Incorrect Asian aerosols affecting the attribution and projection of regional climate change in CMIP6 models

Zhili Wang,Yangyang Xu,Hua Zhang,Xiaoye Zhang,Huizheng Che,Chense Wang,Bing Xie,Lei Lin,Ke Gui,Wenjie Dong

doi:10.1038/s41612-020-00159-2

Abstract

Anthropogenic aerosol (AA) forcing has been shown as a critical driver of climate change over Asia since the mid-20th century. Here we show that almost all Coupled Model Intercomparison Project Phase 6 (CMIP6) models fail to capture the observed dipole pattern of aerosol optical depth (AOD) trends over Asia during 2006–2014, last decade of CMIP6 historical simulation, due to an opposite trend over eastern China compared with observations. The incorrect AOD trend over China is attributed to problematic AA emissions adopted by CMIP6. There are obvious differences in simulated regional aerosol radiative forcing and temperature responses over Asia when using two different emissions inventories (one adopted by CMIP6; the other from Peking university, a more trustworthy inventory) to driving a global aerosol-climate model separately. We further show that some widely adopted CMIP6 pathways (after 2015) also significantly underestimate the more recent decline in AA emissions over China. These flaws may bring about errors to the CMIP6-based regional climate attribution over Asia for the last two decades and projection for the next few decades, previously anticipated to inform a wide range of impact analysis.

Highlights

Asia is one of the most vulnerable regions facing climate change risks because of its large and dense population, rapid industrial development, and severe water stress[1,2]
Consistent with the growth in previous decades, aerosol optical depth (AOD) in India steadily increases in the early 21st century (Fig. 1b), with a trend of +14.7% per decade for
There is the largest increase of +18% per decade from Moderate Resolution Imaging Spectroradiometer (MODIS) data, followed by smaller trends of +13% per decade from MERRA-2 and Multiangle Imaging Spectroradiometer (MISR) data (Supplementary Fig. 1)

Summary

Introduction

Asia is one of the most vulnerable regions facing climate change risks because of its large and dense population, rapid industrial development, and severe water stress[1,2]. Climate change due to anthropogenic factors, such as greenhouse gases (GHGs), aerosols, and land use, has seriously impacted natural ecosystems (e.g., agriculture, biodiversity, water, and ocean) and human society in Asia[3,4]. The absolute value of aerosol radiative forcing is even larger than GHG in Asia during certain periods[6]. Many studies have shown that AA forcing is a key factor driving historical climate change over Asia[7,8,9,10,11]. Recent studies showed that AA forcing dominated the observed interdecadal upper-tropospheric cooling over East Asia during summer[10] and weakening of the East Asian summer monsoon after the 1950s11

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Results

Conclusion