Observation-constrained climate change in China over 1850–2014 by aerosols in CMIP6 models

Abstract Aerosols play a very important role in climate change with large uncertainties. Using the multi-model results from CMIP6, we analyzed the aerosol effective radiative forcing (ERF) and aerosol-induced surface air temperature (SAT) change in China in the present day (PD, 11-year mean of 2004–2014) relative to the pre-industrial time (PI, 11-year mean of 1850–1860). With the increase in the anthropogenic emissions, the simulated surface PM 2.5 concentration and aerosol optical depth (AOD) averaged over eastern China (EC, 18–44°N, 103–122°E) increased by 21.43±7.58 μg m −3 and 0.47±0.33, respectively, from PI to PD. The simulated aerosol ERFs in EC were −4.91±2.56 and −5.35±2.40 W m −2 from equilibrium and transient simulations, respectively. The simulated change in SAT caused by the increases in aerosols was −1.37±0.38℃ in EC from PI to PD. The simulated values of equilibrium and transient climate sensitivity to aerosols (CSA, aerosol-induced SAT change per unit aerosol ERF) in EC were 0.236 and 0.222℃ (W m −2 ) −1 , respectively. By using the observed AOD from MODIS to constrain aerosol ERF, the constrained aerosol equilibrium and transient ERFs over EC were −4.66 W m −2 and −4.93 W m −2 , respectively, which were smaller in magnitude than the simulated values directly from the models. By using the observed SAT from the Climatic Research Unit temperature version 5 to constrain aerosol-induced cooling, the surface cooling caused by aerosols was magnified to −1.47℃. The adjusted CSA after the constraint was calculated by dividing adjusted aerosol-induced SAT change by adjusted aerosol ERF. Adjusted equilibrium and transient CSA values in EC were 0.32 and 0.34℃ (W m −2 ) −1 , respectively.