Hansen, Sato, Ruedy, Lo, Lea and Medina-Elizade have published their latest screed on "Global temperature change" in the Proceedings of the National Academy of Sciences.
and if you actually use the GISS or the Hadley Center temperature records the agreement is excellent. Of course, if you want to falsify the prediction, you can always engage in climate fraudit, straight out denial is also a popular sport in comments sections as well. Eli has had a series of posts on the Hansen paper and testimony in 1988 where the original prediction was made (the graph above is an update of that one, with the same model predictions and data up to 2005). The new paper says (about the old predictions)
Observed warming (Fig. 2) is comparable to that simulated for scenarios B and C, and smaller than that for scenario A. Following refs. 18 and 14, let us assess ‘‘predictions’’ by comparing simulated and observed temperature change from 1988 to the most recent year. Modeled 1988–2005 temperature changes are 0.59, 0.33, and 0.40°C, respectively, for scenarios A, B, and C. Observed temperature change is 0.32°C and 0.36°C for the land–ocean index and meteorological station analyses, respectively.....Not bad for a first generation model, and they got a lot of other things right too. Now this does not say the model was perfect, just that it was useful, moreover there are good scientific reasons why it worked, including good physics, and a relatively short period between then and now.
Close agreement of observed temperature change with simulations for the most realistic climate forcing (scenario B) is accidental, given the large unforced variability in both model and real world. Indeed, moderate overestimate of global warming is likely because the sensitivity of the model used (12), 4.2°C for doubled CO2, is larger than our current estimate for actual climate sensitivity, which is 3 1°C for doubledCO2, based mainly on paleoclimate data (17). More complete analyses should include other climate forcings and cover longer periods. Nevertheless, it is apparent that the first transient climate simulations (12) proved to be quite accurate, certainly not ‘‘wrong by 300%’’ (14). The assertion of 300% error may have been based on an earlier arbitrary comparison of 1988– 1997 observed temperature change with only scenario A (18). Observed warming was slight in that 9-year period, which is too brief for meaningful comparison.14 is Michael Cricheton, 18 is Pat Michaels.
In the period between 1988 and 2005 CO2 concentrations increased about 30 ppm, or about 1/10th of that equivalent to a doubling. Thus, the higher assumed climate sensitivity (~40% high) would only result is a ~4% difference in the forcing if you assume a linear trend, less if you use the proper logarithmic dependence of CO2 forcing on CO2 mixing ratios. I think Hansen et al are being much too modest.