Influence of anthropogenic and natural forcings on future changes in precipitation projected by the CMIP6-DAMIP models

Warming has already changed the patterns of precipitation and increased the risk of extreme climate events. An assessment of the influences from anthropogenic and natural forcings on future changes in precipitation is therefore essential to define appropriate mitigation and adaptation policies. We assess the effects of natural (NAT) and anthropogenic forcings (greenhouse gases [GHG] and anthropogenic aerosols [AA]) on precipitation over land areas simulated under the Coupled Model Intercomparison Project Phase 6 (CMIP6) SSP2-4.5 scenario. Our results indicate that changes in precipitation due to GHG forcing, AA forcing and all external forcings (ALL) are projected to increase by about 3.0%-24.8%, 1.1%-6.9% and 4.2%-31.2%, respectively, across most land areas in the twenty-first century, especially over the mid- and high latitudes of the Northern Hemisphere and central Africa, with an increase in the mean and flattening of the probability distribution functions (PDFs). By contrast, the NAT-induced changes are relatively small, with a slight increase in the mean of the PDFs. The frequencies of both future extreme precipitation and dry events are projected to increase by 11%-101% and 3%-72%, respectively, over many continental regions under the influence of external forcings, especially under GHG forcing. Fingerprinting detection shows that the signals of GHG (except for Australia), AA and ALL forcing are detectable at the likely level (signal-to-noise ratio >0.95; 66% confidence) over most land areas. The GHG signals are stronger and detected earlier (after 2010s, likely level) than the AA signals (after 2060s, likely level).