The Obama administration issued long-awaited, long-delayed guidelines Friday to insulate government scientific research from political meddling and to base policy decisions on solid data. Under the guidelines, government scientists are in general free to speak to journalists and the public about their work, and agencies are prohibited from editing or suppressing reports by independent advisory committees. And the agencies are instructed that when communicating a scientific finding to the public, they should describe its underlying assumptions. For instance, they are told to describe 'probabilities associated with both optimistic and pessimistic projections' -- a guideline that, had it been in place last summer, might have helped the administration avoid overly optimistic estimates of the BP oil spill. In a blog entry on the White House website, John P. Holdren, President Barack Obama's science adviser, said the guidelines set 'minimum standards' that federal agencies will be expected to meet. The agencies are to report to Holdren within 120 days, detailing how they will carry out the policy. Some scientists praised the new guidelines. 'I think they represent several steps in the right direction,' said Albert H. Teich, director of science and policy programs at the American Association for the Advancement of Science in Washington. But others were disappointed that the four-page document did not provide more specifics. 'The guidelines are substantively quite thin,' said Roger A. Pielke Jr., a professor of environmental studies at the University of Colorado. The guidelines have their roots in a series of scientific controversies that erupted during the administration of President George W. Bush. Officials were repeatedly accused of suppressing or even altering research findings, particularly on climate change, to match the political views of the White House. So in March 2009, when Obama overturned Bush administration limits on stem cell research, he set out several principles to 'guarantee scientific integrity throughout the executive branch' and added, 'We make scientific decisions based on facts, not ideology.' But although the president called on Holdren to come up with recommendations within four months, the guidelines did not emerge for over a year and a half. Pielke said Friday that considering the guidelines were merely 'a starting line for agencies to consider these issues, what is surprising is how long it took to get these out.' Holdren told a House panel in February that the process took longer than expected because of 'the difficulties of constructing a set of guidelines that would be applicable across all the agencies and accepted by all concerned.' With the delay, some Republicans have charged that the Obama administration was manipulating scientific data in the same way it said the Bush administration had done -- to justify policy decisions on climate change, fuel mileage standards, nuclear waste disposal and other issues. 'In fact, what I see from this administration, seems to me they're holding on to the idea that the world is flat,' Rep. Paul Broun, R-Ga., said at the panel hearing. Francesca T. Grifo, director of the scientific integrity program at the Union of Concerned Scientists, praised the guidelines but cautioned, 'A lot of the details are left to the agencies.' The document states, 'Federal scientists may speak to the media and the public about scientific and technological matters based on their official work,' but then adds a caveat: 'with appropriate coordination with their immediate supervisor and their public affairs office.' 'That could mean so many different things,' Grifo said -- for example, that a scientist should keep their colleagues informed, or that a supervisor could prohibit appearances. Grifo said the language would not prevent a recurrence of the kind of situation that arose in 2006, when James E. Hansen, director of the NASA Goddard Institute for Space Studies in New York, accused White House officials of trying to keep him from talking about findings that connected emissions of carbon dioxide with rising global temperatures. 'I don't like the ambiguities,' Grifo said. 'I don't like the discretion it gives to the agencies.' 