I have not liked to post anything on global warming outside of the economic implications. In this case, I think it is simply worth raising the observation that the modelers who do climate projections and the modelers who do macroeconomic projects know little more than jack squat. Regular readers understand the macro problems – to think that we can take an economy of hundreds of millions of different people and tens of millions of different firms, with millions of things changing from minute to minute such as tastes, availability of substitutes, tax rates, weather, and so on, and then think that we can write down a 100 equation model with 100 unknowns (or more) or even a 4 equation model with 4 unknowns, and think that not only explains past macroeconomic activity, but that can also be used to predict future macroeconomic activity is a fool’s errand. Actually, it’s worse than that. It’s a fool’s journey around the entire universe. But for some reason we in the economics profession remain enamored with the modeling and prediction of the macroeconomy. Plus, we only have about 100 years of data with which to estimate these models. How many of you would even base your decision on what cold medicine to take after having the experience of only 100 people to rely on for evidence?
The deal with the climate modeling is far worse. I don’t know the first damn thing about global warming outside of the fact that it has gotten warmer and that humans have tossed a helluva lot of CO2 into the air. Beyond that, I am not sure the scientists know much more. Here is the latest summary of what we know and don’t from Richard Lindzen:
Here are two statements that are completely agreed on by the IPCC. It is crucial to be aware of their implications.
1. A doubling of CO2, by itself, contributes only about 1C to greenhouse warming. All models project more warming, because, within models, there are positive feedbacks from water vapor and clouds, and these feedbacks are considered by the IPCC to be uncertain.
2. If one assumes all warming over the past century is due to anthropogenic greenhouse forcing, then the derived sensitivity of the climate to a doubling of CO2is less than 1C. The higher sensitivity of existing models is made consistent with observed warming by invoking unknown additional negative forcings from aerosols and solar variability as arbitrary adjustments.
Given the above, the notion that alarming warming is ‘settled science’ should be offensive to any sentient individual, though to be sure, the above is hardly emphasized by the IPCC. 4
And of course, coming right on the heels of this is the following proclamation about the results of the 5th IPCC report, research on which has yet to commence:
Robert Orr, UN under secretary general for planning, said the next Intergovernmental Panel on
Climate Change report on global warming will be much worse than the last one.
Hmm, that kind of confirms what critics have been saying for years, that the IPCC has nothing to do with science. Because, you see, to my knowledge the scientists of the next IPCC have not even started their work, but the UN leadership has already determined what the report will say. Which is consistent with their process in the last go around, where the UN political guys crafted the management summary first, and then circulated it to the scientific teams with instructions to adjust their sections of the report to fit the pre-existing conclusion.