Climate change and the opportunity cost of conflict
Climate change and the opportunity cost of conflict
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DOI：
10.1073/pnas.1914829117
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发表时间：
2020-01
期刊：
影响因子：
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通讯作者：
K. Roche;Michèle Müller-Itten;D. Dralle;D. Bolster;M. Müller
中科院分区：
文献类型：
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作者：
K. Roche;Michèle Müller-Itten;D. Dralle;D. Bolster;M. Müller
意义学者们越来越一致地认为，气候变化可能会放大暴力冲突的风险。尽管人们对潜在机制知之甚少，但长期以来，人们一直认为与气候变化相关的负面收入冲击将发挥重要作用。我们联系最新的水文学和微观经济学的进展来研究这一主张的理论基础。结果规定，在解释气候变化背景下气候变异性和冲突之间的经验关系时要谨慎。虽然战斗主要发生在气候异常期间，但更频繁的异常可能不会产生更多的冲突。通过改变整个降雨量的分布，气候变化有效地重新定义了气候异常的概念。对这种新常态的适应可能会对冲突的概率产生主导的、往往是违反直觉的影响。越来越多的实证文献将气候异常与暴力冲突风险的增加联系在一起。这种联系被描绘成未来社会不稳定的风向标，因为极端天气事件的频率和强度预计将会增加。本文对这一主张的理论基础进行了探讨。机会成本的一个开创性的微观经济学模型--一种通常被认为推动气候-冲突关系的机制--通过考虑依赖气候的农业收入分配的现实变化而得到扩展。结果建议在使用短期气候异常和冲突之间的经验关联来预测气候制度持续变化的影响时要谨慎：尽管战争发生在糟糕的年份，但如果代理人预计更频繁的糟糕年份，冲突可能会减少。理论表明，气候变化和冲突之间存在非单调关系，当代理人适应和调整自己的行为以适应新的收入分配时，这种关系就会出现。我们确定了收入分配的三个可测量的统计数据，每个统计数据都明确地与冲突可能性有关。总而言之，这些统计数据提供了一个独特的特征，可以将机会成本与可能将气候异常与冲突联系起来的竞争机制区分开来。
Significance There is growing consensus among academics that climate change may amplify the risk of violent conflicts. While underlying mechanisms are poorly understood, negative income shocks associated with climate variability have been long hypothesized to play an important role. We relate recent hydrologic and microeconomic advances to investigate the theoretical foundation of this claim. Results prescribe caution in interpreting empirical relations between climate variability and conflict in the context of climate change. While fighting preferentially occurs during climate anomalies, more frequent anomalies may not yield more conflicts. By shifting the entire distribution of rainfall, climate change effectively redefines the very notion of climate anomaly. Adaptation to this new normal can have a dominant, and often counterintuitive, effect on conflict probability. A growing empirical literature associates climate anomalies with increased risk of violent conflict. This association has been portrayed as a bellwether of future societal instability as the frequency and intensity of extreme weather events are predicted to increase. This paper investigates the theoretical foundation of this claim. A seminal microeconomic model of opportunity costs—a mechanism often thought to drive climate–conflict relationships—is extended by considering realistic changes in the distribution of climate-dependent agricultural income. Results advise caution in using empirical associations between short-run climate anomalies and conflicts to predict the effect of sustained shifts in climate regimes: Although war occurs in bad years, conflict may decrease if agents expect more frequent bad years. Theory suggests a nonmonotonic relation between climate variability and conflict that emerges as agents adapt and adjust their behavior to the new income distribution. We identify 3 measurable statistics of the income distribution that are each unambiguously associated with conflict likelihood. Jointly, these statistics offer a unique signature to distinguish opportunity costs from competing mechanisms that may relate climate anomalies to conflict.