What happened here?
this post was submitted on 08 Feb 2025
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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).
Well, not all ice core data is equal. It depends on the rate of ice accumulation, so high accumulation sites will give much higher precision, especially for more recent years (say, the last few centuries). But my assumption is that low accumulation sites are where we get most of our much older data. I could be totally wrong as I'm talking out my behind.
Low accumulation sites will smooth out the peaks to the scale of centuries, according to that other post, so what looks like 200 years of 300ppm could be a lot spikier in reality. Whether one can do some 'further analysis' I have no idea.
I agree 100% with your second paragraph, there's nothing I'm aware of that suggests CO2 has spiked liked this before. And it seems highly unlikely that it would've. And we may well have evidence to actually disprove such a theory.
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:
The British Antarctic Survery says:
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.
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.