<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.
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.
I've never found a CO2 estimate, but did find that it's a significant amount of that mass, as is SO2.
It wasn't worth me doing more of a sketch since it's not clear how to model the effects of such a massive system.
I was struck tho, that the magnitude of this and a few other events in the not too distant past, are vastly larger than even all put nuclear war
It's not clear to me that our CO2 emissions are very significant in comparison