The challenge of accurately quantifying future megadrought risk in the American Southwest
The challenge of accurately quantifying future megadrought risk in the American Southwest
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DOI：
10.1002/2016gl070445
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发表时间：
2016-09-01
影响因子：
5.2
通讯作者：
Mankin, Justin S.
中科院分区：
文献类型：
--
作者：
Coats, Sloan;Mankin, Justin S.
美国西南部(ASW)特大旱灾代表了十年尺度的干旱状况，其近期风险来自自然低频的水文气候变异性和人为强迫。一个大型的单一气候模型集合表明，人为强迫使近期ASW巨灾风险增加了100倍；然而，准确的风险评估仍然是一个挑战。在全球范围内，我们发现，人为强迫可能会改变导致55%的陆地地区发生特大干旱的变异性，破坏对其风险的准确评估。对于剩下的地区，目前的总体规模太小，无法描述特大灾害的驱动变异性。例如，要将近期ASW巨型风险的不确定性高置信度地限制在5个百分点以内，需要进行287次模拟。这样的集合规模超出了目前的计算和存储资源，这些限制表明，即使在潜在变异性固定的地方，目前也不可能以高度可信的方式限制近期巨型风险预测的误差。
American Southwest (ASW) megadroughts represent decadal-scale periods of dry conditions the near-term risks of which arise from natural low-frequency hydroclimate variability and anthropogenic forcing. A large single-climate-model ensemble indicates that anthropogenic forcing increases near-term ASW megadrought risk by a factor of 100; however, accurate risk assessment remains a challenge. At the global-scale we find that anthropogenic forcing may alter the variability driving megadroughts over 55% of land areas, undermining accurate assessments of their risk. For the remaining areas, current ensembles are too small to characterize megadroughts' driving variability. For example, constraining uncertainty in near-term ASW megadrought risk to 5 percentage points with high confidence requires 287 simulations. Such ensemble sizes are beyond current computational and storage resources, and these limitations suggest that constraining errors in near-term megadrought risk projections with high confidenceeven in places where underlying variability is stationaryis not currently possible.