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Climatology Professor
Mostly Agree
The global mean surface temperature increase (land and ocean combined) in both the NASA GISS data set and the Hadley Centre/ Climatic Research Unit data set is 0.33°C for the 16 years since 1990, which is in the upper part of the range projected by the IPCC. Given the relatively short 16-year time period considered, it will be difficult to establish the reasons for this relatively rapid warming, although there are only a few likely possibilities.
Climatologist
Mostly Agree
It takes about 20 years to evaluate because there is so much unforced variability in the system — the chaotic component of the climate system — that is not predictable beyond two weeks, even theoretically. ... [Our predictions from 20 years ago] have been more or less validated, given both the imperfections we had at the time and the uncertainty in how we thought things would change in the future. So there is a track record that shows that these models are realistic.
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