"Global warming increases the potential for conflict," Janos Bogardi, head of the UN University's Institute for Environment and Human Security in Bonn, told Reuters.

"The most imminent effect is probably desertification and land degradation," he said. His group says climate change may force hundreds of millions from their homes in the long term.

Bogardi said violence in the Darfur region of Sudan, where 200,000 people have died, was "probably the most prominent example" of a conflict partly caused by land degradation.

In the longer term, rising seas caused by melting icecaps and glaciers could swamp large tracts of countries such as Bangladesh, forcing millions to migrate and raising the chances of conflicts over shrinking land.

"Climate change has the potential to be a huge security issue," said Paul Rogers, professor of peace studies at Bradford University in England. Still, he said disputes over oil were now more likely to cause war than climate change.

The UN Security Council will discuss climate change on Tuesday for a first time. Britain, which holds the rotating presidency, is spearheading the debate but has not won strong backing from nations, including its ally the United States.

US SECURITY

"It is our view that there are many factors other than climate change that have an impact indirectly on security," said Gerald Anderson, deputy assistant secretary at the US Bureau of International Organizations Affairs.

"There are already a number of international fora for dealing with the issue, and we don't really see the Security Council as the optimal place to deal with it," he told Reuters at a UN meeting in Nairobi.

A report to be released on Monday by a group of 11 retired US generals and admirals will look at how "changing global climate may present serious threats to US national security."

A study by the world's top climate scientists on April 6 warned climate change could cause water shortages and hunger for millions, which could bring migration and spread disease.

Bogardi said global warming could worsen the divide between rich and poor. The April 6 UN report said nations such as Canada, Russia and many in Europe might get some benefits from moderate climate change, such as higher crop yields.

"Countries such as India and China, and Africa are likely to be the losers. This creates a further imbalance of resources and standards of living that could trigger conflict," he said.

Unlike political refugees who can still hope of returning home, "climate refugees" -- like those affected by expanding deserts in sub-Sarahan Africa or islanders whose low-lying homes disappear beneath rising waves -- will be permanently displaced.