Twenty-First Century Drought Projections in the CMIP6 Forcing Scenarios
Twenty-First Century Drought Projections in the CMIP6 Forcing Scenarios
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DOI：
10.1029/2019ef001461
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发表时间：
2020-06-01
期刊：
影响因子：
8.2
通讯作者：
Anchukaitis, K. J.
中科院分区：
文献类型：
--
作者：
Cook, B. I.;Mankin, J. S.;Anchukaitis, K. J.
有强有力的证据表明，气候变化将增加干旱风险和严重程度，但这些结论取决于正在考虑的地区、季节和干旱指标。在耦合模式比较项目(CMIP6)第六阶段的预测中，我们分析了整个水文循环(降水、土壤水分和径流)中干旱的变化。多模式组合显示，即使遵循更激进的缓解途径(SSP1-2.6和SSP2-4.5)，到21世纪末，许多地区和指标的平均状态仍表现出强劲的干燥。强干旱的区域热点包括北美西部、中美洲、欧洲和地中海、亚马逊、南部非洲、中国、东南亚和澳大利亚。然而，与SSP3-7.0和SSP5-8.5相比，较低变暖情景下的干旱严重程度大大降低，许多地区的降水量避免了进一步下降。伴随着平均状态的干燥，历史上最极端的干旱事件的风险也随着变暖而增加，在一些地区增加了200-300%。CMIP6的土壤水分和径流干燥比降水更强劲、更广泛、更严重，这表明它在其他温度敏感型干旱过程中发挥了重要作用，包括蒸散和降雪。鉴于CMIP5和CMIP6在干旱响应方面的相似性，我们推测两代模型都受到类似的不确定性的影响，包括植被过程、降水的模型表示以及模型对变暖的响应与观测的一致程度。应进一步探讨这些主题，以评估CMIP6模型是否提供了增强对干旱预测信心的理由。
There is strong evidence that climate change will increase drought risk and severity, but these conclusions depend on the regions, seasons, and drought metrics being considered. We analyze changes in drought across the hydrologic cycle (precipitation, soil moisture, and runoff) in projections from Phase Six of the Coupled Model Intercomparison Project (CMIP6). The multimodel ensemble shows robust drying in the mean state across many regions and metrics by the end of the 21st century, even following the more aggressive mitigation pathways (SSP1-2.6 and SSP2-4.5). Regional hotspots with strong drying include western North America, Central America, Europe and the Mediterranean, the Amazon, southern Africa, China, Southeast Asia, and Australia. Compared to SSP3-7.0 and SSP5-8.5, however, the severity of drying in the lower warming scenarios is substantially reduced and further precipitation declines in many regions are avoided. Along with drying in the mean state, the risk of the historically most extreme drought events also increases with warming, by 200-300% in some regions. Soil moisture and runoff drying in CMIP6 is more robust, spatially extensive, and severe than precipitation, indicating an important role for other temperature-sensitive drought processes, including evapotranspiration and snow. Given the similarity in drought responses between CMIP5 and CMIP6, we speculate that both generations of models are subject to similar uncertainties, including vegetation processes, model representations of precipitation, and the degree to which model responses to warming are consistent with observations. These topics should be further explored to evaluate whether CMIP6 models offer reasons to have increased confidence in drought projections.