Biological and Environmental Research - Earth and Environmental System Sciences
Earth and Environmental System Modeling

Human Influence on Joint Changes in Temperature, Rainfall and Continental Aridity

TitleHuman Influence on Joint Changes in Temperature, Rainfall and Continental Aridity
Publication TypeJournal Article
Year of Publication2020
JournalNature Climate Change
Abstract / Summary

Despite the pervasive impact of drought on human and natural systems, the large-scale mechanisms conducive to regional drying remain poorly understood. Here we use a multivariate approach to identify two distinct externally forced fingerprints from multiple ensembles of Earth system model simulations. The leading fingerprint, FM1(x), is characterized by global warming, intensified wet–dry patterns, and progressive large-scale continental aridification, largely driven by multidecadal increases in greenhouse gas (GHG) emissions. The second fingerprint, FM2(x), captures a pronounced interhemispheric temperature contrast, associated meridional shifts in the intertropical convergence zone, and correlated anomalies in precipitation and aridity over California, the Sahel and India. FM2(x) exhibits nonlinear temporal behavior: the intertropical convergence zone moves southwards before 1975 in response to increases in hemispherically asymmetric sulfate aerosol emissions, and it shifts northwards after 1975 due to reduced sulfur dioxide emissions and the GHG-induced warming of Northern Hemisphere landmasses. Both fingerprints are statistically identifiable in observations of joint changes in temperature, rainfall, and aridity during 1950–2014. We show that the reliable simulation of these changes requires combined forcing by GHGs, direct and indirect effects of aerosols, and large volcanic eruptions. Our results suggest that GHG-induced aridification may be modulated regionally by future reductions in sulfate aerosol emissions.

URLhttp://dx.doi.org/10.1038/s41558-020-0821-1
DOI10.1038/s41558-020-0821-1
Journal: Nature Climate Change
Year of Publication: 2020
Publication Date: 07/2020

Despite the pervasive impact of drought on human and natural systems, the large-scale mechanisms conducive to regional drying remain poorly understood. Here we use a multivariate approach to identify two distinct externally forced fingerprints from multiple ensembles of Earth system model simulations. The leading fingerprint, FM1(x), is characterized by global warming, intensified wet–dry patterns, and progressive large-scale continental aridification, largely driven by multidecadal increases in greenhouse gas (GHG) emissions. The second fingerprint, FM2(x), captures a pronounced interhemispheric temperature contrast, associated meridional shifts in the intertropical convergence zone, and correlated anomalies in precipitation and aridity over California, the Sahel and India. FM2(x) exhibits nonlinear temporal behavior: the intertropical convergence zone moves southwards before 1975 in response to increases in hemispherically asymmetric sulfate aerosol emissions, and it shifts northwards after 1975 due to reduced sulfur dioxide emissions and the GHG-induced warming of Northern Hemisphere landmasses. Both fingerprints are statistically identifiable in observations of joint changes in temperature, rainfall, and aridity during 1950–2014. We show that the reliable simulation of these changes requires combined forcing by GHGs, direct and indirect effects of aerosols, and large volcanic eruptions. Our results suggest that GHG-induced aridification may be modulated regionally by future reductions in sulfate aerosol emissions.

DOI: 10.1038/s41558-020-0821-1
Citation:
Bonfils, C, B Santer, J Fyfe, K Marvel, T Phillips, and S Zimmerman.  2020.  "Human Influence on Joint Changes in Temperature, Rainfall and Continental Aridity."  Nature Climate Change.  https://doi.org/10.1038/s41558-020-0821-1.