Aerosols are small particles in the atmosphere that are a by-product of human activities, such as transportation and industry, and also emitted naturally.  Since aerosols can have both warming or cooling climate effects, as well as pose severe air pollution problems that aggravate human health, there is a tradeoff issue between reducing air pollution and mitigating warming from greenhouse gases in terms of policy making on aerosol emission controls.

In this talk, I will first illustrate an estimation of the masking effect of atmospheric aerosols on the greenhouse gases warming based on the IPCC best estimates of aerosol forcing, and discuss several physical and computational challenges in modeling aerosols and their interactions with clouds and other components in climate models in comparisons with observations. Among aerosol species, the radiative forcing of absorbing aerosols such as black carbon (BC) from fuel combustion and biomass burning is still much debated and large gap exists between model estimates and observationally-based methods. We recently identified brown carbon (BrC), a class of organic carbon, as another key absorber of solar radiation second to BC, in a global modeling study. Our calculations suggest that absorbing BrC induces a positive radiative forcing up to +0.11 W m-2 approximately one-third as large as BC forcing. This additional warming changes organic aerosols that are generally regarded as a cooling aerosol species to warming agent over many regions. Since BrC has potentially three times the abundance of BC in the atmosphere and originates primarily from biomass burning and biofuel combustion, further investigation of climate impacts of BrC due to their emission changes will have a significant effect on near-term climate predictions.

BIO
Dr. Yan Feng is an assistant computational atmospheric scientist from Environmental Science Division, Argonne National Laboratory. She obtained her Ph.D. in Atmospheric Science (2005) and M.S. in Computer Science and Engineering (2002) both from University of Michigan, Ann Arbor. Dr. Feng has extensive experiences of modeling atmospheric chemistry and aerosols using both regional climate model (WRF-CHEM) and global chemical transport model. She has 19 peer-reviewed journal publications and contributed to three book chapters. Dr. Feng is a contributing author to the IPCC 3rd Climate Change Assessment Report, Chapter 5 on aerosols. Her work on nitrogen heterogeneous chemistry in dust aerosol is cited by the IPCC fourth Climate Change Assessment Report.