New paper speculates on volcanoes during the Little Ice Age

From NCAR/UCAR, they’re still trying to stamp out solar influence as a potential cause of the Little Ice Age. One of the things I wonder about is that during low sunspot activity, does the reduced solar-magnetic influence have any effect on Earth’s plate tectoncs and vulcanism? Does a reduced solar-magnetic influence prompt more volcanism? We may get the answer to this question in the coming years as the Ap solar-geomagnetic activity index is at an all-time low in the records.

image

Study may answer longstanding questions about Little Ice Age

January 30, 2012

BOULDER — A new international study may answer contentious questions about the onset and persistence of Earth’s Little Ice Age, a period of widespread cooling that lasted for hundreds of years until the late 19th century.

gifford miller

Gifford Miller collects vegetation samples on Baffin Island. (Photo courtesy University of Colorado Boulder.)

The study, led by the University of Colorado Boulder with co-authors at the National Center for Atmospheric Research (NCAR) and other organizations, suggests that an unusual, 50-year-long episode of four massive tropical volcanic eruptions triggered the Little Ice Age between 1275 and 1300 A.D. The persistence of cold summers following the eruptions is best explained by a subsequent expansion of sea ice and a related weakening of Atlantic currents, according to computer simulations conducted for the study.

The study, which used analyses of patterns of dead vegetation, ice and sediment core data, and powerful computer climate models, provides new evidence in a longstanding scientific debate over the onset of the Little Ice Age. Scientists have theorized that the Little Ice Age was caused by decreased summer solar radiation, erupting volcanoes that cooled the planet by ejecting sulfates and other aerosol particles that reflected sunlight back into space, or a combination of the two.

“This is the first time anyone has clearly identified the specific onset of the cold times marking the start of the Little Ice Age,” says lead author Gifford Miller of the University of Colorado Boulder. “We also have provided an understandable climate feedback system that explains how this cold period could be sustained for a long period of time. If the climate system is hit again and again by cold conditions over a relatively short period—in this case, from volcanic eruptions—there appears to be a cumulative cooling effect.”

“Our simulations showed that the volcanic eruptions may have had a profound cooling effect,” says NCAR scientist Bette Otto-Bliesner, a co-author of the study. “The eruptions could have triggered a chain reaction, affecting sea ice and ocean currents in a way that lowered temperatures for centuries.”

The study appears this week in Geophysical Research Letters. The research team includes co-authors from the University of Iceland, the University of California Irvine, and the University of Edinburgh in Scotland. The study was funded in part by the National Science Foundation, NCAR’s sponsor, and the Icelandic Science Foundation.

Far-flung regions of ice

Scientific estimates regarding the onset of the Little Ice Age range from the 13th century to the 16th century, but there is little consensus, Miller says. Although the cooling temperatures may have affected places as far away as South America and China, they were particularly evident in northern Europe. Advancing glaciers in mountain valleys destroyed towns, and paintings from the period depict people ice-skating on the Thames River in London and canals in the Netherlands, places that were ice-free before and after the Little Ice Age.

“The dominant way scientists have defined the Little Ice Age is by the expansion of big valley glaciers in the Alps and in Norway,” says Miller, a fellow at CU’s Institute of Arctic and Alpine Research. “But the time in which European glaciers advanced far enough to demolish villages would have been long after the onset of the cold period.”

Miller and his colleagues radiocarbon-dated roughly 150 samples of dead plant material with roots intact, collected from beneath receding margins of ice caps on Baffin Island in the Canadian Arctic. They found a large cluster of “kill dates” between 1275 and 1300 A.D., indicating the plants had been frozen and engulfed by ice during a relatively sudden event.

The team saw a second spike in plant kill dates at about 1450 A.D., indicating the quick onset of a second major cooling event.

To broaden the study, the researchers analyzed sediment cores from a glacial lake linked to the 367-square-mile Langjökull ice cap in the central highlands of Iceland that reaches nearly a mile high. The annual layers in the cores—which can be reliably dated by using tephra deposits from known historic volcanic eruptions on Iceland going back more than 1,000 years—suddenly became thicker in the late 13th century and again in the 15th century due to increased erosion caused by the expansion of the ice cap as the climate cooled.

“That showed us the signal we got from Baffin Island was not just a local signal, it was a North Atlantic signal,” Miller says. “This gave us a great deal more confidence that there was a major perturbation to the Northern Hemisphere climate near the end of the 13th century.”

The team used the Community Climate System Model, which was developed by scientists at NCAR and the Department of Energy with colleagues at other organizations, to test the effects of volcanic cooling on Arctic sea ice extent and mass. The model, which simulated various sea ice conditions from about 1150 to 1700 A.D., showed several large, closely spaced eruptions could have cooled the Northern Hemisphere enough to trigger the expansion of Arctic sea ice.

The model showed that sustained cooling from volcanoes would have sent some of the expanding Arctic sea ice down along the eastern coast of Greenland until it eventually melted in the North Atlantic. Since sea ice contains almost no salt, when it melted the surface water became less dense, preventing it from mixing with deeper North Atlantic water. This weakened heat transport back to the Arctic and created a self-sustaining feedback on the sea ice long after the effects of the volcanic aerosols subsided, according to the simulations.

The researchers set solar radiation at a constant level in the climate models. The simulations indicated that the Little Ice Age likely would have occurred without decreased summer solar radiation at the time, Miller says.

About the article

Title: Abrupt onset of the Little Ice Age triggered by volcanism and sustained by sea-ice/ocean feedbacks

Authors: Gifford Miller, Áslaug Geirsdóttir, Yafang Zhong, Darren J. Larsen, Bette L. Otto-Bliesner, Marika M. Holland, David A. Bailey, Kurt A. Refsnider, Scott J. Lehman, John R. Southon, Chance Anderson, Helgi Bjornsson, Thorvaldur Thordarson,

Publication: Geophysical Research Letters

=============================================================

Here’s the paper abstract, the actual paper is not yet available (another science by press release that we can’t check).

http://www.agu.org/pubs/crossref/pip/2011GL050168.shtml

GEOPHYSICAL RESEARCH LETTERS, doi:10.1029/2011GL050168

Abrupt onset of the Little Ice Age triggered by volcanism and sustained by sea-ice/ocean feedbacks

Key Points

  • Little Ice Age began abruptly in two steps
  • Decadally paced explosive volcanism can explain the onset
  • A sea-ice/ocean feedback can sustain the abrupt cooling

Authors:

Gifford H Miller

Aslaug Geirsdottir

Yafang Zhong

Darren J Larsen

Bette L Otto-Bliesner

Marika M Holland

David Anthony Bailey

Kurt A. Refsnider

Scott J. Lehman

John R. Southon

Chance Anderson

Helgi Björnsson

Thorvaldur Thordarson

Northern Hemisphere summer temperatures over the past 8000 years have been paced by the slow decrease in summer insolation resulting from the precession of the equinoxes. However, the causes of superposed century-scale cold summer anomalies, of which the Little Ice Age (LIA) is the most extreme, remain debated, largely because the natural forcings are either weak or, in the case of volcanism, short lived. Here we present precisely dated records of ice-cap growth from Arctic Canada and Iceland showing that LIA summer cold and ice growth began abruptly between 1275 and 1300 AD, followed by a substantial intensification 1430-1455 AD. Intervals of sudden ice growth coincide with two of the most volcanically perturbed half centuries of the past millennium. A transient climate model simulation shows that explosive volcanism produces abrupt summer cooling at these times, and that cold summers can be maintained by sea-ice/ocean feedbacks long after volcanic aerosols are removed. Our results suggest that the onset of the LIA can be linked to an unusual 50-year-long episode with four large sulfur-rich explosive eruptions, each with global sulfate loading >60 Tg. The persistence of cold summers is best explained by consequent sea-ice/ocean feedbacks during a hemispheric summer insolation minimum; large changes in solar irradiance are not required.

Received 29 November 2011; accepted 30 December 2011.

Citation: Miller, G. H., et al. (2012), Abrupt onset of the Little Ice Age triggered by volcanism and sustained by sea-ice/ocean feedbacks, Geophys. Res. Lett., doi:10.1029/2011GL050168, in press.

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Trey

“powerful climate models” did not these show no little ice age at all before ? (see hockey stick)

I guess the Hockey Stick just took a beating….sort of. Had to be something other than the sun alone!

I have read a book near 40 years ago about the influence of the solar cycle and earth’s climate. That included a link between the solar cycle and the number of earthquackes and volcanic eruptions, which seem to cluster in the rising edge of the solar cycle. I haven’t done the math, but it is worth to see if there is some correlation and a possible link via the earth’s and sun’s magnetic field interactions and continental shelves floating atop of a magnetic earth kernel…

One of the things I wonder about is that during low sunspot activity, does the reduced solar-magnetic influence have any effect on Earth’s plate tectoncs and vulcanism? Does a reduced solar-magnetic influence prompt more volcanism?
An interesting question. From an energy point of view, it doesn’t seem likely — I’ve estimated the power associated with magnetic induction and although it is a very large number, it is a very small number compared to the size the Earth. Of course, I could have made a mistake in my arithmetic, but I wouldn’t think that the forces are large compared to, say, tidal forces.
rgb

David A. Evans

Even if there is no Solar influence, this is a sort of scientific game over!
If the LIA was caused by volcanoes, that’s an admission that it was warmer before and since the LIA, we’ve had a relatively quiet period as regards volcanoes.
Who needs CO2 if it’s reduced volcanic activity that caused the warming?
DaveE.

NavarreAggie

“One of the things I wonder about is that during low sunspot activity, does the reduced solar-magnetic influence have any effect on Earth’s plate tectoncs and vulcanism? Does a reduced solar-magnetic influence prompt more volcanism?”
I’ve wondered the same thing but have never voiced the question to anyone. On the surface it seems implausible, but stranger things have been correlated before. GCRs inducing cloud formation, anyone???

Babsy

Don’t you get a little giddy when you read the words “powerful computer climate models”? I know I sure do! I wonder if they discuss amongst themselves how much RAM is necessary to show the true beauty that can only be CO2? Bawhahaha!

Volcanoes in the sub-arctic regions (particularly frequent Kamchatka peninsula eruptions) may be causes of the effect known as the ‘sudden stratospheric warming’ SSW. The SSW is usually Arctic winter occurrence event; it is thought that influences severity of the Northern Hemisphere winters. For more details and a review of the SSW cases from 2005 to 2010 see:
http://hal.archives-ouvertes.fr/docs/00/56/34/77/PDF/SSW.pdf

NucEngineer

I thought the Little Ice Age either did not not exist or was localized to northern Europe. Just ask Michael Mann and his famous Hockey Stick (a study of tree rings in one very very small region of Northwest Siberia). His trees didn’t find this cooling.

Alan Watt

They assert:

Intervals of sudden ice growth coincide with two of the most volcanically perturbed half centuries of the past millennium.

but do not provide supporting details. Have these two periods been recognized as having significantly greater volcanic eruptions than any other comparable periods?
Let me guess: models all the way down?

carol

In the Clube and Napier astronomical theory (1980s and 1990s) the Little Ice Age had an association with increased meteoric activity as that was hypothesized to cause large amounts of dust in the upper atmosphere and create an opaque sky – virtually the same kind of thing as suggested by increased volcanic activity. In the same theory meteoric activity was responsible for the downturn in climate in the Late Roman period, 4th, 5th and 6th centuries ad roughly, and the 9th century ad short spell cold/wet weather episodes (coinciding with the Vikings, spurred on by an excited sky) and so back into history. This sort of thing became lost in the hypothetical 1500 year Bond cycle that never quite seems to fit into a 1500 year series. Clube and Napier were popular for awhile and wrote a couple of books and countless articles that all just kind of disappeared. They were never on the radar in the US.

models…..
if only they were Bunny Girls.
Similar IQs anyway.

Jim

Would heavy volcanic emissions mask sunspots, resulting in low sunspot numbers?

oldseadog

This just goes to show that generally climatologists just don’t know enough even to start to pronounce on what drives climate change, even with all their “most powerful computer programmes”.

Yarmy

Wasn’t Gifford Miller in that Ice Age “documentary” with Mr Spock in the 1970s warning of the impending march of the ice sheets

Jit

I think I can explain the MWP with this theory too. Inverse volcanoes. They sucked aerosols in rather than emitting them for the LIA.
Thus, the global temperature prior to the carbon era was flat, and the handle of the hockey stick was crooked no more.

J Cuttance

Some ‘alarmist’ bells started ringing when I read “there appears to be a cumulative cooling effect”.
All that needs is a reference to the Truth…

Camburn

This paper would somewhat confirm what Dr. Svalgaard has found. TSI, even during minimums, is bascially flat. This also demonstrates that the earth recovers from a long period of cooling. It took centuries, after it was so cold, to warm to equalibrium again.
For our clmate to work effectively, it requires the Arctic to be virtually ice free in the summers.
It is well documented that the Arctic warmed enough approx 6,000YBP to be ice free in the summer. This lasted for approx 3500 years, and then it cooled, prob from volcanic erruptions.
The resolution of past temp proxies is not good enough to rule out that we may be as warm as the MWP now. The current period of warmth is well within the error bounds of the proxy reconstructions.
The good thing in all of this is…..we seem to be finally getting back to what would be considered a “average” temperature of the Holocene.

stricq

Are these the eruptions being referenced?
Billy Mitchell Bougainville & Solomon Is. 6 1580
Bardarbunga Iceland 6 1477
1452-53 ice core event New Hebrides Arc 6 1452-53
Quilotoa Andes, Northern Volcanic Zone 6 1280

Manfred

Amazing what inconsistencies these guys shoulder just to avoid the solar influence.
There is no little ice age in most Hockey Stick graphs
http://wotsupwiththat.files.wordpress.com/2010/11/ipcc_ar341.jpg

Yarmy

I’m fine with the idea that increased Volcanism could have caused such events, but is there any direct physical evidence for these eruptions? It’s not clear from the press release.

pat

Since the little Ice Age interrupts the Medieval Warm Period, are we all clear now that the optimum temperature is a lot warmer?

bacullen

I guess all that dust made the sunspots invisible. sarc off/

More Soylent Green!

oldseadog says:
January 30, 2012 at 12:28 pm
This just goes to show that generally climatologists just don’t know enough even to start to pronounce on what drives climate change, even with all their “most powerful computer programmes”.

Does anybody know why climate models show increased CO2 causes CAGW? Because that’s how the models were programmed!
Climate models are computer programs and merely do what they are programmed to do. At best, computer models illustrate an hypothesis. The models work they way they do because that’s how the models believe the climate works.

ZZZ

Skeptics have pointed out how the climate models originally used to promote global warming were designed — with no real evidence behind it — to be unstable to slight warming due to increases of atmospheric CO2 (water vapor was supposed to increase and amplify the CO2 warming). Now, to explain the LIA, they have set up a climate model that is unstable in the cold direction to several closely-spaced volcanic eruptions. The take away fact, then, is
The greatly reduced numbers of sunspots during the LIA were just a coincidence. We can make our climate models unstable to slight cooling to show this must be so!
This not really very persuasive.

pokerguy

“Does a reduced solar-magnetic influence prompt more volcanism?”
Anthony,
I’m pretty sure I’ve heard Joe Bastardi opine that it does. It’s been a while, and perhaps I misinterpreted, but I do believe I’ve heard him say something to this effect.

pat

By the way. All this missing heat has been found. Seems that the instrument readings just need a bit more homogenizing: http://www.sciencedaily.com/releases/2012/01/120127173235.htm

Richard M

I find it hard to believe that this was the only active period for volcanoes during the Holocene. What happened during other active times? What, you forget to look?
Also, we had a couple of fairly good sized volcanoes in the last 30 years. While they did drop temps for a year or so, the temps bounced back right away. Was this non-supportive evidence covered in the paper?
Finally, I thought that less ice in the Arctic was supposed to slow the Gulf stream. Are they now saying it is more ice? The way things keep changing I need a program to keep up.

Jerker Andersson

I would like to see this team in the same room with “The Team” discussing little ice age. Mann has declared that there was none, and no MWP.

Robert Brown says:
January 30, 2012 at 12:04 pm
From an energy point of view, it doesn’t seem likely
Furthermore since the solar effect on the ionosphere ( and the lithosphere electrical induction) is strongest during solar max, it would follow that number of volcanic eruptions would correlate with the peaks rather then troughs of the sunspot cycle.
There are some indications that solar storms may be loosely linked to the earthquake occurrence, currently there is a strongish geomagnetic disturbance is in the progress (Z vector about 0.5% of the Earths field intensity, really strong ones exceed 1% of the static GMF)
http://flux.phys.uit.no/cgi-bin/plotgeodata.cgi?Last24&site=tro2a&
Last march Japan’s M9 geomagnetic storm was approaching 1% for vertical component and about 10% for the horizontal component. H vector is considered to be occasional quake trigger in a fault which may entered the critical phase. Currently H component has changed by about 4%.
For more details see:
http://www.vukcevic.talktalk.net/gms.htm
Each storm shifts Z vector one notch up in the Eastern magnetic Hemisphere (cantered on Siberia), and one notch down in the WH cantered on the Hudson Bay area, hence drift of the virtual magnetic pole is Russia bound.
http://www.vukcevic.talktalk.net/Tromso.htm
The most recent World Magnetic map is available here:
http://www.ngdc.noaa.gov/geomag/data/mag_maps/pdf/F_map_mf_2010.pdf
It is worth noting that the Siberian field has surpassed the Hudson Bay in mid 1990s, and currently is about 4% stronger (total field 61 against 59 microT).
The bifurcation changes in the Earth’s Nth Hmsphr’s field (not present in the SH) strongly correlate with the Arctic temperature anomaly:
http://www.vukcevic.talktalk.net/NFC1.htm

Jerker Andersson

Camburn says:
January 30, 2012 at 12:39 pm
“This paper would somewhat confirm what Dr. Svalgaard has found. TSI, even during minimums, is bascially flat. ”
They did not make any studies of the sun. They set the irradiance to a constant in the model so the study confirms nothing regarding the sun. With that said I do not make any claims that it is not true that sun has very low variability in it’s irradiance.

kcom

“powerful climate models”
Accurate climate models would be even more impressive – and more useful.

Rosco

Why is it that small changes in albedo induces by aerosols, even though not man made, can cause rather dramatic changes in temperatures BUT any changes in output from a dynamic star cannot ??
Surely their theory simply argues against their argument that solar forcings do not count as reflecteing energy back into space would have the same effect as reduced solar energy due to the Sun.
Are they trying to claim they have absolute proof that the Sun’s input to Earth is actually a constant and never varies by an amount to affect Earth’s temperatures ??
I’d like to see that data and how it was measured.

The BBC’s take on this press release can be found at : –
http://www.bbc.co.uk/news/science-environment-16797075
Richard Black’s opening paragraph: –
“The Little Ice Age was caused by the cooling effect of massive volcanic eruptions, and sustained by changes in Arctic ice cover, scientists conclude”
No CO2 there, then.
But – as AleaJactaEst has noted, there were models.
And the f’our’ ‘tropical’ eruptions are as yet unidentified. Is that state of the art for medieval volcanoes?
Interesting to see the BBC adding
“Analysis of the later phase of the Little Ice Age also suggests that changes in the Sun’s output, particularly in the ultraviolet part of the spectrum, would also have contributed cooling.”
And the link from the BBC’s “Analysis of the later phase” [emboldened in the original] –
goes to http://www.bbc.co.uk/news/science-environment-15199065
which starts: –
“Recent cold winters that brought chaos to the UK and other places in northern Europe may have their roots in the Sun’s varying ultraviolet emissions”.
Now, maybe the volcanoes did set off a Local [but why European, when the volcnoes, we are told, were tropical] cooling but to putatively dismiss solar radiation variance seems, to me, rather a lot to read into the models presented. Not necessariy wrong – but possibly more than the evidence presented – from models – can confirm.
At least the plants were from the non-model universe.

Rosco

Are these the same guys who tried to tell us temperatures had been stable before the modern man induced warming – ie hockey stick ??
If so how do they reconcile a Little Ice Age only a few hundred years ago ??

Alcheson

One thing is for sure…. it is a great thing that CO2 emissions continued along the business as usual scenario and the alarmists weren’t successful in getting CO2 emissions since 2000 drastically reduced or they would be pointing to Hansen’s famous 1988 graph and claiming they were wildly successful, They would be crowing that the current downward temperature trend proves the models are accurate and that they had saved the world. We skeptics and the world would be royally screwed starting about now.

commieBob

… large changes in solar irradiance are not required.

Am I missing something or is this a paper tiger. Who, exactly, postulated large changes in solar irradiance?

Jim G

“The study, which used analyses of patterns of dead vegetation, ice and sediment core data, and powerful computer climate models”
Not just computer models but “powerful” computer models. And where and when were these volcanic eruptions? Evidence upon which they are based in this “study”? I suppose the model says they happened. There are a multitude of coulda, woulda, shoulda variables that could be introduced to explain the cooling that was, I note, previously denied by these folks.

GeologyJim

Miller and all don’t seem to list any particular volcanic eruptions (where? when? how big?) in this study. Call me naive, but I would think that the simulations on these “most powerful computer programs” would have to include some kind of such data.
Pinatubo and El Chicon both produced cooling effects of >0.5C, but their effects didn’t last more than a couple of years. If these hypothesized serial volcanoes were to have had any “cumulative cooling effect”, they must have been geologically instantaneous/simultaneous
Color me skeptical (as always)
There’s just no money to be made off blaming the Sun

Dave Wendt

The supposed Kuwae eruption fits the 1450+/- window and is speculated to be about 6X Mt Pinatubo in size, which suggests possible global cooling impact. This paper identifies an unknown eruption in the 1250-1260 time period in the Dome A core
http://www.igsoc.org/journal/current/207/j11J138.pdf
A detailed 2840 year record of explosive volcanism in a shallow ice
core from Dome A, East Antarctica

fred houpt
NoAstronomer

“…paintings from the period depict people ice-skating on the Thames River in London”
More than just ice-skating. Paintings show they used to spit-roast whole pig/cow/deer on the ice.

“The researchers set solar radiation at a constant level in the climate models”
Then the models did not even have the correct input data. End of.

cbone

“The researchers set solar radiation at a constant level in the climate models. The simulations indicated that the Little Ice Age likely would have occurred without decreased summer solar radiation at the time, Miller says.”
No, what it says is the models are tuned to give the desired result regardless of changes in solar radiation.

Camburn

HI M.A.
I agree with your post above. There has been a demonstrated correlation between the magnetic field strength etc for quite some time.
Dr. Svalgaard is also showing that TSI is pretty flat over very long periods of time.
I have never bought into the theory that TSI was the cause of the LIA, NOR the MWP. I had always looked at the MWP as a rebound period, just as the present period is. When one examines long term temps, and take the noise of weather out, it is readily apparant that a somewhat drastic stimuli quickly changes the climate.
carol says:
January 30, 2012 at 12:22 pm
Concerning a Bong Type Event. There is more evidence being found now as the the cycle of a Bond Event. It is apparant in ice proxy data from the Arctic. Whether it is world wide is still somewhat in question, but that is mainly because so much of the Southern Hemisphere is water. Hard to get good proxy data there.
I would not count it out at this time.
Overall, I am just thankful that we are getting back to “normal” temperatures now.

adolfogiurfa

@M.A.Vukcevic says:
January 30, 2012 at 1:06 pm
Really important!, you are being a Galileo Galilei
However: You are being, like him, blasphemous!. How do you dare to doubt of the holy dogmas of Climate Change Church and the sainthood of its most renowned bishops?
Your publications will be included in the INDEX!!

Jaye Bass

“…powerful computer climate models”
Well that says it all doesn’t it?

pochas

I ran across an interesting web page “Harris-Mann Climatology” with a climate chart that indicates some of these volcanic periods.
http://www.longrangeweather.com/global_temperatures.htm

We’re in for some experimental time.

Camburn

Jerker Andersson says:
January 30, 2012 at 1:08 pm
“They did not make any studies of the sun. They set the irradiance to a constant in the model so the study confirms nothing regarding the sun. With that said I do not make any claims that it is not true that sun has very low variability in it’s irradiance.
I know they left the TSI flat. That was my point. With a flat TSI, they were able to replicate the temperature pattern based on the volcanoes at that time. By not trying to discount solar variation, they actually proved there is very little.