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.
I have a different question. The mechanism by which the solar cycle has influenced climate is hypothesised to be a change in the ionisation rate altering the density of cloud seeding particles in the upper atmosphere. What interests me is whether this mechanism is still going to function in an age of air travel and industrial particulate emissions. There are a lot of anthropogenic cloud seeds up there now that were not there is the past. I wonder to what extent this will interrupt the mechanism.
The paper is another hit against the CAGW supporting science of the IPCC. Natural events, once again, can be used to support arguments that the climate for the last +1000 years has a natural variation. There is increased credence that the modern period has a natural climate variation; with the IPCC’s postulated anthropogenic influence to the contrary notwithstanding.
John
So if we cancel out the LIA cause by volcanoes, the current warming is just one long continuation of the Medieval Warming Period, Roman Warming Period, all the way back to …..
Great! Big mystery solved, nothing to worry about, can I have my taxes back please?
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.
Ap is constructed from geomagnetic data. Such data is available back to the 1840s and Ap can be constructed from that data just as well as from the standard ~12 observatories used since 1932. Here is such a construction http://www.leif.org/research/Ap-1844-now.png The current low values are not exceptional. Similar levels were reached in 1901-1902 and 1878-1879. Since 1844 there has been no significant long-term trend in Ap.
Here is such a construction http://www.leif.org/research/Ap-1844-now.png
The most important words in the abstract, IMHO…
“…century-scale cold summer anomalies, of which the Little Ice Age (LIA) is the most extreme…”
So, coming after the “most extreme” “cold summer anomaly” might explain a little warming. Right?
Sunspot link to Earthquakes ??? This could only happen if the Earth and Sun were strogly linked by magnetic & electric forces. This is getting dangerously close to Electric Universe / Plasma Universe theory !!
Just reading along and then you inevitably hit …”according to computer simulations”. hmmmm
They had the audacity to state:
“powerful computer climate models, provides new evidence”
ok great….now the science is really settled
there was a LIA, it was caused by volcanoes…
…which masked the warming that started before the LIA………..
Only now that warming has greatly accelerated because of a trace gas…
…that was a whole lot higher in the ice ages
..and the warming has stopped for the past 15 years
because, because………..
..but it’s going to come back…with a vengeance..right after they adjust Envisat to show even more sea level rise
I have a hard time believing science when they advertise a new medicine….
…and it’s immediately followed by an ad from an attorney
“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.”
No, they proved that the climate models do not account for solar variation.
I still prefer it that they’re trying to explain the LIA rather than deny its existance.
Should we now place NCAR/UCAR firmly in the “Mann’s hockey stick is full of it!” camp with the rest of the right-thinking people?
ggm says:
January 30, 2012 at 1:56 pm
Sunspot link to Earthquakes ??? This could only happen if the Earth and Sun were strogly linked by magnetic & electric forces.
There is no evidence for such a link. Here [ http://www.leif.org/research/Earthquake-Activity.png ] is the number of strong earthquakes [two different data sets – Pager and Centennial] as a function of days from a change in the interplanetary magnetic field as it sweeps past the Earth [top] and from the start of a geomagnetic storm [middle]. The bottom panel shows the response of the aa index [similar to ap] to those same storms.
From the Wikipedia page on the Kuwae eruption
Climatic consequences of the 1452 – 1453 event
A study by Dr Kevin Pang of the Jet Propulsion Laboratory[7] drew on evidence found in tree rings, ice cores and in the historic records of civilizations in Europe and China. Oak panels of British portrait paintings had abnormally narrow rings in 1453–55.
In Sweden, grain tithes fell to zero as the crops failed; western U.S. bristlecone pines show frost damage in 1453; and the growth of European and Chinese trees was stunted in 1453–57.
According to the history of the Ming Dynasty in China in the spring of 1453, “Nonstop snow damaged wheat crops.” Later that year, as the dust obscured the sunlight, “Several feet of snow fell in six provinces; tens of thousands of people froze to death.”
Early in 1454, “it snowed for 40 days south of the Yangtze River and countless died of cold and famine.” Lakes and rivers were frozen, and the Yellow Sea was icebound out to 20 km from shore.
The eruption occurred just before the Fall of Constantinople, the last bastion of the once-mighty Byzantine Empire. The Ottoman Turks, led by Sultan Mehmed II, laid siege to the city on April 5, 1453, and conquered it on May 29. Pang found mention of the volcano’s aftereffects in chronicles of the city’s last days. Historians noted the city’s gardens that spring produced very little. On May 25, a thunderstorm burst on the city: “It was impossible to stand up against the hail, and the rain came down in such torrents that whole streets were flooded”. On the night of May 22, 1453, the moon, symbol of Constantinople, rose in dark eclipse, fulfilling a prophecy of the city’s demise. Four days later, the whole city was blotted out by a thick fog, a condition unknown in that part of the world in May. When the fog lifted that evening, “flames engulfed the dome of the Hagia Sophia, and lights, too, could be seen from the walls, glimmering in the distant countryside far behind the Turkish camp (to the west),” historians noted. Residents of the city thought the strange light was due to reflection from a fire set by the Turkish attackers. Pang said, however, such a “fire” was an optical illusion due to the reflection of intensely red twilight glow by clouds of volcanic ash high in the atmosphere. Many such false fire alarms were reported worldwide after the 1883 Krakatoa eruption in Indonesia.
“I conclude that Kuwae erupted in early 1453,” Pang said. “The residual volcanic cloud could have made the apocalyptic June 1456 apparition of the Comet Halley look ‘red’ with a ‘golden’ tail, as reported by contemporary astronomers.”
Any mention of ‘powerful computer models’ in the area of Climatology triggers my giggle reflex.
Leif Svalgaard says:
January 30, 2012 at 1:51 pm
Here is such a construction http://www.leif.org/research/Ap-1844-now.png
———————————————–
Is there any data for the Dalton minimum 1790-1830 ?
Spot the Difference.
Anthony writes:
“New paper speculates on volcanoes during the Little Ice Age”
Richard Black Environment correspondent, BBC News writes:
“The Little Ice Age was caused by the cooling effect of massive volcanic eruptions, and sustained by changes in Arctic ice cover, scientists conclude.”
And what conclusion will the BBC audience come to?
Richard M wrote: “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.”
Given the scale of natural year-on-year variability, can we really know what would otherwise have been the case? Look at the UAH-MSU graph wiggling around: http://www.junksciencearchive.com/MSU_Temps/UAHMSUglobe.html
Can we really say that, but for the 1991 Pinatubo eruption the UAH-MSU would have been 0.5C higher? The wicked warmists allow themselves the luxury of pointing to an untick or downtick and declaring, “THIS was caused by THAT.” We sceptics need to be more rigorous.
If I remember correctly, the freezing of the Thames in London was partly due to the old London Bridge, which greatly restricted the river flow and allowed the ice to build up. So even if the temperatures dip to the same extent as they did then it is unlikely to result in complete freezing of the river again. Personally i hope the temperatures don’t go down that much! I prefer a warmer climate with plenty of CO2!
I remain puzzled as to how the authors make the attribution of the Little Ice Age to volcanic eruptions when the eruptions they site could not make very much more than a slight dip in temperatures worldwide.
To cool down the Earth over a period of centuries would require something near a supervolcano in size and explosivity.
I think what they’ve actually done (with powerful climate models) is rediscover the old theory of “post hoc ergo propter hoc”
Leif Svalgaard says:
January 30, 2012 at 2:16 pm
http://www.leif.org/research/Earthquake-Activity.png
Dang it Dr. Svalgaard……you even included sigma. Blows what I thought I knew right out of the water again…..
Thank you.
Not buying this at all. I think they need more authors as well. They only have 4 modeling points per author. Another over-fitted paper.
So which volcano are they blaming the “travesty” on?
Maybe this begs a cartoon showing MM trying to smuggle a frakking drill in to Yellowstone.
The year: 1815
The Tambora volcano in Indonesia erupted on April 5th with the largest eruption on April 10th and 11th. The volcanic rain, meteotsunami and climate change killed livestock and destroyed crops. More than 92,000 people died, maybe 100,000, from starvation making this eruption the most deadly on record. Tambora was 100 times the power of the Vesuvius eruption of 79 AD. Tambora is 14,107 feet high and is located on the Sumbawa Island of Indonesia. The chamber with centuries accumulation of magma was emptied of its contents. The ash and gases caused substantial climate change lowering global temperatures one degree, denyig two summers and lasting through the next year. Scientists have calculated that Tambora has erupted three times before. The 1815 eruption of the Tambora volcano is one of four eruptions in the past 10,000 years to have been assigned a Volcanic Explosivity Index of 7. This Tambora eruption was the most powerful eruption in recorded history.
_______________________
LIA and short freezing seasonal time fames in years show this remarkable link to volcanic activity. However these times of climatic temperature drops always are linked as to how much out gassing of dust clouds projected into the atmosphere remain air borne over longer time durations thereby blocking sunlight over vast areas of continents.
To be fair: LIA and MWP are shown on all reconstructions. The extent of those times are firmly reconstructed and these times are well known by all climate scientists. It is a matter of interpretation just how widespread those warming periods were. The controversy of increasing temperatures rests not on a 20th century upper boundary of a hockey stick. It all goes back to 1998 when the world for the first time experienced a record temperature spike. However what has happened contrary to opinion is that the hottest years since 1998 are still happening despite a record low sun activity along with a record breaking LA Nina (2010/2011) that is one of the highest temperature rated La Nina since records began. Indeed a temporal drop in temperatures does exist.
What we do know is this:
1. A quiet cycle sun does last forever.
2. We do have ongoing La Ninas forever
3. We are increasing levels of CO2 that contribute to warming/ warmer climate.
4. Out gassing of dust have occurred over this present period of time from volcanic activity.
“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”
The correlation between glacier/temperature changes with solar changes during the last 1000 year is well established.
See for example
http://img.photobucket.com/albums/v207/neuralnetwriter/GlobalWarming/JK_Austrian_Speleothem.jpg
http://img.photobucket.com/albums/v207/neuralnetwriter/GlobalWarming/JK_Holocene.jpg
Or better, read my booklet
http://scienceandpublicpolicy.org/images/stories/papers/originals/climate_change_cause.pdf
for example figure 6 and 7, and appendix D, E and F.
There exists also a volcano cooling effect, of course. But its cooling capability on a multidecadal scale is at least 5 times smaller than the cooling from prolonged low solar activity.
The problem is that this study uses a computer model to estimate the volcano effect, but it does not test first whether the computer model can reproduce the volcano cooling activity observed during the last 150 years!
I have shown that these computer models greatly overestimate the volcano cooling when compared to the actual data. See for example my last paper discussed here
http://wattsupwiththat.com/2012/01/09/scaffeta-on-his-latest-paper-harmonic-climate-model-versus-the-ipcc-general-circulation-climate-models/