Do you disagree with the final para, or do you think it is incomplete? Do you disagree with the effect carbon offsets will have on individual behavior, or with the term "uncertainty?"

I'm more optimistic than Posner is that carbon offsets can positively affect individual behavior. Here's why: the people most likely to participate in offset buying is the idle rich, celebrities, and generally a small but socially influential population. If those sorts start changing their behavior, they may influence others who otherwise would not even think about these issues. Think Coach bags, on an environmental scale.

Aren't the Coach Bag folks more likely to be among the pseudo-environmentalist Left anyway? I think offsets only enhance the pseudo.

Besides, I think Posner's over-arching point is that offsetters influence in this case is to fool the rest of the world into thinking voluntary efforts are enough. Posner would probably argue that this negative effect would overwhelm any positive Coach Bag-effect.

My other disagreement with him then would be that offsetters will not overinflate the perceived effectiveness of voluntary efforts. For example, if the right person gets elected to office in 2008, I expect we'll see a major change in governmental policy with respect to energy -- i.e., it's not as if scientists and policy makers will be fooled.

I too think the celebs can have an influence on behavior. Green chic, right? Some regular people might buy offsets; some will get the hybrid instead of the regular Toyota Camry. It won't convince everyone, but the combined effect might be substantial.

"There is nothing wrong with emitting carbon dioxide. The wrong lies in the quantity being emitted, which is excessive."
-Isn't this seriously disputable too? I mean, in a perfect world, maybe, but under the current conditions it seems to me that we obviously would want to reduce further emissions to zero if we could.

(I mean, that's sort of beside the point- I'm just saying...)

But I thought that there are American companies that are voluntarily buying into carbon-trading to some extent- is that true? Also, from what I understand, and which is alluded to in that post- the carbon-trading system is not at this point even effective in enforcing the offsets that have been purchased, whether by individual consumers or larger entities. I realize that's apart from the specific argument he's making, but then it does seem somewhat pertinent- it takes the symbolic gesture one step further and empties it of any significance at all- so if you have a bunch of celebrities w/ coach bags stimulating a trend that ultimately doesn't accomplish what it aims to, what then? Although, perhaps a real upsurge in carbon trading will bring with it more effective measures to ensure that the deal is actually kept.

Well, the idea is that the coach bag celebrities will begin to embrace environmental technologies in other ways, inspired by their attempt -- futile or not -- to help by offsetting. So for one, as Geoff said, making hybrids cool. This has already started to happen -- hybrids took off among the California elite years ago, which has helped increase their profile and has started to bring prices down.

True enough. Hopefully there can be some kind of critical mass of general green consumption that is achieved. Unfortunately, my more cynical half tends to dominate on this issue. It will be fantastic if the cynical me is wrong.