A counterpoint and something to take into account:
all those studies don’t take lifetime exposure (as in “from conception to death”) into account, which might show much more pronounced effects
and the thing that isn’t directly connected: the increased CO2 levels are already causing issues for marine organisms which cannot fixate calcium for shells etc. good enough in the rapidly dropping pH levels in the oceans. I would say this is by far the larger immediate threat to humanity, because if the pH of the oceans drops too far, we will see a mass extinction that is not even comparable to the shit going on right now.
The costs of a RCT to subject a population of humans over their lifespan to 600 ppm CO2 would be insane. Does this mean that we can’t say anything about how humans interact with elevated CO2 levels and have to guess from mice and first principles about blood bicarbonate levels? Well, there are a few groups of humans who regularly encounter elevated CO2 levels - highly urban populations, indoor office workers (especially in highly urban societies), and submariners.
Well we were at 300ppm - humans didn’t face a “potentially toxic” atmosphere.
We’re at 400ppm - atmosphere not feeling “potentially toxic” to me.
Indoor office workers get a workweek’s worth of indoor time at 1000 ppm CO2, then however long they spend commuting (I’m thinking trains here) more elevated CO2, then stay at home with 500+ ppm CO2 (levels can vary widely). Sure, office workers tend to be less healthy, but a “potentially toxic” atmosphere seems like stretching it.
Finally, there are submariners (and technically astronauts, but they tend to be fewer) who can spend months underway at a time and years cumulatively at 1000+ ppm CO2. How do they suffer? Not too differently from the rest of us -
https://pmc.ncbi.nlm.nih.gov/articles/PMC1128685/https://pubmed.ncbi.nlm.nih.gov/34412099/https://pubmed.ncbi.nlm.nih.gov/8515322/https://pmc.ncbi.nlm.nih.gov/articles/PMC5623552/
Okay, suppose that actually at 500ppm of CO2, it turns out that toddlers spontaneously combust. I think it’s probable that at some point in some urban city that there have been toddlers that have spent almost all of their time indoors and thus could have already been exposed to this condition without dying.
Is it possible that a 500, 600, 700, 800ppm CO2 cause conditions hazardous to human life or incompatible with human life? Yes, it’s possible and we won’t know for sure until we start pushing people into that condition for their whole life. Do I think it’s likely given that we know that people aren’t dropping like flies in highly urban societies like Hong Kong and Singapore and that submariners seem ok? No.
I myself am on team wet bulb event, but I think there is a subset of the population that believes (correctly) that they will be able to survive and thrive no matter how much they destroy the earth or whatever mass mortality events occur.
A counterpoint and something to take into account:
And thwse dissolving phytoplankton in our increasingly acidic oceans also produce something like 60 to 80 percent of the oxygen in our atmosphere.
The costs of a RCT to subject a population of humans over their lifespan to 600 ppm CO2 would be insane. Does this mean that we can’t say anything about how humans interact with elevated CO2 levels and have to guess from mice and first principles about blood bicarbonate levels? Well, there are a few groups of humans who regularly encounter elevated CO2 levels - highly urban populations, indoor office workers (especially in highly urban societies), and submariners.
Well we were at 300ppm - humans didn’t face a “potentially toxic” atmosphere. We’re at 400ppm - atmosphere not feeling “potentially toxic” to me. Indoor office workers get a workweek’s worth of indoor time at 1000 ppm CO2, then however long they spend commuting (I’m thinking trains here) more elevated CO2, then stay at home with 500+ ppm CO2 (levels can vary widely). Sure, office workers tend to be less healthy, but a “potentially toxic” atmosphere seems like stretching it. Finally, there are submariners (and technically astronauts, but they tend to be fewer) who can spend months underway at a time and years cumulatively at 1000+ ppm CO2. How do they suffer? Not too differently from the rest of us - https://pmc.ncbi.nlm.nih.gov/articles/PMC1128685/ https://pubmed.ncbi.nlm.nih.gov/34412099/ https://pubmed.ncbi.nlm.nih.gov/8515322/ https://pmc.ncbi.nlm.nih.gov/articles/PMC5623552/
Okay, suppose that actually at 500ppm of CO2, it turns out that toddlers spontaneously combust. I think it’s probable that at some point in some urban city that there have been toddlers that have spent almost all of their time indoors and thus could have already been exposed to this condition without dying.
Is it possible that a 500, 600, 700, 800ppm CO2 cause conditions hazardous to human life or incompatible with human life? Yes, it’s possible and we won’t know for sure until we start pushing people into that condition for their whole life. Do I think it’s likely given that we know that people aren’t dropping like flies in highly urban societies like Hong Kong and Singapore and that submariners seem ok? No.
I myself am on team wet bulb event, but I think there is a subset of the population that believes (correctly) that they will be able to survive and thrive no matter how much they destroy the earth or whatever mass mortality events occur.