Expansion of drylands in China with an additional half a degree warming

摘要

To contribute a more ambitious target of Paris Agreement, that is, limiting global warming to 1.5 degrees C instead of 2.0 degrees C above preindustrial levels, it is essential to quantitatively reveal regional impacts of an additional 0.5 degrees C warming to inform climate policymaking. Based on bias-corrected simulations of four models from the half a degree additional warming, prognosis and projected impacts (HAPPI), we examine how dry-wet condition may change in China at 1.5 and 2.0 degrees C warming levels, focusing on the projected changes in the area of drylands. Results showed that China is projected to be dominated by a decrease Surface Wetness Index (SWI), due to a larger increase in potential evapotranspiration (PET) than precipitation, implying a drying signal, in both 1.5 and 2.0 degrees C warming levels against a present-day scenario. Correspondingly, an expansion of drylands is expected, the larger expansion with the higher warming level, with changes approximately 0.77 +/- 2.02% in 1.5 degrees C level, and 2.29 +/- 2.69% in 2.0 degrees C level, although there exists considerable intermodel variability. For an additional warming of 0.5 degrees C, there is high confidence of the projected decrease of SWI and expansion of drylands, approximately 1.52 +/- 0.77%. That is to say, limiting global warming to 1.5 degrees C is suggested to robustly reduce the likelihood of emerging aridification compared to 2 degrees C, and China might obtain considerable benefits in term of socio-economic impacts related to the reduction of aridification. Thus, it is necessary for continued efforts to limit global warming to 1.5 degrees C.