Britain's Prince Charles urged the world Tuesday to fight climate change, saying that while the global credit crunch may be temporary, the effects of the "climate crunch" were irreversible.

The heir to the British throne issued his appeal on a visit to Tokyo, where he and his wife Camilla are marking the 150th anniversary of diplomatic relations between Japan and Britain.

"Given the current turbulence in the international financial system and the immediate and damaging effect it is having on the whole world, the credit crunch is rightly a preoccupation of vast significance and importance," Charles said.

"But we take our eye off the 'climate crunch' at our peril," he said in a speech at Japan's National Museum of Emerging Science and Innovation.

"While we hope and pray that the underlying strengths of the global economy will once again enable it to bounce back, the effects of climate change will be far from temporary and will, indeed, be irreversible," he said.

Global markets have been battered in recent weeks by a global crunch in credit as some of the world's top financial institutions crumble under the weight of toxic subprime housing loans.

Charles, who has long championed environmental causes, cited predictions by UN scientists that temperatures could rise by more than six degrees Celsius by 2100 if no action is taken.

He called it a "level unprecedented in human experience."

Rising sea levels would "threaten the survival of coastal cities such as Tokyo, London and indeed New York," the prince said.

"With the melting of the Himalayan glaciers, three billion people living beside Asia's major rivers, the Ganges, Yellow River and Yangtze, would face flooding and then water shortages," he said.

"Nothing less than an urgent, full-scale transformation to a low-carbon society is needed," he said.

Charles said that rich nations such as Britain and Japan needed to cut carbon emissions by 70 to 80 percent by 2050.

Leaders of the Group of Eight rich nations -- Britain, Canada, France, Germany, Italy, Japan, Russia and the United States -- called at a summit in Japan in July for global cuts of at least 50 percent by 2050, without specifying the base year.

Negotiations are under way to draft a new environmental treaty covering the period after the Kyoto Protocol's obligations expire in 2012.

Key ways to slash carbon emissions are developing new green technology and finding alternatives to deforestation, Charles said.

The prince had a taste of Japanese technology during his visit to the museum, where he was welcomed by a dancing Asimo, the humanoid turned robot celebrity designed by Honda Motor Co.

Charles, who is on his first visit to Japan since 1990, and Camilla afterwards attended a dinner hosted by Emperor Akihito and Empress Michiko.

Charles and Camilla will later tour the ancient western Japanese town of Nara, home to some of the country's most famed Buddhist temples, and the central mountain city of Nagano.