My research interests are in climate modeling, aerosol-climate interactions, and air quality. Aerosols (or “particulate matter”) reflect incoming radiation and exert a cooling effect on climate, opposing the warming of greenhouse gases (GHG). Aerosol effects on climate, unlike greenhouse gases, are not well understood but are important for predictions of future climate change. Aerosols have likely “masked” additional warming from greenhouse gases, confounding the sensitivity of climate to greenhouse gases, which is an important parameter for climate models. Particulate pollution also has adverse human health effects. Hundreds of thousands of premature deaths every year can be attributed to air pollution. As governments introduce measures to reduce climate-cooling particulate pollution, we will see the unfortunate side effect of increasing global warming.

Current funded projects include:

  • Regional climate response to changes in aerosol forcing. The impact of changes in emissions in specific regions on local and remote climate. Aerosol impacts on clouds and precipitation. The effect of absorbing aerosols on tropical monsoon systems. I use and develop three coupled chemistry-climate models: GFDL, GISS, and NCAR.

  • Air quality modeling. Current projects include quantifying the effect of emissions policies and climate change in China on particulate matter concentrations and mortality. Other projects include sensitivity of PM2.5 concentrations to meteorology and climate change.

  • Aerosol impacts on atmospheric oxidation and photochemistry. Using chemistry-climate models, remote airborne observations, and satellite products, we aim to asses the impact of pollution and biomass burning aerosols on atmospheric oxidation, including concentrations of oxidants, photolysis rates, and reaction rates.

  • New particle formation and aerosol physics. Besides being directly emitted, aerosol particles can be formed via a nucleation process in which metastable atmospheric gas molecules cluster together to form small particles. Understanding this source of particles and their impact on climate is currently an area of ongoing research. I develop and use the NASA GISS-ModelE2-TOMAS chemistry-climate model with online aerosol microphysics.

  • Air quality monitoring, modeling, and analysis in developing countries. In cooperation with the US State Department, I have started an air quality monitoring network in Kinshasa, DR Congo, a megacity with population over 11 million which suffers from poor air quality yet has no monitoring infrastructure. Other projects include air quality knowledge capacity building in Accra, Ghana (partner with Ghana EPA), sensor deployments in Nairobi, Kenya, Kampala, Uganda, and Lomé, Togo, and using models and remote sensing techniques in India, China, and sub-Saharan Africa.