Aridity—the ratio of atmospheric water supply (precipitation; P) to demand (potential evapotranspiration; PET)—is projected to decrease (that is, areas will become drier) as a consequence of anthropogenic climate change, exacerbating land degradation and desertification^1,2,3,4,5,6. However, the timing of significant aridification relative to natural variability—defined here as the time of emergence for aridification (ToEA)—is unknown, despite its importance in designing and implementing mitigation policies^7,8,9,10. Here we estimate ToEA from projections of 27 global climate models (GCMs) under representative concentration pathways (RCPs) RCP4.5 and RCP8.5, and in doing so, identify where emergence occurs before global mean warming reaches 1.5 °C and 2 °C above the pre-industrial level. On the basis of the ensemble median ToEA for each grid cell, aridification emerges over 32% (RCP4.5) and 24% (RCP8.5) of the total land surface before the ensemble median of global mean temperature change reaches 2 °C in each scenario. Moreover, ToEA is avoided in about two-thirds of the above regions if the maximum global warming level is limited to 1.5 °C. Early action for accomplishing the 1.5 °C temperature goal can therefore markedly reduce the likelihood that large regions will face substantial aridification and related impacts.

干旱-人为气候变化，加剧土地退化和荒漠化的结果，预计大气水供应（降水；P）与需求（潜在的蒸散量； PET）之比将降低（即，区域将变得更干燥）^{， 2,3,4,5,6}。但是，相对于自然变异而言，重要的干旱化时间（此处定义为干旱化出现时间（ToEA））是未知的，尽管它在设计和实施缓解政策中很重要^7,8,9,10。在这里，我们根据代表性浓度路径（RCPs）RCP4.5和RCP8.5下27个全球气候模型（GCM）的预测来估算ToEA，并在此过程中确定在全球平均变暖达到1.5°C和2°C之前出现的地方高于工业化前的水平。根据每个网格单元的总体中位数ToEA，在全球平均温度变化的总体中位数达到2°C之前，干旱化已超过陆地总表面的32％（RCP4.5）和24％（RCP8.5）。每个方案。此外，如果最大全球变暖水平限制在1.5°C，则在上述区域的三分之二左右应避免使用ToEA。因此，为实现1.5°C的温度目标而采取的早期行动可以显着降低大区域面临实质干旱和相关影响的可能性。