Cooperative Institute for Research in Environmental Sciences

Margaret Tolbert's Research Interests

My interests are in the area of atmospheric chemistry, a focus area at the interface between fundamental chemistry and applied atmospheric science. I am specifically interested in the "new" chemistry of the atmosphere, focusing on the chemistry and physics of atmospheric particulate. In addition to fundamental studies of particles, I am also interested in exploring how atmospheric particles impact current problems such as stratospheric ozone depletion, global climate change, and urban smog.

My involvement in this research began in 1986 with the report by researchers at the British Antarctic Survey of massive and unexpected ozone depletion in the Antarctic spring stratosphere. Shortly after the discovery, Solomon and co-workers suggested that a key step in the mechanism for the ozone hole might be heterogeneous (gas-surface) reactions occurring on polar stratospheric clouds in the cold Antarctic stratosphere. Working at SRI International, my co-workers and I were among the first scientists to test this hypothesis in the laboratory. We found that indeed, heterogeneous reactions on polar stratospheric clouds converted inert, non-reactive chlorine, into forms of chlorine capable of ozone destruction. This laboratory work provided an essential link between the observations of ozone loss and an understanding of the ozone loss mechanism.

In the last 20 years, I have continued and expanded our research in heterogeneous atmospheric chemistry. In one study, we found that heterogeneous reactions on sulfuric acid aerosols from volcanic eruptions could be playing an important role in the decadal ozone loss observed globally. This had major implications for policy makers in controlling the ozone loss precursors, the chlorofluorocarbons. We have also expanded our studies to probe how the destructive clouds form in the first place and to enable predictions of future cloudiness and ozone destruction in a world impacted by climate change.

A more recent emphasis has been on understanding how clouds and aerosols impact global climate. Many atmospheric aerosols have anthropogenic sources such as biomass burning, desertification, and as byproducts of the energy production industry. Because the indirect effect of these aerosols on clouds is one of the most uncertain aspects of future climate change, it is essential to probe how such aerosols take up water to become clouds. We are performing laboratory experiments to provide fundamental data that will help in understanding how both ice and liquid water clouds form from the ambient atmospheric aerosol.

While most of my research career has focused on the Earth’s atmospheric particulate and applications to current and future problems, I have recently begun to expand into new areas. Specifically, I have begun novel studies to probe the particles that might have been present at the earliest times in Earth’s history, and to unravel how those particles might have impacted the climate of early Earth and the development of life on Earth. For these studies, we also turn outward to get clues about Earth’s history from other planetary bodies such as Mars, Venus and Titan. Laboratory studies on these aerosols thus provide insight into atmospheric chemistry on faraway worlds, as well as on our own world long ago.