History

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I'm curious (hexbear.net)

submitted 2 weeks ago by BountifulEggnog@hexbear.net to c/history@hexbear.net

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[–] CarbonScored@hexbear.net 8 points 2 weeks ago* (last edited 2 weeks ago) (4 children)

Sadly practical prefix that I am not at all a skeptic - I just think this graph doesn't show as much as one might argue.

Isn't ice core data actually only an indicator of 'average' CO2 concentration rolling over so many years (decades-centuries)? CO2 diffuses in fresh forming ice, and is already averaged over the 'trapping' period, so historical peaks and troughs would be largely smoothed out. I don't think this graph alone is really precise enough to claim CO2 levels could never have reached current levels for at minimum some decades (not that we have any evidence to suggest it did).

[–] BountifulEggnog@hexbear.net 4 points 2 weeks ago (1 children)

So- I'm actually not too familiar with how precise ice core measurements are. If you have something specific you think I should read I'd love to see. I'm also recovering from getting my wisdom teeth out, so I can't spend too long looking for information.

this (preprint) paper says:

broadly speaking, the shortest resolvable signal at high-accumulation sites is about one decade Trudinger, Etheridge, et al. 2002). At the lowest accumulation sites, centennial-scales features are markedly smoothed but still resolvable Nehrbass-Ahles et al. 2020

The British Antarctic Survery says:

The fastest natural increase measured in older ice cores is around 15ppm (parts per million) over about 200 years. For comparison, atmospheric CO2 is now rising 15ppm every 6 years.

Which- to me- says it jumping 100+ ppm for a few decades and then returning would leave evidence behind? And like, why would it jump so drastically?

I don't know, sorry if this isn't a lot of information, I really need to go lay down now.

[–] CarbonScored@hexbear.net 1 points 2 weeks ago

Nah that's fair, and I certainly have no idea what I'm talking about either. But my understanding is that "ice core data" is a compilation of data from various ice core sampling, including those 'lowest accumulation sites' where they're saying you can only measure to the precision of centuries.

Again, I don't know, but I'm assuming we don't have "high accumulation" ice core data for all of that history, so jumping 100+ ppm for a few decades and then falling again wouldn't necessarily show up in those low accumulation sites.

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