Dr. Steven Wofsy

Abbott Lawrence Rotch Professor of Atmospheric and Environmental Chemistry

Harvard University School of Engineering and Applied Science/Department of Earth and Planetary Science Cambridge, MA 02138

Greenhouse Gases Across Time and Space, from the Global Scale to the Urban Dome

A key problem for atmospheric science is to determine the emission rates for greenhouse gases and pollutants using atmospheric observations. Inverse models have been widely and successfully applied to this problem, but the results often depend on assumptions such as the model structure, inversion approach, and the spatial/temporal distributions of sources in the domain. These "model uncertainties" do not lend themselves to estimation by statistical means. In this talk we examine results from recent field measurement programs to assess how to design observational strategies that provide the strongest possible constraints on emissions, emphasizing the importance and challenges of sounding the complete depth of the atmosphere. We consider studies of methane and nitrous oxide at global scales from the HIPPO campaign, regional scales from CalNEX and the NOAA tall tower and aircraft network, and urban scale from an ongoing study in the Boston area.

About the Lecturer
Human beings have enormous impact on the chemical composition of the atmosphere, both regionally and globally. Combustion of fossil fuel, clearing of forests, agriculture, and chemical industry have caused concentrations of key atmospheric trace gases (CO2, CH4, N2O) to increase over the past 200 years, with accelerating change in the last 50 years. Emissions of industrial halocarbons (CFCs, such as CF2Cl2, "CFC-12") have caused stratospheric ozone to decrease. These changes may have serious impacts, such as climatic warming, regional and urban air pollution, and increased exposure to solar ultraviolet light.

Professor Wofsy's work is motivated by the need for scientific information and analysis to make wise decisions on the future development of the world's resources. We need quantitative information defining the sources and sinks for important atmospheric gases, and deeper understanding of underlying processes and of the rates for chemical transformations and transport in the atmosphere. We need to understand the interactions between the gases in the atmosphere and the vegetation, soils, and oceans at the earth's surface. We must learn how ecosystems respond to climate change, and learn how to manage biotic resources better.

Prof. Wofsy and colleagues study CO2, CH4, CO, and other important atmospheric gases at long-term measurement stations, located from the subarctic to the equator, and in atmospheric measurement campaigns using aircraft such as the University of North Dakota Citation II, University of Wyoming King Air, and NASA's ER-2 and WB-57F.

The group projects include developing new airborne sensors to make accurate measurements of CO2, CH4, CO, and N2O, and devising new analysis and modelling procedures to extract quantitiative information about sources, sinks, transformations, and transport of atmospheric trace gases. The long-term goal of these efforts is to understand the factors that regulate atmospheric composition and to help design programs to mitigate undesirable change.

More Information
https://www.seas.harvard.edu/directory/swofsy

Dr. Steven Wofsy
Dr. Steven Wofsy

Friday, March 22, 2013
4:00-5:00 PM

Reception to follow
CIRES Auditorium
University of Colorado at Boulder
(Directions to CIRES)