Washington New estimates of the United States' contribution to global warming show that forest growth, crops and rivers absorb a quarter to a half of the nation's yearly 1.5 billion tons of carbon dioxide emitted from burning fossil fuels.
But that cushion against a buildup in atmospheric greenhouse gases likely will disappear over the next century as forests mature and absorb less carbon, said Stephen Pacala, a Princeton University re-searcher.
"That means the greenhouse problem is going to get worse, not better, because fossil fuel emissions are going up at the same time," said Pacala, lead author of one of two carbon absorption studies appearing today in the journal Science.
In the other study in Science, researchers estimate there is enhanced carbon storage in China as the result of timber management programs and reforestation efforts.
President Bush's opposition to the Kyoto climate treaty, a 1997 international plan to curb global warming, has brought attention to the issue of increasing man-made gases, principally carbon dioxide from the burning of oil, gas and coal.