New report adds to evidence that greenhouse gases cause global warming
Paul Recer
April 13, 2001 | WASHINGTON (AP) --
Computer models developed independently by two teams of researchers give new evidence that global warming is influenced by man-made gases.
In a study appearing Friday in the journal Science, researchers report that the two models, using slightly different techniques, linked rising global temperatures to an increase in atmospheric greenhouse gases, principally carbon dioxide from the burning of oil, gas and coal. 1
"We think this is some of the strongest evidence to date that human-induced effects are changing our climate," said Sydney Levitus, a researcher at the National Oceanic and Atmospheric Administration and co-author of one of the studies.
President Bush decided last month to reject the Kyoto climate treaty, a 1997 international plan to reduce the emission of greenhouse gases as a way to curb global warming. Bush said the plan, which specifies a sharp reduction of carbon dioxide emissions, was too expensive and unwise during a time that the United States faces energy and economic problems.
Levitus said the model produced by his group is in close agreement with another computer model that was produced independently and analyzed by Tim Barnett and two co-authors at the Scripps Institute of Oceanography at the University of California, San Diego. Their work also appears in Science.
Barnett said the "fingerprint" of human influence on the warming climate is "so bold and big that you don't have to do any fancy statistics to beat it out of the data. It's just there."
The results, he said, "are certainly compatible" with the idea that the warming of the Earth "has been caused by anthropogenic (human) sources."
George Boer, a researcher at the Meteorological Service of Canada in Victoria, British Columbia, said the climate modeling work "is a good study."
"This is collaborative evidence" that human activity is causing the global climate to warm, he said.
Global temperatures are thought to have risen by about 1.1 degrees over the last century. The top few thousand feet of the ocean waters have increased in temperature by about one-tenth of a degree.
The new studies tie in the observed effects on the ocean temperatures with those of the land and the atmosphere.
The computer models mathematically express the effects of various elements of the climate. The researchers found that the computer models precisely matched the observed temperature rises only when factoring in the greenhouse gases added to the atmosphere by man-made activities, said Levitus.
"The fact that the model ocean warms by approximately as much as our observed estimate indicates that the models are very robust in simulating the observed changes in the Earth's climate system during the past 100 years," said Levitus.
Levitus said the new models are more accurate than earlier studies because they include effects of the oceans.
Oceans tend to absorb some of the heat from the atmosphere. A study last year by Levitus, based on hundreds of water temperature measurements, showed that the ocean has warmed since 1955.
Global warming has been blamed for a number of climate effects, including the melting of mountain glaciers, shrinkage of polar ice caps, increases in storms and seasonal changes in flowers and plants.
Critics contend, however, that these effects are part of the natural climate variation of the planet and are not caused by human influences.
Associated Press