Cool times ahead for the upper atmosphere.Cool times ahead for the upper atmosphere Not all parts of the atmosphere will warm as carbon dioxide carbon dioxide, chemical compound, CO2, a colorless, odorless, tasteless gas that is about one and one-half times as dense as air under ordinary conditions of temperature and pressure. and other greenhouse gases accumulate above Earth. A new computer modeling of the upper atmosphere shows that the thin air high above the planet's surface should cool substantially -- an effect that may help some satellites stay in orbit longer. Most climate projections for the next century have focused on how accumulating greenhouse gases will affect the troposphere troposphere: see atmosphere. troposphere Lowest region of the atmosphere, bounded by the Earth below and the stratosphere above, with the upper boundary being about 6–8 mi (10–13 km) above the Earth's surface. and the stratosphere, the two layers closest to Earth. This is the first time researchers have used complex computer models to predict the effect on the two highest regions, the mesosphere mesosphere: see atmosphere. and thermosphere ther·mo·sphere n. The outermost shell of the atmosphere, between the mesosphere and outer space, where temperatures increase steadily with altitude. ther , says Raymond G. Roble of the National Center for Atmospheric Research The National Center for Atmospheric Research (NCAR) is a non-governmental U.S.-based institute whose stated mission is "exploring and understanding our atmosphere and its interactions with the Sun, the oceans, the biosphere, and human society. in Boulder, Colo. Roble and colleague Robert E. Dickinson discuss their findings in the December GEOPHYSICAL RESEARCH LETTERS Geophysical Research Letters is a publication of the American Geophysical Union. GRL is the organization's only letters journal. Since its introduction in 1974, GRL has published only short research letters, typically 3-5 pages long, which focus on a specific discipline or . Their computer simulations suggest that when carbon dioxide and methane reach double their 1970s levels throughout the entire atmosphere, the mesosphere (about 50 to 90 kilometers in altitude) will cool by about 10 degrees C and the thermosphere (90 to 500 km) by 50 degrees C. Simulations by others have indicated that temperatures in the stratosphere (about 12 to 50 km) will also drop as greenhouse gases accumulate, but temperatures in the troposphere (reaching from Earth's surface Noun 1. Earth's surface - the outermost level of the land or sea; "earthquakes originate far below the surface"; "three quarters of the Earth's surface is covered by water" surface to 12 km) will rise. The predicted cooling in the stratosphere, mesosphere and thermosphere stems from carbon dioxide's ability to absorb atmospheric heat-energy and emit it as infrared radiation, Roble explains. As the number of carbon dioxide molecules in the upper atmosphere increases, this region will send more of its heat-energy toward space and therefore will cool. Closer to home, a doubling of carbon dioxide should warm the troposphere because this layer holds far more carbon dioxide and other greenhouse gases than does the upper atmosphere. In the troposphere, radiation emitted by these gases cannot travel far before it hits another molecule and is absorbed, becoming trapped at that level. In the upper atmosphere, where greenhouse gases are more diffuse, emitted radiation stands a much greater chance of escaping into space. A cooling in the stratosphere will likely worsen the ozone depletion Ozone depletion describes two distinct, but related observations: a slow, steady decline of about 4 percent per decade in the total amount of ozone in Earth's stratosphere since around 1980; and a much larger, but seasonal, decrease in stratospheric ozone over Earth's polar regions around Earth's poles. But researchers say they cannot tell what will happen to the planet as a result of a cooling in the mesosphere and thermosphere. "We really are fairly ignorant about a lot of the major processes occurring in that region," says Darrell Strobel, an atmospheric physicist at Johns Hopkins University Johns Hopkins University, mainly at Baltimore, Md. Johns Hopkins in 1867 had a group of his associates incorporated as the trustees of a university and a hospital, endowing each with $3.5 million. Daniel C. in Baltimore. Strobel says some researchers have jokingly used the term "ignorosphere" to describe the mesosphere and the lower portion of the thermosphere, which are too high for research balloons and too low for satellites to study. Several scientists say an upperatmosphere cooling could influence certain space missions. As the thermosphere cools, it will contract, pulling the edges of the atmosphere closer to the planet. This should extend the lifetime of low-orbiting satellites, says Roble. As their orbits weaken with time, such satellites slowly descend toward Earth until atmospheric friction eventually knocks them out of orbit. |
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