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

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.

The role of anthropogenic aerosols in the anomalous cooling from 1960 to 1990 in the CMIP6 Earth system models

“…East Asian emissions clearly increased from 2000 to 2005, followed by a decrease with large uncertainties (Aas et al, 2019). The decade-long emission reduction since 2006 over East China is not well represented by the CMIP6 emission (Wang et al, 2021).…”

Anthropogenic aerosol effects on tropospheric circulation and sea surface temperature (1980–2020): separating the role of zonally asymmetric forcings

“…An improved understanding can help shed light on other relevant problems on regional forcings, such as land use changes (e.g., deforestation over the Amazon vs. Africa), volcanic eruption (Verma et al, 2019), geoengineering solutions (such as stratospheric or tropospheric aerosol injection conducted over different locations), and the potential contrast of China and India's future emission trajectories in future decades (Samset et al, 2019;Wang et al, 2021). The fossil-fuel-related aerosols are projected to further decrease in future decades (Andreae et al, 2005;Zheng et al, 2020), even for Asian regions, with more strict air quality measures in developing nations.…”

Understanding Top‐of‐Atmosphere Flux Bias in the AeroCom Phase III Models: A Clear‐Sky Perspective

“…The vastly different trends among the models are due to different emission data used between 2015-2017 for the three models, and the fact that some pathway scenarios significantly underestimate the recent decline in anthropogenic aerosol emissions over China (Z. Wang et al, 2021).…”

“…The most notable difference among the models is over eastern China and the adjacent oceanic regions where MODIS indicates a decreasing trend. The vastly different trends among the models are due to different emission data used between 2015 and 2017 for the three models, and the fact that some pathway scenarios significantly underestimate the recent decline in anthropogenic aerosol emissions over China (Z. Wang et al., 2021).…”