der Spiegel reports:
It was a dramatic prediction that was widely picked up by the world's media. In 2005, the United Nations Environment Programme (UNEP) and the United Nations University declared that 50 million people could become environmental refugees by 2010, fleeing the effects of climate change.More:
But now the UN is distancing itself from the forecast: "It is not a UNEP prediction," a UNEP spokesman told SPIEGEL ONLINE. The forecast has since been removed from UNEP's website.
Official statistics show that the population in areas threatened by global warming is actually rising. The expected environmental disasters have yet to materialize.
In October 2005, UNU said: "Amid predictions that by 2010 the world will need to cope with as many as 50 million people escaping the effects of creeping environmental deterioration, United Nations University experts say the international community urgently needs to define, recognize and extend support to this new category of 'refugee.'"
It added that "such problems as sea level rise, expanding deserts and catastrophic weather-induced flooding have already contributed to large permanent migrations and could eventually displace hundreds of millions."
In 2008, Srgjan Kerim, president of the UN General Assembly, said it had been estimated that there would be between 50 million and 200 million environmental migrants by 2010. A UNEP web page showed a map of regions where people were likely to be displaced by the ravages of global warming. It has recently been taken offline but is still visible in a Google cache.
The rest of the article is worth reading. It ends:
Meanwhile a new forecast is doing the rounds. At the annual meeting of the American Association for the Advancement of Science (AAAS) in February, Cristina Tirado, an environment researcher at the University of California in Los Angeles, warned of 50 million environmental refugees in the future. That figure was a UN projection she said -- for 2020.
I think lots of people need to realize that climate change, excepting the possibility of some kind of climate regime shift, is a problem that unfolds over decades, not years, though the solution cannot (but probably will not, if it does at all). In fact, in some way that's a big part of the problem. And to assign definite years to definite numbers, though that's what governments and policy makers are always going to want, is just going to get you in trouble -- at least at this state of the science. Error bars, people!
PS: der Spiegel has a nice photo gallery that goes along with their article.