Algae are very, very good at using sunlight and CO2 to replicate themselves. But they're stuck on the surface of the water where they bloom and die, turning the CO2 into methane, which is 28 times worse ...

So, start with algae and let's engineer a critter that does more like what we want. It's gotta be small, airborne. It wafts about making copies of itself out of CO2, same as an alga. Helpfully, that'll occlude sunlight and assist with GlobalDimming.

Now we just need to dispose of 'em. And the best way to do that is to have 'em convert themselves into fertilizer when they land on the ground - or into inert graphite when they wind up in water.

''This is absurd. The proposal requires either SyntheticBiology or MolecularNanoTechnology. And if we have either of these, we'll be using it to create useful products, not shit. Actually, when we have either of these technologies, we'll have to start worrying about depleting atmospheric CO2. Which is why all of those predictions about CO2 levels in 2100 based on current patterns are just stupid. And so are any demands that we do something about the problem '''now''' when it will just solve itself pretty soon. Assuming only that we don't kill ourselves.''

So you're suggesting there's a GreatRace - that we may develop the technology to save ourselves, but that we might perish first. Well then, developing CarbonSeekingNanobots asap seems like a good step towards winning that race, doesn't it?

''Any molecular nanotech we develop wouldn't "seek" carbon anymore than plants do. It would have it pumped to it. The crucial factor is that once we have molecular nanotech, CO2 ceases to be a waste product and becomes an industrial input. Not the best of industrial inputs but the most easily obtainable by far. And even if nanotech weren't more efficient than photosynthesis, at least its products would never decompose and produce methane, or even release CO2 back into the atmosphere. The CO2 would basically be sucked down a black hole, never to return. Which would be a real problem.''

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Part of the GrandOpenSourceProject called PutTheCarbonBack