We have that. They're called "plants." If we just stop cutting down all the trees and poisoning the seas, plants will capture the carbon in the air and return it to the ground when they die. Or it will become part of the natural food chain.
So don't worry, either we will stop destroying all of the ecosystems, or the plants can fix the planet after we're all gone.
Because we added carbon by burning stuff that was underground (commonly known as coal oil and gas), so just planting trees won't do, as we would need to plant more trees than we have space there are options that include plants, but all of them include putting them away forever. If we would have only burned trees and charcoal this wouldn't be a problem, but we took carbon from underground.
Climate change won't kill all humans itself, we are too efficient in adapting to environments, it can kill 90% of us if shit really hits the fan however thats unlikely. It will however definitely impact the quality of life and make everything harder cause wars and what not.
I wouldn't underestimate our capacity to fuck up the planet. When the food runs out and the water riots spread, things are going to go south very quickly for the human race. We like to make post apocalyptic movies about how we survive in the desert that used to be Iowa, building war-cars from scrap and isolated communities from the remainders. The reality is that almost everyone will die off without the electricity, medicine, and food production we have all come to rely upon. Gasoline will expire in the tanks of a million cars, and the ammo will run out faster than the potato chips. Farms will be pillaged, and GM seed stocks don't produce a new generation.
When society breaks down, all the little things will fall away, and we'll all realize how actually few survival skills people actually have.
Well, as said if shit really hits the fan it may end in 90% less humans, but eradication is almost impossible unless we accidentally spread a virus that has a 100% mortality rate and several months until it shows symptoms we would have to fuck up so hard that it would be a actual achievement to do it.
Shure quality of life degrades massively but its not impossible to live, knowledge still exists and its not a one day to the next event. Its more than possible to prepare for such things its however more expensive than solving the problem itself.
Cutting the trees down is fine (well the ones we plant for the purpose I mean) - turn them into books and then store the books. As an added benefit you get books!
We have a simple biologocial solution for all of that. Peatlands. They transfer the carbon into more and more stable chemical compounds that end up being sequestered. All the coal that is extracted now used to be peat some hundred million years ago.
I'm not a scientist by any stretch, but would disposing of plastics with these mushrooms in a terrarium of sorts help? They would have to be big and numerous.
The mushrooms would break down the plastics into CO2 and water and the plants would absorb the CO2 and water. As the plastics start to go away, we could add more of our excess plastic to keep the cycle going.
If this works, it also keeps the plastic eating mushrooms contained and away from all the essential plastics we have today.
Sounds like a good plan. I don't know. Considering the rate at which we produce plastic, I doubt we could ever grow enough mushrooms to keep up, but it would be worth funding the research.