Back in 2009, it was 200 million climate refugees according to this article in the NYT:
There could be 200 million of these climate refugees by 2050, according to a new policy paper by the International Organization for Migration, depending on the degree of climate disturbances.
Now the claim is up to 5 times that by 2050 in the space of five years, at this rate of increase, the entire world population will be ‘climate refugees’ by 2050.
From Smithsonian Magazine by Jerry Adler:
The Reality of a Hotter World is Already Here
As global warming makes sizzling temperatures more common, will human beings be able to keep their cool? New research suggests not
The various environmental effects of greenhouse gases are potentially devastating, as we have often heard. The latest Intergovernmental Panel on Climate Change report, made public in March, underscored the danger of widespread hunger, even starvation, resulting from crop failures. Other health threats have been enumerated by Robert Repetto, a United Nations Foundation economist, who says climate change will intensify smog, leading to “increased outbreaks of asthma and allergies,” and “exacerbate vector-borne diseases such as hantavirus, West Nile virus, Lyme disease and dengue fever.” Repetto also worries about the “extreme weather events” that some researchers say climate change will engender. “Biological systems and engineering systems are all designed for a range of climatic conditions,” he says. “Within those limits, we’re OK, …but outside those limits, the damage increases rapidly and becomes catastrophic, and we’re going outside those limits.” Heat waves themselves pose a health risk, especially for young children and the elderly—and world-class athletes. Temperatures at the Australian Open in January reached 104 degrees for four consecutive days, a condition that one tennis player called “inhumane” after competitors collapsed on the court.
(Gosh, it gets hot in Australia in summer? Who knew?)
There may be hordes of climate refugees, fleeing homes on islands and coasts made uninhabitable by climate change—anywhere from 25 million to 1 billion people by 2050, according to the International Organization for Migration. Even people who don’t have to move will experience a bewildering sense of dislocation as the environment changes around them—as Northern winters start to be measured in weeks rather than months. Glenn Albrecht, an Australian philosopher, coined the term “solastalgia” for this emotion, a kind of homesickness you can experience without leaving home.
“We will see the emergence of novel climates, environments we’ve not seen before in human times, and the extinction of others, around the Arctic and in high Alpine regions,” says Laurence C. Smith, a professor of geography at UCLA and author of The World in 2050. Smith says cities, industry and agriculture may benefit in places such as Canada and Scandinavia, though at some cost in psychological and cultural disruption. “Very bitterly cold winters will be less common in some places,” he says, “but instead of a nice blanket of white snow, they will have slush.” And people who move north for the weather, or for jobs that may open up as the Arctic melts, will discover that climate change doesn’t make the winter nights any shorter.