Recent exceptionally hot droughts in Amazonia have highlighted the potential role of global warming in driving changes in rainfall and temperatures in the region. The previous generation of global climate models projected that eastern Amazonia would receive less future precipitation while western Amazonia would receive more precipitation, but many of these models disagreed on future precipitation trends in the region. Here Coupled Modeling Intercomparison Project, Phase 6 (CMIP6) models are used to examine the shifting risk of eastern Amazonian droughts under high and low future greenhouse gas emissions scenarios. This new generation of models shows better agreement that most of the Amazonian basin will receive less future rainfall, with particularly strong agreement that eastern and southern Amazonia will dry in the 21st century. These models suggest that global warming may be increasing the likelihood of exceptionally hot drought in the region. With unabated global warming, recent particularly warm and severe droughts will become more common by midcentury, but reducing the rate of greenhouse gas emissions can make extremely hot and dry years less common in the future. Simulated future rainfall changes in Amazonia under high greenhouse gas emissions are associated with changes in the tropical Pacific, but many climate models struggle to reproduce observed trends in the tropical Pacific. These shortcomings highlight the need to improve confidence in global climate models' ability to simulate observed trends in the tropics, even if more CMIP6 models agree on the sign of future rainfall trends.

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CMIP6预测的干燥趋势对21世纪亚马逊干旱风险的影响

亚马逊地区最近异常炎热的干旱凸显了全球变暖在推动该地区降雨和温度变化方面的潜在作用。上一代全球气候模型预测，东部亚马逊地区的未来降水量将减少，而西部亚马逊地区的未来降水量将增加，但是其中许多模型对该地区未来的降水趋势均持不同意见。在这里，耦合模型比较项目第六阶段（CMIP6）模型用于检查未来温室气体排放量高低情景下东部亚马逊干旱的转移风险。新一代模型显示出更好的共识，即大多数亚马逊河流域未来的降雨将减少，特别有力的共识是，东部和南部的亚马逊河流域将在21世纪干旱。这些模型表明，全球变暖可能正在增加该地区异常高温干旱的可能性。随着全球变暖的加剧，到本世纪中叶，最近特别是温暖和严重的干旱将在本世纪中叶变得更加普遍，但是降低温室气体排放量将使未来极度炎热和干旱的年份变得不那么普遍。高温室气体排放下亚马逊河地区未来降雨的模拟变化与热带太平洋的变化有关，但是许多气候模型都难以重现热带太平洋观测到的趋势。这些缺点突出表明，即使更多的CMIP6模型同意未来降雨趋势的迹象，也有必要提高人们对全球气候模型模拟热带地区观测趋势的能力的信心。