Depends on what one means by "overrun" - people talk about the European migrant crisis of 2015, with 1.3 million refugees in a year. With climate change, even

Depends on what one means by "overrun" - people talk about the European migrant crisis of 2015, with 1.3 million refugees in a year. With climate change, even 100 million is not out of question - it will put a severe strain on every affected country, to put it mildly.