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Climate change as predicted in 1981. Grey shows predictions from global temperature rise via computer models run of Hansen et al 198. Red shows real world data taken since paper was published. (Geert Jan van Oldenborgh and Rein Haarsma, KNMI, RealClimate)

How Good Were Climate Models 30 Years Ago?

Jul 17, 2012

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Models vs Reality: Gray lines are predictions from 1981 models of global temperature increase.  Red line is real world data.

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Pretty good it appears.

In a piece back in April at RealClimate, guest bloggers Geert Jan van Oldenborgh and Rein Haarsma of the Dutch Meterological Institute (KNMI) look at back at a 1981 paper by the now famous James Hansen and others. At the time, of course, neither Hansen or global warming were household names. Still the paper got noticed. As the Oldenborgh and Haarsma explain:

"They got 10 pages in Science, which is a lot, but in it they cover radiation balance, 1D and 3D modelling, climate sensitivity, the main feedbacks (water vapour, lapse rate, clouds, ice- and vegetation albedo); solar and volcanic forcing; the uncertainties of aerosol forcings; and ocean heat uptake."

The Hansen et al paper includes (among other things) a plot of predicted global temperatures as a function of time. Oldenborgh and Haarsem take this figure and overplot the actual real world data gathered since the paper appeared. The fit between the Hansen et al predictions and the behavior of the Earth's climate is remarkably good. This is even more remarkable when you realize your iPhone now might have comparable computing power to the machines they were running their simulations on.

The lesson to draw from all of this is obvious. The basic principles of climate science has been mature for a while. While there remain significant issues to understand such as the local response to global (human-driven) CO2 increases, the links between greenhouse gas emissions and greenhouse driven climate change is decades old news.

Perhaps, during this crazy summer, that news is finally getting past the denier screen and reaching the general public.

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