气候变化不是世界末日

元非 2017-08-13

这是 David Henderson 和 John Cochrane 两位经济学家发表于华尔街日报上的一篇评论的标题。两位学者不是气候变化怀疑论者,他们没有打“未来科学进展不确定”牌(以六七十年代的全球变冷来夸大目前的科学共识在将来被推翻的可能性),也不相信气候门事件彻底动摇了气候科学界的可信度,但不认为目前被普遍接受的科学前提决定了全球减排是人类别无选择的政策路径。首先,

Current models struggle to come up with economic costs commensurate with apocalyptic political rhetoric. Typical costs are well below 10% of gross domestic product in the year 2100 and beyond.
That’s a lot of money—but it’s a lot of years, too. Even 10% less GDP in 100 years corresponds to 0.1 percentage point less annual GDP growth. Climate change therefore does not justify policies that cost more than 0.1 percentage point of growth. If the goal is 10% more GDP in 100 years, pro-growth tax, regulatory and entitlement reforms would be far more effective.

并且,

Global warming is not the only risk our society faces. Even if science tells us that climate change is real and man-made, it does not tell us, as President Obama asserted, that climate change is the greatest threat to humanity. Really? Greater than nuclear explosions, a world war, global pandemics, crop failures and civil chaos?
No. Healthy societies do not fall apart over slow, widely predicted, relatively small economic adjustments of the sort painted by climate analysis. Societies do fall apart from war, disease or chaos. Climate policy must compete with other long-term threats for always-scarce resources.

一些人主张的不惜巨大代价为小概率事件做保险的政策建议也有问题:

[T]hey argue, the projected economic cost seems small, but it could turn out to be a lot worse. But the same argument applies to any possible risk. If you buy overpriced insurance against every potential danger, you soon run out of money. You can sensibly insure only when the premium is in line with the risk—which brings us back where we started, to the need for quantifying probabilities, costs, benefits and alternatives. And uncertainty goes both ways. Nobody forecast fracking, or that it would make the U.S. the world’s carbon-reduction leader. Strategic waiting is a rational response to a slow-moving uncertain peril with fast-changing technology.

这是几年来我个人读过的关于应对全球变暖的最有意思的文章。

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