The key role of atmospheric absorption in the Asian summer monsoon response to dust emissions in CMIP6 models

Abstract

We investigate the Asian summer monsoon (ASM) response to global dust emissions in the Coupled Model Intercomparison Project Phase 6 (CMIP6) models, which is the first CMIP to include an experiment with a doubling of global dust emissions relative to their preindustrial levels. Thus, for the first time, the inbuilt influence of dust on climate across a range of climate models being used to evaluate and predict Earth's climate can be quantified. We find that dust emissions cause a strong atmospheric heating over Asia that leads to a pronounced energy imbalance. This results in an enhanced Indian summer monsoon (ISM) and a southward shift of the western Pacific Intertropical Convergence Zone (ITCZ), consistent across models, with the strength of the ISM enhancement increasing with the magnitude of atmospheric dust shortwave absorption, driven by dust optical depth changes. However, the east Asian summer monsoon response shows large uncertainties across models, arising from the diversity in models' simulated dust emissions and in the dynamical response to these changes. Our results demonstrate the central role of dust absorption in influencing the ASM and the importance of accurate dust simulations for constraining the ASM and the ITCZ in climate models.