By Jonathan Amos
Science reporter, BBC News, San Francisco
The former US Vice President Al Gore has told scientists to speak out more on the issue of climate change.
Al Gore released a movie about climate change this year
In a keynote address at the American Geophysical Union Fall Meeting, he said it was imperative people understood what was happening to the world.
The year's biggest gathering of Earth scientists has heard further evidence of how the planet is warming.
Mr Gore said he was shocked by the report this week that suggested the Arctic may soon lose its summer ice.
Observational and computer modelling studies had indicated the northern polar region was fast approaching a tipping point that could lead to the loss of perennial ice cover by 2040.
"It's time for scientists to play a different role in asserting the value of scientific insight and defending the integrity of the scientific process, and becoming far more active in directly communicating to the American people about the meaning of the research you have underway..." he told his audience.
Mr Gore echoed the views of the Union of Concerned Scientists (UCS) who on Wednesday issued a statement signed by 10,600 researchers complaining about political interference in their work.
The UCS claimed to have documented hundreds of cases of scientists working for US federal agencies being asked to change data to fit policy initiatives, or simply to bury the information.
Alluding to his recent movie on global warming, the Democrat politician said efforts to censor "inconvenient truths" should be resisted.
"We now face a climate crisis without any precedent in all of history and it's imperative that those who have the best evidence of what's occurring spread the knowledge beyond the small discipline in which these studies are usually disseminated," he told the BBC after his speech.