Impacts of natural and anthropogenic forcings on historical and future changes in global-land surface air temperature in CMIP6–DAMIP simulations

Abstract

To better understand the contributions of various external factors to past and future changes in global and regional climate, this study investigates the impacts of natural and anthropogenic forcings on historical and future changes in global land surface air temperature (GLSAT) using model simulations from the Detection and Attribution Model Intercomparison Project (DAMIP) in the Coupled Model Intercomparison Project Phase 6 (CMIP6). Results show that the anthropogenic forcing (ANT) can be robustly detected and separated from the response to the natural external forcing (NAT) since the 1970s. The observed warming changes since the 1950s are primarily attributed to the GHG forcing. ANT contributes a robust warming trend of 0.1–0.2 °C per decade for global landmass during 1951–2020 and cumulative warming by 2011–2020 (relative to 1901–1930) of 1.0–1.6 °C. These attributable warmings largely encompass the observed warming trend of ~ 0.18 °C per decade in 1951–2012 and the observed warming of 1.59 °C by 2011–2020 (relative to 1850–1900) for global landmass reported in IPCC AR5 and AR6, respectively. The anthropogenic warming is projected to increase by 3–6 °C for most global landmass under the SSP2-4.5 scenario, especially in the high latitudes Northern Hemisphere by the late twenty-first century, along with an increase in the mean and widespread flattening of the probability distribution functions (PDFs). The anthropogenic aerosol (AA) cooling effect is projected to decrease only modestly, from 0.7 °C in 2011-20 to 0.6 °C by the late 21st century, for the SSP2-4.5 scenario.