Climate sensitivity: should the climate tail wag the policy dog?
Climate sensitivity: should the climate tail wag the policy dog?
复制标题
气候敏感性：气候尾巴应该摇动政策狗吗？
作者：
G. Roe;Yoram Bauman
全球气温对大气二氧化碳增加做出巨大长期反应的微小但顽固的不屈可能性，可以被称为高气候敏感度的肥尾。最近的经济分析表明，如果与这种高温相关的损害足够大，肥尾应该会主导合理的政策策略。然而，这些分析的结论取决于经济增长、气温变化和气候破坏如何随着时间的推移展开和相互作用。在这篇文章中，我们着重于气候系统的两个强大的物理特性的作用：海洋的巨大热惯性，以及与高气候敏感性相关的长时间尺度。包含气候成分的经济模型，特别是那些关注概率分布尾部的模型，应该恰当地代表这种对高气候敏感性的缓慢反应的物理原理，包括当前强迫和气候敏感性之间的相关不确定性，以及当前气候状态的全球能量学。如果气候敏感度真的很高，这些考虑因素将阻止肥尾的高温在许多世纪内达到。如果不包括这些因素，可能会扭曲由此得出的经济分析。例如，我们的结论是，当经济分析遵循通常的做法时，考虑厚尾因素不会对经济分析产生很大影响，尽管这种做法很有争议，即只对气温变化非常大的结果分配大笔损失，并假设经济增长的基准水平很高。
The small but stubbornly unyielding possibility of a very large long-term response of global temperature to increases in atmospheric carbon dioxide can be termed the fat tail of high climate sensitivity. Recent economic analyses suggest that the fat tail should dominate a rational policy strategy if the damages associated with such high temperatures are large enough. The conclusions of such analyses, however, depend on how economic growth, temperature changes, and climate damages unfold and interact over time. In this paper we focus on the role of two robust physical properties of the climate system: the enormous thermal inertia of the ocean, and the long timescales associated with high climate sensitivity. Economic models that include a climate component, and particularly those that focus on the tails of the probability distributions, should properly represent the physics of this slow response to high climate sensitivity, including the correlated uncertainty between present forcing and climate sensitivity, and the global energetics of the present climate state. If climate sensitivity in fact proves to be high, these considerations prevent the high temperatures in the fat tail from being reached for many centuries. A failure to include these factors risks distorting the resulting economic analyses. For example, we conclude that fat-tail considerations will not strongly influence economic analyses when these analyses follow the common—albeit controversial—practices of assigning large damages only to outcomes with very high temperature changes and of assuming a significant baseline level of economic growth.