 US policy on global warming seems headed for a tipping point, with politicians, business leaders and economists joining environmentalists to call for new laws to limit greenhouse gases that spur climate change. So far, the Bush administration has rejected these calls, but has been at pains to stress its commitment to dealing with global warming. President George W. Bush's fleeting mention of the problem in his State of the Union address last month was seen as significant, even as he stressed alternative fuels and new technologies -- not legal limits on emissions -- as solutions. On Capitol Hill, there have been almost daily hearings on the consequences of and responses to human-induced climate warming, including an extraordinary Senate meeting where dozens of lawmakers themselves testified on the subject. Sens John McCain and Joe Lieberman, an Arizona Republican and a Connecticut independent, have introduced legislation that would require caps on carbon emissions. Lieberman predicted that a US measure requiring cuts in greenhouse gas emissions would be law by late 2008 or early 2009. They were among other legislators, including House Speaker Nancy Pelosi, a California Democrat with longstanding environmental credentials, who addressed a World Bank-sponsored global forum on climate change last week. Their talk of mandatory US emissions limits got a warm response from participants from the Group of Eight industrialised nations, as well as developing countries China, India, Brazil, Mexico and South Africa. The forum's final statement, non-binding but ringing, stated: "Climate change is a global issue and there is an obligation on us all to take action, in line with our capabilities and historic responsibilities." The statement said that establishing a market value for greenhouse gas emissions was "the most efficient and powerful way to stimulate investment" in new technologies. That is in line with an extraordinary call by an unexpected coalition of corporate leaders and environmental groups for federal legislation to cap carbon. The group, known as the US Climate Action Partnership, made it plain at a Jan 22 Washington news conference that this would offer opportunities for business, and that a national law was preferable to a patchwork of state and local regulations. The Bush administration has rejected mandatory caps on emissions of carbon dioxide and other gases that contribute to a documented rise in world temperatures -- which in turn are linked to more severe storms, worse droughts, rising seas and other ills. The White House has recently been on the defensive, especially since the Feb 2 release of a report by the Intergovernmental Panel on Climate Change, which called global warming 'unequivocal' and said with 90 percent probability that human activities help cause it. White House spokesman Tony Snow said on Feb 7 that the United States had done a better job of cutting carbon emissions than had the European Union; he was referring to figures from 2000 to 2004, a narrow timespan that some analysts have said gives a misleading picture of US progress. James Connaughton, head of the White House Council on Environmental Quality, defended Snow in a telephone interview. "Tony was responding to a lot of assertions ... that the United States is doing nothing to address its emissions," Connaughton said. "When all is said and done, we're all making about the same rate of progress. So this is the most important point: There's a popular mythology that somehow Europe is doing more than the United States is. That's not true." He said the 2000-2004 period covered President George W Bush's time in office. Bush came to the White House in 2001; Energy Department figures show that between 2001 and 2004 the European Union outstripped the United States in curbing carbon emissions. The 2004 figures are the most recent available.