Research

 

The interaction of aerosols and chemistry with the earth system.

Atmospheric composition affects the earth’s radiation budget in general, and clouds in particular through the modification of cloud condensation nuclei. In addition, atmospheric composition affects the biosphere through the deposition of nutrients, the effects of surface ozone and the atmospheric radiation budget. These processes are being incorporated in the National Center for Atmospheric Research’s Community climate system Model (http://www.ccsm.ucar.edu/).

Air quality in a future climate.

Rising air temperatures are likely to translate to increased summertime ozone levels over the continents. Rising air temperatures and increased levels of carbon dioxide also effect natural emissions from plants, thereby indirectly affecting future ozone levels.

Biomass burning.

Biomass burning is impacted both through human activity (e.g., clearing trees for cultivation) and by climate. An increase in the rate of biomass burning may be expected in a future climate. For example, the fires in Alaska in 2004 were the largest in recorded history.

Intercontinental transport of air pollutants.

Despite relatively stringent air pollution standards in the United States, the growing economies in Asia may contribute to degradation in U.S. air quality. Peter Hess has participated in simulations for the Task Force on Hemispheric Transport of Air Pollution, organized by the UNECE Convention on Long-range Transboundary air pollution, to quantify the effect of transboundary pollution on air quality.

Ozone trends and interannual variability.

A large number of measurement sites have shown increasing ozone trends over the last decade. To date these trends have not been satisfactorily explained. As part of the Atmospheric Chemistry and Climate initiative Peter Hess is organizing a multi-model simulation of composition trends and variability over the last 30 years.