Images: Radical Cartography, via Quora
Most of the world's population of seven billion people—88 percent of it—is clustered around a lattitude just north of the equator. About 27 degrees north. That's what you're looking at here, in an artfully rendered map by Bill Rankin aka the Radical Cartographer.
The vast majority of that population segment is bunched up in the northwestern hemisphere, around China, India, and Southeast Asia. In fact, so much of it is clustered there that this graph is true:
So that's the global population outlook now (or as of 2000 at least). Here's the problem with it: climate change. Global warming is going to make the real estate along that big lateral spike pretty unpleasant before long—hotter, more arid, and less productive.
In a 2007 Atlantic cover story, Gregg Easterbrook laid out the problem.
"The equatorial and low-latitude areas of the world presumably will become hotter and less desirable as places of habitation, plus less valuable in economic terms," he notes, and adds that "these areas are home to developing nations where living standards are already low."
The populations of many nations in Subsaharan Africa, Central and South America, and Southeast Asia will get hit the hardest. And they'll probably want to move. This is what we talk about when we talk about climate refugees. By 2050, there will be nine billion humans on the planet, and many of them will be seeking a new lattitude.
So where will they be headed? North, mostly.
By accident of geography, except for Antarctica nearly all such land is in the Northern Hemisphere, whose continents are broad west-to-east. Only a relatively small portion of South America, which narrows as one travels south, is high latitude, and none of Africa or Australia is ... More specifically, nearly all the added land-value benefits of a warming world might accrue to Alaska, Canada, Greenland, Russia, and Scandinavia.
Interestingly, the patterns outlined above are unlikely to change too drastically. More people will likely move to the northern America midwest, Canada, and, eventually, Siberia.
But nice little map-lines are decieving. Moving even a few degrees north on that top one will likely mean crossing borders between sovereign states. Last time I checked, the US and Russia weren't exactly boasting open-door immigration policies. And getting from, say, Chad to China is going to be even more of a nightmare than it is now, as the erosion of a region's inhospitality starts becoming more apparent to everyone involved.
Moving those purple lines, in other words, is going to be a colossal, strife-ridden nightmare. At least until someone founds a utopian open border nation in Antarctica.