Rajendra Pachauri, whose panel shared the 2007 Nobel Peace Prize with former US vice president Al Gore, said the downturn could dominate for 2-3 months before politicians return to focus on fixing long-term problems like global warming.

"The evidence is getting stronger by the day. We have much more evidence available of what the human role is in climate change," he told Reuters by phone from India. "One has every reason to take action on what's already been said."

Pachauri's panel, which draws on the work of 2,500 scientists, said last year that it was at least 90 percent sure that mankind was to blame for warming and forecast more droughts, heatwaves, floods and rising sea levels.

He said at the moment everything seemed to be "on the back burner" because of worries about the financial system. "I'm absolutely sure that climate change will be the last thing people will think about at this point in time."

"But it's not going to go away," he said. "Sooner or later, they will come back to it." Arctic sea ice, for instance, shrank to its smallest ever recorded area in September 2007, and came close to breaking the record last month.

He dismissed some skeptics' view that global warming has stopped because the warmest year since records began in the mid-19th century was 1998. That year was warmed by a strong El Nino weather pattern in the Pacific Ocean.

"Eleven of the last 12 years have been the warmest ever recorded. The trend is very clear," he said.

He predicted that the financial crunch would bring "soul searching about how society might act to reduce dependence on fossil fuels" and shift to renewable energies such as wind, solar or hydropower.

More than 190 governments have agreed to work out a new U.N. climate treaty by the end of 2009 to succeed the Kyoto Protocol, which binds 37 industrialized nations to make cuts in emissions of an average of 5 percent below 1990 levels by 2012.

Pachauri said he hoped that the world could agree strong action by the end of 2009.

He said that the next U.S. president, whether Democrat Barack Obama or Republican John McCain, would do more to fight climate change. And he expressed optimism that McCain could fight off skepticism by some Republicans.

He played down the role of Republican vice-presidential candidate Sarah Palin, the governor of Alaska who says natural shifts may explain climate change alongside human influences.

"I wouldn't really worry too much about her," he said, predicting she would have little influence on the issue.

"My feeling is that, in 2-3 months from now, or soon after the new president takes office (in January), he is going to have to look to permanent solutions ... and climate change is going to be an important part of this."

He said the next president "really has a tough job on his hands."