The title is also misleading in that the paper (https://www.pnas.org/doi/10.1073/pnas.2319652121) doesn't claim to determine when the fastest rates of CO2 rise have been. In fact, it starts by saying cores generally can only support analysis of durations >100 years.

I take note of this because I've looked at this problem before and agree that core samples have a hard time supporting claims like "most in the previous XXkya" when compared with the last few decades, be it CO2, CH4, avg temp d02, etc.

Starting with layers as recent as 30kya, the age of the trapped gas often spans multiple centuries, and so e.g. you'd be averaging out point outgassing from even very large volcanoes well beyond detectability. Beyond 50-60kya, the layer durations are all in the few millennia range.

Here's my analysis worksheet:

https://docs.google.com/spreadsheets/d/1p793c3NZFp2e80ufqyJK...

Reference data: Antarctic Ice Core 155,000 Year CO2 and Gas Stable Isotope Data - Eggleston, S.; Schmitt, J.; Bereiter, B.; Schneider, R.; Fischer, H. 2016. Evolution of the stable carbon isotope composition of atmospheric CO2 over the last glacial cycle. Paleoceanography, 31. doi: 10.1002/2015PA002874 https://www.ncei.noaa.gov/access/paleo-search/study/19942

Humans are "natural". Many species have overpopulated and overused the resources they need to survive and eventually became extinct, we are extremely natural.

Two possible takes on "natural":

1. They may mean "in nature", that is, not inside a building, and not even in a city (both of which would tend to give higher numbers).

2. They may mean "using something in nature as a measuring method" - in this case, Antarctic ice.

I agree that it's a confusing/misleading term.