MUST READING.......Satellite pictures show greenhouse effect
Thursday, March 15, 2001
By United Press International
Observations from satellites support a new theory that carbon dioxide and other emissions are to blame for global warming, confirming what some climate models have been implying, that Earth's "greenhouse" effect increased between 1970 and 1997.
The data from space — presented in a report in the British journal Nature — is in sync with the earth-bound estimates of the total effect of emissions of such potential troublemakers as carbon dioxide, which many blame for global warming, and the ozone-depleting chlorofluorocarbons that were once the staple of the refrigeration industry, scientists said.
The report, released on the heels of President Bush's decision not to regulate carbon dioxide emissions from power plants, points to significant changes in the levels of atmospheric levels of methane, carbon dioxide, ozone and CFCs over the 27 years.
In contrast to the historic view that humans could do nothing about the weather, a growing body of evidence suggests that expanding human populations may be altering the climate, researchers said.
One controversial theory has it that burning fossil fuels is warming the atmosphere through the greenhouse effect. Greenhouse gases — carbon dioxide and nitrous oxide from fuel combustion, methane and decomposing organic waste — trap heat in the lower part of Earth's atmosphere, increasing surface temperatures. At higher altitudes, they have the opposite effect, cooling the ozone-containing stratosphere.
Some reports have pointed to a link between recent warming and rising emissions of greenhouse gases. According to a University of Michigan study, the last century was the warmest of the previous five.
The new data, collected by two orbiting spacecraft, is consistent with theoretical simulations that have raised concerns over so-called "radiative forcing" of the climate as a result of human emissions of gases thought to cause global warming, scientists said. Radiative forcing is a measure of the climate effect of greenhouse gases.
This is the first direct observation of the effect over an extended time frame, said lead study author John Harries of the Department of Physics at Imperial College in London.
The researchers analyzed the spectra of Earth's outgoing long-wave radiation, which carries the signature of the planet's cooling to space.
The noted differences point to a significant increase in Earth's greenhouse effect and provide the first direct observational evidence for changes in the radiative forcing of Earth's climate over the past 20 years, the authors said.
"These unique satellite spectrometer data collected 27 years apart show for the first time that real spectral differences have been observed and that they can be attributed to changes in greenhouse gases over a long time period," Harries said.
He and his team analyzed the infrared spectrum of long-wave radiation data gathered from a region over the Pacific Ocean as well as from the whole globe. By comparing the two sets of information for the same region, the scientists observed a change in the outgoing long-wave radiation and, therefore, a change in the greenhouse trapping by the atmosphere, the investigators said.
"Through our modeling studies using independent knowledge of the atmospheric state we have shown that the magnitude of the changes observed can only be explained by long-term changes in the greenhouse gases such as carbon dioxide, methane and chlorofluorocarbons," said co-author Helen Brindley of the Space and Atmospheric Physics Group at Imperial College.
The new data can help improve the accuracy of climate models used to predict future patterns, the scientists said.
"Since these are the models used to predict future climate, and influence policy decisions, it is imperative that they can accurately simulate measurements of what is considered to be the driving mechanism behind climate change," Harries said.
"We are only at the beginning of making use of these spectral observations. Much more information is locked up in the data that we have. This provides a strong motivation for the launch of similar instruments to monitor the state of our climate." |
