but that's not how it works...plants absorb a quarter of total emissions and the oceans about a quarter too. So half the emissions are absorbed, and half are not.
I think you're making a very common mistake, which is misunderstanding the carbon cycle.
We could, theoretically, grow enough plants to get down to pre-industrial levels. However, plants decompose when they die, re-releasing their carbon into the atmosphere, and lots of the plants alive to die are grown using petrochemical fertilizer, which was taken from under the ground, not the atmosphere.. So, we'd have to keep all of those new plants alive, forever, or maintain that extreme level of plant growth forever. This seems like an even harder problem.
You're oversimplifying it. First of all, the ocean is a sink for CO2, it absorbs it and mix it down in the depths, not release it back.
Plants don't sequester the carbon, like you said. But on the other hand, the extra CO2 is causing a bigger plant mass growth. So called greening of the deserts (but not just deserts). So basically the living biosphere is growing and absorbing CO2 as it does, because it can.
The plants evolved when there was more CO2 around, 200-300 is very close to starvation, they thrive in 1000+ environments.
Total Earth biomass is 550 gigatons, much larger than 36 which is what we emit every year. But obviously it cannot keep up...since the year 1750 we emitted 1700 gigatons, so more than 3 times the weight of the biosphere. That being said, I can see how the biosphere can grow by 2% with all the extra CO2 and go from 550 to 560, 570 and so on.
