“Greenhouse cooling” of the upper atmosphere



The release of trace gases such as carbon dioxide and methane through human activity is generally accepted to have the potential to alter the Earth's climate. Various projections indicate that present concentrations of these “greenhouse” gases will double by the end of the 21st century. Studies of the atmospheric effect of these gases suggest that the globally averaged temperature of the troposphere (0–10 km altitude) will increase by about 1-5°K because of an increase in trapped infrared radiation. In the stratosphere (10–50 km), however, the increased concentration of these gases will give rise to a greater infrared cooling to space, and the globally averaged temperature is predicted to cool by 10–20°K, compared with present-day temperatures [Brasseur and Hitchman, 1988]. It should be stressed that this latter prediction applies to the upper atmosphere, and does not address greenhouse warming in the lower atmosphere, which has been treated by other climate modelers.