Europe’s reaction to the recent influx of refugees does not bode well for the future of liberal democracy in a world where climate change will force far more people to migrate. Across the continent xenophobic, right-wing populist parties are on the rise while even mainstream parties are pushing policies of aggressive policing, surveillance, and militarized borders.

Projecting climate-driven displacement forward with any accuracy is tricky. Estimates of how many people might be on the move, when, and under which emissions scenarios vary widely.

The Stern Review in 2006 cited estimates that climate change, by unleashing rising sea levels, more frequent floods, and more intense droughts, could displace 150 to 200 million people by the middle of the century. A year later, the NGO Christian Aid predicted that 250 million people could be “permanently displaced by climate change-related phenomena” in the same period. The United Nations Development Programme’s 2007–8 Human Development Report estimated 330 million people will be displaced if there are global temperature increases of 3 to 4°C.