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.
“Does a reduced solar-magnetic influence prompt more volcanism?”
The typical scenario for large eruptions is that they occur at warm blasts after colder months, most often after colder N Hemisphere winters. There are few exceptions to this pattern.
Earthquacks
Camburn says:
January 30, 2012 at 3:57 pm
Solar radiation does NOT vary much from cycle to cycle. The light composition within the TSI does.
And this is the area you and others should bring yourself up to speed on. UV radiation varies over the solar cycle by very large amplitudes. EUV (100%), FUV (30%) and MUV (1%)
Solar UV changes are responsible for large chemical changes in all levels of our atmosphere above the troposphere. These changes also affect pressure patterns and jet streams in the lower levels.
http://tinyurl.com/2dg9u22/?q=node/236
Manfred says:
January 30, 2012 at 2:47 pm
Is there any data for the Dalton minimum 1790-1830 ?
There is scattered data. Not enough for a meaningful time series.
Camburn says:
January 30, 2012 at 3:04 pm
Dang it Dr. Svalgaard……you even included sigma. Blows what I thought I knew right out of the water again…..
“It is not what you know that gets you in trouble, but what you know that ain’t” Mark Twain.
thingadonta says:
January 30, 2012 at 3:37 pm
“The researchers set solar radiation at a constant level in the climate models. ”
Except that solar radiation wasn’t at a constant level.
No, they don’t usually set it constant, see e.g. slide 11 of http://lasp.colorado.edu/sorce/news/2011ScienceMeeting/docs/presentations/6b_Cahalan_Sedona_9-15-2011.pdf
Paul Wanamaker says:
January 30, 2012 at 4:29 pm
I just don’t understand how a many-times increase in EUV can have so little overall effect…
Because the energy involved is so small. It is like judging a billionaire’s wealth by the varying loose change in his pocket.
“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.”
No one seems to have picked up on the nonsense of this part of the argument to provide the necessary feedback required to maintain the hypothesis.
Don’t we get freezing of the sea off the east coast of Greenland every winter anyway and it does not seem to interfere with the thermohaline circulation? Indeed, the whole of the Arctic happily expands and contracts annually without this positive feedback being observed.
And in the preceding winter season to the summer season melt in which the surface water became less dense, the sea would have frozen more making the surface water more dense and thus aiding transportation.
And how can the effect be maintained from season to season? The circulation would have replenished itself in the time interval from one season to another. The slate would have been wiped clean with the progression of each season.
Stuff and nonsense. I am going to bed.
Guys & Dolls, be cool; what this paper is really trying to state is “We need money!! Give us millions to study this further or we are surely doomed!!” (Alarmism implied in the way they leave disaster unknown lurking)
Some facts (cough cough, it’s hard to call anything from this article that)
Why is it “best” explained by? Gut feeling or is it just that the compter models are already programmed around weakening Atlantic currents? (my speculation based on their speculation).
(my emphasis on all of those confidence inspiring words)
Sure and I may become a rich millionaire climate scientist. yeah, right…
Say again? Increased erosion when the ice cap expanded? Is this a climate scientist way of saying that it rained/precipitated more? Or that the ice cap melted more (while expanding at the same time, but it beats me how that proves ice cap expansion).
To reiterate; liberal use of conditional modifiers, fancy speak about fuzzily defined findings and the translation is give us more money so we can study this more. Yeah, the premise is possible, even plausible, but the study described above is far from convincing.
“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.”
OK, so what put an end to the “self-sustaining feedback” that prolonged the LIA after the volcanic aerosols subsided? Was there an increase in CO2? Was it the Sun? Or did something else happen to end the feedback? It just stands to reason that If the feedback was caused by “expanding Arctic sea ice” and was “self-sustaining” after the volcanic activity subsided, then something had to happen to reversed it. What was it?
[ A new international study ]
I guess that makes it robust. The international consensus it is.
There appears to be evidence that solar changes can and do cause an increase in volcanic eruptions.
The volcanic eruptions correlate with cyclic warm periods followed by cold periods that correlate with cosmogenic isotope changes that are known to be caused by a slow down in the solar magnetic cycle.
It seems likely as there are 23 abrupt climate change events each of which has coincidental cosmogenic isotope changes associated with them (the cosmogenic isotope changes are known to be caused by solar magnetic cycle changes) that the sun is the cause of what is observed. There is additional evidence to support that hypothesis.
http://www.agu.org/pubs/crossref/2003/2003GL017115.shtml
Timing of abrupt climate change: A precise clock by Stefan Rahmstorf
Many paleoclimatic data reveal a approx. 1,500 year cyclicity of unknown origin. A crucial question is how stable and regular this cycle is. An analysis of the GISP2 ice core record from Greenland reveals that abrupt climate events appear to be paced by a 1,470-year cycle with a period that is probably stable to within a few percent; with 95% confidence the period is maintained to better than 12% over at least 23 cycles. This highly precise clock points to an origin outside the Earth system; oscillatory modes within the Earth system can be expected to be far more irregular in period.
The observational evidence shows what is cause and what is effect.
Geological processes including volcanic eruptions are not cyclic with precise periods. Eruptions and earthquakes are random. (i.e. To create cyclic volcanic eruptions requires an external cyclic forcing agent that causes the volcanic eruptions. As noted in the paper below there is simultaneous eruptions in both hemisphere during the cold periods. The hemispheres are geological separated in terms of volcanic activity for geological forcing mechanisms.)
The cold periods are hundreds of years long. Volcanic eruptions cool for a few years. Abrupt changes in the geomagnetic field also correlate with the volcanic eruptions and the cold phases.
It is the reduction in the geomagnetic field by a factor of 3 to 5 which causes the long term cold periods (termination of the interglacials and abrupt cold periods during the glacial phases, Heinrich events.) The Younger Dryas abrupt cold period lasted more than 1000 years.
A restart of the solar cycle after a magnetic cycle interruption is what causes the increase in volcanic activity and the change in the geomagnetic field. There are burn marks on the surface (throughout the Northern Hemisphere, all continents) of the planet that correlate with the Younger Dryas cooling period. There is an aborted geomagnetic excursion (the geomagnetic field becomes weaken and non polar during an excursion and the field intensity drops by a factor of 3 to 5.) at the same time as the Younger Dryas and the are geomagnetic excursions at the termination of past interglacials.
http://www.pnas.org/content/101/17/6341.full
Bipolar correlation of volcanism with millennial climate change
Analyzing data from our optical dust logger, we find that volcanic ash layers from the Siple Dome (Antarctica) borehole are simultaneous (with >99% rejection of the null hypothesis) with the onset of millennium-timescale cooling recorded at Greenland Ice Sheet Project 2 (GISP2; Greenland). These data are the best evidence yet for a causal connection between volcanism and millennial climate change and lead to possibilities of a direct causal relationship. Evidence has been accumulating for decades that volcanic eruptions can perturb climate and possibly affect it on long timescales and that volcanism may respond to climate change. If rapid climate change can induce volcanism, this result could be further evidence of a southern-lead North–South climate asynchrony. Alternatively, a volcanic-forcing viewpoint is of particular interest because of the high correlation and relative timing of the events, and it may involve a scenario in which volcanic ash and sulfate abruptly increase the soluble iron in large surface areas of the nutrient-limited Southern Ocean, stimulate growth of phytoplankton, which enhance volcanic effects on planetary albedo and the global carbon cycle, and trigger northern millennial cooling. Large global temperature swings could be limited by feedback within the volcano–climate system.
This is evidence of five geologically separate volcanoes (separate magma chambers) erupting almost simultaneously and capturing a geomagnetic excursion during there period of eruption. The evidence is overwhelming. The problem is each piece of evidence is a separate scientific specialty. There is additional evidence from an astrophysical standpoint to explain how and why the sun can leave burn marks on the surface of the planet, abruptly change the geomagnetic field, and can cause a bipolar increase in volcanic activity.
http://www.agu.org/pubs/crossref/2006/2006GL027284.shtml
Geomagnetic excursion captured by multiple volcanoes in a monogenetic field
Five monogenetic volcanoes within the Quaternary Auckland volcanic field are shown to have recorded a virtually identical but anomalous paleomagnetic direction (mean inclination and declination of 61.7° and 351.0°, respectively), consistent with the capture of a geomagnetic excursion. Based on documented rates of change of paleomagnetic field direction during excursions this implies that the volcanoes may have all formed within a period of only 50–100 years or less. These temporally linked volcanoes are widespread throughout the field and appear not to be structurally related. However, the general paradigm for the reawakening of monogenetic fields is that only a single new volcano or group of closely spaced vents is created, typically at intervals of several hundred years or more. Therefore, the results presented show that for any monogenetic field the impact of renewed eruptive activity may be significantly under-estimated, especially for potentially affected population centres and the siting of sensitive facilities.
http://geosci.uchicago.edu/~rtp1/BardPapers/responseCourtillotEPSL07.pdf
http://geosci.uchicago.edu/~rtp1/BardPapers/responseCourtillotEPSL07.pdf
Also, we wish to recall that evidence of a correlation between archeomagnetic jerks and cooling events (in a region extending from the eastern North Atlantic to the Middle East) now covers a period of 5 millenia and involves 10 events (see f.i. Figure 1 of Gallet and Genevey, 2007). The climatic record uses a combination of results from Bond et al (2001), history of Swiss glaciers (Holzhauser et al, 2005) and historical accounts reviewed by Le Roy Ladurie (2004). Recent high-resolution paleomagnetic records (e.g. Snowball and Sandgren, 2004; St-Onge et al., 2003) and global geomagnetic field modeling (Korte and Constable, 2006) support the idea that part of the centennial-scale fluctuations in 14C production may have been influenced by previously unmodeled rapid dipole field variations. In any case, the relationship between climate, the Sun and the geomagnetic field could be more complex than previously imagined.
I have to ask again:
Would heavy volcanic emissions mask sunspots, resulting in low sunspot numbers?
I’m skeptical of global warming, but I think it’s an interesting question. I would also like to see a time-line with all the volcanic eruptions shown along side the cooling/warming periods.
paper published: http://www.leif.org/EOS/2011GL050168.pdf
Thanks Leif, for putting up the paper – Anthony
More studies are needed, of course. In perpetuity.
Nicola Scafetta
Post paper:
1. Fitting a curve with a simple model using physically unconstrained parameters is simply not a scientific process,
2. It fails with a hind cast test.
3. Assumed 60 year cycle which was the basis of the L&S model does not show up in Loehle’s own millennial global temperature reconstruction – a glaring contradiction.
4. Correlation is not causation; all you have demonstrated is a non-physical curve fitting exercise for a resultant correlation between cycles and global temperature.
5 Finding a correlation between two very limited references and global temperature, doesn’t mean these variables are causing global warming. WHY?
6. There is NO provable physical mechanism shown on which to base the model – yes it is a model fit but it proves nothing. We all know models – bad bad bad and ever more bad when it comes to a new hypothesis.
7. Any model must firstly identify a realistic physical range of data before running that model.
As nothing physically matching can be identified by doing standard tests, just like Spencer before them, all you are doing is playing pointless curve fitting games, and using results to draw unsubstantiated conclusions.
Herein it for the reader to understand when alternatives on climate theories are presented. Sort of like the light bulb revelation everyone needs a good dose of occasionally.
Endless speculations about our complex climate does nothing. That is difference between a scientific model and well – just another model anchored to prove a pre-conception.
I maintain this does not pass proper scrutiny
rossbrisbane says:
January 30, 2012 at 7:31 pm
Nicola Scafetta […]
I maintain this does not pass proper scrutiny
Plus as has been discussed on other WUWT threads, the correlations are against flawed data to begin with.
adolfogiurfa said @ur momisugly January 30, 2012 at 1:32 pm
Are you accusing Vukcevic of insulting the Pope? That’s not very nice…
Hint: Galileo Galileo was never, ever accused of blasphemy. He was pious to a fault and rather famous for his sermons. Galileo insulted the Pope by putting the Pope’s words into the mouth of Simplicio (literally idiot). The Inquisition couldn’t decide whether or not this was heresy and found Galileo “vehemently suspected of heresy”.
When are people around here going to learn that repeating falsehoods is not a good look?
Here is a chart of volcanic activity and temperature.
http://www.longrangeweather.com/global_temperatures.htm
Leif Svalgaard says:
January 30, 2012 at 7:11 pm
paper published: http://www.leif.org/EOS/2011GL050168.pdf
======================
I see M. Mann and G. Schmidt cited at the end of the last paragraph as well as in the acknowledgements. If you only know how to use a hammer, would you only seek nails to work with? Homage to the ‘Team’?
Interesting paper! The authors conclude:
“Together with climate modeling and supported by other proxy climate reconstructions, our
results suggest that repeated explosive volcanism at a time when Earth’s orbital configuration resulted in low summer insolation across the NH acted as a climate trigger, allowing
Arctic Ocean sea ice to expand. Increased sea ice export may have engaged a self-sustaining sea-ice/ocean feedback unique to the northern North Atlantic region that maintained suppressed summer air temperatures for centuries after volcanic aerosols were removed from the atmosphere. The coincidence of repeated explosive volcanism with centuries of lower-than-modern solar irradiance (Figure 2a) [Schmidt et al., 2011] indicates that volcanic impacts were likely reinforced by external forcing [Mann et al., 2009], but that an explanation of the LIA does not require a solar trigger.”
rossbrisbane says:
January 30, 2012 at 7:31 pm
Nicola Scafetta…”all you are doing is playing pointless curve fitting games, and using results to draw unsubstantiated conclusions”
Amazing putdown rossbrisbane! I suppose you would also trash using tide tables as well, since they are constructed using curve fitting games with the moon, sun etc.
eyesonu says:
January 30, 2012 at 7:54 pm
Homage to the ‘Team’?
You can pay your own homage to whomever you like. How about some substance instead?
Ed_B writes,
“Amazing putdown rossbrisbane! I suppose you would also trash using tide tables as well, since they are constructed using curve fitting games with the moon, sun etc.”
No, you missed rossbrisbane’s point about needing a physical mechanism. Read his note again?
“a related weakening of Atlantic currents, according to computer simulations ”
Now, real science where you go out an take samples, shows that the Gulf Stream slows down during cold periods and speeds up during warm periods. Based on the viscosity of water, this makes sense. BUT, slowing of the current does not mean weakening, just a thicker fluid.
rossbrisbane says:
January 30, 2012 at 7:31 pm
I have to agree with your analysis on this one. Nothing against Dr. Scafetta, but the tail does not wag the dog.
Hopefully soon, I will be reading studies using gravitational variance, solar magnetic output and regional volcanic and earthquake data to monitor and study the worlds major trouble spots. I am not sure if there is ongoing monitoring of the gravitational variance of the earth from Grace or GOCE satelites but there should be.
I am a layman way out of my field but I would like to say that the Sun’s magentic force has to play a role in the seemingly random dynamic under the crust. What other variables are there… tides, sea level, some unknown core dynamic? Teutonic plate movement begs the question about the force which moves the plates. It certainly cannot be utterly random. There is a system that has pattern. This is the reason the Grace and GOCE satellites were launched in the first place or am I all wet?
eyesonu says:
January 30, 2012 at 7:54 pm
Swing the bat often enough and you are bound to hit the ball.
It appears that some now have a batting average of .001%.
Better than a no hitter.