...about tackling global warming? Despite talk of a volte-face on climate change by Bush, US scientists remain sceptical of his Administration's commitment. Stephen Phillips reports

As issues that connect science and public policy go, none is bigger than climate change, says John Holdren, president of the American Association for the Advancement of Science.

The topic will be centre-stage at this year's AAAS meeting in San Francisco, which runs from February 15 to 19, as the subject of a town-hall meeting designed to "expand the dialogue among scientists, teachers, students, policymakers, business leaders and the general public on climate change".

Plenary speaker Susan Solomon, senior scientist at America's National Oceanic and Atmospheric Administration, will present the latest "state-of-the-science" on climate change from the much anticipated fourth assessment report from the Intergovernmental Panel on Climate Change, to be released on February 2.

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Earlier this month, Britain's Met Office warned that 2007 could be the warmest year ever because of an El Nino warming cycle and continuing greenhouse gas build-up.

"We've already reached the position of dangerous anthropogenic interference," says Holdren, director of the Woods Hole Research Center in Massachusetts, and professor of environmental policy at Harvard University.

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"The question is: are we smart enough to avoid catastrophe? It's a horse race, and we have to do a lot (to avoid) a cooked planet."

But despite the urgency, US climate change researchers say their work has been hampered by a campaign of misinformation on the scientific consensus about global warming by oil and coal industry-backed groups for more than a decade.

Some energy companies have long since disavowed such tactics. In 1997, BP withdrew from the now defunct Global Climate Coalition, which was sceptical about global warming. Shell followed shortly afterwards.

But the US Union of Concerned Scientists issued a report at the beginning of the month that claims to document how, from 1998 to 2005, ExxonMobil "funnelled nearly $16 million (?8.28 million)I to a network of 45 advocacy organisations that seek to confuse the public on global-warming science" while "(attempting) to portray its opposition to action as a positive quest for sound science, rather than business self-interest".

Last September, Britain's Royal Society wrote to ExxonMobil, urging it to stop funding 39 organisations - to which it gave $2.9 million in 2005 - "featuring information on their websites (misrepresenting) the science of climate change".

ExxonMobil says the UCS report is "deeply offensive and wrong", that it accepts 0the link between fossil fuel use and global warming and is upfront about contributions to "various public policy organisations". "We don't control their views and messages, and they do not speak on our behalf... With respect to the full range of policy positions taken by these organisations, we find some... persuasive and enlightening, and some not," it adds.

Researchers say that sceptical positions have delayed policy action.

Michael Mann knows more than most about global warming contrarianism. The associate professor of meteorology at Pennsylvania State University was lead author of the 1998 "hockey-stick" graph, which plotted average global temperature over the past millennium as a roughly flat line with a sharp upswing in the 20th century.

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His findings have held up. "The study was the first of a large number... to come to the same conclusion - that the rate of late 20th-century warming in the northern hemisphere is anomalous," Mann says.

But it has also become a lightning rod for criticism of the scientific consensus on manmade global warming. The journal Nature has branded it "the most politicised graph in science".

Mann says: "It has become a straw man [for] a number of disingenuous individuals who appear to have a contrarian agenda."

Claims by a Canadian economics professor and Canadian "mineral-exploration"

consultant that the results are invalidated by methodological flaws were seized on in 2005 by the Republican Congressman Joe Barton, who chairs the House of Representatives' Energy and Commerce Committee and is an arch foe of restricting industrial emissions. Barton called for an inquisition into Mann's research and demanded that he turn over his notes. The move provoked uproar, prompting another lawmaker to intercede, referring the study to the National Academies of Science in an effort to settle matters.

The NAS review, released in June, upheld Mann's research. But that did not deter James Inhofe, outgoing Republican chairman of the Senate's Committee on Environment and Public Works. In a speech in September, he said the hockey-stick graph had been "debunked", citing two Canadian researchers and an independent researcher.

The case shows how sceptics have seized on the maverick views of a minority of academics. "The rules they are governed by are not truth but the effectiveness of their talking points," Mann observes. "It forces us to spend time rehashing what's been done, rather than moving forward."

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It's also intimidating, Mann says. "They're serving warning to other scientists that if they do work that might play against [a certain] agenda, they're going to [face similar] attacks."

He prefers to call them contrarians rather than sceptics. Scepticism is an admirable quality, he says. "These individuals claim the mantle of scepticism but don't turn their scepticism on their own claims." He also attacks what he calls a "Galileo phenomenon", where-by contrarians cast themselves in mythic terms as truth-seekers, ranged against the inertia and authoritarianism of scientific orthodoxy. "It's an appealing meme, but it doesn't hold water," he says.

But despite President George W. Bush's Administration dragging its feet over tackling climate change, there has been a plethora of climate-friendly initiatives trialled on a regional basis. In September, New York officials commissioned an audit of the city's greenhouse gas emissions and appointed a "sustainability" czar to lead efforts to reduce its environmental footprint. California, America's most populous state, also enacted legislation that committed it to aggressively curbing emissions.

But, says Stephen Schneider, professor of biological sciences at Stanford University, such efforts could force corporations with vested interests in fossil fuels to rally behind US-wide regulation on climate change.

Meanwhile, the release in the UK last October of the Stern report and this week's State of the Union Address have fuelled hopes that the Bush Administration may be taking tougher action to counter climate change. Sir Nicholas Stern, who will take up the first IG Patel chair in economics and government at the London School of Economics this summer, is visiting Washington, Yale University and New York next month.

With its stark delay-now-pay-later message, Stern represents the most sweeping review yet of the economic impact of global warming in terms of famine, displaced people and ravaged lands. The report says that it would take 1 per cent of the world's gross domestic product to counter the effects by 2050.

But scientists are dubious about whether talk of change is anything more than just, well, talk. Harlan Watson, US negotiator to last month's United Nations climate change summit, appeared to categorically rule out any change of heart under the President's watch. He told journalists: "I certainly got no indication that there's any change in our position, nor is there likely to be during this presidency."

The implications of last month's Democrat takeover of Congress remain unclear, observers say. Ross Gelbspan, a former Boston Globe journalist and author of two books that track global warming politics, notes that the issue was "conspicuously absent" in the run-up to the midterm elections.

In a letter sent in November last year, Democrat Barbara Boxer, Inhofe's replacement as Senate Environment Committee chair, called on Bush "to work with the new Congress to pass meaningful climate change legislation in 2007".

But James Connaughton, chairman of the White House Council on Environmental Quality, signalled the President's continued opposition to any Bill that would be harmful to US economic interests. He told journalists: "We still have very strong reservations about an overarching, one-size-fit-all mandate about carbon."

Daniel Schrag, professor of earth and planetary sciences at Harvard, is not optimistic about political change despite growing public interest in the environment after catastrophes such as Hurricane Katrina. "The good news is that solving the problem will take only 1 per cent of world gross domestic product - not that much," he says.

But such a commitment would be way beyond "the first steps people are talking about". He fears that nothing short of a cataclysmic event will provide sufficient impetus. "When in history have we taken action at the level of 1 per cent of world GDPI in advance of a problem, based on a report?"

Meanwhile, universities are continuing their research into technology that could slow global warming.

One of the most high-powered is Stanford's ten-year $225 million Global Climate and Energy Project (GCEP). The identity of GCEP's lead sponsor, ExxonMobil, which chipped in $100 million, raised concerns that the research would focus unduly on mitigating the effects of continuing fossil fuel usage rather than on renewable energy alternatives. But Schneider says he is satisfied that the researchers enjoy full independence.

Franklin Orr, the project's director, says the biggest focus of the programme is on solar energy. The project is taking a "portfolio" approach, hedging its bets across multiple technologies, he says. Similar efforts include Princeton University's Carbon Mitigation Initiative, financed by Ford and BP.

Meanwhile, geo-engineering solutions are becoming more mainstream. In August, Paul Crutzen, a Nobel laureate in chemistry, floated the idea of shooting sulphur into the atmosphere to deflect the sun's rays into space.

Although this sounds like science fiction, Schneider suggests that the main hurdles to geo-engineering are social rather than technological, centring around international haggling over who would control climate change.

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He adds that environmentalists hate geo-engineering. "It's like a heroin addict about to kill themselves. They either go cold turkey or use methadone. Geo-engineering is methadone."