Global warming of 2C could render 25% of globe arid
Global temperature rises of 2C above pre-industrial levels could result in over 25% of the earth’s surface becoming considerably drier, increasing the risk of drought and wildfires and threatening agriculture and biodiversity, according to new research. Restricting global warming to less than 1.5C would save two-thirds of such areas from such severe change. The study analysed projections from 27 global climate models in order to identify the regions that were most at risk, including Central America, southeast Asia, southern Africa, southern Australia and southern Europe. These regions are home to 20% of the world’s current population. 
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 desertification1,2,3,4,5,6. 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 policies7,8,9,10. 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.