Anthropogenic warming has increased drought risk in California
Anthropogenic warming has increased drought risk in California
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DOI：
10.1073/pnas.1422385112
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发表时间：
2015-03-31
影响因子：
11.1
通讯作者：
Touma, Danielle
中科院分区：
文献类型：
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作者：
Diffenbaugh, Noah S.;Swain, Daniel L.;Touma, Danielle
加州目前正处于创纪录的干旱之中。这场干旱始于2012年，现在包括历年最低降雨量和12个月降雨量，年度最高气温，以及有记录以来最极端的干旱指标。极端温暖和干燥的条件导致了严重的水资源短缺、地下水透支、极低的径流，并增加了野火风险。分析加利福尼亚州的历史气候观测，我们发现，如果发生在气候温暖的年份，加州降水不足导致干旱的可能性是后者的两倍以上。我们发现，尽管近几十年来出现负或中等负降水异常的概率并没有发生实质性的变化，但近20年来干旱年的发生比前一个世纪更严重。此外，降水不足与温暖条件并存的概率以及降水不足导致干旱的概率都有所增加。气候模型实验表明，无论有没有人为强迫，人类活动都增加了干旱年变暖的可能性。此外，一大批气候模型的实现表明，未来几十年进一步的全球变暖很可能造成类似于100%的概率，即任何年度尺度的干旱时期也是极端温暖的。因此，我们得出结论，人为变暖正在增加暖干条件共存的可能性，这种情况已经造成了与2012-2014年“异常”加州干旱相关的严重人类和生态系统影响。
California is currently in the midst of a record-setting drought. The drought began in 2012 and now includes the lowest calendar-year and 12-mo precipitation, the highest annual temperature, and the most extreme drought indicators on record. The extremely warm and dry conditions have led to acute water shortages, groundwater overdraft, critically low streamflow, and enhanced wildfire risk. Analyzing historical climate observations from California, we find that precipitation deficits in California were more than twice as likely to yield drought years if they occurred when conditions were warm. We find that although there has not been a substantial change in the probability of either negative or moderately negative precipitation anomalies in recent decades, the occurrence of drought years has been greater in the past two decades than in the preceding century. In addition, the probability that precipitation deficits co-occur with warm conditions and the probability that precipitation deficits produce drought have both increased. Climate model experiments with and without anthropogenic forcings reveal that human activities have increased the probability that dry precipitation years are also warm. Further, a large ensemble of climate model realizations reveals that additional global warming over the next few decades is very likely to create similar to 100% probability that any annual-scale dry period is also extremely warm. We therefore conclude that anthropogenic warming is increasing the probability of co-occurring warm-dry conditions like those that have created the acute human and ecosystem impacts associated with the "exceptional" 2012-2014 drought in California.