evidence: The global volcanic CO2 flux in modern Earth remains inadequately known11,12 and, ironically, is less constrained for subaerial volcanoes than for the less-accessible mid-ocean ridges, for which the 3He flux13 or the CO2/Ba ratio14 proxies have successfully been applied. Direct volcanic CO2 observations at subaerial volcanoes are technically challenging from both ground11,15 and space16 due to the large atmospheric CO2 burden, and thus remain limited in number17,18. The volcanic CO2 flux can be quantified indirectly by combining simultaneous acquisitions of UV-sensed sulphur dioxide (SO2) fluxes11,15,19,20 and gas compositions (CO2/SO2 ratios), but gas observational networks are still in a developing stage21,22, resulting in sparse and incomplete gas catalogues23,24. CO2 flux data have so far been obtained11,15 for only <60 of the several hundred currently degassing Holocene volcanoes25. CO2 flux records are continuous enough only for a few (<10) volcanoes where permanent instrumentation is operating26,27,28,29, while sparse results (one or a few campaign-style measurements at most) are available for the remaining ~50. In addition, scarce or even no information exists for several top-ranking degassing volcanoes30 in remote regions of the world (e.g., Vanuatu31, Papua New Guinea, the Solomon arc, and the Sunda-Banda arc in Indonesia32,33). [...] Pérez, N. M. et al. Global CO2 emission from volcanic lakes. Geology39, 235–238, https://doi.org/10.1130/G31586.1 (2011).