The Bush administration was yesterday accused of systemic tampering with the work of government climate. At a hearing of Congress, scientists and advocacy groups described a campaign by the White House to remove references to global warming from scientific reports and limit public mention of the topic to avoid pressure on an administration opposed to mandatory controls on greenhouse gas emissions. Such pressure extended even to the use of the words "global warming" or "climate change", said a report released yesterday by the Union of Concerned Scientists and the Government Accountability Project. The report said nearly half of climate scientists at government agencies had been advised against using those terms.