Increasing Coarse Aerosols Mitigated the Warming Effect of Anthropogenic Fine Particle Reductions in Europe

Abstract Recent decades have seen substantial variations in the physicochemical characteristics of atmospheric aerosols with expected continued changes in the future. While sustained global emission controls have yielded significant environmental benefits, the associated climate penalty from complex radiative effects has induced additional warming, raising public concern. Our study reveals that increased coarse particles enhance fine particle coagulation, contributing to higher coarse particle levels and a reduction in coarse particle peak size, thereby scattering more solar radiation and mitigating the warming from reduced fine particles in Europe. From 1999 to 2021, changes in coarse particles offset 24.6% (26.3%) of the reduced cooling effect at the top (ground) of atmosphere from fine particle reductions. Our findings highlight the complex but significant role of aerosol size changes in influencing solar radiation budget, offering potential relief for global warming concerns and bolstering emissions reduction efforts, with important global and European implications amid ongoing and expected anthropogenic emission cuts.