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Comment by ghastmaster | Hacker News Reader

> Earth’s oceans absorb carbon dioxide from the atmosphere, providing a valuable carbon sink as humans burn fossil fuels. But this process also makes the oceans more acidic, which can disturb the formation of shells and coral skeletons and affect fish life cycles, per the report.

Atmospheric CO2 levels are at historic lows.[1]

Bivalves have shells and evolved during the Cambrian Explosion. The Cambrian explosion took place around 540 to 520 million years ago (Mya)[2].

During the early history of bivalves atmospheric CO2 levels were around 4,000-5,000ppm. Current levels are around 400ppm.

References:

1 - https://en.wikipedia.org/wiki/Carbon_dioxide_in_Earth's_atmo...

2 - https://en.wikipedia.org/wiki/Bivalvia

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Definitely not historic lows. Perhaps it's been higher, but it's definitely been lower than now.

In the last 400,000 years the concentration has fluctuated from about 180ppm to about 300 many times.[1] My historical reference in the previous post was the last 500,000,000 years. In that context we are low.

1 - https://en.wikipedia.org/wiki/Carbon_dioxide_in_Earth's_atmo...

Since our species' collective life comprises the last 400,000 years, and we are 420ppm now, do you think it's also fair to say that we are historic highs?

Maybe ghastmaster is a super-intelligent bivalve.

Meanwhile:

https://en.m.wikipedia.org/wiki/2022_Hunga_Tonga%E2%80%93Hun...

It's time for the bivalves to rise again!

It's an interesting point to cherry-pick, and it's fair to question the affect of atmospheric CO2 on aquatic life, but you can't say that CO2 levels are at historic lows when they're up 30% in the past 60 years [1].

[1] - https://keelingcurve.ucsd.edu/

> but you can't say that CO2 levels are at historic lows when they're up 30% in the past 60 years

I thought I made it very clear the historic period I was referring to. Questioning the relevance is indeed apropos. However, the semantics, I do not understand.

Regarding the last 60 years, I think it is very unlikely that the earth has not had a period where atmospheric CO2 concentrations have not rose as quickly. The volcanism, planetary impacts, and die offs of the past had to have had similar impacts. Yet, shelled creatures survived to the extant that they are ubiquitous in the earth's waters today.

There indubitably have been extinction events and perhaps some of them have been caused by ocean acidification.

What about some of us creatures who aren't shelled? Should we be as blase about the sharp spike in CO2 as you are?

Completely irrelevant. Humans cannot survive in the conditions of the Cambrian. Merely going back to the Cambrian is enough to ensure our extinction. No one cares that the CO2 levels were higher then. What matters is that we will all be dead if we go anywhere near those levels.

I'm not sure "historic" means what you think it means. Obligatory XKCD so that no one is taken in by this spurious argument, which is often made for temperature rather than C02, https://xkcd.com/1732/.

The animals alive in it today aren't adapted to these Cambrian conditions though?

That's the $50,000,000,000,000 question.[1] Are they adapted? Will they adapt? Who knows?

1 - https://www.globalgiving.org/learn/cost-to-end-climate-chang...

Well yeah, of course it will... eventually

What we're going to extract value from in the meantime would be the question or, rather, problem

"Historic"?

I do not think it means what you think it means

500,000,000 years of my understanding of atmospheric CO2 concentration is what I was referring to as "Historic".

(Since there's no other definition of historic that I know of (500M years seems as arbitrary as any other number), I think the person was referring to the literal definition of historic, namely, written records. Not that I think this is a very fruitful argument to make, or whether weather recorded in shells could be considered written is perhaps also debatable)

Technically that's prehistoric. History conventionally starts with the invention of writing

Not sure that's conventional. Looking up the dictionary definition, it's clearly being used generally. It's the definition I was taught in school and probably it's used in this technical way in some fields or perhaps in science generally, but commenting on someone casually using "historic values" and going "I don't think you know what that means!" is the best way to help anyone get a better understanding of anything

("conventional" in meaning 1 of the word as per Wordnik, namely that it's in accordance with general practice, before we start another such discussion...)

You’re right that "history" starts with writing, but "prehistoric" refers to the human period before written records, starting with the use of stone tools around 2.5 million years ago.

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