St Louis, Missouri

The rift between US scientists and the administration of President George W. Bush widened last weekend, as Nobel-prizewinning biologist David Baltimore used the annual meeting of the American Association for the Advancement of Science (AAAS)in St Louis to denounce government suppression of scientific findings.

Speaking last Saturday to a packed conference room, Baltimore — the president-elect of the AAAS — urged scientists to challenge perceived censorship of their research. Tensions between the Bush administration and researchers have been high for years, but Baltimore said he had recently grown convinced that the problem cannot be shrugged off as the usual battles between science and politics.

“It is no accident that we are seeing such extensive suppression of science,” he said. “It is part of a theory of government, and I believe it is a theory that we must vociferously oppose.” In particular, Baltimore condemned the “unitary executive” theory of government — the notion that a president can bypass Congressional and judicial oversight and run the country single-handedly (see page 891). Baltimore argued that this approach threatens to undermine the independence of science conducted under the auspices of the federal government.

David Baltimore has called for opposition to the Bush administration's “suppression of science”.

Major US science agencies such as NASA, the National Science Foundation and the National Institutes of Health are all part of the executive branch of government, meaning that their employees answer ultimately to the president. In recent weeks, several researchers have gone public with charges that their government minders censored or otherwise manipulated their findings (see ‘Censored Science?’).

The latest round began last month, when James Hansen, a climate scientist at NASA's Goddard Institute for Space Studies in New York, charged that NASA was trying to stop him doing media interviews that might cover policies on greenhouse-gas emissions. The 24-year-old NASA press officer who was the source of many of Hansen's complaints eventually resigned (see Nature 439, 643; 2006).

The accusations have left many government-funded researchers wondering about their role in public debate over science policy. Are they allowed to speak their mind based on the latest science? Or must they hold their tongue and respect their employer's wishes?

“There's no precise line that has been laid down,” says Daniel Greenberg, a guest scholar at the Brookings Institution, a non-partisan think-tank based in Washington DC. Instead, scientists must navigate the grey zone where science meets public policy.

Scientists employed by the government have different rights from those at universities or other private institutions, says Louis Clark, president of the Government Accountability Project, a Washington-based non-profit that is advising Hansen. Federal scientists, he says, can present their data publicly but must be clear that they are not representing their agency or government policy. “The cardinal rule,” Clark says, “is that you can speak for yourself, but you can't speak for the government unless you're authorized to do so.” Australia's largest funding agency, where scientists are also claiming to have been blocked from talking about climate and energy research, makes a similar argument.

Hot topic: researchers have attacked official denials that hurricanes are linked to climate change. Credit: NOAA

Still, Hansen and others say that they must speak their minds for science to proceed. Hansen, for instance, is an expert on global temperature records, which are relevant to policies on greenhouse gases. “How can a democracy function,” he asks, “if the public is not informed, honestly and fully informed?”

Such tales are not unique to the Bush administration. In 1993, physicist William Happer resigned unwillingly as head of the Department of Energy's Office of Energy Research after contradicting then-vice-president Al Gore. The vice-president had stated that ozone depletion at the South Pole would lead to dangerous amounts of ultraviolet-B radiation; Happer pointed out that the oblique angle at which the sun hit the pole meant that even a thin ozone layer could absorb the rays.

But the current administration's policies on climate change, which most scientists agree are far out of step with the best available data, have exacerbated the situation.

Not all government employees have felt pressured. Rita Colwell, who headed the National Science Foundation under presidents Clinton and Bush, told the AAAS meeting that she had “not at any time come under political pressure from any quarter”.

But speaking after Colwell, Susan Wood, a former scientist at the Food and Drug Administration, spoke of her reasons for resigning last August, after her boss repeatedly delayed a decision to make the Plan B contraceptive more widely available (see Nature 437, 179; 200510.1038/437179a). The morale of scientists at her former agency was at its lowest point ever, Wood said. She got a standing ovation.