Anthropogenic Aerosols Influence Tropical Pacific Sea Surface Temperature Gradient Trends

Abstract The tropical Pacific is warming more in the west than the east. This observed strengthening of the tropical Pacific east‐to‐west Sea Surface Temperature (SST) gradient is poorly reproduced in climate models—a prominent model bias with far reaching global impacts. We explore the tropical Pacific SST gradient response to anthropogenic aerosols in large‐ensembles of CMIP6 simulations between 1950 and 2014. We find that anthropogenic aerosols are cooling the tropical Pacific—the cooling is more pronounced in the east Pacific—while greenhouse gases have the opposite response. Tropical Pacific gradient strengthening is not due to the anthropogenic aerosol effective radiative forcing magnitude or top of atmosphere energy imbalance. This suggests that pathways connecting the regional radiative response to the tropical Pacific are important. In the future, all models predict a weakening gradient, irrespective of historical trends. Anthropogenic aerosol forcing plays an important role in driving changes in tropical Pacific SSTs.