A long-term decline in downward surface solar radiation

Abstract Downward surface solar radiation (DSSR) is critical for the Earth system. It is well-known that DSSR over land fluctuated on decadal timescales in the past. By utilizing a combination of station observations and the latest CMIP6 simulations, here we show that DSSR has a global consistent decline during 1959–2014, with comparable contributions from greenhouse gases (GHG) and anthropogenic aerosols. The role of GHGs is even more important in the satellite period. The contribution from GHGs comes through rising temperature, which reduces the DSSR by increased water vapor but is partly offset by reduced cloud. Future changes of DSSR are heavily dependent on climate change scenarios, which can be predicted well by global mean temperature (GMST) and aerosol concentrations. The sharp aerosol reduction and weak temperature rise in the SSP245/SSP126 scenarios will limit or stop the long-term decline of DSSR with a brighter future.