I can reduce my energy use as far as possible. Apart from the online stuff I'm pretty low CO2. I can reduce, reuse, and recycle. (I need to get better at that.)
But what else can I do?
https://www.sunfunder.com/ https://joinmosaic.com/
Also, don't become too pessimistic. Even here, its pretty obvious that people tend to fall into two camps: doomers or deniers. Very few in between. I have spent the better part of a year struggling with depression related to the realization of the scale of environmental and sustainability issues facing civilization. I was a doomer, and some days, I still am. That said, I also see that the uptake of renewable energy is accelerating. Electric car sales were considered negligible two years ago, and now they are growing fast. Thats not to say that there aren't HUGE challenges facing us. But I also feel more hopeful that things will eventually change in time.
Everyone who can vote has at least some power. Please vote for pro-science and reality-based candidates whenever possible.
However, I'm not confident that individual contributions like that are very effective in a global economy based on perpetual growth and consumption.
We're well past the point where changing individual behaviour will be enough (and also, this strategy has been promoted over the last 30 years and largely failed - emissions are still rising). We need protests and actions that will lead to policy changes around the world and the shutdown of the fossil fuel industry.