Thursday, January 31, 2008

Bob Carter on Climate Change (Part I)

One of my professors, Dr. Lester Hunt, turned me on to a very interesting lecture given by Australian geologist Bob Carter on the subject of climate change. I figured that it would be worth critiquing the lecture as I listened to it, because it seems like one of the more respectable attacks on the mainstream views regarding climate change, and it might be helpful to have gone through an exercise like this to respond to skeptics in the future. Since Carter's talk is broken up into four parts, I'll break my critique into four parts as well (this post responding to the first part). I'll also keep my comments to points of disagreement or tension between my own views and Carter's. He has a lot to say, and I'll likely agree with most of it.

One of the first points Carter brings up is one which was made most famous by Bjorn Lomborg, which is that it would require significant energy and resources to do something about climate change, and more benefit would come from doing things about more pressing current problems like global poverty. Though Lomborg has written multiple books on the subject, his views are more or less captured in this speech he gave to Congress last year. I have a lot of sympathy for this viewpoint, though most people who hold it come to their conclusions by discounting future costs by something of a “social discount rate.” I’ve written about discounting damage caused by climate change in a paper I can make available by request. But it’s possible that even without discounting, the damage associated with climate change is significantly outweighed by the damage caused by things like poverty, hunger and AIDS. I’ve discussed this possibility here, concluding that while I see where Lomborg is coming from, I believe that if we're responsible for causing climate change, then the damage it causes is morally different than damage caused by things we're not responsible for bringing about, like hunger and AIDS.

Carter moves on to a slide discussing the long term temperature trends displayed by "Greenland ice cores." This is an intriguing move, because one of two things could be happening, and because I'm writing this critique as I'm watching, I'm not sure which it is. The first is that he's being honest and showing that different proxies in different regions show very different things, and that it's extremely difficult to separate global trends from regional anomalies and noise. This is especially important because the time period we're analyzing in discussing climate change is extremely short. And when talking about climate change in the context of historical climate conditions, we're forced to rely on these proxies because before about 100 years ago, we weren't able to acquire reliable human-instrument-measured temperature data.

This sort of view was put best, I think, by Stephen Gardiner in his 2004 essay, "Ethics and Global Climate Change," in Ethics, Vol. 114 , No. 3, pages 555-600 (and yes, I think I will cite this quote in every post on climate change, thank you very much). On page 567, he wrote, "The skeptics are right...when they assert that the observational temperature record is a weak data set and that the long-term history of the climate is such that even if the data were more robust, we would be rash to conclude that humans are causing it solely on this basis. Still, it would be a mistake to infer too much from the truth of these claims. For it would be equally rash to dismiss the possibility of warming on these grounds. For, even though it might be true that the empirical evidence is consistent with there being no anthropogenic warming, it is also true that it provides just the kind of record we would expect if there were a real global warming problem."

But the dishonest thing he could be doing, which is so obviously dishonest that it would be fair to question his intentions if he were doing it, is suggesting that the Greenland ice cores are representative of the historical global temperature record. To do so would be just as dishonest as focusing on the fact that in North America, 1998 was no warmer than 1934, even though worldwide, 1934 was a significantly cooler year than 1998 (which is true, by the way). But it would be especially dishonest of him to infer from this something like "Global warming is likely due to natural variability" or "Over the last 8 years, global warming has halted, as we can see from these Greenland ice cores." But let's see what he actually does say.

What he does, incidentally, is move onto the idea that we're currently in an unusually warm period of time, and that we can expect that in the future, the world will become much colder than it is today. This time I'm not sure what point he's trying to make if he's not being intellectually dishonest. It's true that some time over the next several millenia (or maybe less), it's probably fair to predict that the Earth will enter a prolonged cooler period, where humans will likely be driven towards the equator in order to avoid the encroaching ice caps characteristic of the Pleistocene era (the period between 1.8 million years ago and about 11,550 years ago), as there is indeed no reason to believe that the Holocene warming (the period we live in) represents an end to the Pleistocene.

But it's also true that all of human civilization arose during the Holocene warm period, so it's irrelevant to point out that the climate is "typically" colder than it is today. This is especially significant because I haven't heard any predictions that the next glaciation is to come any time soon. If we can predict dangerous warming over the next several centuries, then I'm not really sure how it's relevant to point out that in several thousand years, we'll likely experience another ice age. Impacts on humans need to be discussed over smaller time scales than the extremely large geological time scales that he's using.

The last point he makes in this section, regarding the polar bears, is an important one. Most scientists don't believe that polar bears will likely become extinct as the result of climate change, though their habitat will likely be reduced significantly. Polar bears have been around a very long time, and will likely figure out how to make do. That being said, this speaks more to sensationalism in the media than the scientific basis for concern about climate change, and so it's not clear why he brings it up at this point, unless it's just for comic relief. I wonder, though, if that's a penguin on that grill; polar bears and penguins live on opposite ends of the Earth.

So far, I can't object to any of the facts Carter has brought up, but I'm sort of uncomfortable about the way that he's presented them. He's been good about not actually saying anything that's false, or drawing any conclusions which he has no right to draw. But he has seemed to imply a lot of things which aren't right, and if I didn't know better, I would think he was trying to lead people astray. Anyway, on to the next section!

[Go on to part II]

1 comment:

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