[wheelerof4te]

"75,000 years ago: Toba Volcano supereruption that may have contributed to human populations being lowered to about 15,000 people."

The key question is: How much CO2 did that super-eruption emit into the atmosphere?

In our hurry to attribute climate change to our meager impact on this planet, we tend to forget what horrors an eruption of this magnitude can cause. And who knows how many of them happened during the past millennia.

[pmayrgundter]

The figure I've found is 2800 km^3 of approximately granite, which at 2.7 tonnes per cubic meter gives about a billion gigatons ejecta.

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

[dredmorbius]

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...>

[pmayrgundter]

Good finds. Thanks!

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.

[dredmorbius]

DRE == dense rock equivalent:

<https://en.wikipedia.org/wiki/Dense-rock_equivalent>

[pmayrgundter]

Math glitch. It was a million gigatons DRE, so 1000 Gt CO2

[FireBeyond]

I think people struggle with the magnitude.

Mt St Helens, for example. Not the largest eruption.

But a landslide of approximately 2.5km^3 (over 3 billion cubic yards).

Okay, some say, so that is a lot of earth...

and then you learn that the landslide was moving at speeds of up to 160mph.

That's a LOT of energy.

[wheelerof4te]

It sure is. And we've yet to survive our modern-day supervulcano eruption.

[groby_b]

"And who knows how many of them happened during the past millennia.

Geologists. And the answer is "none" for the past 25 or so millenia, and "one" since Toba.

Also, unless you've had supervolcanoes go off in your bedroom and didn't tell anybody, the evidence for human impact is exceedingly clear.

[wheelerof4te]

"Geologists."

Geologists might know, same as astronomers might know what Black Holes and Pulsars really are.

On the other hand, it is a geologist's call to search for answers and for truth. Saying that they truly know is the same as saying nothing.

[mschuster91]

> And who knows how many of them happened during the past millennia.

We at least have a significantly large list of what we know [1] - that's part of the purpose of core drilling, the ash deposits worldwide can be linked together to estimate where ash traveled to. Also, craters and their surrounding can be drilled into to determine eruption events.

[1] https://en.wikipedia.org/wiki/List_of_large_volcanic_eruptio...

[pmayrgundter]

Here's a study:

The size and frequency of the largest explosive eruptions on Earth, Mason 2004

https://www.researchgate.net/publication/227000709_The_size_...

[sci_prog]

Not even close to what we as humans emit. The rate of the global annual natural CO2 emissions are 1-2 orders of magnitude slower than anthropogenic emissions.

[saltymug76]

If you're trying to minimize human caused warming with the rare eruption of super volcanoes, it's pretty weak.

[wheelerof4te]

Where is the evidence of human effect on the climate change? There is a huge effect on pollution, but hardly any on the global climate.

[saltymug76]

Considering the rapid rise in temperature on a relatively miniscule geological timescale, I'd be more interested to see evidence that it's not a manmade phenomenon.

[wheelerof4te]

There's a huge increase of human population living in very large cities, when compared to 100 years ago. Especially in China and India.

Of course the people will feel the local rise of temperature in asphalt-ridden and industry-polluted streets. It's logical.

This does not mean that global climate has changed.

[staunton]

Volcanoes aren't about the CO2, they're about the ash which blocks out the sun and makes it colder.