[0]: https://www.antarcticglaciers.org/glaciers-and-climate/ice-c...
https://www.cambridge.org/core/journals/journal-of-glaciolog...
They have found some meltwater layers with unexpectedly large quantities of CO2 > 750ppm.
But they also show that there is unexpected heavy diffusion around the meltwater layers. And they argue very compellingly, that the ice core CO2 records have been smoothed through natural diffusion.
Why is this information not given when showing this graph?
What's the causal explanation behind that much CO2 though? Super-volcano eruptions?
But from the layers around it, it becomes clear that through the years these high CO2 bubbles leak CO2 to nearby layers.
And so CO2 highs are diminished in the ice core record and CO2 lows have been raised.
It is well-understood that many ice cores give the same relative shape of peaks of various gasses through time.
Going from there to claiming knowing the absolue concentrations without very large error bars, is just not science.
"Carbon dioxide measurements from older ice in Greenland is less reliable, as meltwater layers have elevated carbon dioxide (CO2 is highly soluble in water)."