Running in Place


In a recent post Iain highlights that the current UN IPCC estimate for the global temperature impact of a doubling of CO2 is 1.90C – 5.40C, or on average about 3.70C. The big issue that was highlighted that could produce a lot of error is how the models handle clouds.

What’s really amazing is that in 1975, Syukuro Manabe was the lead author for a landmark paper called “The Effects of Doubling the CO2 Concentration on the Climate of a General Circulation Model.” in the Journal of the Atmospheric Sciences. Their estimate for the impact of a doubling of CO2: 3.50C. The authors warned that “it is not advisable to take too seriously” the specific numbers they published. The big problem: clouds.


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