U.S. Study Contradicts White House's Global Warming Stand

"Warmer temperatures in North America since 1950 were likely caused in part by human activities, the Bush administration said in a report that seems to contradict the White House position there was no clear scientific proof on the causes of global warming...The brief passage in the report was surprising because President Bush and other senior administration officials have long insisted there was no clear scientific proof to link human activities to global warming."