Report: Satellite data proves greenhouse effect

In this story: Political debate heats up Clouds obscure the future RELATED STORIES, SITES

LONDON, England (CNN) -- Satellite data has provided the first "direct observational evidence" that the greenhouse effect is producing long-term changes in the Earth's atmosphere, scientists said Wednesday.

Comparing satellite observations from 1970 and 1997, British researchers said accumulating greenhouse gases have limited the amount of infrared radiation escaping into space.

ALSO Groups blast Bush for reversing position on emissions reductions   INTERACTIVE Greenhouse effect

An Imperial College of London team looked at readings of infrared light from the Earth's surface, specifically in the wavelengths absorbed by greenhouse gases such as carbon dioxide, methane and ozone.

"We're absolutely sure, there's no ambiguity: This shows the greenhouse effect is operating and what we are seeing can only be due to the increase in the gases," said lead investigator John Harries of London's Imperial College.

Evidence was also found of smaller increases in chlorofluorocarbons, refrigerants blamed for destroying the ozone layer that protects Earth from ultraviolet radiation.

The study was reported in Thursday's issue of the journal Nature.

Political debate heats up

Atmospheric scientists not involved in the study said the satellite data provide concrete confirmation that greenhouse gases are building up.

The findings come as the political debate intensifies over whether global warming is a real danger.

A report released in January in China by an international panel predicted global temperatures could rise as much as 5.8 degrees Celsius (10.5 degrees Fahrenheit) over the next century, primarily because of pollution.

U.S. and European environmental officials, however, have not been able to agree on how to implement the 1997 Kyoto Protocol, which calls for reductions in greenhouse-gas emissions.

On Tuesday, President Bush backed away from a campaign pledge to restrict carbon dioxide from coal-burning power plants, saying mandatory controls would lead to higher electricity prices.

The decision angered environmentalists, who for years have pushed for reduced carbon dioxide emissions from U.S. power plants.

Clouds obscure the future

However, the study did not tackle the question of whether Earth's surface temperature is actually increasing. In fact, whether this greenhouse effect will lead to global warming or global cooling is unclear, the study scientists said.

The greenhouse effect could start a cycle in which more clouds are formed, stopping the sun's energy from reaching Earth's surface in the first place, Harries said.

"The effect of clouds on the planet is very complex, and frankly we don't understand it," Harries said.

In the British study, the researchers compared data from the Japanese ADEOS satellite, which produced about nine months of data starting in 1996, and NASA's Nimbus 4 satellite between April 1970 and January 1971. Only clear-sky readings of the atmosphere over the central Pacific were compared.

Drew Shindell, an atmospheric physicist at NASA's Goddard Institute for Space Studies in New York, said the research should end the debate over the greenhouse effect, but not over how to address the problem.

"One of the main things that cause people to be skeptical of global warming is the lack of that real, definite connection between greenhouse gases and the planet getting warmer," Shindell said. "This really gives concrete evidence for the first time that greenhouse gases are changing the energy balance of the planet."

Scientists will have more opportunities to compare infrared data following the launch later this year of a new NASA satellite carrying the first of the next generation of infrared instruments.

Environmental Correspondent Natalie Pawelski and The Associated Press contributed to this report.

Groups blast Bush for reversing position on emissions reductions
March 14, 2001
Climate talks secure U.S. support
March 5, 2001
Conflicts over global warming theory
February 19, 2001
Scientists warn of climate devastation
February 19, 2001
Ocean fertilization yields hope, uncertainty for global warming
January 23, 2001
Global warming may 'double heat deaths'
November 21, 2000

NASA Goddard Institute for Space Studies
 • NASA Goddard Institute: Radiation
Nature

Note: Pages will open in a new browser window

External sites are not endorsed by CNN Interactive.