Monday, October 19, 2009
The Climate Sensitivity is Probably Really High
I'm not surprised by the trend for recent research to come up with higher values of the climate sensitivity - the change in temperature in the long-term for a doubling of atmospheric carbon dioxide. The piece I linked suggests that current levels of carbon dioxide are associated in the long-run with 25 to 50m higher sea levels, though we do need to be cautious in basing current predictions to paleodata for a world where the continents and oceans were configured slightly differently. My research found climate sensitivities in the range of 4-8C depending on model configuration. I gave up on publishing the second paper though in the climate literature and decided to focus on energy economics. It's hard to keep up to date in too many fields at once...
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I am always perplexed by the climate sensitivity values. Right now the policy debate - 350, 450, 550ppm - is over smaller numbers. Do we not have credible estimates for long term effects over that sort of range of variation? Is it so badly understood that I may as well say 'if climate sensitivity turns out to be 8, then a 50% increase means 4 degrees' - I'm wary of thinking about the medium term that way, but it seems to be more or less the default.
ReplyDeleteI began to write a response but it got so long it'll be my next blog post :)
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