By JOHN K. CARLISLE

For more than a decade, environmentalists have warned that man-made greenhouse gases are causing a litany of disasters such as soaring temperatures, melting glaciers and rising sea levels that will flood coastal cities.

These warnings are increasingly falling on deaf ears because environmentalists can’t back up their apocalyptic predictions with evidence. John Immerwahr, who did a study for the American Geophysical Union, noted, "The more we talk about global warming, the [more the] public’s concern goes down."

Take the predictions of rapid warming. Officials with the United Nations Intergovernmental Panel on Climate Change (IPCC), the principal advocate of the global warming theory, admit their predictions of major temperature increases were wrong. In 1990, they predicted global temperatures would rise six degrees F by 2100. Just three years later, IPCC adjusted its projection downward forecasting temperatures would rise less than two degrees F, a noticeable temperature increase but hardly cause for concern.

Natural temperature rises of three to four degrees F have occurred in past centuries and have generally benefitted humanity by prolonging growing seasons sons and promoting mild weather.

But it is significant that the world’s temperature is not rising. Predictions of global warming are not coming true. NASA’s Tiros weather satellites, the most accurate barometers of global temperature, show that the Earth has slightly cooled since 1979, contradicting global warming doomsayers who predicted that human-induced warming should have caused the temperature to increase 0.6 degrees F by now.

Recent scientific research is also disproving claims that global warming is causing the sea level to dangerously rise. In October 1999, a team of scientists led by Dr. Howard Conway of the University of Washington reported that the massive West Antarctic Ice Sheet, considered especially vulnerable to al-leged global warming, is not melting due to human influences. Conway said the gradual melting of the WAIS "appears to be part of an ongoing natural cycle" of melting that began when the ice age ended 10,000 years ago. It will take several thousand years before this melting ice sheet would even begin to affect seaboard cities - assuming the Earth doesn’t enter a new ice age.

In light of such mounting evidence, environmentalist efforts to claim scientific support for the global warming theory are foundering. The Union of Concerned Scientists, a liberal advocacy organization, points to the 1,500 scientists who signed a 1997 document endorsing major cuts in greenhouse gases as evidence of scientific support for the global warming theory.

Since then, nearly 17,000 scientists signed a petition, organized by the Oregon Institute of Science and Medicine, which declares, "There is no convincing scientific evidence that human release of... greenhouse gases is causing or will, in the foreseeable future, cause catastrophic heating of the Earth’s atmosphere."

Signers include 2,100 climatologists, meteorologists and environmental scientists who are especially well qualified to evaluate the effects of carbon dioxide on the Earth’s climate. When it comes to global warming, environmentalists may have cried wolf one too many times.

John K. Carlisle is director of The National Center for Public Policy Research’s Environmental Policy Task Force.