中国气候变化信息网 China Climate Change Info-Net

Agreeing how to help poor countries adapt is a major challenge as negotiators work on a new climate change treaty to take effect in 2013.

"Climate has always been one element, one of the reasons forcing people to move, but not the primary reason," Jose Riera, a senior policy adviser with the UN High Commissioner for Refugees, told reporters. "What we risk seeing in the coming ... years is climate suddenly becoming the main driver of the movements."

Riera said conservative estimates predict about 250 million people being forced to move by climate change by 2050 — and "if we break that down annually, that's about 6 million people on the move," in addition to the roughly 10 million refugees UNHCR currently takes care of.

Many of those are likely to be displaced within their own countries, he said — and the most vulnerable countries are in the developing world and least able to respond.

He added that it was important to start discussing with countries questions such as "who will be taking care of these people, what kinds of rights will they enjoy, will they be forced back to their countries even if conditions are not there?"

The UN and Red Cross pointed to a wider need to put more effort into preparing people for the risks they face from climate change, through activities such as protecting water wells before flooding, planting trees to guard against landslides or desertification, ensuring that homes are not built in high-risk areas and simply dispensing advice on how to deal with floods.

The bill for reducing risks from disasters might add up to "tens of billions of dollars a year," said Reid Basher, of the UN International Strategy for Disaster Reduction.