Scientists attribute the phenomenon to heat-trapping gases in the atmosphere.
The gases result in part from human activities, such as burning fossil fuels. The president was proposing an effort to study global warming and bolster coordination among research institutions throughout the world, aides said. He also was calling for a separate initiative that would fund research for the development of new technologies to cut greenhouse gases. Even before Bush unveiled his initiatives, there was new criticism of his approach toward the global warming. The Environmental Defense Fund said any proposal without mandatory caps on greenhouse gas emissions would be inadequate.