> Doesn't Mauna Loa spew CO2 by the metric ton on a regular basis?

The 1960-present chart in the article is anything but regular, instead showing a steady rise, and doesn't appear to blip up for either the 1984 or 2022 eruptions.

historical reasons. volcano aside the location is reasonable: altitude and relative isolation from human sources wothout being too out of the way to make maintenance a bear. hawaiian trade winds help with dispersal.

as for volcanism Supposedly it's in a rock creche on the mountain face facing away from the volcano, but you're right to be suspicious.

It's high up in the atmosphere and has relatively few nearby point sources like cities since it's in the middle of the Pacific ocean. It's a unique environment that provides a valuable data point.

Clean wind from the pacific is captured at the observation tower. Another point like it is Cape Grim Tassie which gets clean wind from the southern ocean.

Both of these points observe vastly cleaner air and provide that baseline.

Maybe they’ve thought about this and measure that too? Maybe they can adjust measurements based on data from multiple sensors?

https://gml.noaa.gov/obop/mlo/programs/esrl/volcanicco2/volc...

You're thinking of Mauna Kea, which is some distance - both horizontally and vertically - from Mauna Loa.