Forget the Doha climate jamboree that ended earlier this month. The theological discussions in Qatar of the arcana of climate treaties are irrelevant. By far the most important debate about climate change is taking place among scientists, on the issue of climate sensitivity: How much warming will a doubling of atmospheric carbon dioxide actually produce? The Intergovernmental Panel on Climate Change has to pronounce its answer to this question in its Fifth Assessment Report next year.
The general public is not privy to the IPCC debate. But I have been speaking to somebody who understands the issues: Nic Lewis. A semiretired successful financier from Bath, England, with a strong mathematics and physics background, Mr. Lewis has made significant contributions to the subject of climate change.
He first collaborated with others to expose major statistical errors in a 2009 study of Antarctic temperatures. In 2011 he discovered that the IPCC had, by an unjustified statistical manipulation, altered the results of a key 2006 paper by Piers Forster of Reading University and Jonathan Gregory of the Met Office (the United Kingdom’s national weather service), to vastly increase the small risk that the paper showed of climate sensitivity being high. Mr. Lewis also found that the IPCC had misreported the results of another study, leading to the IPCC issuing an Erratum in 2011.
Mr. Lewis tells me that the latest observational estimates of the effect of aerosols (such as sulfurous particles from coal smoke) find that they have much less cooling effect than thought when the last IPCC report was written. The rate at which the ocean is absorbing greenhouse-gas-induced warming is also now known to be fairly modest. In other words, the two excuses used to explain away the slow, mild warming we have actually experienced—culminating in a standstill in which global temperatures are no higher than they were 16 years ago—no longer work.
In short: We can now estimate, based on observations, how sensitive the temperature is to carbon dioxide. We do not need to rely heavily on unproven models. Comparing the trend in global temperature over the past 100-150 years with the change in “radiative forcing” (heating or cooling power) from carbon dioxide, aerosols and other sources, minus ocean heat uptake, can now give a good estimate of climate sensitivity.
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