Another interesting post from Willis:
James Hansen of NASA has a strong defense of model reliability here In this paper, he argues that the model predictions which have been made were in fact skillful (although he doesn’t use that word.) In support of this, he shows the following figure:
(Original caption)Fig. 1: Climate model calculations reported in Hansen et al. (1988).
The three scenarios, A, B, and C, are described in the text as follows:
Scenario A has a fast growth rate for greenhouse gases. Scenarios B and C have a moderate growth rate for greenhouse gases until year 2000, after which greenhouse gases stop increasing in Scenario C. Scenarios B and C also included occasional large volcanic eruptions, while scenario A did not. The objective was to illustrate the broad range of possibilities in the ignorance of how forcings would actually develop. The extreme scenarios (A with fast growth and no volcanos, and C with terminated growth of greenhouse gases) were meant to bracket plausible rates of change. All of the maps of simulated climate change that I showed in my 1988 testimony were for the intermediate scenario B, because it seemed the most likely of the three scenarios.
I became curious about how that prediction had held up in the years since his defense of modeling was written (January 1999). So I started looking more closely at the figure.
The first thing that I noted is that the four curves (Scenarios A, B, C, and Observations) don’t start from the same point. All three scenarios start from the same point, but the observations start well above that point … hmmm.
In any case, I overlaid his figure with the very latest, hot off the presses, HadCRUT3 data from Phil Jones at the CRU … and in this case, I started the HadCRUT3 curve at the same point where the scenarios started. Here’s the result:
Fig. 2: Climate model calculations reported in Hansen et al. (1988), along with HadCRUT3 data.
A few things are worthy of note here. One is that starting the scenarios off at the same point gives a very different result from Hansen’s.
The second is the size of the divergence. Scenario C, where greenhouse gases stop increasing in 2000, can be ignored “€? obviously, that didn’t happen. Looking at the other scenarios, the observed temperature in 2005 is a quarter of a degree C below Scenario B, and 0.6°C below Scenario A.
Finally, the observations have mostly been below both all of the scenarios since the start of the record in 1958. Since according to Hansen Scenarios A and C were "meant to bracket plausible rates of change", I would say that they have not done so.
A final note: I am absolutely not accusing James Hansen of either a scam or intellectual dishonesty, he clearly believes in what he is saying. However, he has shaded his original conclusions by starting the observational record well above where the three scenarios all start.
Mainly, the problem is that the world has not continued to heat up as was expected post 1998, while his Scenarios A and B did continue to warm. The post-1998 climate actually is acting very much like his Scenario C … except, of course, that the CO2 emissions didn’t level off in 2000 as in Scenario C.
The values for Hansen’s scenarios are not archived anywhere. Willis obtained them by digitizing the graphic in the pdf file; the values are provided in comment #63 below. Willis reports that he downlowded the HadCRUT3 dataset from http://hadobs.metoffice.com/hadcrut3/diagnostics/global/nh+sh/monthly
and the GISTEMP dataset is from http://data.giss.nasa.gov/gistemp/tabledata/GLB.Ts+dSST.txt
Hansen aligned all three scenarios at the same starting point as noted by Willis, who aligned the two temperature series at the same starting value as used by Hansen. (See comment 63.) This procedure has been criticized by Tim Lambert.