“It is extremely likely (95 – 100% certain) that human activities caused more than half of the observed increase in global mean surface temperature from 1951 to 2010.”
— From the “Summary for Policy-Makers” of the IPCC’s AR5 Working Group I. Unfortunately, there is no consensus about the timing and magnitude of future warming.
On March 29 the House Science, Space, and Technology Committee held a hearing on “Climate Science: Assumptions, Policy Implications, and the Scientific Method“. The star witness, in terms of public profile, was Michael Mann — Professor of Atmospheric Science and Director of the Earth System Science Center (ESSC) at Pennsylvania State. Mann gave a remarkable demonstration of why the 29 year-long climate change campaign has produced such small results. He opens strongly and closes with even more strongly. But his own evidence undercuts his claims.
(1) A consensus about current adverse impacts of climate change?
Mann opens with this claim, one that has been often said during the past several years.
“The U.S. National Academy of Sciences, the Royal Society of the U.K., and all of the scientific societies of all of the industrial nations — the more than 30 scientific societies in the U.S. that have weighed in on the matter, and at least 97% of scientist publishing in the field have all concluded, based on the evidence, that that climate change is real, is human-caused, and is already having adverse impacts on us, our economy, and our planet.”
Yes, there is a consensus that climate change is real and largely human-caused. The third claims, about already causing adverse impacts, is quite false — as shown by the three footnotes Mann provides.
1. “Joint science academies’ statement: Global response to climate change” signed by representatives of 11 national science academies in 2005. It says that “Climate change is real.” No mention of current adverse impacts, just “changes in Earth’s climate.” Excerpt…
“However there is now strong evidence that significant global warming is occurring. The evidence comes from direct measurements of rising surface air temperatures and subsurface ocean temperatures and from phenomena such as increases in average global sea levels, retreating glaciers, and changes to many physical and biological systems. It is likely that most of the warming in recent decades can be attributed to human activities. This warming has already led to changes in the Earth’s climate.”
2. “Scientific Consensus on Global Warming” by the Union of Concerned Scientists, undated. Gives excerpts from the statements by many scientific societies. Few mention current “adverse impacts”. The UCS summary…
“However, there is now an overwhelming scientific consensus that global warming is indeed happening and humans are contributing to it.”
3. “Consensus on consensus: a synthesis of consensus estimates on human-caused global warming” by John Cook et al in Environmental Research Letters, April 2016. The abstracts says “The consensus that humans are causing recent global warming is shared by 90%–100% of publishing climate scientists according to six independent studies by co-authors of this paper.” It says little about current adverse impacts.
(2) Mann describes the Serengeti Strategy
“I coined the term “Serengeti Strategy” back in 2012 in The Hockey Stick and the Climate Wars: Dispatches from the Front Lines to describe how industry special interests who feel threatened by scientific findings — be it tobacco and lung cancer, or fossil fuel burning and climate change — single out individual scientists to attack in much the same way lions of the Serengeti single out an individual zebra from the herd. In numbers there is strength, but individuals are far more vulnerable.
“Science critics will therefore often select a single scientist to ridicule, hector, and intimidate. The presumed purpose is to set an example for other scientists who might consider sticking their neck out by participating in the public discourse over certain matters of policy-relevant science.”
Mann coined the term for this strategy, and activists have used it skillfully and often. It is quite daft to portray himself — lavishly rewarded in fame and income — as a victim. Activists’ victims have not done so well. Roger Pielke Jr. was a professor of environmental science. For accurately describing the conclusions of the IPCC and peer-reviewed research, he is now in the Department of Athletics. For details about this shameful story see The Left stages a two minute hate on Roger Pielke Jr. and Roger Pielke Jr. describes the smear attacks on him.
Mann follows this explanation of the “Serengeti Strategy” with a demonstration of how it works.
“Bates’ allegations were also published on the blog of climate science denier Judith Curry (I use the term carefully — reserving it for those who deny the most basic findings of the scientific community, which includes the fact that human activity is substantially or entirely responsible for the large-scale warming we have seen over the past century”
Normal academic practice would be to support such an incendiary accusation with citations of Curry’s statements that “deny the most basic findings of the scientific community.” Instead he cites a peripheral news story (WaPo: “Scott Pruitt’s office deluged with angry callers after he questions the science of global warming“) and an attack on Curry by an activist scientist (“IPCC attribution statements redux: A response to Judith Curry” by Gavin Schmidt, RealClimate).
Oddly in the Q&A Mann has amnesia about his sworn statement and says “A number of statements have been attributed to me. I don’t believe I’ve called anybody a denier.” Steve McIntyre found some relevant tweets by Mann.
When Mann speaks about the strategy to “ridicule, hector, and intimidate” opponents, he speaks from experience.
I think @MichaelEMann deserves a lot of credit for putting up with continued nonsense from Judith Curry: https://tonyhellerakastevengoddardisnotasociopath.wordpress.com/2015/08/20/in-latest-blog-post-judith-curry-continues-to-beat-the-hiding-the-decline-drum/ …
Julie Kelly at National Review debunks some of Mann’s testimony, such as this fun trivia (which he could have easily followed afterwards with a correction and apology – but didn’t).
“Turns out Mann appears to be a bit of a denier himself. Under questioning, Mann denied being involved with the Climate Accountability Institute even though he is featured on its website as a board member. CAI is one of the groups pushing a scorched-earth approach to climate deniers, urging lawmakers to employ the RICO statute against fossil-fuel corporations. When asked directly if he was either affiliated or associated with CAI, Mann answered ‘no.’” [Judith Curry notes: Mann also lists this affiliation on his CV.]
This resort to insults plus erroneous statements must eroded Mann’s credibility to any informed and fair observer.
(3) About climate science: Mann destroys his own case
Most of the first 11 pages of Mann’s testimony concerns squabbles between activists and skeptics, mostly about the degree of past warming (about which there is a strong consensus among climate scientists). None of which is of much relevance to the public policy questions of interest to Congress.
Then he skips to the question of climate science of most importance to public policy: how accurate and reliable are climate models? Mann gives a confident answer.
“While we’re at it, let me address another favorite talking point of the critics, the claim that climate models we use to project future climate change are unreliable and untested. The reality is that the models have been tested vigorously and rigorously in numerous ways, and have passed a number of impressive tests in the past, such as James Hansen’s famous successful predictions from the 1980s and 1990s.
“Let me take the opportunity to bring your attention to one particular analysis that appears in the latest issue of Nature Climate Change. Back in 1989, legendary climate scientists Ron Stouffer (a graduate of our program at Penn State I’m proud to say) and Suki Manabe made a prediction not just of the average warming of the globe, but of the precise global pattern of that warming. That pattern matches the observed pattern of warming that has ensued remarkably well.”
He gives two citations to support this massive claim. The first is a blog post: “Hansen’s 1988 projections” by Gavin Schmidt, 15 May 2007. It discusses “Global climate changes as forecast by Goddard Institute for Space Studies three-dimensional model” by Hansen et el in Journal of Geophysical Research, 20 August 1988. But if the evidence for this prediction was strong, why has Hansen — or somebody — not published peer-reviewed confirmation. It would be headline news.
The second citation Mann gives is peer-reviewed: “Assessing temperature pattern projections made in 1989” by Ronald J. Stouffer and Syukuro Manabe in Nature Climate Change, March 2017. Mann materially misrepresents the findings. The paper says that limitations in their model cause …
“problems in comparing models to observations and makes the comparisons shown here qualitative in nature. It is one of the reasons why we focus our attention on the geographical distribution of surface temperature change rather than the magnitude of change in this study.”
These are the two strongest citations Mann finds to support models’ forecasts, on the basis which we are supposed to restructure the world economy. On that high note Mann closes his presentation. Nothing in the testimony of the three skeptics proves the weakness of activists’ reasoning as effectively as Mann’s own advocacy.