Climate change is increasing the likelihood of extreme autumn wildfire conditions across California
Climate change is increasing the likelihood of extreme autumn wildfire conditions across California
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DOI：
10.1088/1748-9326/ab83a7
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发表时间：
2020-09-01
影响因子：
6.7
通讯作者：
Diffenbaugh, Noah S.
中科院分区：
文献类型：
--
作者：
Goss, Michael;Swain, Daniel L.;Diffenbaugh, Noah S.
近年来，加州经历了毁灭性的秋季野火。这些秋季野火与海上强风期间的极端火灾天气条件相吻合，同时由于异常温暖的条件和秋季降水晚来，植被异常干燥。在这项研究中，我们量化观测到的导致加州极端秋季野火的气象因子的发生和量级的变化，并使用气候模式模拟来确定这些变化是否归因于人为引起的气候变化。我们发现，在过去40年里，全州范围内秋季气温的升高（约1摄氏度）和秋季降水的减少（约30%）导致了总火灾天气指数的升高（+20%）。结果，自20世纪80年代初以来，观察到的秋季极端（第95百分位）火灾天气的频率（我们显示，这种天气优先与极端秋季野火有关）在加州增加了一倍多。我们进一步发现，自1950年以来，气候模型估计的这些极端秋季条件的概率有所增加，包括加州北部和南部极端火灾天气条件同季同时发生的长期趋势。我们的气候模型分析表明，到本世纪末，持续的气候变化将进一步增加极端火灾天气的天数，尽管与联合国巴黎承诺一致的途径将大大遏制这种增加。鉴于近年来极端秋季野火对社会的严重影响，我们的研究结果对加州和其他地区管理野火风险的持续努力具有重要意义。
California has experienced devastating autumn wildfires in recent years. These autumn wildfires have coincided with extreme fire weather conditions during periods of strong offshore winds coincident with unusually dry vegetation enabled by anomalously warm conditions and late onset of autumn precipitation. In this study, we quantify observed changes in the occurrence and magnitude of meteorological factors that enable extreme autumn wildfires in California, and use climate model simulations to ascertain whether these changes are attributable to human-caused climate change. We show that state-wide increases in autumn temperature (similar to 1 degrees C) and decreases in autumn precipitation (similar to 30%) over the past four decades have contributed to increases in aggregate fire weather indices (+20%). As a result, the observed frequency of autumn days with extreme (95th percentile) fire weather-which we show are preferentially associated with extreme autumn wildfires-has more than doubled in California since the early 1980s. We further find an increase in the climate model-estimated probability of these extreme autumn conditions since similar to 1950, including a long-term trend toward increased same-season co-occurrence of extreme fire weather conditions in northern and southern California. Our climate model analyses suggest that continued climate change will further amplify the number of days with extreme fire weather by the end of this century, though a pathway consistent with the UN Paris commitments would substantially curb that increase. Given the acute societal impacts of extreme autumn wildfires in recent years, our findings have critical relevance for ongoing efforts to manage wildfire risks in California and other regions.