As soon as the nonsense about global temperature not changing in a decade started, the lab bunnies knew what was coming, so they took out their crayons (very traditional they are, no magic markers allowed in the burrow) and started adding points to Hansen's 1988 graph
Of course, being ethical Rabetts, we used the GISS surface stations record which includes the polar regions. As we all know the models, including Grandpa Hansen, predict that the greatest warming will be in the Arctic, so if you use a surface temperature method or one of the MSU records that do not include the Arctic, it will appear that the models
under overpredict (the logic was fine, the execution sucked. Thanks to Mike for pointing this obvious nuttiness out, anyhow youse knew what Eli meant).
The 1988 model appears to be a bit low even compared to scenarios B and C. Only Pat Michaels thinks that scenario A was the most likely, but still. Climate model forecasts depends on the scenario that predicts greenhouse gas concentrations. (OK, if your name is Piers Corbyn maybe not). We OTOH need to look at the predicted forcings which we can get from the NOAA annual greenhouse gas index (btw, the latter has a neat little toy under data visualization that let the little guys look at station data. Auditor's delight)
The total forcing is well fit by a hinged line with a break at 1990. What happened was the Montreal Protocols which flattened the concentration of the CFCs and better recovery of methane from oil wells, so it could be sold. Let's take a look at the forcings that were predicted in the 1988 paper and compare with what actually happened. So let's start from the forcings shown in Hansen, et al (1998) and put the NOAA forcings on top of them and extrapolating Hansen, et Als. (apologies to the Als, the anonymice of scientific papers) forcings to the future we get
where we have set the zero of the NOAA forcings to 1960 to better match that of Hansen, et Als. Since Hansen, et Als. forcings are noiseless, and the NOAA ones are compared to some average value around 1750, this is not a full Eschenbach not even a half one because as anyone can see from the figures, there is a lot less noise in the forcings than in the global surface temperatures.
The sharp eyed Auditoriums have seen that the NOAA forcings are higher than the GISS ones. These are all calculated from concentrations, but using slightly different formulas. So, what does this say about the model. In Hansen's 1988 words
The climate model we employ has a global mean surface air equilibrium sensitivity of 4.2 C for doubled CO2. Other recent GCMs yield equilibrium sensitivities of 2.5-5.5 C.....We are getting to the point, twenty years on, where the high estimate of climate sensitivity is making itself felt. OTOH, the 1988 paper estimated the forcings slightly on the low side. The result was a pretty good prediction. Definitely in the class of useful models.
Forecast temperature trends for time scales of a few decades or less are not very sensitive to the model's equilibrium climate sensitivity (reference provided). Therefore climate sensitivity would have to be much smaller than 4.2 C, say 1.5 to 2 C, in order for us to modify our conclusions significantly.