Climate Crisis

"The climate crisis is by far the biggest danger for the civilization," Gore said at the meeting which was organized at the last minute.

In addition, Gore praised Merkel's "political leadership" in combating global warming, especially during Germany's presidency of the G8 group of industrialized nations this year.

"She understood early on the crisis that climate change presented," Gore said, adding that the invitation to Merkel's chancellery was an honor.

The meeting was one of Gore's first public appearances since winning the Nobel Peace Prize, which he shared with the UN Intergovernmental Panel on Climate Change for raising awareness of global warming.

Climate challenge

For her part, Merkel said that climate change was one of the world's biggest challenges, and commended Gore's stance on combating global warming.

"I am delighted to have been able to meet Al Gore here today," Merkel said.

After the meeting with Merkel, Gore was the keynote speaker at a climate conference held by the energy giant EnBW in Berlin.

Speaking before some 300 guests, the former US vice president held a lecture, "The Inconvenient Truth," named after his Academy-award winning documentary which warns of the terrible consequences of failing to curb the effects of global warming.

Gore renewed a call to speed up the timetable for a post-Kyoto Protocol agreement to cut greenhouse gas emissions. He also said he thought future generations would look back on 2007 as a pivotal year in which people found the courage to fight climate change together.

"Either they will ask about us: 'What were they doing? What were they thinking about and how could they let that catastrophe happen?'"

"Or will they ask another question. I want them to look back at 2007 and ask: 'How did they find the moral courage to rise up and solve the problem everyone said was impossible to solve?'"

War over the North Pole

Earlier in the day at the EnBW conference, German Foreign Minister Frank-Walter Steinmeier warned of escalating conflicts in the North Pole as melting ice frees up the Arctic's natural resources.

"We have to avoid a cold war at the North Pole," Steinmeier said, emphasizing that the contrary claims of countries on the resources there should be decided by international law.

In August, Russian researchers planted a rust-free flag underneath the North Pole, thereby making indirect claims on the Arctic's energy sources. Denmark has sent an Arctic mission to back up its claims to the region, and Canada has also made claims.