Not sure that is the most important downstream effect. Harvard School of Public Health measured a 15% lower cognitive ability score at 950 ppm and a further 50%

Not sure that is the most important downstream effect. Harvard School of Public Health measured a 15% lower cognitive ability score at 950 ppm and a further 50% decline at 1400 ppm. (https://www.hsph.harvard.edu/healthybuildings/2021/09/09/impacts-of-indoor-air-quality-on-cognitive-function/ https://www.hsph.harvard.edu/healthybuildings/2021/09/09/imp...) So at 1000ppm everyone in the world is just 15% dumber than their baseline ability should be, and 1000ppm atmospheric CO2 will make it much more likely that indoor levels will go up to 1400ppm or even higher unless we start utilizing carbon scrubbing technology for indoor spaces. It's pretty scary to think that modern society could be basically mentally stunted by high CO2, even if crops enjoy it.