Simultaneous reductions in emissions of black carbon and co-emitted species will weaken the aerosol net cooling effect

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.

The effect of future reduction in aerosol emissions on climate extremes in China

“…The aerosol reduction will weaken the aerosol net cooling effect and produce an additional warming of the Earth's climate system (Shindell et al 2008;Wang et al 2015a), thus affecting future extreme temperature and precipitation events. Our results show that reduced aerosol emissions will lead to marked increases in TXx, TNn, and TR over China.…”

“…To mitigate environmental pollution and the resulting impacts on human health, governments worldwide will likely take continuous and stringent measures to reduce the emissions of most anthropogenic aerosols and their precursors during the twentyfirst century. This will result in gradual decreases in atmospheric aerosol concentrations and the net cooling effect of aerosols in the future (i.e., contributing to an additional warming) (Shindell et al 2008;Wang et al 2015a). Sillmann et al (2013b) showed that future reduction in aerosol emissions could greatly enforce the warming effect due to GHG and increase the temperature and precipitation extremes in Europe.…”

Projected response of East Asian summer monsoon system to future reductions in emissions of anthropogenic aerosols and their precursors

“…Zhang et al (2012Zhang et al ( , 2014, and Wang et al (2014). The performance of the model has been evaluated by Wang et al (2014), Zhang et al (2014), and Wang et al (2015) in detail. They demonstrated that the model has a good ability to simulate aerosols, cloud properties, and meteorological fields.…”

Sensitivity of precipitation extremes to radiative forcing of greenhouse gases and aerosols

“…GHGs and aerosols will continue to be the two most important anthropogenic forcing agents in the 21st century [Myhre et al, 2013]. The expected declines of anthropogenic aerosols in the 21st century from present-day levels would impose an additional warming on the Earth [Rotstayn et al, 2013;Wang et al, 2015;Lin et al, 2015], which will aggravate the climate extremes caused by GHGs-induced warming Wang et al, 2016a]. Separating the contributions by different forcing agents to extreme precipitation increases under different emission scenarios would be beneficial to policy-making on climate mitigation and adaptation.…”