Gordon Brown and ex-US vice president Al Gore have jointly chaired a seminar on climate change at 11 Downing Street.
Gordon Brown and Al Gore in Downing Street
Environment Secretary David Miliband, other fellow ministers, MPs and think tanks also took part in discussions.
Mr Brown is later introducing a private screening of Mr Gore's environmental documentary An Inconvenient Truth.
The film sets out the case for action using a PowerPoint presentation Mr Gore devised in the wake of his 2000 presidential defeat by George Bush.
Earlier Mr Gore said he believed people would conclude climate change was a moral rather than a political issue which would ultimately force politicians to alter their views.
He said a few wealthy polluters were spending millions of dollars on persuading the public that scientists were not yet certain climate change was caused by human activity.
"It is exactly the same thing that was done by some of the tobacco companies after the doctors and scientists firmly linked lung disease to smoking," Mr Gore told BBC News.
His documentary shows photographs of changes to glaciers around the world, with snow disappearing from the Alps, Antarctica and the South Pole.
"People have been moved by it," Mr Gore said. "People coming out feeling a sense of urgency."
He stressed the problem was moral, not political, and said he hoped the current US government would re-think its environmental strategy and sign up to the successor to the Kyoto treaty.