Global Warming and Model Dependence
By Arnold Kling
J.S. at Environmental Economics writes,
We all are aware of the well-funded campaigns to discredit the science of global warming, and I’m the last one who wants to add more uncertainty to the mix.
He points to this set of charts put together by Monte Hieb, which shows that man-made carbon dioxide is a very small component of total greenhouse gases. The charts make the point that water vapor is 95 percent of greenhouse gases.
Not sure whether those charts were credible, I got some confirmation from NOAA’s National Climactic Data Center.
Water Vapor is the most abundant greenhouse gas in the atmosphere, which is why it is addressed here first. However, changes in its conentration is also considered to be a result of climate feedbacks related to the warming of the atmosphere rather than a direct result of industrialization. The feedback loop in which water is involved is critically important to projecting future climate change, but as yet is still fairly poorly measured and understood.
I am starting to appreciate how extremely model-dependent the field of climate forecasting is. That is not a good thing. As I wrote here, “The complexity of the process far exceeds the availability of data needed to verify the model. Even a broad consensus may prove fragile.”
Under the circumstances, I think that the language that climate forecasters should be using ought to be careful and cautious about what they claim to know. The argument for trying to control carbon dioxide emissions is actually quite subtle and nuanced.
The argument would have to start by saying that the relationship between man-made carbon dioxide and global temperature is highly nonlinear, and there is a very large margin of error in estimating the effect. The error could be that we over-estimate the effect of emissions on global warming, but it could be that we under-estimate the effect. Particularly if we under-estimate the effect, we would want to err on the side of curbing emissions.
To me, that is the strongest argument that one can make for curbing emissions and still retain credibility. The more that Al Gore and company argue something differently, the more I am inclined to reject their religion.