Two Points on Climate Change

In past posts I have discussed a variety of issues concerned with climate change. Here are two more.

Confusing Moral And Practical Arguments

In controversies on global warming, one issue that keeps coming up is whether it is anthropogenic, whether the world getting warmer is our fault. So far as I can tell, the question is almost entirely irrelevant to the controversy, reflects a confusion between moral and practical arguments.

Suppose the cause of global warming is not human action but changes in solar activity or some other external factor. Suppose also that the consequences of global warming will be catastrophic. Finally suppose that there is something we can do to prevent global warming, say raising the albedo of the earth with orbital mirrors, high altitude pollution, or whatever. Isn’t the argument for doing it precisely the same as if we were causing the warming? Hence isn’t “whose fault is it” an irrelevant distraction?

Of course, the questions of causation and prevention are not unrelated. If we are causing global warming that suggests one possible way of preventing it — stop whatever we are doing that causes it. But doing that might be, very likely is, enormously costly, perhaps more costly than letting global warming happen. It might even be impossible, if what we have already done is enough to cause long run catastrophe even if we don’t do any more of it. And even if we are causing it and could stop doing so, there might be better solutions to the problem. Falling birth rates are at present a problem; one of the causes is probably the existence of reliable contraception. It does not follow that the best solution is to ban the birth control pill.

Implications of Uncertainty

Multiple forms of uncertainty are relevant to climate policy, most obviously uncertainty over how climate will change, how fast it will change, and the effects of the changes; my past posts have been mostly about the last. One uncertainty that has largely been ignored is uncertainty about features of the next century and more that are not due to climate change

To take one example, a Nature article estimating the cost of carbon dioxide emissions, discussed in a past post, finds almost half the total cost due to increased mortality from increased temperature. Mortality, from temperature or almost anything else, depends in part on the level of medical care. By using past data to relate temperature to mortality for their calculations the authors, who are summing cost from now until 2300, are implicitly assuming no medical progress for the next three centuries as well as no change in heating or cooling technology and no effect of the increased income in their projections on vulnerability to temperature.

Doing that is arguably fraudulent, given that the authors do not mention the implicit assumptions that go into their calculations, but it is not clear what they should have done instead. We have no way of knowing how much progress in medicine will occur how fast or what effect it will have on mortality from high temperatures, increased by warming, on low temperatures, decreased by warming, hence on the net increase or decrease of mortality due to warming.

This is one example of a problem common in the literature. For another, consider the effect on human welfare of the effect of carbon fertilization on nutrition.¹ An increased concentration of CO₂ in the atmosphere increases crop yield but alters the mix of nutrients, decreasing the proportion of some minerals. Whether that matters depends on how available mineral supplements, common and inexpensive in developed countries, are in the future. If the present pattern of economic progress in poor countries continues, very nearly everybody will be at developed world standards of living in a century, probably sooner, which should substantially reduce the costs due to climate change. But there is no guarantee that that will happen; we could have the rate of growth in world GNP that goes into models of carbon emissions with most of the growth in countries already rich.

As I put it almost twenty years ago in a book on future technology:

… with a few exceptions, I have limited my discussion of the future to the next thirty years or so. That is roughly the point at which both A.I. and nanotech begin to matter. It is also long enough to permit technologies that have not yet attracted my attention to start to play an important role. Beyond that my crystal ball, badly blurred at best, becomes useless; the further future dissolves into mist. (Future Imperfect)

If the world is changing in ways that cannot be predicted, estimates of costs in the distant future ought to be heavily discounted for uncertainty, given little weight relative to costs in the near future. That is a problem mostly ignored in the climate literature.

Serious estimates of the rate of change, such as the IPCC reports, show it too slow to have significant effects in the next few decades. Sea level rise is estimated as half a meter to a meter by the end of the century, temperature change one or two tenths of a degree per decade, decline of ocean pH about .017/decade, a rate that will take almost four centuries to get it back down what it is estimated to have been nineteen thousand years ago.

I conclude that the next century is sufficiently uncertain so that it makes little sense to take expensive precautions against risks a century, let alone three centuries, in the future. By the time the risk arrives we may have already wiped ourselves out in some other way. If we have not wiped ourselves out, our lives may have changed in a way that eliminates the problem; commuting via virtual reality produces little CO₂. If we are still around and the problem is still around we are likely to have a level of technology and wealth that will make possible a range of solutions well beyond what we are currently considering.

All of these are reasons why I think a persuasive case for doing something about global warming requires evidence, not yet available, of serious negative effects in the fairly near future. Which may explain why people arguing for climate action make inflated claims about near term effects.

An earlier post, based on other sorts of uncertainty, offered a different argument for the same conclusion:

The question we are answering is not “what should we do?” but “what should we do now?” Waiting will raise the cost of dealing with the problem but will also provide additional information. The more information we have, the better our ability to decide what precautions are worth taking. Or not worth taking. Uncertainty that will be reduced over time is an argument against immediate action.

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1. Discussed under the subhead “And Nutrition” in this post.