A new report warns that climate change has already begun to affect global migration, and over the next few decades, could be a massive force in human displacement around the globe. The human cost of this is obvious, as people are forced to leave their homelands in search of new places to live, and as people are forced across borders, the immigration could take on the form of strained international relations. And here all we thought we had to worry about was smog and ozone layers.

The New York Times’ Green Inc. tells us that the report, co-written by several non-governmental agencies, gives both empirical evidence of migrations, as well as demographic and climate data to provide a large overview of the growing problem. For example,

Large populations in Asia, for example, rely on shrinking Himalayan glaciers — “the Water Tower of Asia” — to feed rivers and provide water. Should the shrinking continue, millions of downriver residents might be forced to move.

Drought and natural disasters, too, could put populations on the move in Mexico and Central America, the report suggested. And more than five million Bangladeshis live in areas vulnerable to storm surges and, should global warming continue apace, rising sea levels.

All this points towards general trends, but no one can say for sure how this will ultimately play out. In fact, some researchers debate that there is anything happening at all that can be attributed to merely climate change, and not a combination of factors. However, the raw numbers seem to prove that there certainly is massive immigration taking place, and the source is climate change.

At the low end are those put forth by the United Nations Refugee Agency, which estimated in 2005 that 25 million people, spurred by environmental or climate changes, had already been on the move by the middle of the past decade.

Norman Myers, a prominent environmentalist and Oxford professor, nudged things forward with an oft-cited suggestion that the United Nations’ number might well double to 50 million by 2010 and reach 200 million by 2050.

Some authors of the report want to call the displaced “climate change refugees,” however because this study might be used at the UN Climate Change Conference at Copenhagen in December, the United States is disputing that term. Because if they’re called “refugees,” you see, the United States would have all sorts of responsibilities to the displaced under all sorts of international law, and we just can’t have that.

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photo credit: U.S. Geological Survey’s flickr photostream/Creative Commons