Evidence is growing that the human species is altering the global climate by emission of gases that trap heat that would otherwise be emitted to space. The climate of the Earth is a highly complex and nonlinear system that does not necessarily respond as one would expect. For instance, computer model simulations suggest that an increase in certain clouds in the upper troposphere could enhance this warming while an increase in certain cloud types in the lower troposphere could offset the warming. Currently, the leading climate models differ substantially in their predicted global warming and even more significantly, they differ widely in the predicted regional changes. Several leading scientific organizations including the World Meteorological Organization and the Intergovernmental Panel on Climate Change have identified the influences of clouds as the leading cause of this uncertainty. We are currently quite active in this research arena.

The U.S. Department of Energy initiated a research project, known as the Atmospheric Radiation Measurement (ARM) program, designed to improve the characterization of clouds in climate models. The program is establishing several heavily instrumented research sites in climatically significant locales. A site was established in the early part of this decade in north central Oklahoma, and sites in the tropical western Pacific and on the North Slope of Alaska will become active during 1997 and 1998. These sites use state of the art remote sensors such as millimeter and laser radar to probe clouds that occur over the sites. Our task is to examine this continuous data stream, identify when clouds occur and deliver quantitative analyses of the cloud properties and their effect on the solar and terrestrial radiation streams. Presently, we are developing and implementing a suite of computer algorithms that determine the water content and particle sizes of ice and liquid-phase clouds.

NASA, through their Mission to Planet Earth program, is also quite active in examining the Earth's changing climate. Soon, the first of a series of satellites will be launched into Earth orbit that will attempt to answer many of the outstanding questions regarding climate and climate change. This satellite will be known as the Earth Observing System (EOS) and will be launched into a sun synchronous orbit sometime in 1999. A satellite sensor observes upwelling energy from the Earth's surface. These energy observations must be converted into the properties of interest.  For instance, NASA scientists will attempt to convert visible light scattered from clouds into an estimate of the cloud properties.  This conversion requires a computer algorithm that is built around certain assumptions. These assumptions and the products generated by these algorithms must be checked for validity. We have been funded by NASA to generate a data set suitable for this validation exercise. Dr. Ken Sassen has established a research facility on the University of Utah campus known as the Facility for Atmospheric Remote Sensing. When the EOS satellite passes over the University of Utah, we will collect data, convert the data to quantities similar to those generated by EOS and then compare our data with NASA's. Furthermore, during selected overpasses, we will have an instrumented Lear jet operated by Stratton Park Engineering Inc. collected cloud data over the ground based instruments and under the satellite.

Our research program is quite active and growing. With effort, we hope to help in addressing many of the outstanding questions regarding the influence of clouds on the Earth's climate. Answering these questions will ultimately improve our understanding of the human-induced climate change that may be a major societal issue of the next century.