So, if 450 ppm is bad, wouldn't 900 ppm be worse? It wasn't so long ago in the climate's history that it was that way. Not so long before that, it was 1800. Wouldn't that make the world ultra-XXXL screwed beyond belief? What happened there?
The Last Time CO2 Was This High, Humans Didn’t Exist https://www.climatecentral.org/news/the-last-time-co2-was-th...
CO2 – Why 450 ppm is Dangerous and 350 ppm is Safe https://sustainabilityadvantage.com/2014/01/07/co2-why-450-p...
And of course this one: https://skepticalscience.com/co2-higher-in-past.htm