Several years ago in National Review Online, Kevin Williamson did a post on “What to Think about Global Warming.” His main point was as follows:
The debate is polarized, and it is natural to throw one’s lot in with one camp or another—The World Is Ending vs. Global Warming Is a Hoax—but there are more than two propositions to consider. And those propositions are not mostly scientific in character, but political.
I post this not to debate the subject of his essay, but rather to point to it as an example of how to divide or untangle a complex cluster of issues.
There are a lot of important strategies for working through arguments, such as defining terms, following the rules of logic, sniffing out unstated assumptions and presuppositions, etc. But determining the actual claims—which often involves dividing the issue—can be a neglected step.
Here is how Williamson went about breaking down and analyzing the claims within the claim.
- The planet is getting warmer. This seems to accord with what we know. From 1906 to 2005, the average surface temperature rose by 0.74 degrees Celsius by most estimates. The planet seems to have warmed much more quickly during the second half of that interval than in the first half. There has been a recent cooling trend, it is true, but the larger trend seems to be upward. While the Climate Research Unit fraud has given us reason to be skeptical of much of the data touching the global-warming debate, this fundamental claim seems to be reasonably well documented.
- The planet is getting warmer, and human activity is the reason. This is the real crux of the debate, and, in truth, there are several different ways of considering this claim: Human activity may be the only reason for global warming, it may be one important factor among many, it may be one minor factor among many, or it may be a trivial factor or, possibly, no factor at all. The Intergovernmental Panel on Climate Change does not seem to be an irresponsible organization, and I know of no obvious reason to suspect that it is involved in any shenanigans of the CRU variety. At the same time, IPCC does not do its own research; it is dependent upon the research of others, and therefore upon the scrupulousness of others. Nonetheless, they write: “The observed widespread warming of the atmosphere and ocean, together with ice mass loss, support the conclusion that it is extremely unlikely that global climate change of the past 50 years can be explained without external forcing and very likely that it is not due to known natural causes alone.” (That “very” is an escalation from their previous position of just “likely.”) Having no scientific basis to disregard this conclusion, and no strong basis to suspect IPCC’s honesty, we ought to consider this claim carefully and sympathetically.
- The planet is getting warmer, human activity is a main factor, and the consequences will be catastrophic. It is here that the claims cease being mostly scientific in nature and begin to become political and economic questions. Unsurprisingly, it is here that the emotional tenor of the debate starts to become shrill, with visions of maritime nations lost, New York City under water, and the like. In truth, the IPPC predicts a warming, over the next century, of 1-3.5 degrees Celsius. Much of that warming, IPPC concludes, will take place at the poles; it will not be evenly distributed around the globe, and the organization writes that “on regional scales, confidence in future climate projections remains low. . . . The degree to which regional climate variability will change also remains uncertain.” In economic terms, which Jim Manzi has considered extensively, the damage is equivalent to 1-2 percent of global GDP — a century from now. Yale economist Robert Mendelsohn concludes that the damage is more like 0.08-0.24 percent of global GDP — again, 100 years from now, when global GDP is expected to be many times larger than it is now. Real damage, to be sure, but something less than Armageddon.
- The planet is getting warmer, human activity is a main factor, the consequences will be catastrophic, and some U.N.-style climate policeman is going to be able to manage a mitigating response. Here we make the transition to the purely political questions, and they do not look very promising for the warming-activist camp. Any international coalition to manage or prevent global warming will have to include China and India to be effective. China and India have made it abundantly clear that the price they are willing to pay to prevent global warming is, approximately, zero. The West’s willingness to subsidize global-warming projects on behalf of China and India is not zero, but it is not very much higher than zero. The international community has very little credibility in dealing with real and present danger — such as Pyongyang’s nuclear arsenal and Tehran’s ambition to possess one — and so it seems unlikely that they will be effective in dealing with a less concrete, less immediate, more complex set of challenges, particularly one in which the various members of the international community have different and often conflicting economic incentives.
- The planet is getting warmer, human activity is a main factor, the consequences will be catastrophic, and some U.N.-style climate policeman is going to be able to manage a mitigating response — in an economically efficient manner. It is at this point, it seems to me, that the argument for a Kyoto-style climate regime enters into the realm of fantasy. Even if we could imagine an international response that was 100 percent effective in achieving its climate-mitigation goals, the price ceiling on such an effort would have to be, at most, 1-2 percent of global GDP. In all likelihood, the better response would be to take corrective and adaptive steps as we go rather than investing our hopes, and our capital, in the United Nations or a comparable organization.
- The planet is getting warmer, human activity is a main factor, the consequences will be catastrophic, and some U.N.-style climate policeman is going to be able to manage a mitigating response — in an economically efficient manner that also is consistent with our political liberties and national sovereignties. And the rational response to this is: Yeah, right.
Again, the point of this is not to debate Williamson’s arguments. My motivation is rather to hold this up as an example of how helpful it can be to untangle various claims, which can help us determine where we agree and where we actually disagree.
Here is the article in chart form: