250,000,000 environmental refugees by 2050 looking likely.

"A growing body of evidence, including analyses from military experts in the United States and Europe, supports the estimate that by midcentury, climate change will make vast parts of Africa and Asia uninhabitable. Analysts say it could trigger a migration the size of which the world has never before seen.

Some of the big questions remain unanswered: How many people will really move? Where will they go? How will they go? Will they return?

But experts estimate that as many as 250 million people -- a population almost that of the entire United States -- could be on the move by 2050. They will go because temperatures are rising and desertification has set in where rainfall is needed most. They will go because more potent monsoons are making flood-prone areas worse. They will go because of other water events caused by melting glaciers, rising seas and the slow and deadly seepage of saline water into their wells and fields.

The worst migration cases will be nations like the Maldives and small islands in the Pacific. Their inhabitants will go because their homelands will likely sink beneath the rising sea.

According to the Intergovernmental Panel on Climate Change, a minimum of 207 million people in Latin America, Asia and Africa will not have enough water inside a decade. In Asia, an extra 130 million people will be at risk of hunger by the middle of the century. By 2100, crop revenues in Africa will drop 90 percent. And scientists see Bangladesh as ground zero."

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