Graphic showing interactions between clouds and particles under different radiative conditions
Effective radiative forcing (ERF) for particles is comprised of the radiative forcing from direct and rapid climate adjustment effects from aerosol-radiation interactions (RFari) and from direct and rapid climate adjustment effects from aerosol-cloud interactions (RFaci). The first graphic shows the direct scattering and absorption, while the second graphic shows rapid adjustments to this from semi-direct effects (e.g., from cloud thinning/thickening due to aerosol heating). The third graphic shows the direct aerosol-cloud interaction from cloud brightening due to more numerous and smaller cloud droplets. The fourth and fifth graphics show rapid adjustment semi-direct effects due to other cloud interactions, and from interactions with ice clouds, respectively. In this figure, blue and orange arrows indicate shortwave and longwave fluxes respectively, while solid is for initial and dashed is for adjusted fluxes. Credit: Bender 2020, Figure 1, modified from IPCC 2013, Ch. 7, Fig. 3
Source: AGU Advances

There exist a broad range of possible pathways for aerosol influence on the Earth’s energy budget and climate. Some include cooling and heating by reflection and absorption of solar radiation, and alteration of cloud properties.

In Reviews of Geophysics, Bellouin et al. [2020] provide a framework for encompassing all these effects of atmospheric particles. In a commentary in AGU Advances, Bender [2020] responds and adds to the review article by pointing to issues that require additional consideration. For example, what was the content of particles in the preindustrial atmosphere? Also, because the effects of aerosols can depend on the particle composition, the dependence of radiative effects on composition must be understood. This commentary adds further insights to uncertainties in the complexity of particle effects on climate.

Citation: Bender, F. [2020]. Aerosol forcing – still uncertain, still relevant. AGU Advances, 1, e2019AV000128.

—Don Wuebbles, Editor, AGU Advances

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