CO2 levels don't actually poison us though. The problem isn't CO2 levels per se, but the effect they have on global climate change, by trapping more heat. If less light gets through, then the planet cools, even if CO2 levels remain high. If temperatures stabilize or drop by 1.5C, then plants should eventually be able to remove the excess CO2, as long as we stop increasing our output. OTOH, the decreased amount of light getting through might make solar panels less efficient, and may reduce plant growth since they kinda need sunlight too. Sooooo...