[admiralfluff]

There are 3 relevant ends:

The end of our civilization, the extinction of humanity, the end of our planet.

There's no way that any war, disease, severe climate change, or other man-made disaster will wipe out humanity. We are capable of surviving in diverse climates, are adaptive, and cover too much of the earth. Sure, global warming induced strife, or a catastrophic plague could decimate our civilization and reduce our numbers by several orders of magnitude, but as long as animals like us (large mammals) can survive on this planet, there will be humans. I expect any semblance of our civilization will be wiped out within 100k years.

After that, when the human race is dissociated in an awesome post apocalyptic world filled with mutants and whatnot, our extinction will almost certainly come from SEVERE climate change, which significantly alters the makeup of our atmosphere. In the major fossil record extinctions, this was likely caused by meteor impacts. This will make the earth inhospitable for most of the larger complex organisms on the planet. This will probably happen within the next 100 million years.

A billion or so years from now, A violent climate swing, the sun's expansion, will burn off most of our atmosphere and all liquid water on the planet, wiping out all but the simplest and most robusto of organisms. (Think mars).

In a few more billions of years, the sun will expand to a red giant in its death throws, and will eventually consume the earth, before collapsing into a brown dwarf.

In many trillions of years, the universe's rate of expansion will increase to the point where every particle of matter is independently isolated in its own little prison of space, with every other particale expanding away from it faster than the speed of light. Information will cease to exist, and entropy and coldness will reign supreme.