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Comment by stupendousyappi | Hacker News Reader

Over the very long term, I see no reason to think that higher CO2 levels are fundamentally worse for life than pre-industrial levels. In general, plants are the foundation of the food chain, and higher CO2 levels are better for them. In addition, life depends on liquid water, and given that surface temperatures are generally closer to the freezing point of water than the boiling point, I could see how higher temperatures might increase the amount of land and ocean surface hospitable to life. The problem is the transition period, during which most things go extinct until evolution can slowly regenerate the lost diversity over 10+ million years.

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Good for plants, but not necessarily for humans. Human mental performance seems to reduce at higher CO2 levels, which makes sense as humans (by any definition... behaviorally modern humans ~50,000 years ago, anatomically modern humans 300,000 years ago, the overall genus homo within about 2 million years) have never experienced CO2 levels near the current level, let alone what they may be by the end of the century. Perhaps CO2 levels will be higher than ever experienced by great apes since we first evolved 14 million years ago: https://earth.org/data_visualization/a-brief-history-of-co2/

Do you got a source for the idea that human mental preformance suffers in the the hundred ppm CO2 range? I don't see how it would since the body has homeostatic mechanisms. CO2 has only increased by several hundred ppm since the industrial revolution. Maybe you are confusing CO2 with CO which has completely different biochemistry (it binds more efficiently with hemoglobin than oxygen and or does not release as easily once bound).

No, I'm not confusing CO for CO2.

Yes, I do have sources that human mental performance suffers at elevated CO2 levels (800-1000ppm, not uncommon in buildings... but could be the CO2 level outdoors and even if it's not quite that high, it'll be harder and harder to keep building CO2 levels below that as external CO2 levels increase). https://www.nature.com/articles/s41370-018-0055-8

https://ehp.niehs.nih.gov/doi/10.1289/ehp.1510037

Current levels aren't really problematic except in stuffy buildings. But if we don't stop changing the chemistry of the atmosphere, it becomes a problem.

It would be interesting if the study could be duplicated. More importantly it does not seem to distinguish between the acute effect of a sudden increase in CO2 in an experimental setting and the chronic effect of gradually rising ambient rates over the span of years. It stands to reason that the body would adapt to higher CO2 levels over longer time ranges vs. just injecting a sudden pulse of 2500 ppm into a closed chamber.

Well, good news! We’re conducting a planetwide, n = 8 billion, study on this topic right now! We don’t have a control group, though, except maybe a handful of rich folk who can afford to scrub CO2 from their penthouses.

You have as hypothesis that the current process will stop in very short time leaving things like today, more or less. I don't know when it will stop, but before it does, it will have to deal with the excess of greenhouse gases on the atmosphere until reaching an equilibrium point, and the positive feedback mechanisms that are being triggered already (and that they are emitting their own quota of GHG).

It not may stop till the yearly global average temperature is several degrees over what is it now, CO2 in the air or not, and that will not bring nice living conditions. And as a difference of the other times in Earth's history that it happened without massive extinctions, it is happening too damn fast at geological/evolution times. If species doesn't adapt fast enough, they get extinct.

Yes, at the other side of that process, some millions of years after, they could be a new age for life. But we won't be there.

CO2 levels from hundrer million years ago busted in myth #3:

https://www.youtube.com/watch?v=FBF6F4Bi6Sg

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