Sir

The recent UN World Conference on Disaster Reduction in Kobe, Japan, was dominated by discussion of the Indian Ocean tsunami (“Solo efforts hamper tsunami warning system” Nature 433 343; 2005). However, we must not forget the extreme vulnerability of small islands and low-lying coastal areas to sea-level rise caused by climate change.

The accumulation of greenhouse gases in the atmosphere during the past few hundred years is likely to result in a sea-level rise of up to half a metre, possibly more, by 2050 (R. J. Nicholls & J. A. Lowe, Glob. Environ. Change, in the press). Many of the affected countries do not have the resources to adopt protective measures such as sea walls and embankments, nor can they afford insurance. By the end of the century, millions are likely to have been driven from their homes by sea-level rise.

One of the ironies of climate change is that, although wealthy countries are responsible for most of the accumulated greenhouse gases in the atmosphere, they will probably face less damage than poor countries. As climate negotiations ‘beyond Kyoto’ take shape, it is time to consider a framework wherein people living in areas likely to be rendered uninhabitable by climate change would have the early option of migrating elsewhere — specifically to those countries that are largely responsible.

The number of vulnerable ‘climate-change exiles’ received by a host country would be in approximate proportion to that country's cumulative greenhouse-gas emissions. Estimates suggest that roughly 50 million to 200 million people will be displaced by the 2080s, owing to the direct impacts of climate change under a plausible range of emissions scenarios (R. J. Nicholls Glob. Environ. Change 14, 69–86; 2004). Assuming that all these climate-change exiles are absorbed by the top ten ‘emitter’ countries, new annual immigrants would range from a few thousand for the Czech Republic to about three-quarters of a million for the United States.

Once the basic principle (which is consistent with Articles 1 and 4.8 of the United Nations Framework Convention on Climate Change) is accepted, there will be several ways to determine who should be considered for immigration benefits, which countries should bear the costs of immigration, and what institutional and political mechanisms are needed in order to minimize the risks of a massive refugee crisis as climate impacts become more severe.

Figuring out an international strategy to address the needs of these climate-change exiles will be easier now than later.