Abstract

Abstract. Black carbon (BC), a distinct type of carbonaceous material formed from the incomplete combustion of fossil and biomass based fuels under certain conditions, can interact with solar radiation and clouds through its strong light-absorption ability, thereby warming the Earth's climate system. Some studies have even suggested that global warming could be slowed down in the short term by eliminating BC emission due to its short lifetime. In this study, we estimate the influence of removing some sources of BC and other co-emitted species on the aerosol radiative effect by using an aerosol–climate atmosphere-only model BCC_AGCM2.0.1_CUACE/Aero with prescribed sea surface temperature and sea ice cover, in combination with the aerosol emissions from the Representative Concentration Pathways (RCPs) scenarios. We find that the global annual mean aerosol net cooling effect at the top of the atmosphere (TOA) will be enhanced by 0.12 W m−2 compared with recent past year 2000 levels if the emissions of only BC are reduced to the level projected for 2100 based on the RCP2.6 scenario. This will be beneficial~for the mitigation of global warming. However, both aerosol negative direct and indirect radiative effects are weakened when BC and its co-emitted species (sulfur dioxide and organic carbon) are simultaneously reduced. Relative to year 2000 levels, the global annual mean aerosol net cooling effect at the TOA will be weakened by 1.7–2.0 W m−2 if the emissions of all these aerosols are decreased to the levels projected for 2100 in different ways based on the RCP2.6, RCP4.5, and RCP8.5 scenarios. Because there are no effective ways to remove the BC exclusively without influencing the other co-emitted components, our results therefore indicate that a reduction in BC emission can lead to an unexpected warming on the Earth's climate system in the future.

Highlights

  • Aerosols in the atmosphere can alter the amount of sunlight reaching the Earth, perturb the temperature structure of the atmosphere, and influence cloud cover by directly scattering sunlight (e.g., sulphate, organic carbon (OC) and nitrate) or absorbing it (e.g., black carbon (BC) and dust) (Boucher et al, 2013)

  • The global annual mean aerosol net cooling effect at the TOA is enhanced by 0.12 W m−2 compared with recent past levels when just Black carbon (BC) emission is reduced to the level projected for the end of this century under the RCP2.6 scenario (Table 3)

  • We assess the impact of removing some sources of BC and other co-emitted species on aerosol radiative effects by using an aerosol–climate atmosphere-only model BCC_AGCM2.0.1_CUACE/Aero with prescribed sea surface temperature (SST) and sea ice cover (SIC), in combination with the Representative Concentration Pathways (RCPs) scenarios

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Summary

Introduction

Aerosols in the atmosphere can alter the amount of sunlight reaching the Earth, perturb the temperature structure of the atmosphere, and influence cloud cover by directly scattering sunlight (e.g., sulphate, organic carbon (OC) and nitrate) or absorbing it (e.g., black carbon (BC) and dust) (Boucher et al, 2013). BC, and OC are the main aerosol species in the atmosphere, and the emissions of sulphate and OC will be reduced if the emission of BC is reduced Both sulphate and OC are strongly scattering and hygroscopic aerosols, and they can cool the climate system by directly scattering solar radiation and increasing the cloud albedo and lifetime by acting as CCN (Boucher et al, 2013). Focusing on the issue mentioned above, the impact of removing some BC sources and other co-emitted species on the aerosol radiative effects was studied in this paper by using an aerosol–climate atmosphereonly model BCC_AGCM2.0.1_CUACE/Aero (Atmospheric General Circulation Model of Beijing Climate Center, BCC_AGCM2.0.1, coupled with the aerosol model of China Meteorological Administration Unified Atmospheric Chemistry Environment for Aerosols, CUACE/Aero)

Model description
Simulation details
Aerosol optical depth for present-day conditions
Global mean statistics
Global distributions
Discussion and conclusions
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