(It is likely that elevated CO2 levels will harm human cognition, it isn't widely known probably because it's too depressing. There are counterarguments like "oh that happens only above 1000ppm we're far from that" but they're based only on short-term experiments.)
My assurance is reality. Reality isn’t a science fiction novel.
Interestingly you only get these absurd predictions from a very narrow group of people, which lines up quite well with what my original comment said. It’s a religious movement, not an accurate assessment of climate science.
The real effects of climate change will be difficult enough. We don’t need to waste energy on inventing fantastical ones.
https://penntoday.upenn.edu/news/continued-CO2-emissions-wil...
Combine this with wetbulb temperatures which force everyone to stay in airconditioned indoors for weeks or months in large part of world (this too is supported by climate science). Fantasies? I hope so but expect the worst.
A single study that predicts brain damage from CO2 “by the end of the century” is pure speculation at this point. The link you shared even says it’s still very unclear what the effect is.
I’ll say it again; the actual science says that climate change is a serious problem. It doesn’t say that we are headed into the apocalypse in the next decade.
The actual paper linked from the article links to some research like: "systematic relationships were found between most of the cognitive function scores and CO2 concentration, including from 550–945 ppm". Thinking that in 20 years we could go over 550ppm outside certainly isn't a fantasy, or?