Charles Ehrhart of CARE thinks UNHCR will remain central, but wonders how it or anybody can now distinguish between “forced” and “voluntary” migration. He says climate change may cut agricultural output by half in lowland Africa by 2020. “In such a context, does migration constitute a choice or a necessity?”

Migrants’ rights may be easy to assert for islanders whose homes are drowned — but hard in the case of big, messy movements across Africa and Asia. Most of the displaced will drift to the next-most-liveable place, as the poor do anyway.

“Many states are already overwhelmed by internally displaced populations,” says Mr Ehrhart. “Will they be able to support even more people on the move? If not, whose duty is it to make up the difference?”. At the least, the gap between carbon usage and climate change’s effects portends angry North-South rows.

Meles Zenawi, who as Ethiopia’s prime minister will speak for Africa at several global gatherings this year, predicts that some parts of the continent will become uninhabitable and “those who did the damage will have to pay.” At the December summit on climate change in Copenhagen, he hopes that Africa will “aggressively” demand compensation for environmental damage as well as help with migrants and the mitigation of climate change: in his view a demand of $40 billion would be reasonable.

Many agree that more research is needed to pinpoint the reasons why migrants pick up sticks. People concur that climate change fuels conflict in Darfur, but nobody knows how big a factor it is. Drought helped jihadist fighters seize bits of south Somalia, but was it the main reason?

... contd.