Observed pattern effect contribution to recent warming from reduced aerosol emissions

Global surface warming has accelerated since around 20111, 2, 3. Earth system models indicated the contributions of reduced aerosol emissions from East Asia to recent greater warming4. An observed analysis attributed the temperature surge to record-low planetary albedo due mainly to reduced low-cloud cover over the North Pacific (NP)5. However, it is undetermined how much of the reduced low-cloud cover arises from internal variability, reduced aerosol concentrations, or cloud feedback, leaving the basic forcing for the acceleration unclear. Using satellite and reanalysis data, we show that increased spatial inhomogeneities in sea surface temperature (SST) warming largely accelerated global warming rate (0.12 ± 0.06 ℃/decade) through the pattern effect of SST. Reduced aerosol emissions from East Asia caused anomalous warming in eastern NP by triggering warm blob events in the Northeast Pacific6 and affecting the trends in the Pacific Decadal Oscillation phase7 through atmosphere teleconnections. These processes enhanced the pattern effect of SST (0.73 ± 0.08 Wm-2/decade). The enhanced pattern effect accelerated global surface warming by affecting thermal radiative feedback rather than aerosol radiative forcing that yields relatively little net global impact (0.23 ± 0.07 Wm-2/decade). Approximately 92% of the observed reduction in low-cloud cover is subsequently caused by cloud shortwave feedback responding to increased surface temperature, yielding an increased Earth energy imbalance (0.43 ± 0.34 Wm-2decade-1) due to more absorbed solar radiation. This underlines the importance of understanding aerosol radiative forcing and their derivative effects to avoid any detrimental climate consequences from the air quality policies of countries.