Simple definition of carbon dating
In point of fact, the total worldwide estimate of roughly 55 Mt Cpa is by one researcher, rather than "scientists" in general.
More importantly, this estimate by Gerlach (1991) is based on emission measurements taken from only seven subaerial volcanoes and three hydrothermal vent sites.
If we neglect to ask how the greenhouse effect of various gases is quantified in terms of real, measurable thermodynamic properties, the idea of anthropogenic global warming may well survive long enough for us to ask how the carbon budget establishes that observed increases in CO is one of the lightest volatiles (materials of relatively low melting point), found in the mantle (Wilson, 1989).
The fluid nature of the aesthenosphere, or upper mantle of the earth, ensures that lighter volatiles are fractionated, buoyed towards the surface, and either extruded or outgassed into the atmosphere via volcanoes and faults.
For example, Cape Kumukahi is located in a volcanically active province in Eastern Hawaii, while Mauna Loa Observatory is on Mauna Loa, an active volcano - both observatories within 50km of the highly active Kilauea and its permanent 3.2 Mt COpa plume.
Samoa is within 50 km of the active volcanoes Savai'i and/or Upolo, while Kermandec Island observatory is located within 10 km of the active Raoul Island volcano.
To make matters worse, the reported output of any individual volcano is itself an estimate based on limited rather than complete measurement.
One may reasonably assume that in each case, such estimates are based on a representative and statistically significant quantity of empirical measurements.
This estimate includes both subaerial and submarine volcanoes, about in equal amounts.
Giggenbach et al., 1991), which can be cut by fracture zones that consequently provide a path to the surface (Morner & Etiope, 2002).
This may raise doubts concerning measurements taken at the La Jolla observatory, which is located near the focal point of a radial fault zone extending seaward from the San Andreas Fault (see imagery sourced to SIO, NOAA, USN, NGA, & GEBCO by Europa Technologies & Inegi, for Google Earth).
The same potential problem exists with the observatory at Alert in Northern Canada, because it is located inside the circumpolar wind zone along with the Arctic Rift and thousands of venting seamounts along key parts of the Northwest Passage.
That leaves us with Point Barrow, arguably the only CO measurements are unlikely to be influenced by magmatic gas plumes.