This is an incredibly misleading use of graph axes.<p>The baseline should be 200000 ppm, but a change of 500 wouldn't be noticeable. So they just show the change from a recent year, which lets them baseline at zero.
<a href="https://www.co2levels.org/" rel="nofollow">https://www.co2levels.org/</a> (same source, apparently) shows the amount of CO2 from 1990 until now has gone from about 355 ppm to 420 ppm, so 65 ppm. Each CO2 binds an O2, so I guess that could account for 65 ppm of the "missing" oxygen.
I wonder if humanity's cognitive levels have been affected? [1]<p>[1] <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4107523/" rel="nofollow">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4107523/</a>