“We have known since the 1800s that carbon dioxide traps heat in the atmosphere. The right amount keeps the climate conducive to human life.” -James Hansen
Thanks to our position in space, the energy output of the Sun, and the right atmospheric conditions on Earth, we have temperatures conducive to liquid water on our planet. Over the past 4.5 billion years, that’s led to the flourishing and evolving of life, with our present existence marking something unlike anything else our planet’s ever seen.
But it’s only a precarious set of circumstances that allowed it to be this way right now, and it won’t stay this way for long. The Sun is gradually warming, and has been its entire life. In another 1 or 2 billion years, it will increase its luminosity by so much that the oceans will boil, ending life-as-we-know-it on our world. We might be able to escape to other planets or star systems by then, but that doesn’t change the fact that global warming will eventually, if slowly, bring this all to an end.