For the first, he provided 3 scenarios, indicating perhaps a certain uncertainty about what would happen after his forecast. Looking at these GHG emissions scenarios, it looks like a pretty big variation in what might happen. However, he did not provide us with scenarios or error estimates on the other 2 forecasts, those of GHG retention and any impact of such retention on the measured temperatures. I would argue that these 2 elements are not settled science, even today. Yet the use of point estimates in his model suggests that these elements were know with precision. If the researcher had provided reasonable error estimates for all of the relationships modeled, I think the predictions would have come with very wide error bars, probably even permitting an ice age in time, because so many of the relationships are poorly understood. If, as I think we should, we implicitly place very wide error bars on the 3 scenarios, then the current temperature record would fall comfortably within the error bars of all 3 scenarios.

In other words, the model was largely a means to illustrate a point to get some specific policy actions.

Lubos,

Yeah, that little bit seems to get overlooked by too many folks. Love your blog by the way. Too much geo and not enough physicist in my education to grapple all the issues you post, but your style carries through.

Interesting articles, by the way – worthy of a careful read.

Gary,

I assume you are capable of reading Steve McIntyre’s posting and come to your own conclusions. Do you need anyone else’s help in that regard? Please read the post at the top of this page in its entirety and let us know what you think of the veracity of what Desmog is posting.

I expect the kind folks at other blogs have trouble interpeting Steve McIntyre’s final paragraph, which includes the following:

One has to distinguish skill as a GHG emissions forecaster from model evaluation – a distinction that Hansen fairly makes. I think that Scenario B is close enough to observed emissions that, in the absence of NASA being able or willing to re-run the actual 1988 model with actual forcings, one can be reasonably use Scenario B for comparisons.

Observed forcings are close to Scnario B. Observed temperatures are below Scenario C. Does recognition of that constitute accepting Hansen’s work and the hockey stick? It must be a pretty twisted logic pretzel whereby one can reach that conclusion.