Abstract
The contrasting rainfall between the wet tropics and the dry subtropics largely determines the climate of the tropical zones. A southward shift of these rain belts has been observed throughout the latter half of the twentieth century, with profound societal consequences. Although such large-scale shifts in rainfall have been linked to interhemispheric temperature gradients from anthropogenic aerosols, a complete understanding of this mechanism has been hindered by the lack of explicit information on aerosol radiative effects. Here we quantify the relative contributions of radiative forcing from anthropogenic aerosols to the interhemispheric asymmetry in temperature and precipitation change for climate change simulations. We show that in model simulations the vast majority of the precipitation shift does not result from aerosols directly through their absorption and scattering of radiation, but rather indirectly through their modification of cloud radiative properties. Models with larger cloud responses to aerosol forcing are found to better reproduce the observed interhemispheric temperature changes and tropical rain belt shifts over the twentieth century, suggesting that aerosol–cloud interactions will play a key role in determining future interhemispheric shifts in climate.
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Acknowledgements
We acknowledge the World Climate Research Programme’s Working Group on Coupled Modeling, which is responsible for CMIP, and we thank the climate modelling groups (listed in Supplementary Table 1 of this study) for producing and making available their model output. For CMIP the US Department of Energy’s Program for Climate Model Diagnosis and Intercomparison provides coordinating support and led development of software infrastructure in partnership with the Global Organization for Earth System Science Portals. This study was supported by grants from the NASA ROSES Program.
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E.-S.C. and B.J.S. designed the study, performed the analysis, and wrote the paper.
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Chung, ES., Soden, B. Hemispheric climate shifts driven by anthropogenic aerosol–cloud interactions. Nature Geosci 10, 566–571 (2017). https://doi.org/10.1038/ngeo2988
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DOI: https://doi.org/10.1038/ngeo2988
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