Sunday, July 05, 2009

Does climate crisis pass the giggle test?

David Friedman doesn't think so.

The notion of a global climate crisis depends on three things being true:

  1. The climate is in a warming trend.
  2. Humans are in a position to change this trend.
  3. The consequences of not changing this trend are severe.

I've phrased these the way I did to remove carbon dioxide emissions from the equation. If CO2 emissions are a major factor in warming, we can certainly change our emissions. If warming is due to something else, we can still change our emissions. We can probably do other things, like put up a space umbrella and cut down on solar heating of the planet. Eventually, we'll be able to move the planet out to a higher orbit and cool it down that way. The question then becomes whether any proposed change is worth it.

This is the meaning of "severe consequences". The cost of putting up with the climate change is much greater than than the cost of averting it.

From David Friedman's blog:

The argument for doing drastic things to prevent global warming has two parts. The first has to do with climate change, with reasons to think that the earth is getting warmer and that the reason is human action, in particular the production of CO2. The second has to do with consequences of climate change for humans.
What I find unconvincing is the second half of the argument. More precisely, I find unconvincing the claim that climate change on the scale suggested by the results of the IPCC models would have catastrophic consequences for humans. Obviously one can imagine climate change large enough and fast enough to be a very serious problem—a rapid end of the current interglacial, for example. And if, as I believe is the case, climate is not very well understood, one cannot absolutely rule out such changes.

But most of the argument is put in terms not of what might conceivably happen but of what we have good reason to expect to happen, and I think the outer bound of that is provided by the IPCC models. They suggest a temperature increase of about two degrees centigrade over the next hundred years, resulting in a sea level rise of about a foot and a half. What I find implausible is the claim that changes on that scale at that speed would be catastrophic—sufficiently so to justify very expensive measures now to prevent them.
Climate aside, we do not live in a static world—consider the changes that have occurred over the past century. The shifts we can expect to occur due to technological progress alone, even without allowing for political and demograpic shifts, are much larger than the shifts required to deal with climate change on the scale I am discussing.

My conclusion is that this version of climate catastrophe, at least, does not pass the giggle test. There may be other versions, based on more pessimistic predictions of climate change, that do. But the claim that we now have good reason to expect climate change on a scale that will produce not merely problems for some but catastrophe for many is one that no reasonable person should take seriously.

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