The world's population is projected to increase 33% during the next three decades, to 8.1 billion. Nearly all of the projected growth is expected to be concentrated in urban centers. These rapidly expanding urban regions and surrounding suburban areas are leading to the phenomenon of megacities, which are broadly defined as metropolitan areas with populations exceeding 10 million inhabitants. These mega-centers of human population are tied directly to increasing demands for energy and associated industrial activities that lead to accelerated stress and impacts on the environment. These impacts are significant and act on urban, regional and global scales. Air pollution has become one of the most important problems of megacities and has serious impacts on public health, visibility, and can cause heat island effects on the urban scale. On the regional scales, releases of aerosols and precursor gases can lead to regional haze and acidic deposition, as well as regional oxidant impacts. Release of longer lived greenhouse gases, aerosols, and other radiatively important species from megacity sources will be significant contributions to climate change. Participants in this session will present atmospheric science studies conducted in large urban centers around the world, highlighting the following areas:
1. Emissions;
2. Photochemistry;
3. Aerosol and trace gas measurements;
4. Meteorological measurements;
5. Dynamics and radiative effects;
6. Regional climate;
7. Air quality modeling;
8. Satellite remote sensing of air quality in cities;
9. Implications of policy to reduce air pollution (air quality, health, climate change).

Invited speakers:
Professor Jose Luis Jimenez
Department of Chemistry & Biochemistry, University of Colorado
"Ambient particulate matter during MILAGRO in Mexico City: Main findings, impacts, and future research needs"

Dr. Matthias Beekmann
Centre National de la Recherche Scientifique, Laboratory Inter-universitaire des Systèmes Atmosphériques, University of Paris
"The Paris MEGAPOLI campaign to better quantify organic aerosol formation in a large agglomeration: first results"

Prof. Maria Kanakidou
Environmental Chemical Processes Laboratory, Department of Chemistry, University of Crete
"Impact of growing urbanization on air quality and climate in the East Mediterranean - An overview of the first results from the CITYZEN project"

Dr. Peter Suppan
Karlsruhe Institute of Technology, Institute for Meteorology and Climate Research, Atmospheric Environmental Research Division (IMK-IFU)
"Climate change and air pollution in megacities: A challenge for interdisciplinary research"