By Jeremy Lovell
    Reuters

    Tuesday 21 November 2006

    London - The world has less than a decade to take decisive action in the battle to beat global warming or risk irreversible change that will tip the planet towards catastrophe, a leading US climate scientist said on Tuesday.

    And the United States, the world' biggest polluter but major climate laggard, has a vital role to play in leading that fight, James Hansen, director of NASA's Goddard Institute for Space Studies, told Reuters on a visit to London.

    "The biggest problem is that the United States is not taking an active leadership role - quite the reverse," he said.

    "We have to be on a fundamentally different path within a decade," said the man who earlier this year caused an outcry when he revealed that scientific warnings on the climate crisis were being rewritten by White House officials.

    He said reliance on - and growing use of - fossil fuels like coal both in the United States and in boom economy China had to be stopped and reversed to avoid the planet's climate tipping into catastrophe with floods, droughts and famines.

    Scientists say that unless action is taken to stop emissions of greenhouse gases like carbon dioxide from burning fossil fuels for power and transport, global temperatures will rise by between two and six degrees Celsius by the end of the century.

    But the United States under President George W. Bush has argued vehemently that such actions would cripple its economy and in 2001 turned its back on the Kyoto Protocol - the only global pact on curbing carbon emissions.

    However, a report last month by former World Bank chief economist Nicholas Stern said that while actions now to curb carbon emissions would cost one percent of world economic output, delay could push the price up to 20 percent.

    "We need to be at 25 percent less CO2 emissions by mid-century," Hansen said. "If we begin now it can be much less painful and have possible economic, health and developmental gains."

    "We need gradual, progressive change starting now not abrupt, drastic changes in a decade or so," he added.

    Hansen was in London to receive the Duke of Edinburgh Conservation Medal, awarded annually by environmental group WWF for outstanding services to the environment.

    He said there were signs of movement in the United States, particularly at state level, and rumours of imminent changes from the Bush administration. But so far these were just rumours.

    With Bush having only two more years in office and with his Republican Party having lost control of both US houses of parliament in a voter rejection of the war in Iraq, there has been speculation Bush might make some move on the environment.

    "The great danger is that they will take some minimal steps that give the appearance of doing good but in fact do very little or even some damage because they fool people into relaxing," Hansen said. "Cosmetic acts are no solution."

    "On the other hand it would be good for Bush's legacy if he did take constructive action on the environment," he added.