Is the problem that we're simply creating more CO2 than can be manufactured back into O2 by plants? Would the practicality of a "CO2 vent to space" work? We vent the excess but obviously not everything considering we wouldn't want to destroy all plant life on earth (and subsequently our own in the process). The one major downside is if this wasn't tightly controlled and a "leak" happened we could foster the end of life on the planet. It looks like ocean acidification would do that already so if it'd be the lesser of two evils I'd go for the one we could control.
The more obvious choice is to reduce our dependency on fossil fuels. How's that really been going all this time? Yeah that's what I thought. Rock? Meet Hard Place.
The problem is that the carbon cycle is pretty much closed at the plant side. They create O2, but during burning, rotting or other biological activity it gets transformed into C02 again. You can see this in the data - during the northern hemisphere winter CO2 goes up, during summer it goes down. There's also a similar day-night cycle.
What happens then is that more CO2 is added, and it seems to be clear at this point that the plants are not keeping up - even losing ground due to land use change and deforestation.
Main carbon sinks are ocean uptake (the problem discussed in the article), weathering and the small amounts of organic matter that sink below the ground/sea/lakes without rotting (and which will create new coal and oil in time).
Apart from the first point, these processes happen on geologic time scales. (Also, shells of small sea animals, but again a miniscule factor. Those will be the next lime rocks.)
What you suggest is a new sink for carbon. However, it would probably cost more energy than can be gotten from fossil fuels because gravity. (Sry, too tired to run the calculations right now.)
> Would the practicality of a "CO2 vent to space" work?
No. The atmosphere is not isolated from space in way that could be addressed by venting (selective or not).
You could in principal isolate CO2 and launch it into space (long-term, that's an oxygen-depletion strategy, but, ignoring the resource requirements, it might be better than building it up in the atmosphere on some time scales), but when you consider the resource (including energy) costs of launching material into space, that's a pretty bad idea, especially given that if you can isolate it, you can sequester it on earth with the same atmospheric effect without launching it into space.
The more obvious choice is to reduce our dependency on fossil fuels. How's that really been going all this time? Yeah that's what I thought. Rock? Meet Hard Place.