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How Does Water Vapor Affect Climate? Scientists To Discuss Latest Findings

October 5, 1999
American Geophysical Union
Scientists will discuss the role of water vapor, the most abundant greenhouse gas, at a conference sponsored by the American Geophysical Union in Potomac, Maryland, October 12-15.

WASHINGTON -- The role of water vapor in the Earth's climate system will be discussed at a scientific conference organized by the American Geophysical Union in Potomac, Maryland, October 12 to 15. Scientists will concentrate on developments since the last such conference five years ago, a period during which theoretical and observational advances have been made.

Water vapor is the most abundant greenhouse gas and therefore significantly affects climate. It is involved in the global hydrological cycle, affecting both evaporation and precipitation. It participates in chemical reactions both in the troposphere, or lower atmosphere, where it is the major source of the hydroxyl (OH) radical, and in the stratosphere, which begins 6-10 miles (10-16 kilometers) altitude, where it affects the quantity of ozone (O3). But, despite water vapor's importance, its distribution and variability has not been as well studied as scientists would wish.

One of the conference goals is to bring together specialists in the troposphere and the stratosphere, according to Dr. Dian Gaffen of the National Oceanographic and Atmospheric Administration (NOAA) in Silver Spring, Maryland. Gaffen is one of the conference's conveners, along with Rebecca Ross, also of NOAA, and Dr. John Gille of the National Center for Atmospheric Research (NCAR) in Boulder, Colorado. Over 80 participants are expected from the United States and abroad.

In Potomac, a suburb of Washington, D.C., atmospheric scientists will focus on three major themes:

1. Water vapor and the greenhouse effect. At the 1995 conference, the notion that water vapor might have a negative feedback on the greenhouse effect evoked some controversy. Since then, considerable effort has been made to clarify this issue, and results will be presented at the conference.

2. The global hydrological cycle, i.e., the precipitation and evaporation of water in the atmosphere. Extreme precipitation events, both flood-producing rains and prolonged drought, may result from an intensification of the cycle, in which water vapor plays a key role.

3. Water vapor in the upper troposphere and lower stratosphere. A region difficult to study, it has been the object of intense research in recent years, in part because of the greenhouse effects of water vapor there and because water vapor patterns reveal aspects of the circulation of air in the stratosphere.

Papers presented at the October conference will be published in a forthcoming issue of the Journal of Geophysical Research.

Conference organizers have taken advantage of the presence of so many leading water vapor researchers to organize a town meeting the evening of October 14 on the subject of U.S. participation in the Global Energy and Water Experiment and the Water Vapor Program, known by the acronyms GEWEX and GvAP. These are international research efforts, under the auspices of the World Climate Research Programme. The town meeting will include scientists and government agency program managers.

A special effort has been made to attract younger scientists to the conference, says Gaffen. The 1995 conference was influential in encouraging young atmospheric scientists to continue in the field and investigate water vapor as a climate factor, she says. The conveners hope this conference will provide a similar impetus.

Sponsors of the conference include the American Meteorological Society (AMS), EUMETSAT, the National Aeronautics and Space Administration (NASA), the National Oceanic and Atmospheric Administration (NOAA), the National Science Foundation (NSF), Pacific Northwest Laboratories/Battelle, and Stratospheric Processes And their Role in Climate (SPARC).

Further information about this conference may be found on the AGU web site:

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American Geophysical Union. "How Does Water Vapor Affect Climate? Scientists To Discuss Latest Findings." ScienceDaily. ScienceDaily, 5 October 1999. <>.
American Geophysical Union. (1999, October 5). How Does Water Vapor Affect Climate? Scientists To Discuss Latest Findings. ScienceDaily. Retrieved May 23, 2017 from
American Geophysical Union. "How Does Water Vapor Affect Climate? Scientists To Discuss Latest Findings." ScienceDaily. (accessed May 23, 2017).