No mention of what happened 800,001 years ago.
Anyone who has taken lessons for Scuba diving knows that gases are absorbed and released into and out of water quite freely depending on temperature and pressure. With all due respect to people who stayed in college longer than did I, I cannot help but think that this trapped CO2 they are measuring must migrate in the ice.
It it not “trapped” in the ice like one traps a bug in a sealed bottle. It is free to move, and indeed it has had 800,000 years to move.
I would be interested in details about how this group of scientists have firmly resolved the issue of CO2 v temperature change. Which came was the leading variable in upward temperature movement and then which was leading in downward movements?