A study forecasts that global heating effects could drive a billion people from their homes by 2050.

Even if the study is off by a factor of two, and only half a billion become refugees for this reason, so many people won't find places that will let them in. A million or so refugees were enough to convinced the European Union to take firm measures to keep refugees out, even unjust measures.

However, many of the billion will be armed, and ready to fight for other people's land rather than sit down and die. We will see wars around the world.