Summary: The internet overflows with commentary about climate change, much by scientists. Yet all this talk generates more heat than light. Here’s a small but telling example, about an IPCC finding that should be a standard note in articles about Obama’s Clean Power Plan — but is ignored by journalists and so little known.
“Ignorance and confidence are constant companions.”
— Into the Heart of Truthby John McAfee (2001).
Obama’s sweeping Clean Power Plan rests on a finding in Chapter 10 of Working Group I of the IPCC’s latest report, AR5 — something important and little known. See page 884, emphasis added…
“We conclude, consistent with Hegerl et al. (2007b) {i.e., chapter 9 of AR4}, that more than half of the observed increase in GMST {global mean surface temperature} from 1951 to 2010 is very likely due to the observed anthropogenic increase in GHG {greenhouse gas} concentrations.”
AR4’s statement about the effect of GHGs was similar (although put in its Summary for Policy-makers, not page 884): “Most of the observed increase is global average temperature since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations.”
In both AR4 and AR5 the IPCC defines “Very likely” as having a “likelihood of the occurrence/outcome” at “>90% probability”. That’s below the 95% standard usually used in both science research and making of vital public policy decisions (e.g., by the EPA and FDA).
This finding about the effect of GHGs is relatively little known compared to AR5’s better known finding in the Summary for Policymakers about all anthropogenic forcings…
“It is extremely likely {95%+ certainty} that more than half of the observed increase in global average surface temperature from 1951 to 2010 was caused by the anthropogenic increase in greenhouse gas concentrations and other anthropogenic forcings together.”
I learned of the AR5’s lower level of confidence about the effect of GHG from a comment by attorney Tom Curtis in a comment at Skeptical Science, There are few mentions of this on Google. I asked two climate scientists if they know of this (they didn’t) — understandable since it’s buried on page 884 of AR5. This factoid about the effect of greenhouse gases has several kinds of significance.
First, this is the IPCC finding most relevant to President Obama’s Clean Power Plan to reduce US CO2 emissions. Such sweeping policies usually demand 95% confidence or the equivalent in the underlying research. This doesn’t have it. It has 90%. Journalists and scientists should report it correctly.
Second, a central tenet of the publicity campaign about climate change has been the consensus of scientists about their strong confidence about the effect of greenhouse gases on global temperatures since 1950. So it’s important that we understand that confidence.
Surveys of varying quality have shown strong agreement among climate scientists with the IPCC’s findings. The most recent and detailed was a survey about this of approximately 6,550 scientists studying climate change published as “Scientists’ Views about Attribution of Global Warming” by Bart Verheggen et al in the 19 Aug 2014 issue of Environmental Science and Technology.
Unfortunately, the public has been misled about the consensus of scientists and their confidence by the propaganda campaign to enact strong public policy changes. Absurdly broad claims have been made about the “95%” or “97%” of scientists, with little or no factual support. Also the meaning of statistical confidence has been grossly distorted. For example, see the NYT op-ed “Playing Dumb on Climate Change” by Naomi Oreskes (Prof, History of Science at Harvard). As many have pointed out, much of this is incorrect…
About the meaning of these statistics
For a clear explanation of these matters see “The New York Times Op Ed page needs a statistician” by Michael Lavine (Prof Statistics, U of MA-Amherst) and “Significance Levels are Made a Whipping Boy on Climate Change Evidence: Is .05 Too Strict?” by Deborah G. Mayo (Prof at VA Tech). I strongly recommend reading the discussion in the comments of Mayo’s post.
For a more advanced discussion of these issues — which apply to all sciences — see “The fickle P value generates irreproducible results” by Lewis G. Halsey et al in Nature Methods, March 2015. It’s part of a larger and growing debate among scientists about proper use of statistical tools, driven by the growing realization that much of today’s research cannot be replicated.
“Error is a delicate concept; for if we can call on it at will, or willfully, then
it no longer explains anything or accounts for anything. And if we can’t
call on it when we need it, none of our theories … will stand up.— Philosophy of Science: A Formal Approach
by Henry Ely Kyburg (1968).
For More Information
If you liked this post, like us on Facebook and follow us on Twitter. For more information see The keys to understanding climate change and My posts about climate change. Also, see these posts about the IPCC…
- Climate scientists speak to us. What is their consensus opinion?
- Another disturbing article about climate change. Fortunately we have the IPCC!
- Is our certain fate a coal-burning climate apocalypse? No!
- The 97% consensus of climate scientists is only 47%.
To help you better understand today’s extreme weather
To learn more about the state of climate change see The Rightful Place of Science: Disasters and Climate Change
