Short-Lived Climate Forcing Agents and Their Roles in Climate Change

Short-lived climate forcing agents (SLCFAs) such as black carbon and ozone offer important policy opportunities to reduce radiative forcing in the short term (this decade), while also reducing air pollution impacts. Because of the combination of high absorption, a regional distribution roughly aligned with solar irradiance, and the capacity to form widespread atmospheric brown clouds in a mixture with other aerosols and ozone, emissions of black carbon are the second strongest contribution to current global warming, after carbon dioxide emissions. The interception of solar radiation by atmospheric brown clouds leads to dimming at the Earth's surface with important implications for the hydrological cycle, and the deposition of black carbon darkens snow and ice surfaces, which can contribute to melting, in particular of Arctic sea ice. Reducing SLCFAs is a challenge as they are emitted and produced across a wide spectrum of source-sectors. In this paper we summarize our capabilities to predict the impacts of short-lived forcing agents, and their local, regional and global extents, building upon studies done in Asia. We also discuss possible policy measures for reducing them.