Doomerism isn't the answer. You may not have kids, but other people still will, and they'll have to live through the world we leave them. Instead of giving up and saying fuck it, use your anger, hope, love, whatever you need to fuel you, and do what you can. Plant trees to create shade you will not be under, find ways to minimize your energy usage, get to know your community, talk to them, prepare together.

It's far more fulfilling than waiting out your death in despair, so even if you think it's all useless, you'll have a much better time of it either way.