The "Scientific Assessment of the Effects of Global Change on the United States" released on Thursday synthesized previous reports, including those by the government's climate change science program and last year's work by the UN's Intergovernmental Panel on Climate Change.

It is intended to give US government agencies and lawmakers in Congress a single document to refer to when forming climate policy.

The assessment was praised by environmental groups at the forefront of the lawsuit that led to the court order forcing the administration to issue the report by the end of May.

"Hats off to the federal scientists who were allowed to do their work," Kassie Siegel, climate program director of the Centre for Biological Diversity, said by telephone.

But she criticized the administration for waiting until the last months of the Bush presidency to release the assessment.

A 1990 law, the Global Change Research Act, requires the government to do an assessment on global warming every four years. The last one had been issued in 2000 during President Bill Clinton's administration.

The Bush administration has worked to get large-emitting countries to agree to non-binding goals on reducing output of carbon dioxide and other gases blamed for trapping heat in the Earth's atmosphere and altering the climate.

But Bush has opposed regulating greenhouse gases and withdrew the United States from the Kyoto Protocol, saying it would hurt the economy.

The Kyoto Protocol binds some 37 industrialized nations to limits on their greenhouse gas emissions between 2008 and 2012, but allows countries which undercut their caps to sell that unused quota to other states busting theirs.

By most counts, the United States is the world's top emitter of carbon dioxide but is expected to be overtaken soon by China.

In 2006, the Bush government was accused of censoring its scientists on global warming, such as NASA expert James Hansen, which led to the firing of an official at the space agency.

Sharon Hays, the White House associate science director, said Thursday's document offered "a greater focus on what scientists know about climate change impacts in the United States" than the 2007 reports by the UN panel.

Siegel, echoing the sentiment of many environmental groups, said now that the government had an assessment, it should launch a cap-and-trade program on greenhouse gases and federal limits on emissions to slow climate change.

"Now it's time to actually do something about climate change," she said.

The Senate is expected to take up the leading climate bill next week, although few analysts expect it to pass before the next administration comes to power.