zondag 20 februari 2011

Superfreakonomics and climate engineering

With Freakonomics, Steven Levitt and Stephen Dubner had written a very enjoyable overview of how the standard techniques of economic analysis can be applied to a wide variety of less standard issues (how to detect cheating teachers and sumo wrestlers, how liberalizing abortion laws eventually translates in lower crime rates , why most drug dealers live with their mothers, etc ).
With Superfreakonomics, they do it again. The range of topics is just as wide as in their first book: why walking drunk is more dangerous than driving drunk, why wages of prostitutes have gone down over the last century, why your month of birth is a good predictor of future professional achievement, how to detect from someone’s bank account whether he is likely to be a suicide terrorist, why children (at least in the US) are more likely to visit their parents in retirement homes if they have siblings, etc.
These two unconventional books are the result of a just as unconventional team. Stephen Dubner, who writes for The New York Times and the New Yorker, had joined efforts with Steven Levitt,  a professor of economics at the University of Chicago. In case the subjects listed above would make you doubt, Steven Levitt is no crank: for his original research, he has won the John Bates Clark medal, which is arguably harder to get than a Nobel Prize.
As the authors explain, both books have one grand unifying theme: (a) people respond to incentives (b) they do not necessarily do this in ways that are predictable or manifest. In the first book, the emphasis was on professor Levitt’s own research in this field, while Superfreakonomics  covers more work undertaken by other researchers.
The general appreciation of the book can be relatively short:  just as its predecessor, it is very well written and chockfull of facts and insights that are both amusing and revealing. If you have any interest in human behavior, you should read it.
However, in this review, I would like to elaborate more on one specific chapter that is specifically relevant for the subject of this blog: the discussion on climate engineering.
The chapter can be summarized as follows. The authors do accept the hypothesis that climate is changing, and that these changes are anthropogenic (even though they rightly point out that a lot of processes are still very poorly understood). However, they doubt very much that a binding international agreement to reduce the emissions of greenhouse gasses (GHG) will ever be signed. Moreover, they argue that, even if such an agreement would be reached today, it would probably be too late to prevent significant climate change.  Finally, scenarios that assume that significant climate change mitigation still falls within the realm of the possible, tend to overestimate the potential of technological solutions (for instance, because they do not take into account the GHG emissions during the production of “clean” technologies such as photovoltaic cells).
In a previous post of this blog, I had already discussed one possible approach to plan B – climate change adaptation.  Levitt and Dubner discuss plan C: climate change engineering.
The idea is really quite simple: just as the presence of greenhouse gasses in the atmosphere tends to increase average temperatures,  the presence of sulfur dioxides tends to decrease average temperatures. This phenomenon is well documented and quite well understood. For instance, important volcano eruptions can lead to a marked decrease in average temperatures for several months or even years.
Does this mean that simply putting huge quantities of sulfur dioxides  will be enough to stop climate change?
Actually, it’s not that simple. In case you’ve forgotten, or are simply too young, we have already been through this: before we started imposing environmental regulations in the 1970s, we had already been emitting huge quantities of sulfur dioxides (the big worry about climate change in the beginning of the 1970s was global cooling, not warming). The ensuing decrease in the emissions of sulfur dioxides is actually one of the really big success stories of  environmental policy, leading to significant health benefits.
Again, one may be tempted to jump to conclusions and think that the choice is now between facing intolerable temperature increases or inhaling particles that directly affect our health and life expectancy.
However, this reasoning overlooks one potential way out that Levitt and Dubner discuss: instead of pouring the sulfur dioxides in the atmosphere at ground levels, we could develop tools to release them directly in the stratosphere instead. In their book, Levitt and Dubner report interviews with several scientists who argue that this should be technically possible at an economic cost that would be a fraction of the cost of climate change mitigation.
 Would this work?
I am not a physicist nor an engineer, so I do not feel qualified to comment on this specific point.  However, if it would work, and if its cost would really be so low (that’s admittedly two big ifs) than moving the focus from climate change mitigation to climate engineering looks like a no-brainer.
Maybe surprisingly, this approach faces some stark opposition, and it is important to understand why.
One counter-argument is that climate engineering comes down to tinkering with the climate. I agree completely with Levitt and Dubner that this argument makes no sense: everything we do involves tinkering. There’s just tinkering that involves doing something and tinkering that involves not doing anything. Some moral philosophers may think there is a deep difference between the two, but from a policy point of view, this seems irrelevant to me.
One argument that merits some discussion is that the possibility of climate engineering would just be an excuse for a continuation of “business-as-usual”.  Of course, unless one thinks that emitting green house gasses is a sin in itself, this argument is in the same category as the previous one: symbolism and not substance.  Thus, the relevant question is: is it a sin to emit greenhouse gases if there an antidote to the global warming effect?
The answer is: in some cases, yes. Well, not in the case of CO2, but there are a lot of less widely known gasses that do not only trap heat in the atmosphere but also hurt the environment in other ways. It has been known for some time that several ozone depleting substances are also very potent greenhouse gasses.
A forthcoming report by the United Nations Environmental Programme now confirms that there are other villains out there: methane and black carbon. The negative environmental effects of black carbon (or soot)  , which is emitted massively by primitive stoves and  old diesel engines, are already well known. However, recent research suggests that black carbon is also a potent greenhouse gas. Moreover, it has a relatively short atmospheric life time, implying that  reducing the emissions of black carbon would not only improve air quality (notably in developing countries), it could lead to significant climate benefits in the short term.  The emissions of methane, in turn, lead to increased formation of tropospheric  ozone, which has also well-documented adverse health effects (contrary to stratospheric ozone which blocks ultraviolet rays).
Even though the science of black carbon is far from settled, this insight somehow turns the problem raised by climate engineering on its head. Because black carbon and tropospheric ozone are local pollutants, individual countries have a strong incentive to reduce emissions of soot and methane (well, at least if governments can be held accountable by their people), and this can lead to climate benefits even if we cannot agree on reducing CO2 emissions. I also think no one would dispute that the Conventions on Long Range Transboundary Air Pollution have been far more successful than the Framework Convention on Climate Change: this suggest that it is far easier to sign successful environmental treaties when the benefits occur in the short run and when there is a little scientific uncertainty surrounding these benefits.
So, if you ask me, I think the first priority is now to work on greenhouse gasses that bring strong co-benefits in terms of local air quality. And, in the meanwhile, we should work further on our understanding of climate engineering, as a possibly quick fix in case we run out of other options.
And more people should read what Levitt and Dubner write on the subject.

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