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Comment by prpl | Hacker News Reader

no mention of the Hunga Tonga–Hunga Ha'apai eruption?

It sounds like that eruption at least changed atmospheric composition by throwing tons of water into it.

https://link.springer.com/article/10.1007/s00376-022-2034-1

Unlikely. At least a single volcanic eruption is not enough to change the long-term climate trend, you need a clusters of eruptions to persist through centuries for that. HTHH will likely decrease the global mean surface temperatures by 0.004°C in the first year.

Compared to that human activity is a thousand times more significant, everything else is statistical noise next to it, which at least means that it is easy to spot.

> At least a single volcanic eruption is not enough to change the long-term climate trend, you need a clusters of eruptions to persist through centuries for that.

https://en.m.wikipedia.org/wiki/1883_eruption_of_Krakatoa

“ The eruption caused a volcanic winter.[17] In the year following the eruption, average Northern Hemisphere summer temperatures fell by 0.4 °C (0.72 °F).[18] The record rainfall that hit Southern California during the water year from July 1883 to June 1884 – Los Angeles received 970 millimetres (38.18 in) and San Diego 660 millimetres (25.97 in)[19] – has been attributed to the Krakatoa eruption.[20] There was no El Niño during that period as is normal when heavy rain occurs in Southern California,[21] but many scientists doubt that there was a causal relationship.[22]

The eruption injected an unusually large amount of sulfur dioxide (SO2) gas high into the stratosphere, which was subsequently transported by high-level winds all over the planet. This led to a global increase in sulfuric acid (H2SO4) concentration in high-level cirrus clouds. The resulting increase in cloud reflectivity (or albedo) reflected more incoming light from the sun than usual, and cooled the entire planet until the sulfur fell to the ground as acid precipitation.[23] “.

Yes, I’m aware of “but many scientists doubt that there was a causal relationship” regarding the rain but the climate has been affected by a single eruption.

Also https://en.wikipedia.org/wiki/Year_Without_a_Summer with Mount Tambora

There's good evidence this has happened multiple times in history by a single eruption.

That was the consequence of at least two eruptions, one of which emitted up to 60 Tg of sulphur dioxide. HTHH only emitted 0.4 Tg.

It is not impossible that HTHH affected the monsoon, but there is a thousand pound elephant in the room that will make it's effect hard to quantify.

GP said "long-term climate trend" and then mentioned centuries. Yes, an especially large eruption can influence things for a year or two. But then the effect settles out.

Well this flooding is occurring 8 months after the eruption mentioned so it seems a reasonable question to ask.

Ah, fair. A single eruption will not perturb the long-term trend, but we're discussing the short-term incident in Pakistan, and a single eruption can have notable short-term impact. (I don't know anything about whether the specific eruption in question could have any impact on this specific crisis in Pakistan.)

Human activity is responsible for less than 5% of greenhouse gasses. One eruption can spew decades worth of gases into the air

This is misinformation. Volcanoes are responsible for less than 0.5 Gt of the global CO2 emissions a year. That's a bit less than the 50 Gt we are responsible for. Volcanoes and solar flares would have caused a slight cooling in the last 100 years, not a sharp warming we are experiencing.

There is a natural carbon cycle, which is quite balanced in that there is barely any radiative forcing, which is the difference between how much energy enters the atmosphere and how much of it leaves. Human activity amounts to all, I repeat all of the radiative forcing in the last century, and more actually, because naturally there would have been negative forcing.

It’s not misinformation. We don’t have major eruptions every year. And only 5% of annual carbon emissions are anthropomorphic.

I agree humans are responsible for increasing CO2, but not because of emissions. The earth should act as a buffered system, with utility of atmospheric carbon rising with carbon levels.

There’s another paper in nature describing how the mass slaughter of baleen whales broke the iron cycle at the poles. Mass whale poop fed the krill who are critical to fixing iron…the high iron krill poop is what feeds the plankton blooms. Polar plankton was critical to sinking excess atmospheric carbon.

It's misinformation because the natural carbon cycle adds and removes CO2 that keeps a balance. Around 750 Gt of carbon moves through the carbon cycle each year, and the keyword here is that it moves through. The natural emissions are always counterbalanced. The biological pump is one of the most important part of this system, which evolved to work like this.

Unfortunately as it turns out this system can't cope with the extra emissions. Most of it is still absorbed, but a lot of it lingers in the atmosphere, causing trouble. Even the oceans have trouble absorbing the extra emissions. They now threaten the biological pump itself.

This is why people are so depressed when it comes to climate change, because never mind the greenhouse effect, which is in itself substantial, but once you screw with things like the biological pump there is no telling what will happen. This is a big, fine-tuned system, not unlike a spaceship. It is very risky to poke it. Granted it is likely that the system will snap back into working conditions in a few million years, but that's not exactly reassuring for us.

The krill - whale poop cycle was the fertilizer that fed the mass algae blooms in the Arctic that sink increasing emissions. That’s the point. It isnt burning fossil fuels that is the problem… it’s the fact that polar algae is way below normal levels because of a lack of nutrients due to the lack of baleen whales

https://www.academia.edu/314989/Southern_Ocean_iron_fertiliz...

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4254789/

Not directly, though I can't guess at indirect effects. If 100% of the water from that landed in the flooded area of Pakistan, it would've only added 2.6 mm:

http://www.wolframalpha.com/input/?i=146%20million%20cubic%2...

I had only been alluding to indirect effects - an increase in the greenhouse effect, which certainly would raise temperatures (and increase the amount water air can hold).

I think we will find that, even during an increase in anomalous years from climate change, 2022-2023 will be anomalous.

In that case I certainly wouldn't be surprised either way. IIRC the altitude of the water makes a difference.

Do you have any sources that discuss this?

The undersea eruption also ejected 146 million tons of South Pacific Ocean water into the stratosphere.[56] The amount of water vapor ejected was 10 percent of the atmosphere's typical stock.[57] It was enough to temporarily warm the surface of Earth. This water vapour was estimated to remain for 5–10 years.[55]

https://en.wikipedia.org/wiki/2022_Hunga_Tonga%E2%80%93Hunga...

Interesting as water vapour is in itself also a greenhouse gas.

Thanks for sharing this. That certainly is a lot of water.

10% of the stratosphere's typical stock.

If true, the article should be changed. Isn't the stratosphere extremely dry?

Yes, that's why a single eruption can have a noticeable effect.

Stratospheric water may also set the upper limit on how many launches to orbit can be done per year, since all the propellant consumed in or above the stratosphere makes water that ends up in the stratosphere.

How would it limit launches?

You would not want to make so many launches that it perturbed the climate, due to water vapor increase in the stratosphere. We are nowhere close to this happening yet at current launch rates, btw.

Here's a practical examination of what effect the 10% increase in stratospheric water vapor caused by the eruption has on global weather: https://www.severe-weather.eu/global-weather/cold-anomaly-st...

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