The earth's tropical forests are vanishing 50 percent faster than previously estimated, raising concerns about global warming, a private environmental research group said yesterday.

"Every year the world loses an area of tropical forests almost as big as the state of Washington," said James Gustave Speth, president of World Resources Institute.

The report by the Washington-based organization said data from satellites and ground sensors, along with reports from individual governments, indicates that official estimates of tropical forest losses are far too low.

The report suggested from an analysis of 1987 data that 40 million to 50 million acres of tropical forests are stripped each year, compared with the official estimate of about 28 million acres -- based on 1980 data -- that is still used by the United Nations and many governments.

Deforestation is a major concern to scientists and environmentalists because tropical forests absorb carbon dioxide and, therefore, serve as a "sink" for the manmade gas, which contributes to global warming. As forests disappear, more carbon dioxide is free to drift into the atmosphere, where it and other manmade pollutants act much like a greenhouse and cause the earth to warm.

Some scientists believe such warming, if not checked, will cause severe changes in weather patterns, coastal flooding and economic disruptions by the mid-21st century.

Allen Hammond, who headed the institute's research effort, said that the satellite findings and data from studies in several countries with vast tropical forests provide the first exhaustive look at the current extent of deforestation worldwide.