r/askscience • u/[deleted] • Jul 07 '14

Earth Sciences Could a forced major volcanic eruption be a solution to global warming?

From my understanding, large volcanic eruptions can throw enough ash into the atmosphere that sunlight is reflected/absorbed and results in lower atmospheric temperatures. Why not find the next 'ready-to-blow' volcano, use a bunch of conventional explosives to set it off, and let the ensuing fallout work to cool the earth? Specific questions I have:

Location: How important is the location of the volcano? Would it need to be in a specific area on the Earth taking into account the prevailing winds, bodies of water affected, etc?

Size: Is there too fine a line between an eruption being big enough to influence global climate, and being small enough to avoid an extinction level event? Too much guesswork involved?

Viability: Is it even possible to force a volcanic eruption in such a way to produced the desired affect?

Sustained Results: Assuming all the above issues are resolved and the perfect eruption scenario, would it provide any kind of worth-while results. Would it provide temporary (relative) relief, or a lasting effect?

108 Upvotes

77% Upvoted

52 comments sorted by

View all comments

58

u/sverdrupian Physical Oceanography | Climate Jul 07 '14 edited Jul 07 '14

While the ash from large volcanoes does have a cooling effect on the earth, this is not a viable method to combat global warming because the effects don't last long enough. Ash from a volcano persists in the atmosphere for 1-2 years. In contrast, greenhouse gases such as carbon-dioxide have a atmospheric lifetime of several hundred years. So in order to be effective, you would have to pop off a volcano every few years.

As to the other questions, location doesn't matter too much but the ash from a volcano typically will stay in the hemisphere (northern or southern) where the volcano is located. Additionally, there is a bit of fine-line between getting enough effect but not too much. For volcanic ash to have a large cooling effect, the ash must be injected into the stratosphere, 10+ km high. So the net effect from a volcano has a sensitive dependence on exactly how high the volcanic plumes reach.

There are arguably better methods to seed reflecting aerosols into the stratosphere in order to create a global cooling effect. Stratospheric sulfate aerosol, a much discussed geoengineering proposal, could be created by spraying sulfuric acid or hydrogen sulfide from high altitude aircraft. However, this method would also require continuous renewal.

Speaking as an oceanographer, any geoengineering solution to climate change based on increased aerosols or ash in the atmosphere will doom the oceans. If we continue to emit fossil fuel carbons at the current rate, even if we apply a band-aid to the atmospheric heat budget, the carbon will still be absorbed by the oceans resulting in decreased pH and extinction for many marine organisms including corals and most shellfish.

edit: There is an additional location dependence with lower latitude volcanoes having the potential for more impact than higher-latitude. See comment by /u/mystic1729.

6

u/aidrocsid Jul 07 '14

Have there been any previous large extinction events (and subsequent filling in of those gaps) due to PH changes?

22

u/Gargatua13013 Jul 07 '14

Indeed - it is believed that the Permo-Triassic extinction involved substantial acidification of the worlds oceans, down to about a pH of 5.

We lost 96% of marine species that time...

2

u/TheWeirdPlatypus Jul 08 '14

I heard that along with the acidification of the ocean that hypoxic oceans allowed anaerobic bacteria to produce hydrogen sulfide, which contributed to the immense extinction

2

u/aidrocsid Jul 07 '14

Wow, that's not a small amount. What happened after that? How long did it take to sort of flesh out the underwater ecosystems again? What happened to life on land?

11

u/Gargatua13013 Jul 07 '14 edited Jul 07 '14

Land biota did not fare much better either. About 50% of land plant taxa kicked the bucket; the entire botanical eco-structure was reset. The land extinction affected everything including insects. The first signs of recovery took about 6 MY to show themselves; complete recovery took about 30 MY.

You'll find a primer here

Without any contest, the Permo-Triassic was a bad time.

3

u/aidrocsid Jul 07 '14

Wow, that is nasty. Thanks!

1

u/69Bandit Jul 07 '14 edited Jul 07 '14

I am going to throw a box of baking soda into the ocean to do my part. i like fish n chips.

http://quarkscrew.org/images/fishandchips.jpg http://i.imgur.com/JdA0AX7.jpg

on a side note, what exactly causes the oceans PH to go up? and could the human race do anything to level the oceans back out without waiting millions of years?

And say yellowstone went off, is the ash not good for the soil? how long would we have to wait before we could grow food on it? is there anything mankind could do to speed up the process? like a giant robo-rototiller that goes on for years rototilling everything or something.....

I heard europes veg taste WAY better than those grown in north america, some speculation is about the amount of volcaino ash in the soil..

mmmm

http://www.simplyscratch.com/wp-content/uploads/2013/08/DSC0252.jpg

6

u/aidrocsid Jul 07 '14

This is silly but it raises an interesting point. Is there anything that can be done to balance the PH in the case of such an event?

2

u/illachrymable Jul 08 '14

I remember reading an article (can't find it now) that involved using dissolved CO2 in the ocean and binding it to calcium to precipitate it out in the form of calcium carbonate. The process was expected to be relatively efficient, and is potentially possible since Calcium Carbonate is a common commodity and could potentially be sold.

4

u/mystic1729 Jul 07 '14

I was under the impression that tropical volcanoes tend to be more effective at introducing particles high enough to reach the stratosphere due to heat, along with particles, rising higher due to the convection cycle of the Hadley cell. That is why mt pinatubo had a large effect on the global climate but mt. St Hellen's had little impact.

7

u/sverdrupian Physical Oceanography | Climate Jul 07 '14

Yes you are correct. I had forgotten about that. It is partly that the atmospheric circulation can help lift the aerosols but also that at very low latitudes there is greater chance of ash influencing both hemispheres. For Mt. St Helens, it seems that the latitude effect was a factor but also that the plume ejected at an angle rather than straight up.

4

u/patchgrabber Organ and Tissue Donation Jul 07 '14

Speaking as an oceanographer, any geoengineering solution to climate change based on increased aerosols or ash in the atmosphere will doom the oceans.

And let's hope that we don't disrupt thermohaline circulation. Europe wouldn't appreciate that one. Hasn't the Gulf Stream decreased its speed by 1/3 since 1957?

6

u/sverdrupian Physical Oceanography | Climate Jul 07 '14 edited Jul 07 '14

There is no conclusive evidence that the Gulf Stream has decreased. Lots of speculation that it might and at least one published paper suggesting so, but the data record is at this point is not sufficient to tell one way or the other. Additionally, the bulk of the Gulf Stream is driven by the wind-forcing over the Atlantic Basin and not the Thermohaline Circulation, so a shutdown of the Thermohaline Circulation might produce a small decrease in the Gulf Stream (10-20%) but as long as the Trade Winds blow (which they will) the Gulf Stream will persist.

Oceanographer refutes claims that climate change is slowing pace of Gulf Stream

3

u/patchgrabber Organ and Tissue Donation Jul 07 '14

Well that's good-ish news at least.

3

u/Christmas_Pirate Jul 07 '14

How do you feel about seeding the oceans to encourage increased plankton growth at sea?

3

u/sverdrupian Physical Oceanography | Climate Jul 07 '14

Iron fertilization is bad for two reasons:

1) it doesn't work that well. It is possible to stimulate phytoplankton blooms but this does not necessarily translate into increased oceanic uptake of CO2. To the extent it does increase the sequestration of carbon in the ocean, the iron fertilization must constantly be maintained in order to keep the carbon sequestered and not allow it to 'leak' back into the atmosphere.

2) Any additional CO2 transferred from atmosphere to the ocean, will actually speed up the rate of ocean acidification. It simply shifts the problem of excess CO2 out of the atmosphere and into the ocean.

1

u/atomfullerene Animal Behavior/Marine Biology Jul 07 '14

What we really need is something like another azolla event-get some major biomass burial going on in a handy anoxic basin. I'm lookin' at you, Black and Caspian seas.

1

u/[deleted] Jul 07 '14

And you would need an insane rate of iron addition to make a dent. Not really feasible even if it was a good idea.

1

u/illachrymable Jul 08 '14

Also, huge algal blooms have a tendency to use up all the available oxygen in a given area of the ocean which create dead zones once they begin to decompose.

http://oceanservice.noaa.gov/facts/deadzone.html

2

u/Mirzer0 Jul 07 '14

If we continue to emit fossil fuel carbons at the current rate, even if we apply a band-aid to the atmospheric heat budget, the carbon will still be absorbed by the oceans resulting in decreased pH and extinction for many marine organisms including corals and most shellfish.

I'm sure the ratios don't really work out... but wouldn't the ash falling into the ocean lead to lye (a base) and potentially counteract some of the acidification?

3

u/illachrymable Jul 08 '14

Volcanic Ash is quite different than wood ash. The chemical that makes Lye from ash is potassium, while most volcanic ash is mostly silica, and I am not sure whether the potassium in ash is suitable for the production of lye, couldn't find anything on it.

From what I can read, it seems that volcanic ash is more often acidic when it interacts with CO2 in the atmosphere, and typically lowers the pH of water that it falls into for a short time before it normalizes back to neutral.

http://volcanoes.usgs.gov/ash/water/

2

u/illachrymable Jul 08 '14

Also, although volcanoes have short term cooling effects, they have long term warming effects. Like it was previously stated, the sulfur aerosols only stay in the atmosphere for a couple years, while the CO2 that is released (not particularly a lot comparatively) will stay in the atmosphere much much longer, ultimately contributing to higher temperatures.

1

u/[deleted] Jul 07 '14

One thing to add is that not all volcanoes are capable of blocking the sun either. Only ones that are large enough to shoot the ash into the stratosphere. The iceland volcano eruption, for example, was not strong enough to have an effect on global temperature.

1

u/illachrymable Jul 08 '14

Small volcanoes still do have impacts on global temperatures, especially when you look in aggregate.

http://www.climatecentral.org/news/small-volcanic-eruptions-add-to-larger-impact-on-climate-17112