Large potential reduction in economic damages under UN mitigation targets
Large potential reduction in economic damages under UN mitigation targets
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DOI：
10.1038/s41586-018-0071-9
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发表时间：
2018-05-24
期刊：
影响因子：
64.8
通讯作者：
Diffenbaugh, Noah S.
中科院分区：
文献类型：
--
作者：
Burke, Marshall;Davis, W. Matthew;Diffenbaugh, Noah S.
国际气候变化协议通常将全球变暖阈值指定为政策目标(1)，但实现这些温度目标的相对经济效益仍然知之甚少（2,3）。不确定性包括温度变化的空间格局，全球和区域经济产出将如何响应这些温度变化，以及社会以当前消费换取未来消费的意愿。在这里，我们将历史证据(4)与国家层面的气候(5)和社会经济(6)预测结合起来，量化与联合国（UN） 1.5摄氏度和2摄氏度全球变暖目标相关的经济损失，以及与当前联合国国家级减排承诺相关的经济损失（这些承诺加起来接近3摄氏度变暖(7)）。我们发现，到本世纪末，将升温限制在1.5摄氏度的可能性超过75%，将减少相对于2摄氏度的经济损失；按3%的贴现率（2010年美元）计算，全球累计收益超过20万亿美元的可能性超过60%。我们还估计，71%的国家（占全球人口的90%）有75%以上的机会在升温1.5摄氏度的情况下减少经济损失，其中较贫穷的国家受益最多。我们的结果可能低估了将升温限制在1.5℃的好处，如果升温2℃发生前所未有的极端结果，如大规模海平面上升(8)，而升温1.5℃则不会发生。纳入其他未量化的不确定性来源，如超出现有社会经济情景的长期增长率的不确定性，也可能导致不太精确的影响估计。我们发现，超过2摄氏度，全球经济产出将大幅减少。相对于2000-2010年水平不变的世界，我们预计，到2100年，根据目前的国家承诺，如果全球变暖幅度达到2.5-3摄氏度，人均产出将减少15%-25%(7)，如果全球变暖幅度达到4摄氏度，人均产出将减少30%以上。因此，我们的研究结果表明，实现1.5摄氏度的目标可能会减少总损失并减轻全球不平等，而未能实现2摄氏度的目标可能会大幅增加经济损失。
International climate change agreements typically specify global warming thresholds as policy targets(1), but the relative economic benefits of achieving these temperature targets remain poorly understood(2,3). Uncertainties include the spatial pattern of temperature change, how global and regional economic output will respond to these changes in temperature, and the willingness of societies to trade present for future consumption. Here we combine historical evidence(4) with national-level climate(5) and socioeconomic(6) projections to quantify the economic damages associated with the United Nations (UN) targets of 1.5 degrees C and 2 degrees C global warming, and those associated with current UN national-level mitigation commitments (which together approach 3 degrees C warming(7)). We find that by the end of this century, there is a more than 75% chance that limiting warming to 1.5 degrees C would reduce economic damages relative to 2 degrees C, and a more than 60% chance that the accumulated global benefits will exceed US$20 trillion under a 3% discount rate (2010 US dollars). We also estimate that 71% of countries-representing 90% of the global population-have a more than 75% chance of experiencing reduced economic damages at 1.5 degrees C, with poorer countries benefiting most. Our results could understate the benefits of limiting warming to 1.5 degrees C if unprecedented extreme outcomes, such as large-scale sea level rise(8), occur for warming of 2 degrees C but not for warming of 1.5 degrees C. Inclusion of other unquantified sources of uncertainty, such as uncertainty in secular growth rates beyond that contained in existing socioeconomic scenarios, could also result in less precise impact estimates. We find considerably greater reductions in global economic output beyond 2 degrees C. Relative to a world that did not warm beyond 2000-2010 levels, we project 15%-25% reductions in per capita output by 2100 for the 2.5-3 degrees C of global warming implied by current national commitments(7), and reductions of more than 30% for 4 degrees C warming. Our results therefore suggest that achieving the 1.5 degrees C target is likely to reduce aggregate damages and lessen global inequality, and that failing to meet the 2 degrees C target is likely to increase economic damages substantially.