The composition of the earth's atmosphere has been altered dramatically by emissions of industrial gases and pollutants, combustion of fossil fuel and biomass, and cultivation of agricultural land. Understanding the associated impacts on climate and on human and environmental health is a challenging problem with enormous societal implications. To manage wisely the world's resources, we need quantitative information defining sources, sinks, and transformations of atmospheric gases and aerosols, and we need deeper knowledge of how the atmosphere works as a chemical and physical system.

Professor Wofsy and associates study the two-way exchange of gases between natural ecosystems and the atmosphere, the emissions, transformations and deposition of atmospheric pollutants, the processes that transport pollutants in the atmosphere, and depletion of stratospheric ozone. The focus is on long-term measurements to help understand processes affecting atmospheric composition on time scales relevant to climate change, and airborne observations to define rates of pollutant transport and sources or sinks of key gases (CO₂, CO, nitrogen oxides) on continental and global scales.

We have programs studying the net carbon balance of major ecosystems, where we measure carbon exchange with the atmosphere and simultaneous ecological changes. Hourly data are carefully aggregated to seasons, years, or a decade. We also measure deposition of pollutants such as ozone or NO_x. We focus on phenomena at the longer time scales, not apparent in short-term data, that represent the primary forcing for sequestration of fossil fuel CO₂ by forest ecosystems or that have long-term effects on forest health and growth. These observations are carried out continuously at remote sites in sub-boreal, temperate, and tropical forests, using advanced instrumentation developed in our laboratory for these measurements. We also measure CO₂ and CO in the stratosphere and on in the lower atmosphere. The measurements in the stratosphere and upper troposphere focus on understanding residence times and transport of pollutants, using an inert tracer with a rich source spectrum (CO₂). The focus of the tropospheric measurements is to develop methods for determining regional- and continental-scale net sources from detailed airborne, and eventually spaceborne, observations. For additional information please see the Forest and Stratospheric Measurements page.