31.07.2003 | Thursday

Greenhouse gases are raising the sky subaru.yauzamotors.ru - сервис subaru два. .

The sky isnt falling in, say scientists, it is rising. And its our fault.

News: The top of the troposphere - the atmospheres lowest layer - has risen by several hundred metres since 1979, mostly because of transport and industrial emissions, says Ben Santer and colleagues of Lawrence Livermore National Laboratory in California. The tropospheres height could even act as a kind of barometer for the extent of global environmental change, they reported in Science last week. The researchers computer-modelled five possible causes for the shift, three human and two natural. They looked at changes in greenhouse gas levels, sunlight reflected from airborne solid particles, atmospheric ozone concentration, the suns output of heat and light, and dust injected into the atmosphere by volcanoes. All of these factors affect air temperature at different altitudes, so they expand or contract different strata of the atmosphere. Destroying the ozone layer, for example, can cool and shrink the stratosphere, which sits above the troposphere. Carbon dioxide, on the other hand, warms and enlarges the troposphere. Such forces pump up or push down the tropopause - the boundary of the troposphere and stratosphere, 9 to 18km above the ground. Santers model increased the tropopauses altitude in line with observations only when all of the factors were included. But it suggests that changes in the levels of greenhouse gases and ozone could account for most of the rise seen in the latter half of the 20th century. (The Guardian)