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.”