. 7; see also Stroeve et al., 2007). Indeed, using unusually vivid language, the authors note that the record for previous Arctic sea ice summer minimum extent was “shattered” in 2007, “something not predicted by climate models . . . This dramatic retreat has been much faster than simulated by any of the climate models assessed in the IPCC AR4” – with summer sea ice now well below the IPCC worst case scenario (Allison et al., 2009, pp. 29-30). Summer minimum sea ice was higher in subsequent years, but still fell near or below the long-term observed downward trend (which, as just noted, declines faster than the model predictions). Then, in 2012, another record minimum was set (Stroeve et al., 2007).

Carbon dioxide emissions were also tracking the high-end scenarios developed in 1999 and applied in AR4, showing that scientists’ “worst-case scenario” has in fact been realized (Allison et al., 2009, p. 9; see also Nakicenovic et al., 2000), for the decade before the global financial disruption. Some people have pointed out that the emissions projections were not meant to be reliable in the short term, but it is interesting to note that, so far as these data may be relevant, they fit the pattern of underestimation.

Bryssa and colleagues conclude with one more very important point about the lack of inclusion of feedbacks rom greenhouse gases emitted by melting permafrost on page 329, section 2.6: “One more topic will help to underscore the point. It is well accepted that certain feedbacks in the climate system, such as increased cloud cover or the Arctic ice-albedo feedback, could work to accelerate or decelerate global warming. One potentially large, positive feedback involves permafrost melting, which could release increasing amounts of greenhouse gases. The total carbon contained in permafrost has been estimated at 1672 gigatons, more than twice the amount of carbon in the atmosphere (Tarnocai et al., 2009). This means that the potential amplifying effect of greenhouse gas release from permafrost melting is enormous. Yet this feedback “has not been accounted for in any of the IPCC projections” (Allison et al., 2009, p. 21). This omission introduces a potentially profound bias in the climate projections – not toward overestimation of climate change, but toward its underestimation.”
https://www.sciencedirect.com/science/article/pii/S0959378012001215

4. Antarctica has begun to lose ice 100 years or more ahead of IPCC predictions . . . Antarctic surface mass balance (SMB) in the 2007 IPCC Report was supposed to increase, not decrease, for all scenarios, through 2100. This means that snow accumulation was supposed to be more than melt, evaporation and iceberg discharge combined . . .

Climate Change 2007: Working Group I: The Physical Science Basis, 10.6.5, Projections of Global Average Sea Level Change for the 21st Century, Table 10.7. Contributions to sea level rise form Antarctica under all scenarios is negative through the 21st century, meaning that ice and snow accumulation is greater than discharge, melt and evaporation.
https://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch10s10-6-5.html

Also see 10.6.4.1, Surface Mass Balance, first sentence, sixth paragraph: “All studies for the 21st century project that Antarctic SMB changes will contribute negatively to sea level, owing to increasing accumulation exceeding any ablation increase.”
https://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch10s10-6-4-1.html

Antarctic Surface Mass Balance 2103 IPCC . . . The average rate of ice loss from the Antarctic ice sheet has likely increased from 30 [–37 to 97] Gt yr.-1 over the period 1992–2001 to 147 [72 to 221] Gt yr.-1 over the period 2002 to 2011.” (2002 to 2011 is 147 +/- 74 Gt per year)

IPCC 2013, Summary for Policy Makers, B3 Cryosphere, page 9, third bullet
https://www.climatechange2013.org/images/report/WG1AR5_SPM_FINAL.pdf

Antarctic Surface Mass Balance 1996 . . . Rignot et al., Recent Antarctic ice mass loss from radar interferometry and regional climate modeling, Nature Geoscience, January 2008, page 8, table 2: Antarctic mass balance in 1996 was (-)112+/-91 Gt of per year.

(Full Article) https://www.ess.uci.edu/~erignot/publications/ngeo102.pdf

5.Methane has 105 times more potential global warming than carbon dioxide in the 20-year time frame . . . Shindell et al., Improved Attribution of Climate Forcing to Emissions, Nature, October 2009, figure 2 description, page 717.
https://www.see.ed.ac.uk/~shs/Climate percent20change/Data percent20sources/Shindell percent20methane.pdf

6.A false sense of the gases impact . . . The standard 100-year time frame global warming potential creates a discount where more warming occurs in the short-term than is projected using virtually all of the existing climate modelling. “Static measures, such as the GWP, give a false sense of the gases’ impacts, and could lead to unintended climate outcomes when used as the basis for policies and planning.”

MIT Article: Edwards and Trancik, Climate impacts of technologies depend on emissions timing, Nature Climate Change, April 25, 2014.
(Paywall) https://www.nature.com/nclimate/journal/v4/n5/full/nclimate2204.html

How to Count Methane Emissions, Commentary, MIT Technology Review, April 28, 2014.
https://www.technologyreview.com/aroundmit/526966/how-to-count-methane-emissions/

MIT News Release: https://newsoffice.mit.edu/2014/how-count-methane-emissions-0425

7.The half-life of carbon dioxide is 300 years . . . “In fairness, if the fate of anthropogenic carbon must be boiled down into a single number for popular discussion, then 300 years is a sensible number to choose, because it captures the behavior of the majority of the carbon. . . . However, the 300-year simplification misses the immense longevity [10,000 years] of the tail on the carbon dioxide lifetime, and hence its interaction with major ice sheets, ocean methane clathrate deposits, and future glacial/interglacial cycles. One could sensibly argue that public discussion should focus on a time frame within which we live our lives, rather than concern ourselves with climate impacts tens of thousands of years in the future. On the other hand, the 10,000-year lifetime of nuclear waste seems quite relevant to public perception of nuclear energy decisions today. A better approximation of the lifetime of fossil fuel carbon dioxide for public discussion might be 300 years, plus 25 percent that lasts forever.”

Archer, Fate of fossil fuel carbon dioxide in geologic time, Journal of Geophysical Research, vol. 110, 2005, page 5 of 6, Summary, final Paragraph.
https://melts.uchicago.edu/~archer/reprints/archer.2005.fate_carbon dioxide.pdf

IPCC 2013 AR5, Chapter 6, Box 6.1, pages 472, 473… Cannot ascribe a single lifetime limit to carbon dioxide – but references Archers work, simply not the subjective evaluation Archer used to describe the equilibrium process.

Life of Methane… 12 years, IPCC Third Assessment Report, Scientific Basis, C1, Table 1.
https://www.ipcc.ch/ipccreports/tar/wg1/016.htm

8.More warming than if nothing was done at all . . . Reducing carbon dioxide emissions alone creates more warming in the short-term than if methane alone were reduced early and more warming in the short and long term than if methane and carbon dioxide were reduced early. See the graph on the first page of the paper (page 1323).
Shoemaker et al., What role for short-lived climate pollutants in mitigation policy, Science, December 13, 2013.
https://ramanathan.ucsd.edu/files/pr200.pdf

9.The IPCC 2013 reports that 42 percent of warming that has already occurred has been caused by methane (CH4) . . . Total methane warming of 0.97 Wm(-2) out of 2.29 Wm(-2) of total warming equals 42 percent. This difference in estimates is caused by concentration changes in ozone and stratospheric water vapor due to CH4 emissions and other emissions indirectly affecting CH4.
IPCC 2013 Summary for Policy Makers (SPM), page 13, C. Drivers of Climate Change, first and fourth bullets. https://www.climatechange2013.org/images/report/WG1AR5_SPM_FINAL.pdf

10.With zero leakage, when natural gas replaces coal there is additional warming out to 2050 . . . The NCAR study finds additional warming out to 2140 if the leakage rate is as high as 10 percent. Replacing more than half of coal burning with natural gas would create even more warming in the 2030 to 2040 time frame because of the reductions of global cooling sulfates from burning less coal.
Wigley, Coal to gas: the influence of methane leakage, Climatic Change Letters, August 26, 2011, abstract, final sentence.
Press Release: https://www2.ucar.edu/atmosnews/news/5292/switching-coal-natural-gas-would-do-little-global-climate-study-indicates
Full paper: https://link.springer.com/article/10.1007 percent2Fs10584-011-0217-3#page-1

11.Oil (transportation sector) is responsible for 2.5 times more warming than coal (energy sector) in the 20-year time frame . . . Unger et al., Attribution of climate forcing to economic sectors, PNAS, December 2009, page 3384, Figure 1: On-road (transportation) radiative forcing (global warming) of 199 Watts per meter vs. Power (coal) 79 watts per meter = 2.52 times more warming.
https://www.pnas.org/content/early/2010/02/02/0906548107.full.pdf

12.Air pollution caused a warming “pause” between World War II and the late 1970s . . . Air pollution caused global cooling between 1940 and the 1970s: Nature: Booth et al., Aerosols implicated as a prime driver of twentieth-century North Atlantic climate variability, Nature, April 24, 2012. https://www.mendeley.com/research/aerosols-implicated-prime-driver-twentieth-century-north-atlantic-climate-variability/

Press release: https://phys.org/news/2012-04-term-north-atlantic-surface-temperature.html

13.The 2013 IPCC report says up to 57 percent of warming masked by aerosols . . . In the summary for policy makers, 57 percent of warming that should have been experienced to date has been masked by aerosols. The major driver in this masking is sulfates from burning coal. The high end of the range suggested by the IPCC has been used in this 57 percent estimate because of the history of underestimation by the IPCC.

IPCC 2013 Summary for Policy Makers (SPM), page 13, C. Drivers of Climate Change, bullet 7. Up to (-)1.9 to (-) 0.1Wm(-2) of warming has been masked by aerosols out of 2.29 Wm(-2) of total warming experienced to date. This equals 57 percent of total warming masked by aerosols and does represent the high end of the range. https://www.climatechange2013.org/images/uploads/WGI_AR5_SPM_brochure.pdf

14.Abrupt climate change as fast as a few years . . . Abrupt Climate Change – Anticipating Surprises, National Research Council of the National Academies of Science, December 2013, Preface, page vii, second paragraph. https://www.nap.edu/download.php?record_id=18373

9 to 15 degrees across the globe . . . Alley, The Two-Mile Time Machine: Ice Cores, Abrupt Climate Change, and Our Future, Princeton University Press, 2000, page 119, Figure 12.2.
https://press.princeton.edu/titles/6916.html

Data for figure 12.2 is from Cuffey and Clow, Temperature, accumulation, and ice sheet elevation in central Greenland through the last deglacial transition, Journal of Geophysical Research, volume 102(C12), pp 26,383 to 26,396.
Abstract: https://onlinelibrary.wiley.com/doi/10.1029/96JC03981/abstract

Greenland temperature change is twice that of the global average . . . Chylek and Lohmann, Ratio of Greenland to global temperature change – comparison of observations and climate models, Geophysical Research Letters, July 2005, Chylek and Lohmann say the Greenland temperature change is 2.2 times greater than the global average. From Alley’s Figure 12.2 (Cuffey and Clow), the 25 to 35 degree F abrupt changes in Greenland would equal 9 to 15 degrees average across the globe.
https://www.iac.ethz.ch/doc/publications/Chylek-Lohmann-GRL2005.pdf

Also see: 25 to 35 degrees in Greenland… National Research Council, Abrupt Climate Change: Inevitable Surprises, Committee on Abrupt Climate Change, 2002. Figure 2.5, page 37.
https://www.nap.edu/download.php?record_id=10136

15.Carbon dioxide is increasing 14,000 times faster than the long-term average for the last 610,000 years . . . Zeebe and Caldeira, Close mass balance of long-term carbon fluxes from ice-core carbon dioxide and ocean chemistry records, Nature Geoscience, Advance Online Publication, April 27, 2008. The 14,000 years quote comes from the University of Hawaii press release for the paper, ninth paragraph.
(paywall) https://www.nature.com/ngeo/journal/v1/n5/abs/ngeo185.html
(Available on ReserachGate with free account) https://www.researchgate.net/publication/232759754_Close_mass_balance_of_long-term_carbon_fluxes_from_ice-core_carbon dioxide_and_ocean_chemistry_records
Press Release: https://www.hawaii.edu/news/article.php?aId=2272