It's gonna be a bitch not getting anything to eat because Earth won't grow our crops anymore because we done fucked up all of its life support systems and it's just too damn hot outside.
So much technology, the pace of development accelerating exponentially, so much having happened in just the last 100 years compared to the past thousands of human history, and all you can see is death and destruction looming.
The real problems facing humanity are the ones that have always been, and always will be, with us.
Get a grip. Go outside, take a deep breath of some fresh air, and try to enjoy the few years you have on this beautiful planet. Try to make a difference where you are, when you are. The rest isn't up to you or anyone else.
Higher temperature = more arable land.
Your beliefs are not scientifically valid.
E.g. https://phys.org/news/2015-06-tide-pools-rapid-die-off-sea.h...