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Atmospheric Composition |
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Updated 12 October, 2003 |
Atmospheric Composition A USGCRP Program Element |
| USGCRP
Home Focus Area
Atmospheric Composition |
| Search |
|
Updated 12 October, 2003 |
Atmospheric Composition A USGCRP Program Element |
|
Atmospheric CompositionOverview
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The composition of the atmosphere—its gases and particles—plays a critical role in connecting human welfare with global and regional changes because the atmosphere links all of the principal components of the Earth system. The atmosphere interacts with the oceans, land, terrestrial and marine plants and animals, and the cryosphere (regions of ice and snow). Because of these linkages, the atmosphere is a conduit of change. Emissions from natural sources and human activities enter the atmosphere at the surface and are transported to other geographical locations and often higher altitudes. Some emissions undergo chemical transformation or removal while in the atmosphere or interact with cloud formation and precipitation. Some natural events and human activities that change atmospheric composition also change the Earth's radiative (energy) balance. Subsequent responses to changes in atmospheric composition by the stratospheric ozone layer, the climate system, and regional chemical composition (air quality), create multiple environmental effects that can influence human health and natural systems. Changes in atmospheric composition are indicators of many potential environmental issues. Observations of trends in atmospheric composition are among the earliest harbingers of global changes. For example, the decline of the concentrations of ozone-depleting substances, such as the chlorofluorocarbons (CFCs), has been the first measure of the effectiveness of international agreements to end production and use of these compounds. Spring
Dust Storm Smothers Beijing A principal feature of the atmosphere is that it acts as a long-term “reservoir” for certain trace gases that can cause global changes. The long removal times of some gases, such as CO2 (more than 100 years) and perfluorocarbons (more than 1,000 years), imply that any associated global changes could persist over decades, centuries, and millennia—affecting all countries and populations. The overall research approach for understanding the role of atmospheric composition is an integrated application of long-term systematic observations, laboratory and field studies, and modeling, with periodic assessments of understanding and significance to decisionmaking. Most of the activities related to atmospheric composition research are part of national and international partnerships. Such partnerships are necessitated by the breadth and complexity of current issues and because the atmosphere links all nations. Current research on atmospheric composition is based on the substantial body of knowledge and understanding available from the work of many scientists.
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CCSP-supported
research focuses on how the composition of the global atmosphere is
altered by human activities and natural phenomena, and how such changes
influence climate, ozone, ultraviolet radiation, pollutant exposure,
ecosystems, and human health. Specific objectives address processes
affecting the recovery of the stratospheric ozone layer from reduced
ozone levels observed in recent decades; the properties and distributions
of greenhouse gases and aerosols; long-range transport of pollutants
and implications for regional air quality; and integrated assessments
of the effects of these changes. Atmospheric composition issues involving
interactions with climate variability and change—such as interactions
between the climate system and stratospheric water vapor and ozone,
or the potential effects of global climate change on regional air quality—are
of particular interest at present. 
