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.
Study may answer longstanding questions about Little Ice Age
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.
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
- 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
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.
Leif Svalgaard says:
January 31, 2012 at 12:32 am
If you care to actually read the paper you’ll learn that it does not claim that the LIA started in 1460:
Missing the point again, you are claiming the Sporer started in 1460 which it clearly does not. Global cooling was well underway without volcanic activity. There is not enough volcanic activity to explain the 1300-1500 cold period, the paper is extremely poor and typical of AGW science. I would not align myself with such weak science, but do so at your own peril.
Leif Svalgaard says:
January 31, 2012 at 12:12 am
The FUV is absorbed in the E-layer and also does not get lower down and varies a lot less.
FUV penetrates down to a height of 30km (within the highest ozone band). FUV varies by 30% over the solar cycle. All of your arguments are false and show complete desperation to follow your agenda. I have already produced several papers that contradict you on another thread, but still you continue?
Earthquakes are a Tectonic Plate event. Whilst there are gravitic influences from the Sun and Moon, they do drive ocean tides, the effect on Plate Tectonics would be minimal. I doubt if earthquakes are due to external drivers but I get a feed from USGS on earthquakes so perhaps some research can be done.
The paper above puts the MWP temperature at 0.2C above today’s. Where do they get these figures. All research on the MWP put temperatures 2-5C above today’s. I cannot believe that there were no volcanic eruptions during this period to cool things down.
This UCB team should get back to the drawing board and stop to drive research conclusions into what they wish to have happened.
Next this you know, this team of “scientists” will propose to use sciene to trigger a massive volcanoe or two to offset global warming.
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?
———
Doesn’t seem plausible. Its 5 nTesla for the interplanetary field vs 50000 nTesla at the earth’s surface.
I hate to rain on anyone’s parade – but in that picture of Mr Miller collecting ‘vegetation samples’ – those are actually – er – PEBBLES….
Leif, your arguments prove as usual your biases asnd your lack of critical thinking.
Look at the figure prepared by Geoff
http://tinyurl.com/2dg9u22/images/miller.png
taken from their figure 2
http://www.leif.org/EOS/2011GL050168.pdf
It is evidentt that the strong peak of Ice cover (1430-1450) occured well before the great volcano eruption of 1452. So, unless you prove us that the time flow was inverted during that time, the strong peak of Ice cover (1430-1450) was not caused by the strong volcano activity in 1452, contrary to the poor opinion of these authors.
Geoff, to better prove my point, may you prepare again the figure by adding the solar record depicted in Figure 2A too? Figure 2A, 2B and 2C should be together. You also need to add two red lines in concomitance of the two Ice cup peaks around 1275 and 1435, and show that they correspond to the two grand solar Wolf and Sporer solar minima exactly. Thank you.
So, Leif, explain us the mistery of how a great volcano eruption occurred in 1452 could cause a strong cooling during the period 1430-1450.
(Note Leif that only the solar recontruction and the data reported and referenced by the authors themselves count in this discussion. If you claim thattheir data are wrong, then you should blame the authors, not me, for having not investigated the issue properly and said non senses such as that solar activity is not important for explaining the LIA).
If the models are so clever then no doubt they will be able to identify the volcanoes?
Once again a model dependent paper got past peer review without including a discussion of the literature. The models are not good at melting snow and ice. The Andreas Roesch (2007) showed that ALL of the AR4 models had a positive surface albedo bias and were behind the observations in their simulation of the high latitude earlier snow melts and reduced snow cover fractions as well as forest stem shadowing of the snow cover. Recall that at the same time there was “alarm” about the Arctic ice cap melt and statements by Scambos and others that the models were 30 years behind. The Roesch effect was not small, the surface albedo bias amounts to more than 3 W/m^2, which is about 4 times larger than the energy imbalance for the 90s. By under representing the snow and ice melt response the models probably over represent the feedback from new ice from the volcanoes. They also will over represent the response to future warming, since they will eventually catch up with the snow and ice mounts, it is reduced, not missing, so the 3+W/m^2 will double the impact of the CO2 doubling, thinking linearly.
The CCSM citations in the paper are from 2006. There is no discussion in the paper of the model diagnostic literature and whether the models have fixed this positive surface albedo bias problem reported in 2007 and known at the time AR4. So of course there is no error estimate for the problem. I thought at the time that the Roesch paper alone was enough to discredit model based conclusions and projections, given the easily appreciated magnitude and correlated nature of the bias. It is just one of dozens of papers diagnostic of issues with the models.
F. Ross says:
January 30, 2012 at 3:34 pm
“…powerful computer climate models, provides new evidence in a longstanding scientific debate over the onset of the Little Ice Age. …”
[emphasis added]
While models may be very useful in making a decision or judgement call, it seems to me that the models cannot provide evidence of anything.
And anyway, I’m certainly glad that they did not use “wimpy” computer models. /snark
I agree with F. Ross. And did a journalist say that modeling was evidence or did a “scientist” make the connection?
Leif Svalgaard says:
“Of course, the sun matter somewhat, like a little bit, but it is clear that the sun is not a major driver and that therefore the LIA has other, natural causes.”
Mind-boggling. Simply amazing!
From the Tips & Notes you can find this post on the link between cosmic rays and volcanic activity:
Ed Mertin says:
January 31, 2012 at 12:41 am
Explosive volcanic eruptions triggered by cosmic rays: Volcano as a bubble chamber 10.1016/j.gr.2010.11.004 : Gondwana Research | ScienceDirect.com
http://www.sciencedirect.com/science/article/pii/S1342937X10001966
http://www.deepdyve.com/lp/elsevier/explosive-volcanic-eruptions-triggered-by-cosmic-rays-volcano-as-a-3p053jxP0S
Geoff Sharp says:
January 31, 2012 at 2:33 am
FUV penetrates down to a height of 30km (within the highest ozone band).
http://www.leif.org/research/Atmospheric-Structure.png
Nicola Scafetta says:
January 31, 2012 at 5:02 am
It is evident that the strong peak of Ice cover (1430-1450) occured well before the great volcano eruption of 1452. </i?
The LIA started in the 13th century.
@jim 12:25 pm:
“Would heavy volcanic emissions mask sunspots, resulting in low sunspot numbers?”
Jim, I just recently read where the (apparently) first observations of sunspots came during just such an event, when the sun was dimmed to the point they could SEE sunspots directly. My recollection is that this was only one or two hundred years before the first scientific notings of sunspots. Sorry, I can’t recall the source. And no mention if anyone went blind.
smg
@carol 12:22 pm
Carol – Yeah, Clube and Napier had some strong evidence for all that. If you are interested in impacts, their history, their effects and the ongoing threat, check out http://www.CosmicTusk.com, a site that is a bit sporadic in postings, but has a lot of archived posts that might be worth your while.
smg
I like the UCAR site though it has some great articles and links. I never really did understand the effects of the Arctic Oscillation until I went to this link.
http://www.washington.edu/news/articles/russian-river-water-unexpected-culprit-behind-arctic-freshening-near-u.s.-canada
Seems that fresh water flowing from the Russian rivers has been diverted from the Eurasian basin between Russia and Greenland and is flowing into the Beaufort sea and adding 10 feet of fresh water to it. Grand effect is that this fresh water no longer protects the sea ice from the warmer Atlantic. When the oscillation stops they expect the fresh water path to switch back and sea ice to increase again. Something the BBC has never told me.
IIRC, Pinatubo (1981) was a VEI 6, and El Chichon (1982) was a VEI 5. The effects of each of these lasted a scant 5-6 years before the stratospheric crud precipitated out. VEI4 eruptions such as Fuego (1975) cause barely a climatic ripple.
There is only 1 known eruption in the 1275-1300 AD time frame – a ‘mere’ VEI 6 from Quilatoa in the Northern Andes. You just can’t hide eruptions that large or larger:
en.wikipedia.org/wiki/List_of_large_volcanic_eruptions
Oops! Typo alert. Pinatubo blew in 1991.
@ur momisugly Leif
Leif, as usually you do not reason as all or are extremely biased or simply dishonest!
Yes, Leif, LIA started in the late 13th century with the solar Wolf minimum. Volcano did little.
That volcanos do little (as shown in my papers, by the way) is clearly proven by the cool peak episode in 1430-1450 that agrees with the Sporer great minimum, not with the volcano eruption of 1452, as claimed by the authors, which occurred later.
Look at the figure prepared by Geoff
http://tinyurl.com/2dg9u22/images/miller.png
taken from their figure 2
http://www.leif.org/EOS/2011GL050168.pdf
Give a close look at fig2 and compare figure 2A, 2B and 2C.
How can you be so biased on this so evident fact?
Someone may have already posted this link. Nevertheless, take a look at http://www.wired.com/wiredscience/2012/01/volcanoes-and-the-little-ice-age-not-the-smoking-gun/
sea-ice/ocean feedbacks ; is that albedo ? If yes could not albedo trigger the warming after the last glacial maximun in place of the CO2 feedback?
Nicola Scafetta says:
January 31, 2012 at 7:52 am
Leif, as usually you do not reason as all or are extremely biased or simply dishonest!
It would be refreshing if you could stick to the science. You miss the point of the paper: The LIA was largely self-sustaining once started so no close timing coincidences are required. This is the interesting idea that is explored.
Leif, there is NO mapping and datation of pertaining ash deposits around identified tropical volcanoes. NONE.
It would be indeed refreshing if many here could stick to science, i.e in this case good ol’ geology.
TomRude says:
January 31, 2012 at 8:36 am
Leif, there is NO mapping and datation of pertaining ash deposits around identified tropical volcanoes. NONE.
Seems to be an obvious research project then to provide such data.
Really, Leif! Interesting idea?
Supported by which empirical evidences? By the fact that a 20-year large ice cover increase peak from 1430 to 1450 was induced, according to the authors, by a volcano eruption occurred in their data in 1452 instead by the great solar Sporer minimum in 1420-1450 so evident in their own data?
This paper proves nothing because the data that these authors present are not in agreement with the theory they would like to support. Nor they analyze the numerous papers showing the very good correlation with solar activity.
This paper is nothing but another computer game with no scientific meaning.
Read also the comment from
http://www.wired.com/wiredscience/2012/01/volcanoes-and-the-little-ice-age-not-the-smoking-gun/
where yo ucan read:
“However, I look at that spectrum and don’t see what Miller et al. (2011) claim – sure, there is a big spike during the late 1200s/early 1300s (more on this later) and a single spike around 1450. However, what about the late 1700s/early 1800s? I’d say it is more “volcanically perturbed” than the 1430-1455 period they identify.”
Come on Leif! you are not a so bad scientist, don’t you?