MAN JUST ISN'T THAT POWERFUL:

[Nic Lewis. A semiretired successful financier from Bath, England, with a strong mathematics and physics background]  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.

The conclusion--taking the best observational estimates of the change in decadal-average global temperature between 1871-80 and 2002-11, and of the corresponding changes in forcing and ocean heat uptake--is this: A doubling of CO2 will lead to a warming of 1.6°-1.7°C (2.9°-3.1°F).

This is much lower than the IPCC's current best estimate, 3°C (5.4°F).

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