Monday, June 22, 2009

Carbon policy will make a difference

Opponents of unilateral US action on global warming usually claim that without the cooperation of China, India, and other major nations, we can accomplish "almost nothing," and it's wasteful to even try. This is bad analysis.

First, policies that accomplish "almost nothing" on a worldwide basis can still be very beneficial. The idea that a cut of 5% in world CO2 emissions is so insignificant that we might as well pretend it's zero is a classic logical error. You can't use your subjective judgment about what constitutes "insignificance" to arbitrarily set benefits at zero before even comparing them to costs! As we emit more carbon, the consequences for the climate become more difficult to predict, and the last 5% of emissions are the most dangerous. On a worldwide basis, they will do a great deal of harm.

You might claim that carbon emissions will simply shift overseas, but this goes much too far. Not all carbon-intensive production will move, and an enormous fraction of our emissions come from electric power generation, transportation, and other functions that can't be readily outsourced. An aggressive emissions policy by the United States will lead to real cuts in worldwide carbon output, and if you acknowledge the tremendous worldwide costs of climate change, you have to admit that there's potential for global benefit even from unreciprocated American effort. If you dispute this on technical cost/benefit grounds, fine, but you need to make this more explicit than a handwaving dismissal of "small" progress.

Admittedly, these are global benefits we're discussing. If you assume that there is zero chance of multilateral bargaining on climate change, and that the United States will be completely alone in whatever it does, the American economy itself will be a net loser. But even putting aside the absurdity of the assumptions, does this really mean that we should do nothing?

Let's try a thought experiment. Say that households in the United States emit a large amount of deadly poison, which kills tens of thousands annually around the world. Other countries emit poison too, but the United States is responsible for a vastly disproportionate amount. Even if it doesn't act as part of an international coalition, and it will suffer a net economic loss from changing policy alone, isn't the US morally obligated to address this? As long it's the single most culpable nation in the deaths of countless people, I think it is. When poison coming from the US is killing thousands elsewhere, it's patently unethical to interpret policy through the narrow prism of American benefit. I cannot imagine any consistent moral philosophy suggesting otherwise.

Of course, "poison" here is a philosophical stand-in for climate change. I plead guilty to overdramatizing my example, but I don't think that it makes any difference to the core issue: whether it's right for the United States to disproportionately harm the rest of the world as long as it's in the nation's interests to do so. In fact, thinking about a case as simple as "poison" allows us to clarify our moral intuition, because it sets aside complications—like the temporal displacement of cause and effect, and the fact that costs lie on a probability distribution rather than at a single point—that have no bearing on the basic moral question yet tend to confuse us.

And remember that the US can still benefit! There is no basis for assuming that concerted global action on climate change is impossible. Yes, China and India will probably be reluctant to take costly action when the US still emits far more carbon per capita. (Frankly, this is reasonable: why should your underdeveloped nation make cuts when a far richer country emits so much more?) But this won't last forever. If we make cuts now, our per capita emissions will be much closer to theirs in just a few decades. At that point, the need for dramatic changes will be even clearer, and since there will not be such obvious "winners" and "losers,", a fair and Pareto-improving policy will be accessible. If we do nothing, however, we risk a perpetual cycle of blame and inaction, as large developing countries refuse to make sacrifices when the US is still polluting so much more.

It's easy to dismiss carbon policy because it "won't make a difference." But I have never seen anyone making this argument appropriately deal with the economic, moral, and political issues I've discussed here.


happyjuggler0 said...

First of all, it is worth pointing out an uncontroversial AGW point, indeed a real consensus.

Before taking into account feedback effects, GGE's (greenhouse gas emissions) effect on temperature, assuming that AGW happens, is decidedly nonlinear. There is a steep curve under a "do nothing" approach for the next 100 years, and then it goes almost horizontal for the next millennium or so.

This is why you never hear about what happens in the next 100-200 year time frame of GGE's, the answer is not much at all. "They" let the general public wrongly assume the issue is linear "forever", when in reality it is "only" for the first 100 years.

As near as I can tell, everyone who understands the scientific hypothesis of AGW agrees that what happens to GGE's after that curve goes sideways is irrelevant. The real debate is about feedback effects, both positive and negative.

To frame it differently, if we can't eliminate man-made GGE's before we get to the flattening of the curve, there is no point in even starting emissions reductions of something like carbon dioxide which actually helps plants grow faster, including food.

So what happens in the rapidly developing world matters deeply. Until someone can persuade me that a rapid decrease to about zero new global GGE's is possible without decimating the US economy, and without immorally decimating the economies of desperately poor countries which are for the first time on the verge of ending poverty, then I can't possibly get on board. The onus is on those who would try such economic destruction to demonstrate they aren't about to commit the moral crime of condemning billions of people into staying in needless poverty, not on me to persuade you that it isn't likely to work.

Matt Rognlie said...

Yes, my understanding is also that before you account for feedback effects, the influence of CO2 on warming is logarithmic. But this isn't "flat" by any means: it's certainly slower than linear growth, and ultimately it will level off to the point where you could call it approximately flat, but we're not at that point.

And like I said, direct warming from CO2 interacts with positive feedbacks in a way that's usually thought to accelerate as warming becomes more dramatic, leaving the "second derivative" of warming with respect to CO2 emissions unclear. Once you add in the fact that the marginal societal cost of adjustment to temperature changes is almost certainly also increasing (it's harder and harder to adjust to more extreme changes), I think there's a very good case that the marginal cost of emissions is increasing (at least at the margin where we're operating).

Not to mention the fact that as we embark on an ever more unprecedented experiment, injecting massive amounts of greenhouse gases into the atmosphere in a geologically instantaneous timeframe, it becomes harder and harder to put an upper bound on the possible reprecussions...