The Global 2000 Report to the President, which three years ago urged major government action to avoid potential worldwide disasters in climate, population and resources, was attacked today as "dead wrong" on every important conclusion.

Challenging the Global 2000 predictions was a panel of economists and experts in other fields, led by Herman Kahn, director of the Hudson Institute, and Julian Simon, a professor of economics and business administration at the University of Illinois.

Simon said that their report, called Global 2000 Revised, was done at the request of officials at the Environmental Protection Agency, who did not want the original Global 2000 "doom and gloom" conclusions to stand unchallenged.

President Carter had commissioned the original report, which was widely circulated. Six months later, a government task force he had appointed proposed policies including research, planning and aid.

The new report was financed partly by the Heritage Foundation and partly by professors who donated their time. Reagan administration officials have declined to embrace the new report as official policy, Simon said. But he said it represents a position more com- patible with the current government than does the report of three years ago.

Simon attacked the 1980 Global 2000 report, saying: Fortunately for this planet, these gloomy assertions about resources and environment are baseless. The facts point in quite the opposite direction . . . ."

The 1980 report said that, "If present trends continue, the world in 2000 will be more crowded, more polluted, less stable ecologically, and more vulnerable to disruption . . . despite greater material output, the world's people will be poorer in many ways than they are today."

By contrast, the report presented at the annual meeting of the American Association for the Advancement of Science today offered completely different conclusions:

"If present trends continue, the world in 2000 will be less crowded, less polluted, more stable ecologically, and less vulnerable to resource-supply disruption than the world we live in now . . . the world's people will be richer in most ways than they are today."

Environmentalists and other scientists at the meeting disputed many of the points in the report. George McCully, a consultant to Earthwatch, acknowledged that the original Global 2000 projections may turn out to be wrong, but said that "is not the point. The idea was to call attention to the fact that we are destroying our habitat. That is still true."

He said the new report is more politics than science. It takes a strong stand against government efforts to protect the environment or regulate natural resources.

"That is what these folks are really against--the intrusion of government," said McCully.

Barry Commoner, a prominent ecologist now at Queens College in New York, said that both Global 2000 and Global 2000 Revised are wrong.

"This is oversimplifying, but the one side says technology and progress are basically bad, and the other side says that technology and progress are basically good," he said.

"It is not technology that is bad or good... We just need to find the right technologies," Commoner said.

Some of the key specific conclusions of the experts on the Kahn and Simon panel:

* The world is not being rapidly deforested, contrary to popular impressions, said Roger Sedjo and Marion Clawson of Resources for the Future. No major regions will be denuded soon, and there will continue to be an adequate wood supply.

The United States is adding forest, not losing it, they said, but in some other locations around the world the land is being stripped, and such situations are "common and serious."

"The possibilities of loss must be weighed against the possibilities of gain from utilization of the forests," they said.

* Any danger to the world climate from increasing carbon dioxide in the atmosphere--the so-called "greenhouse effect" theory--is much exaggerated, according to Helmut E. Landsberg, professor emeritus at the University of Maryland.

The increase in carbon dioxide noted in recent decades may simply be part of a normal fluctuation over centuries, he said. Even if carbon dioxide continues to increase steadily, he said, there would be no significant effects, such as major warming of the climate and melting of the ice caps, until well into the 21st century.

* Soil erosion is declining in the United States, contrary to current reports, and farms where there have been erosion problems are now nearing a level of "tolerance"--the point at which a farmer can lose soil to erosion and still maintain high crop production, according to Earl R. Swanson of the University of Illinois and Earl O. Heady of Iowa State University.

* The 1980 report's estimate that the world may lose 20 percent of all its animal and plant species by 2000 is "utter nonsense," according to a report presented by Simon. He said that the only data used to make that calculation are two facts: that between 1600 and 1900 about one species was lost every four years, and that in the last 80 years the loss rate has been one species every year. He said there is no evidence that the rate will be higher in the future.

Other conclusions of today's report were that mineral resources are becoming less scarce, not more so; that the government should take no action to control the production or distribution of oil; that world oil prices probably will not rise in the next two decades; that nuclear power is no more expensive than coal and costs fewer human lives, and that threats of air and water pollution were "vastly overblown," since the air and water are much cleaner now than two decades ago.