Study in journal Nature Climate Change: 114 out of 117 climate model predictions from 1990’s wildly overestimated global warming
'The predictions forecasted two times more global warming than actually occurred...'I looked at 73 climate models going back to 1979 and every single one predicted more warming than happened in the real world.' -- - John Christy, a professor at the University of Alabama in Huntsville -- 'Many of the overestimations also made their way into the popular press. In 1989, the Associate Press reported: "Using computer models, researchers concluded that global warming would raise average annual temperatures nationwide 2 degrees by 2010." But according to NASA, global temperature has increased by less than half that -- about 0.7 degrees Fahrenheit -- from 1989 to 2010'
Christy said he believes the models overestimate warming because of the way they handle clouds.
“Most models assume that clouds shrink when there is CO2 warming, and that lets in more sun, and that’s what heats up the planet – not so much the direct effect of CO2, but the ‘feedback effect’ of having fewer clouds. In the real world, though, the clouds aren’t shrinking,” he said.
The study also says that an overestimate of the power of CO2 as a greenhouse gas could be why the models over-predict, but that they do not know why the models are wrong at this point.
Christy said he is not optimistic about the models being fixed.
“The Earth system is just too complex to be represented in current climate models. I don’t think they’ll get it right for a long time.”
