Similar spatial patterns of global climate response to aerosols from different regions

Kasoar, Matthew; Shawki, Dilshad; Voulgarakis, Apostolos

doi:10.1038/s41612-018-0022-z

Cited by 48 publications

(68 citation statements)

References 41 publications

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“…The precipitation responses in the individual experiments also positively correlate with that from the NML experiment (Figure S2). Following a similar line of thought, it suggests that there is a preferred response of large‐scale precipitation to aerosols from different regions (Dong et al, ; Kasoar, ; Kasoar et al, ).…”

Section: Resultsmentioning

confidence: 79%

The South Asian Monsoon Response to Remote Aerosols: Global and Regional Mechanisms

et al. 2018

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The South Asian summer monsoon has been suggested to be influenced by atmospheric aerosols, and this influence can be the result of either local or remote emissions. We have used the Hadley Centre Global Environment Model Version 3 (HadGEM3) coupled atmosphere-ocean climate model to investigate for the first time the centennial-scale South Asian precipitation response to emissions of sulfur dioxide (SO 2 ), the dominant anthropogenic precursor of sulfate aerosol, from different midlatitude regions. Despite the localized nature of the regional heating that results from removing SO 2 emissions, all experiments featured a similar large-scale precipitation response over South Asia, driven by ocean-modulated changes in the net cross-equatorial heat transport and an opposing cross-equatorial northward moisture transport. The effects are linearly additive, with the sum of the responses from the experiments where SO 2 is removed from the United States, Europe, and East Asia resembling the response seen in the experiment where emissions are removed from the northern midlatitudes as a whole, but with East Asia being the largest contributor, even per unit of emission or top-of-atmosphere radiative forcing. This stems from the fact that East Asian emissions can more easily influence regional land-sea thermal contrasts and sea level pressure differences that drive the monsoon circulation, compared to emissions from more remote regions. Our results suggest that radiative effects of remote pollution should not be neglected when examining changes in South Asian climate and that and it is important to examine such effects in coupled ocean-atmosphere modeling frameworks.Plain Language Summary Atmospheric aerosols have been shown to exert a strong influence on global and regional climate through their radiative effects. The South Asian summer monsoon, a climate phenomenon on which billions of lives depend, has been suggested to be influenced by aerosols, and this influence can be the result of either local or remote emissions. We have used a global climate model to investigate how sensitive is the monsoon to emissions from remote industrialized regions such as Europe, the North America, and East Asia. Despite the localized nature of the regional heating that results from removing emissions in these regions, all of them featured a similar large-scale rainfall change remotely over South Asia. This similarity reflects a common underlying mechanism, which involves a displacement of the tropical rain belt driven by aerosol effects on the temperature contrast between the two hemispheres of the Earth. We find that the effects of the different regions on South Asia are linearly additive, with East Asia being the largest contributor. This stems from the fact that its emissions can more easily influence regional land-sea thermal contrasts and sea level pressure differences over Asia that drive the summer monsoon circulation, compared to emissions from more remote regions. Our results suggest that influences of remote pollution should not be ...

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Section: Resultsmentioning

confidence: 79%

The South Asian Monsoon Response to Remote Aerosols: Global and Regional Mechanisms

et al. 2018

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“…The strongest cooling occurs locally to the region of forcing. Similarly, Kasoar et al () found that when SO 2 emissions are removed from specific regions, the temperature response does tend to be strongest local to the forcing, but there is also a common broad pattern response regardless of forcing location. The particularly strong cooling over Europe for 10×SO4eur is consistent with high‐latitude forcing being less effectively damped by radiation (Kang & Xie, ).…”

Section: Resultsmentioning

confidence: 91%

Efficacy of Climate Forcings in PDRMIP Models

et al. 2019

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Quantifying the efficacy of different climate forcings is important for understanding the real‐world climate sensitivity. This study presents a systematic multimodel analysis of different climate driver efficacies using simulations from the Precipitation Driver and Response Model Intercomparison Project (PDRMIP). Efficacies calculated from instantaneous radiative forcing deviate considerably from unity across forcing agents and models. Effective radiative forcing (ERF) is a better predictor of global mean near‐surface air temperature (GSAT) change. Efficacies are closest to one when ERF is computed using fixed sea surface temperature experiments and adjusted for land surface temperature changes using radiative kernels. Multimodel mean efficacies based on ERF are close to one for global perturbations of methane, sulfate, black carbon, and insolation, but there is notable intermodel spread. We do not find robust evidence that the geographic location of sulfate aerosol affects its efficacy. GSAT is found to respond more slowly to aerosol forcing than CO2 in the early stages of simulations. Despite these differences, we find that there is no evidence for an efficacy effect on historical GSAT trend estimates based on simulations with an impulse response model, nor on the resulting estimates of climate sensitivity derived from the historical period. However, the considerable intermodel spread in the computed efficacies means that we cannot rule out an efficacy‐induced bias of ±0.4 K in equilibrium climate sensitivity to CO2 doubling when estimated using the historical GSAT trend.

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“…The strong regional variations in aerosol distributions and ERF may matter for determining impacts of aerosol ERF on several aspects of the Earth system (e.g. Bollasina et al, 2011;Chung and Soden, 2017;Kasoar et al, 2018), but those considerations are also not addressed in this review. Both RF and ERF are measured in W m −2 and cover both the solar (shortwave, SW) and terrestrial (longwave, LW) parts of the electromagnetic spectrum.…”

Section: Scope and Definitionsmentioning

confidence: 99%

Bounding Global Aerosol Radiative Forcing of Climate Change

Bellouin

Quaas

Gryspeerdt

et al. 2020

Reviews of Geophysics

538

348

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Aerosols interact with radiation and clouds. Substantial progress made over the past 40 years in observing, understanding, and modeling these processes helped quantify the imbalance in the Earth's radiation budget caused by anthropogenic aerosols, called aerosol radiative forcing, but uncertainties remain large. This review provides a new range of aerosol radiative forcing over the industrial era based on multiple, traceable, and arguable lines of evidence, including modeling approaches, theoretical considerations, and observations. Improved understanding of aerosol absorption and the causes of trends in surface radiative fluxes constrain the forcing from aerosol‐radiation interactions. A robust theoretical foundation and convincing evidence constrain the forcing caused by aerosol‐driven increases in liquid cloud droplet number concentration. However, the influence of anthropogenic aerosols on cloud liquid water content and cloud fraction is less clear, and the influence on mixed‐phase and ice clouds remains poorly constrained. Observed changes in surface temperature and radiative fluxes provide additional constraints. These multiple lines of evidence lead to a 68% confidence interval for the total aerosol effective radiative forcing of ‐1.6 to ‐0.6 W m−2, or ‐2.0 to ‐0.4 W m−2 with a 90% likelihood. Those intervals are of similar width to the last Intergovernmental Panel on Climate Change assessment but shifted toward more negative values. The uncertainty will narrow in the future by continuing to critically combine multiple lines of evidence, especially those addressing industrial‐era changes in aerosol sources and aerosol effects on liquid cloud amount and on ice clouds.

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Similar spatial patterns of global climate response to aerosols from different regions

Cited by 48 publications

References 41 publications

The South Asian Monsoon Response to Remote Aerosols: Global and Regional Mechanisms

The South Asian Monsoon Response to Remote Aerosols: Global and Regional Mechanisms

Efficacy of Climate Forcings in PDRMIP Models

Bounding Global Aerosol Radiative Forcing of Climate Change

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