AbstractThe goal of this study is to reframe the analysis and discussion of extreme heat projections to improve communication of future extreme heat risks in the United States. We combine existing data from 31 of the Coupled Model Intercomparison Project Phase 5 models to examine future exposure to extreme heat for global average temperatures of 1.5, 2, 3, and 4 °C above a preindustrial baseline. We find that throughout the United States, historically rare extreme heat events become increasingly common in the future as global temperatures rise and that the depiction of exposure depends in large part on whether extreme heat is defined by absolute or relative metrics. For example, for a 4 °C global temperature rise, parts of the country may never see summertime temperatures in excess of 100 °F, but virtually all of the country is projected to experience more than 4 weeks per summer with temperatures exceeding their historical summertime maximum. All of the extreme temperature metrics we explored become more severe with increasing global average temperatures. However, a moderate climate scenario delays the impacts projected for a 3 °C world by almost a generation relative to the higher scenario and prevents the most extreme impacts projected for a 4 °C world.

中文翻译：

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重新审视美国未来极端高温的风险

摘要这项研究的目的是重新构建对极端高温预测的分析和讨论，以改善美国未来极端高温风险的沟通。我们结合了耦合模型比对项目第 5 阶段 31 个模型的现有数据，以研究未来全球平均气温比工业化前基线高 1.5、2、3 和 4 °C 的极端高温。我们发现，在美国各地，随着全球气温上升，历史上罕见的极端高温事件在未来变得越来越普遍，并且对暴露的描述在很大程度上取决于极端高温是通过绝对指标还是相对指标来定义的。例如，如果全球气温上升 4 °C，该国部分地区的夏季气温可能永远不会超过 100 °F，但实际上该国所有地区预计每年夏季将有超过 4 周的气温超过历史夏季气温最大限度。随着全球平均气温的升高，我们探索的所有极端温度指标都变得更加严格。然而，相对于较高气候情景，温和的气候情景将预测的 3°C 世界影响推迟了近一代人，并防止了 4°C 世界预测的最极端影响。