My prescription
1. 100% Renewables
Transition to 100% renewables as quickly as possible along with net zero and net positive energy buildings and advanced energy efficiency throughout the society and culture, noting that about 2/3 of the energy we produce is "rejected" or lost to friction, heat, distribution, etc and our annual energy production has been around the same level, 100 quads, since the year 2000. Keep as much carbon, methane, and other greenhouses gases in the ground as possible.
2. Zero Emissions Economies
Use zero emissions as an approachable goal as zero defects is on a production line in W Edwards Deming’s Total Quality Management ("Total Quality Environmental Management" used to be a concept and a magazine once upon a time). I suspect that even just thinking through a zero emissions economy would bring us closer to such a system and possibly uncover significant savings. I remember an energy efficiency expert years ago saying, “Maybe it’s all low-hanging fruit.”
3. Accelerated Removal of Carbon from the Atmosphere
Look at Paul Hawken's Drawdown, the book Geotherapy (my preference over geoengineering by a loooooong distance), and the video proceedings of the conferences organized by Biodiversity for a Livable Planet. That’s a start and it is a good thing that there are so many different methods to draw down carbon from the sky and even individual efforts help, according to what I’ve read, heard, and seen.
I'd start with Solar IS Civil Defense, not least because it is becoming increasingly urgent, but that's another story.