That would be news to the IPCC, which stated in 2007:
From an interview with EurActiv:
EurActiv: Our stories often receive comments from climatesceptics, who say that such statements are just based on unreliable computer models and climate science is not robust enough to compensate for the economic cost of decarbonisation…
Hansen: In fact, we base our understanding more on observations of how the Earth has responded in the past to changes in the boundary conditions, including the atmospheric composition. I’m using models less and less – although they are very helpful in confirming our understanding – but it is not correct to say that these assessments are based on models.
Observations? If you include ‘observing’ model output on your monitor, well, ok….
Damn – so what’s all the fuss about? The past analyses prove that temperature goes up and down all the time! After a period of warming, there will be a period of cooling – if history is anything to write home about. Where’s the catastrophe?
So, discard the models and what do you have? Hansen’s “understanding” which, to date, is at best qualitative (if you give him a pass on the factors he ignored or misunderstood) and forms no basis for any quantitative assessment.
Dr. Hansen’s comments are beginning to drift toward outright self-contradiction. Hansen has been an important shaper of the alarmist side of debate, including the use of models. Now he claims to be basing his concerns — or to have always done — on observations, except that observations don’t support his concerns and never have.
Plus this is the same NASA scientist who has generally ignored the satellite temperature record. Granted that it’s relatively short, only around 35 years now, but it also has been quite stable through the period of alleged rapid warming.
I’d ask how Hansen retains any credibility, except that Al Gore can still get large speaking fees, so obviously there’s a wildly credulous population out thar.