The earth's climate is changing. We burn fuels which release CO2, and we have less trees to absorb the CO2. The earth's temperature is going up. Permanent ice such as glaciers and the North Pole and Greenland melt, raising sea levels and even cutting off water supplies. Drought causes crops to fail, and flooding destroys houses. Rising sea levels push people back from the coast.
Nothing, then unpredictable disasters, and armed conflict over resources and refugees.
Lots.
