A Review of Progress in Constraining Global Black Carbon Climate Effects

摘要

The global aerosol direct and indirect radiative effect remains the largest source of uncertainty in estimations of the global energy budget in climate models. Black carbon (BC) is the largest contributor to aerosol atmospheric radiative absorption, and its contribution to radiative forcing must be better constrained to reduce uncertainties in the overall aerosol radiative effect. This paper reviews the advancement in the understanding of BC radiative forcing, highlighting improved constraints for major sources of model uncertainty as described by Bond et al. (J Geophys Res Atmos 118:5380-5552, 2013), a fundamental review of the climate effects of BC which served as a primary source of the BC uncertainty analysis in the Intergovernmental Panel on Climate Change Fifth Assessment Report (IPCC AR5). Bond identified five primary sources of forcing uncertainty: altitude and removal rates of BC, BC emissions rates, individualized attribution of radiative forcing to absorbing aerosols species, BC effects on clouds, and accuracy of climate models in representing components of the Earth system, such as clouds and sea ice absent of BC. Improved constraints in each of these areas of forcing uncertainty-particularly BC impacts on clouds and atmospheric water vapor-have achieved a narrower uncertainty range in the IPCC Sixth Assessment Report (AR6). This paper excludes a review of the accuracy of the representation of climate models, rather focusing on the interaction of anthropogenic emissions of BC in the climate system. Future research should both expand upon the progress detailed in this paper and address the impacts of BC in the cryosphere, with particular focus on the contribution of BC to observed rapid warming of the Arctic.