Greenhouse Gases in the Atmosphere: What Do We Know*

Abstract

In addition to carbon dioxide there are a number of gases (e.g., N/sub 2/O, CH/sub 4/, CF/sub 2/Cl/sub 2/, CFCL/sub 3/, etc.) which could affect the radiation balance of the earth's atmosphere. Recent measurements indicate that the atmospheric concentrations of these gases are increasing. Incomplete understanding of the sources, sinks, and/or chemical interactions of these gases in the atmosphere makes it difficult to relate human activities to future concentrations and to climatic effects. Atmospheric modeling suggests that during the past decade the trace gases should have had a warming effect that was half as much as CO/sub 2/. To illustrate the magnitude and complexity of the human involvement, the authors reviewed the budget of N/sub 2/O in the atmosphere. Anthropogenic production of N/sub 2/O occurs primarily in the combustion of fossil fuels and in the use of nitrogen fertilizers but acid rain, sewage treatment, electric power transmission, forest clearing, and other activities all impact the global N/sub 2/O budget. Although estimates of N/sub 2/O sources are subject to large uncertainty, the total anthropogenic contribution may be approaching 50% of the natural releases.