Aside from us killing ourselves in myriad spectacular ways, the most looming threats are cosmic. The sun is on a timeline and asteroids hit planets with some measure of regularity. Any cosmic extinction-level event will render the bottom of the ocean just as inhospitable as the south of France or the Midwest US.

An ELE on Earth in the short term future wipes out the human race, full stop. The only thing that can continue our species is having that species on more than one rock in space.