| Wikipedia cites a range of 2,000 -- 13,000 km^3. <https://en.wikipedia.org/wiki/List_of_largest_volcanic_erupt...> As for the gaseous component of ejecta: Water vapour is consistently the most abundant volcanic gas, normally comprising more than 60% of total emissions. Carbon dioxide typically accounts for 10 to 40% of emissions. <https://en.wikipedia.org/wiki/Volcanic_gas> Citing: H. Sigurdsson et al. (2000) Encyclopedia of Volcanoes, San Diego, Academic Press. (Late edit: though I note that this seems to discuss percentages of gaseous emissions, not total ejecta. Anyone have a better source here?) One of the largest volcanic events I'm aware of is the Siberian Traps eruption, about 250 mya, with a volume of about 4 million km^3, another three orders of magnitude greater than Tomba. This has been linked to the Permian–Triassic mass extinction event, with the mechanism being release of methane clathrates and/or stimulating growth of a microbe which released vast quantities of methane into the atmosphere, killing ~81% of all extant marine species and 70% of terrestrial vertebrate species. <https://en.wikipedia.org/wiki/Siberian_Traps> "The level of atmospheric carbon dioxide rose from around 400 ppm to 2,500 ppm with approximately 3,900 to 12,000 gigatonnes of carbon being added to the ocean-atmosphere system during this period." -- Wikipedia, citing Wu, Yuyang; Chu, Daoliang; Tong, Jinnan; Song, Haijun; Dal Corso, Jacopo; Wignall, Paul B.; Song, Huyue; Du, Yong; Cui, Ying (9 April 2021). "Six-fold increase of atmospheric pCO2 during the Permian–Triassic mass extinction". Nature Communications. 12 (1): 2137. Bibcode:2021NatCo..12.2137W. doi:10.1038/s41467-021-22298-7. <https://en.wikipedia.org/wiki/Permian%E2%80%93Triassic_extin...> |
Yeah, it's the comparison between DRE and Gas ejecta that got me bogged down before.
Having now given up, I asked ChatG4. It says "the mass ratio between DRE and gaseous emissions might be on the order of 20:1 to 100:1", no citations ofc.
So, just as a strawman and using your 10-40%, on the low end .01.1 = 0.001, high end .05.4 = 0.02. So .1%-2% of ejecta by mass is CO2 emissions. Hah :)
Using my orig figure for Toba of a billion gigatons of ejecta, of which roughly a million gigatons would be CO2. Correct math?
Human GHG emissions are ~50 Gt/year.