As may know, temperature dips are often attributed to volcanic eruptions. Fuego just erupted. The BBC reports ash flew up as high as 6 km. This is evidently larger than the mid-70s eruption that caused the dip I discussed a while back, see below. The figure only shows forcings, but temperature are known to be affected.
Those who think those swings “just happen”, or might be caused by El Nino or La Nina have probably never compared the big dips to the periods when major stratospheric volcanic eruptions occurred. These were discussed a while back and shown below:
You can scan up and down and begin to notice that, yes, as we have all heard, major stratospheric volcanic eruptions affect the global mean surface temperature. In fact, part of the proof that GCM’s are able to predict some variations in GMST arising from variations in forcings is that they do predict these the dip in temperature after eruption like Pinatubo.
The phenomenology is understood: After a major stratospheric volcanic eruption, the stratosphere fills with aerosols. Radiative forcing decreases, and the global surface temperature drops for a while. Not surprisingly, 7 year trends with their start dates roughly 7 years or less before the eruption tend to dip.
I guess we’ll see what happens this year.
A magnitude 5.5 earthquake shook the Kilauea summit, resulting in an ash plume that reached up to 8,000 feet, according to Hawaii County Civil Defense.
Jan 24, 2018 – The most active volcano in the Philippines, called Mayon, is in danger of a major eruption. It’s been spewing ash for two weeks, and, starting .
Jan 14, 2018 -The Kadovar Island volcano was thought to be dormant before it started erupting.
Mar 22, 2018 – italy active volcano READY TO BLOW: The Campi Flegrei supervolcano in Naples is showing signs of ‘reawakening’.
They always occur when the global temperature is falling and seem to occur after the temperature falls.
Perhaps the ground freezes more, loses it’s ability to flex and hence causes pressure to build up.
Others relate it to the moon [has been full the last week].
Only joking but there has been a little bit more observed activity lately.
Huh. I thought it was Trump’s fault.
( / sillytag )
I don’t think the ground is freezing in either Guatemala or Hawaii. At least not if “freezing” means the water in the ground becomes ice!
Perhaps there is more activity recently. I don’t really know.
A supervolcano “reawakening” is a bit scary.
It will be interesting to see how/if the eruption in Guatemala influences solar intensity at MLO in Hawaii (where there is a good record since the late 1950’s IIRC), and even more interesting to see if there is a switch to El Nino conditions (as appears to have happened following major eruptions).
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In the mean time, I am on Cape Cod…. 53F and rain at mid-day… very unpleasant for we weak Floridians.
I gather that the impact is pretty much gone in 7-10 years, but what’s the average time (roughly) for cooling to peak after an eruption?
(I know, I could go figure this out. I probably ought to. Just asking in case anyone happens to know off the top of their head)
[Edit: Eyeballing the graphs, looks like a couple of years to me I suppose. My visual estimation skills aren’t the greatest though.]
Lucia wrote: “You can scan up and down and begin to notice that, yes, as we have all heard, major stratospheric volcanic eruptions affect the global mean surface temperature.”
But the graphs don’t show temperature (although I can’t tell what is shown in the second graph). In my experience, it is not so easy to spot eruptions in the global temperature record.
I seem to recall that the modeled cooling tends to be greater than observed cooling.
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Mark Bofill (Comment #168280): “I gather that the impact is pretty much gone in 7-10 years, but what’s the average time (roughly) for cooling to peak after an eruption?”
The stratospheric aerosol decays with a lifetime a bit over one year. Given the heat capacity of the surface ocean, I think the pick cooling is after about one year.
I think the easiest one to spot is the 1991 Mt. Pinatubo eruption. That was June 15, 1991. The UAH global LT temp was well below average from July, 1992 to April, 1993. The absolute minimum anomaly of -0.45 was in August, 1992, but the data is noisy and there was an anomaly of -0.43 as late as March, 1993. It’s a little better defined in the UAH NH anomaly, which was at a minimum of -0.6 in July, 1992. So about a year.
The UAH stratospheric anomaly peak was split between September and October, 1991 at 1.52 and 1.56 respectively. So we should have some idea on the relative size compared to Pinatubo in about three months from MLO aerosol density and satellite stratospheric temperature.
DeWitt,
The Pinatubo cooling was partially masked by a concurrent shift to El Nino conditions (which normally increases average global temperature by about 0.2C). Whether the shift to El Nino conditions was caused by Pinatubo is an interesting question. If there is a significant drop in tropical surface radiation due to stratospheric aerosols, one might reasonably expect the (tropical thunderstorm driven) Hadley circulation to weaken, thus weakening tropical easterlies and bringing on El Nino. That doesn’t mean it is true, just that it is plausible.
SteveF,
The unsmoothed data looks something like a double dip, which could be explained by an El Nino in the middle keeping the temperature from dropping as much as it might have.
DeWitt Payne (Comment #168288): “I think the easiest one to spot is the 1991 Mt. Pinatubo eruption.”
Sure, if you know it is supposed to be there, you can see it. But could you spot the volcano, just from the data? How can you tell that the dip centered around Aug. 1992 was a volcano but that the somewhat smaller dip centered around Feb. 1989 was not a volcano?
Mike M.,
There’s no peak in the stratosphere anomaly in 1989. That’s how you know it’s a volcanic eruption and not, say, a La Nina. But yes, looking at only the lower troposphere or surface anomaly, the cause isn’t obvious.
Thanks Mike M.
“Modeled” anything tends to be greater than “actual” anything.
DeWitt Payne (Comment #168293): “There’s no peak in the stratosphere anomaly in 1989. That’s how you know it’s a volcanic eruption and not, say, a La Nina.”
I did not know that. In the context of lucia’s post, that is close to saying “we know it wasn’t a volcano sine there were no eruptions then”.
Why does a volcano produce a rise in stratospheric temperature? Sulfuric acid particle don’t absorb light, they scatter it.
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Lucia wrote: “You can scan up and down and begin to notice that, yes, as we have all heard, major stratospheric volcanic eruptions affect the global mean surface temperature.â€
And: “In fact, part of the proof that GCM’s are able to predict some variations in GMST arising from variations in forcings is that they do predict these the dip in temperature after eruption like Pinatubo.”
I still think that those statements overstate the case.
Mike M,
“Why does a volcano produce a rise in stratospheric temperature? Sulfuric acid particle don’t absorb light, they scatter it.”
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Sulfuric acid droplets do have absorbance in the near infra-red (and there’s plenty of solar energy in the NIR; https://commons.wikimedia.org/wiki/File:Solar_Spectrum.png). See also: “Vibrational and Electronic Spectroscopy of Sulfuric Acid Vapor”
Paul E. Hintze†, Henrik G. Kjaergaard‡, Veronica Vaida*†, and James B. Burkholder.
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Stratospheric aerosols do of course also scatter light.
Mike M.,
Yes. It’s sort of like saying that models are good because they more or less reproduce the global temperature anomaly during the instrumental period. That is a pass/fail test, not a useful measure of goodness or utility.
“The BBC reports ash flew up as high as 6 km.”
That’s nowhere near high enough to get into the stratosphere. We ought to expect the Fuego eruption should have next to no impact on global temperatures on that basis.
TimTheToolMan (Comment #168678): “That’s nowhere near high enough to get into the stratosphere. We ought to expect the Fuego eruption should have next to no impact on global temperatures on that basis.”
The climate effects are not due to ash, since that falls out of the atmosphere quite quickly. It is SO2 gas injected into the stratosphere that affects climate. That gets oxidized and forms tiny sulfuric acid particles that have a lot of surface area and remain in the stratosphere for a long time.
MikeM–
He’s right that we expect the really big impacts from stratospheric. But — evidently– Fuego’s eruption in the 70s had an effect in models. That was a smaller eruption. So…. dunno.
Also… maybe I mistyped the height…
https://en.wikipedia.org/wiki/2018_Volc%C3%A1n_de_Fuego_eruption
That’s got it at 15 km. Stratosphere at the equator is (evidently) 16 km. So…. We’ll see.
DeWitt Payne: ” …. but the data is noisy ….”
Volcanic eruptions such as Mt. Pinatubo are noisy. Mother Nature made them that way to keep the natives restless and constantly on their guard.
lucia: “That’s got it at 15 km. Stratosphere at the equator is (evidently) 16 km. So…. We’ll see.”
OK. The tropopause is a range, not a single height and might be affected by the volcanic eruption column. https://en.wikipedia.org/wiki/Eruption_column#Column_heights
“Eruption columns with heights of over 20–40 km (12–25 mi) break through the tropopause and inject particulates into the stratosphere.”
So maybe this one won’t do much. The peak aerosol concentration occurs about month after an eruption, so we should know fairly soon.
Lucia writes “Also… maybe I mistyped the height…”
According to the site below, they state “During 16-19 June as many as seven explosions per hour produced ash plumes that rose as high as 1.2 km above the crater and drifted as far as 15 km W, SW, and S.”
https://volcano.si.edu/volcano.cfm?vn=342090
The crater is about 3763m high.
And the website goes on to give a reasonably detailed historical table of ash plume heights and drift distances. One might wonder whether the wiki editors have mixed up height with horizontal drift.
Additionally there is an “emissions history” tab giving assumed SO2 emissions heights and they’re all well below the stratosphere too. The highest was in 2012 at 8km. The most recent figure in that table is 2016, though.
None of that points to stratospheric injection of aerosols from Fuego. I’ll be interested to see whether its mentioned as a reason for cooling in the future.
TTTM,
Weird. I wrote this on June 4 and your site reports what happened between 16-19. I must be psychic….
Seriously, there seem to be conflicting reports. Wikipedia is generally reliable for non-controversial things (like the date a volcano erupted!)
TTTM,
This (at the site you give) gives weekly detail
https://volcano.si.edu/volcano.cfm?vn=342090#June2018
Definitely nothing as high as Wikipedia says.
Good! Now models can still be tested. 🙂
Lucia writes “Good! Now models can still be tested.”
…and we’ll see whether they’re tuned to the wiki values or volcano.si.edu 😉
June satellite temperature data is out. No spike in stratosphere temperature yet, but it’s still early. August and September should tell the tale.