There was lots of breathless anticipation last week over the Drew Shindell paper on climate sensitivity, which was embargoed until 1800GMT on Sunday (see the embargoed PR from Nature here), but some people like Climate Nexus couldn’t help themselves and blurted it out anyway, breaking the embargo on Friday.
I asked Shindell within minutes of that email if he was upset about the embargo being broken by email and by telephone (voicemail) and got no response. So I have to assume that he and GISS are OK with such things. We’ll remember that next time.
I sent my copy of the Shindell paper over to Nic Lewis, rather than worry about the embargo, and Nic has responded in great detail with a knockout analysis, see below.
While the usual suspects are now trumpeting the recently published Shindell (no et al, all his) paper which says that despite observations, climate sensitivity really is high, honest, the Shindell paper gets low marks when it is examined in detail. See the analysis below the press release.
First, from GISS: RELEASE 14-073
Long-Term Warming Likely to Be Significant Despite Recent Slowdown
A new NASA study shows Earth’s climate likely will continue to warm during this century on track with previous estimates, despite the recent slowdown in the rate of global warming.
This research hinges on a new and more detailed calculation of the sensitivity of Earth’s climate to the factors that cause it to change, such as greenhouse gas emissions. Drew Shindell, a climatologist at NASA’s Goddard Institute for Space Studies in New York, found Earth is likely to experience roughly 20 percent more warming than estimates that were largely based on surface temperature observations during the past 150 years.
Shindell’s paper on this research was published March 9 in the journal Nature Climate Change.
Global temperatures have increased at a rate of 0.22 Fahrenheit (0.12 Celsius) per decade since 1951. But since 1998, the rate of warming has been only 0.09 F (0.05 C) per decade — even as atmospheric carbon dioxide continues to rise at a rate similar to previous decades. Carbon dioxide is the most significant greenhouse gas generated by humans.
Some recent research, aimed at fine-tuning long-term warming projections by taking this slowdown into account, suggested Earth may be less sensitive to greenhouse gas increases than previously thought. The Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC), which was issued in 2013 and was the consensus report on the state of climate change science, also reduced the lower range of Earth’s potential for global warming.
To put a number to climate change, researchers calculate what is called Earth’s “transient climate response.” This calculation determines how much global temperatures will change as atmospheric carbon dioxide continues to increase – at about 1 percent per year — until the total amount of atmospheric carbon dioxide has doubled. The estimates for transient climate response range from near 2.52 F (1.4 C) offered by recent research, to the IPCC’s estimate of 1.8 F (1.0 C). Shindell’s study estimates a transient climate response of 3.06 F (1.7 C), and determined it is unlikely values will be below 2.34 F (1.3 C).
Shindell’s paper further focuses on improving our understanding of how airborne particles, called aerosols, drive climate change in the Northern Hemisphere. Aerosols are produced by both natural sources – such as volcanoes, wildfire and sea spray – and sources such as manufacturing activities, automobiles and energy production. Depending on their make-up, some aerosols cause warming, while others create a cooling effect. In order to understand the role played by carbon dioxide emissions in global warming, it is necessary to account for the effects of atmospheric aerosols.
While multiple studies have shown the Northern Hemisphere plays a stronger role than the Southern Hemisphere in transient climate change, this had not been included in calculations of the effect of atmospheric aerosols on climate sensitivity. Prior to Shindell’s work, such calculations had assumed aerosol impacts were uniform around the globe.
This difference means previous studies have underestimated the cooling effect of aerosols. When corrected, the range of likely warming based on surface temperature observations is in line with earlier estimates, despite the recent slowdown.
One reason for the disproportionate influence of the Northern Hemisphere, particularly as it pertains to the impact of aerosols, is that most man-made aerosols are released from the more industrialized regions north of the equator. Also, the vast majority of Earth’s landmasses are in the Northern Hemisphere. This furthers the effect of the Northern Hemisphere because land, snow and ice adjust to atmospheric changes more quickly than the oceans of the world.
“Working on the IPCC, there was a lot of discussion of climate sensitivity since it’s so important for our future,” said Shindell, who was lead author of the IPCC Fifth Assessment Report’s chapter on Anthropogenic and Natural Radiative Forcing. “The conclusion was that the lower end of the expected warming range was smaller than we thought before. That was a big discussion. Yet, I kept thinking, we know the Northern Hemisphere has a disproportionate effect, and some pollutants are unevenly distributed. But we don’t take that into account. I wanted to quantify how much the location mattered.”
Shindell’s climate sensitivity calculation suggests countries around the world need to reduce greenhouse gas emissions at the higher end of proposed emissions reduction ranges to avoid the most damaging consequences of climate change. “I wish it weren’t so,” said Shindell, “but forewarned is forearmed.”
For more information about the Goddard Institute for Space Studies, visit:
OK now have a look at what Nic Lewis has to say about it on Climate Audit. It seems the results are all about adjustments and not the actual sensitivity.
Basically Shindell used CMIP5 models does an analysis to show that there are gaps between the climate sensitivity response to different types of forcings.
So, once these are “adjusted for”, Shindell claims that the lower climate sensitivity to carbon dioxide is not possible. He’s claiming that anything lower than 1.3 is bogus.
Some adjustments applied seem almost as large as the effect. Nic Lewis writes at Climate Audit:
One of those adjustments is to add +0.3 W/m² to the figures used for model aerosol forcing to bring the estimated model aerosol forcing into line with the AR5 best estimate of -0.9 W/m². He notes that the study’s main results are very sensitive to the magnitude of this adjustment.
If it were removed, the estimated mean TCR would increase by 0.7°C. If it were increased by 0.15 W/m², presumably the mean TCR estimate of 1.7°C would fall to 1.35°C – in line with the Otto et al (2013) estimate. Now, so far as I know, model aerosol forcing values are generally for the change from the 1850s, or thereabouts, to ~2000, not – as is the AR5 estimate – for the change from 1750. Since the AR5 aerosol forcing best estimate for the 1850s was -0.19 W/m², the adjustment required to bring the aerosol forcing estimates for the models into line with the AR5 best estimate is ~0.49 W/m², not ~0.3 W/m². On the face of it, using that adjustment would bring Shindell’s TCR estimate down to around 1.26°C.
It’s just like what GISS does to the temperature record, they can’t get there without adjusting the data. They don’t represent base reality, but rather an adjusted reality:
To summarise, four out of six models/model-averages used by Shindell are included…in AR5 Figure 10.4 … none of these show scaling factors for ‘other anthropogenic’…that are consistent with unity at a 95% confidence level. In a nutshell, these models at least do not realistically simulate the response of surface temperatures and other variables to these factors.
Yes, adjusted, modeled, non-reality. That’s the world NASA GISS lives in, and it started all the way back in 1988 when Hansen and Wirth decided to adjust the temperature of the Senate Hearing room when Hansen made his “we must do something” pitch on global warming:
Just like the clown show on the Senate Floor last night, it is all sound and fury, signifying nothing.
Now here’s the part that really pisses me off. This paper is done entirely on the taxpayer’s dime, publicly funded at NASA, yet it is behind a paywall at Nature Climate Change. Perhaps the next time I get an “embargoed” paper where GISS and Shindell don’t care about the embargo when notified of a breach, and put publicly funded work behind a paywall, I think I’ll just publish it right then and there.
Here’s the part of the Shindell paper the public is allowed to read:
Inhomogeneous forcing and transient climate sensitivity
Drew T. Shindell Nature Climate Change (2014) doi:10.1038/nclimate2136
- Received 02 October 2013 Accepted 16 January 2014 Published online09 March 2014
Understanding climate sensitivity is critical to projecting climate change in response to a given forcing scenario. Recent analyses1, 2, 3 have suggested that transient climate sensitivity is at the low end of the present model range taking into account the reduced warming rates during the past 10–15 years during which forcing has increased markedly4. In contrast, comparisons of modelled feedback processes with observations indicate that the most realistic models have higher sensitivities5, 6. Here I analyse results from recent climate modelling intercomparison projects to demonstrate that transient climate sensitivity to historical aerosols and ozone is substantially greater than the transient climate sensitivity to CO2. This enhanced sensitivity is primarily caused by more of the forcing being located at Northern Hemisphere middle to high latitudes where it triggers more rapid land responses and stronger feedbacks. I find that accounting for this enhancement largely reconciles the two sets of results, and I conclude that the lowest end of the range of transient climate response to CO2 in present models and assessments7 (<1.3 °C) is very unlikely.
For a dose of reality, read Nic Lewis paper that is observationally based, and without adjustments applied: The Lewis and Crok exposition – Climate less sensitive to Carbon Dioxide than most models suggest