Dr. Roger Pielke Sr. writes on his blog today:
Every once in a while. a nugget of new research insight appears that adds to our understanding of the climate system, and its complexity. One article of this type has appeared.
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.,39,L02708,doi:10.1029/2011GL050168
The Miller et al article is also at Physics Today, and is paywalled, but with an interesting title:
The triggering and persistence of the Little Ice Age with this even more interesting subtitle:
“A mere half century of volcanism seems to have initiated a chill lasting half a millennium”.
The key points from GRL are:
- 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
Abstract:
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.
Here’s one of the figures via GRL:
h/t to Bill Yarber
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What this is telling me is two fold
1) That there is no longer any contradiction in the small changes in solar forcing and the relatively large change in the LIA. Good for the consensus view.
2) The extended impact of these volcanic forcings suggests a major role for ocean circulation (natural variability) in translating external forcings into climate change. Good for the skeptic view.
So something for everybody. Hoorah!
The problems with the Miller et al paper are
(i) it’s model-based
(ii) it assumes that variation in the sunspot cycle only modulates solar irradiance, neglecting eg the solar cycle modulation of galactic cosmic rays reaching Earth’s atmosphere
(iii) it doesn’t identify by location or date the specific volcanic eruptions
I had a look at the SO4 measurements from the Greenland and Antarctica ice cores.
They both show a really large eruption in 1258 AD (twice as large as Tambora) and then again in 1285 (Tambora size). Antarctica has two other Tambora sized eruptions around the time in 1269 and 1277 but these are not evident in Greenland. Antartica has one other very large eruption in 1455 AD.
Interestingly they both have very large spikes for the 1971 Feugo eruption.
The idea of one major eruption VEI6+ as a causative factor for the LIA may appear attractive, but what if there were several VEI2-4 level eruptions within a fairly short time frame? Surely those might have a greater cumulative effect on airborne aerosols than just one massive eruption.
Schroder says: @ur momisugly April 12, 2012 at 10:28 am
The (btw very good) Eruptions blog has this to say about the last study about this subject…
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Your buddy (Erik Klemetti, an assistant professor of Geosciences at Denison University) over at Wired have also taken a look at this study.
He goes on to discuss whether there is any supporting data on volcanoes for this theory.
Wasn’t this paper already covered by a post back at the end of January?
http://wattsupwiththat.com/2012/01/30/new-paper-speculates-on-volcanoes-during-the-little-ice-age/
“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.”
Can somebody explain that, because it doesn’t make sense to me. If the earth wobbles like a top, with one complete wobble every 26,000 years, then if it is summer now in the NH when the earth is on this side of the sun, then in 13000 years, it will be summer in the NH when the earth is on the other side of the sun.
But the same amount of heat will be received by the NH from the sun in summer, whether the earth is on one side of the sun or another. And it will be the same for the other seasons and for the SH.
If the amount of earth’s axial tilt were to change, that would make for a different amount of heat being received during the NH’s summer, but that is not what happens during the wobbling.
kramer says:
April 12, 2012 at 11:58 am
Wow, there have been 4 or 5 ‘new’ findings in the last few months that have put the kabosh on some of what skeptics have been saying such as this one, and the paper that shows CO2 leading temp.
How nice that these are released just before Rio+20.
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And all of them are PAL- reviewed by HONEST upstanding scientists like Peter Gleick. Too bad the public is no longer buying the propaganda, only the Regulating Class is still on board the bus. Of course the Regulating Class are the ones with all the political power.
“robert barclay says: April 12, 2012 at 8:49 am
Does that mean the Maunder and the Dalton minimum didn’t happen. Surface tension blocks heat and is the key to the climate on this planet. The only energy that goes into the ocean goes in via the sun’s rays. The ocean ignores the second law of thermodynamics.”
There are also about 5,000 ocean floor volcanoes that can put heat into the oceans. Now I have no idea if active volcanoes on land release stress in the crust enough to quiet down the ocean floor volcanoes or if there is some other mechanism (ie. Piers Corbyn’s ideas) as to how solar can influence volcanoes.
Katla erupted a lot around then – VEI4 and up.
http://www.volcano.si.edu/world/volcano.cfm?vnum=1702-03=&volpage=erupt
The problem with this is theory is to find a period when there weren’t large eruptions over a short period.
http://www.volcano.si.edu/world/largeeruptions.cfm?sortorder=asc
Is there not evidence of increased volcanic activity coinciding with lower solar output ?. A combination of both over a period is not beyond the boundaries of possibility.
A beautiful painting by Avercamp, although it’s worth noting that Bruegel the Elder painted similar painting 40 years before in 1565:
http://www.ibiblio.org/wm/paint/auth/bruegel/bird-trap.jpg
Bruegel set this style of painting which influenced Avercamp. He was also the first landscape painter. It has been argued that the harsh winters forced this change of style away from paintings where landscapes were stylised, Italianate and idyllic backdrops to more realistic scenes peopled with ordinary people. The harsh conditions may well have precipitated the Reformation.
I thought the climate had been benign and stable until recently. However, Bruegel and Avercamp are just painters so what would they know? (/satire)
Here’s some related things I’d like to see examined and discussed.
http://www.sciencenews.org/view/generic/id/332612/title/Small_volcanoes_add_up_to_ cooler_climate
Small volcanoes add up to cooler climate
Airborne particles help explain why temperatures rose less last decade
By Alexandra Witze August 13th, 2011; Vol.180 #4 (p. 5)
Along with sulfur emitted by coal-burning power plants, volcanic particles spewed high in the atmosphere reduced the amount of global warming otherwise expected during the 2000s, a new study finds…
Volcanoes affect upwelling and ocean currents as static heat sources
NPG – Abstract – The effect of a localized geothermal heat source on deep water formation
http://www.nonlin-processes-geophys.net/18/841/2011/npg-18-841-2011.html
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
You see, I don’t think the timing matches historical (anecdotal) reality. The LIA in Europe really didn’t hit until 1314/5 and in fact the years immediately preceding were supposed to be quite warm, an Indian Summer of the MWP, even.
What would the time lag be, if you had some mega eruption in South America, how long would it take to affect the weather in Europe and how long would this effect last ? If Katla blew her top, would Europe south of Scotland really be affected ? Wouldn’t the winds blow the clouds over Scandinavia and Russia ?
This volcano stuff sounds seductive, but a single eruption ( or 4 ) isn’t going to screw the weather for 50 years or so, feedbacks notwithstanding. The LIA eased off a bit in the 16thC and then really swung between baking summers and freezing winters in the 17thC, so what else caused this “second wind” in the LIA ?
And…there is a bird trap in Avercamp’s painting as well as Bruegel’s
I think there have been too many other volcanoes at other times for the volcanic theory to work.
Cosmic Rays on the other hand.
“Close similarities are evident between the temperature and GCR records, showing an association of high GCR flux with a cooler climate, and low GCR flux with a warmer climate. This pattern has been extended over the last two millennia by a reconstruction of Alpine temperatures with a speleothem from Spannagel Cave in Austria (Fig. 3) [40]. Temperature maxima in this region of central Europe during the Medieval Warm Period were about 1.7C higher than the minima in the Little Ice Age, and similar to present-day values. The high correlation of the temperature variations to the 14C record (Fig. 3) suggests that solar/cosmic ray forcing was a major driver of climate over this period.”
http://arxiv.org/pdf/0804.1938.pdf$$yFulltext
Surveys in Geophysics 28, 333–375, doi: 10.1007/s10712-008-9030-6 (2007).
It is also worth noting that the worst Plague to hit Europe (and the World) was during this cold period, reducing Europes population by 50%. Before that It seems the cold that followed the end of the MWP brought smaller harvests followed by death and disease:
http://en.wikipedia.org/wiki/Black_Death
“In Europe, the Medieval Warm Period ended some time towards the end of the 13th century, bringing the “Little Ice Age” and harsher winters with reduced harvests. In northern Europe, new technological innovations such as the heavy plough and the three-field system were not as effective in clearing new fields for harvest as they were in the Mediterranean because the north had poor clay soil. Food shortages and rapidly inflating prices were a fact of life for as much as a century before the plague. Wheat, oats, hay and consequently livestock were all in short supply. Their scarcity resulted in malnutrition, which increases susceptibility to infections due to weakened immunity. Consistently high fertility rates, at five or more children per woman throughout Europe, resulted in high population growth rates and contributed to food shortages. In the autumn of 1314, heavy rains began to fall, followed by several years of cold and wet winters. The already weak harvests of the north suffered and the seven-year famine ensued. In the years 1315 to 1317 a catastrophic famine, known as the Great Famine, struck much of northwest Europe. It was arguably the worst in European history, reducing the population by perhaps more than 10 percent.”
So which is worse, warming or cooling?
The paper seems to point the finger at decreased solar insolation as the direct cause of the LIA, but as noted above, the LIA was characterized by frequently warmer summers but colder winters, which indicates decreased cloud cover, which would result in increased insolation.
Which suggests to me the cause was volcanoes plus something else. That something else could well be anthropogenic as post 1300 there were large human population declines, from famine, the Black Death and wars. I don’t find persistent sea ice convincing. Sea ice is a negative feedback to cooling as it acts as an ocean insulator.
Small volcanoes add up to cooler climate
Airborne particles help explain why temperatures rose less last decade
The climate models over-estimate volcanic aerosol cooling by a factor of 2 or 3. They are one of the main ways the models fiddle the fact their GHG warming predictions are nowhere near reality. Note there no actual measurements in that study, just models.
There hasn’t been a large volcanic eruption since 1991. Yet the climate has cooled, when the models say it should be rapidly warming.
This link has a good chart of temperature and volcanoes going back to 2000 BC: http://www.longrangeweather.com/global_temperatures.htm
Whatever caused the LIA, the LIA in turn may have something to do with the massive deaths of the Black Death of time frame of 1348 and 1350. See http://en.wikipedia.org/wiki/Black_Death
Whatever caused the LIA might also be involved in the Black Death of 1348 and onwards. A massive slaughter indeed. See http://en.wikipedia.org/wiki/Black_Death
Colder conditions can easily lead to changes in both human and animal behavior, and possibly bacterial behavior.
Brian R says
I don’t buy it. We’ve seen the effect on climate from large volcanic eruptions. Remember Mount St. Helens, Mt. Pinatubo.
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These 2 eruptions were babies. So you saw very little effect. A repeat of Tambora you would definitely notice.
higley7 says
Those worthless models again—they still do not include solar cycles and the solar/cosmic wind connection.
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I bet the models do include solar cycles.