It terrifies me that we're asphyxiating ourselves and increased CO2 can seriously impair human cognition. At a global, population-level scale this is almost certainly statistically significant and it scares me that we could quite literally stupefy ourselves to the point of no return. We need to find solutions now before we're unable to stop ourselves from drowning in our own atmosphere.
[0] https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/201...