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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I somehow do not believe that changes in snow/ice cover make such strong feedbacks. There was record snow cover in recent winters in Northern hemisphere and what. Until ENSO is somehow affected, it is only something happening up there.
I bet at the time vulcanism and the resulting weather changes were explained by the sins of man, and people were offered to repent, change their ways and give generously to the church/shaman.
What has changed? Humans really would do with evolving further.
Miller got the dates from radio carbon dating dead plant material from beneath receding ice margins on Baffin Island in the Canadian Arctic. The kill dates were clustered between 1275 and 1300 with a second cluster at about 1450 indicating that this region at least was ice free between 550 and 700 years ago.
At the very least this shows that the retreating ice in that part of the artic is nothing new.
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.
I don’t understand the histograms, and would welcome an explanation or interpretation of what the data is saying. Because it does seem to be of interest …
All depends where. Central pacific may be, Kamchatka an Iceland unlikely.
@TerryS
Good points. The existence of ice-free regions is confirmed by the Iceland, Greenland and Newfoundland settlements of the time. The implications for the ‘permafrost’ are also large as it means those frozen bogs are not permanent, and contain large amounts of relatively recent vegetation. You might have noticed the consistent avoidance of recognition in alarmist comments about retreating ice and permafrost: that obviously biomass regrowth will commence immediately it is warm enough to do so. Emphasis has instead concentrated on ‘carbon emissions’ from rotting vegetation in the ground with not even a nod to the obvious: that it got there by itself, literally.
” … transient climate model simulation … ”
Here we go again.
Pointman
But I thought the scientific alarmist hierarchy told us that we humans are responsible for ‘climate change’ and everything bad that has / is / will ever happen.
Obviously some human skeptic jokers must have been stoking the volcanoes.
On a serious note, the theory sounds plausible (unlike CAGW).
Is this a well founded study and conclusion?
No, no, no. He’s got it all wrong. There *must* have been a sudden decrease in CO2 to cause it, because the science is settled and only CO2 drives the climate.
So the LIA did happen. Someone should tell Mann & Jones fast.
Jasper Kirkby’s graphs on page 3 suggests solar variability for the onset/retreat of the LIA.
http://arxiv.org/PS_cache/arxiv/pdf/0804/0804.1938v1.pdf
Interesting. So the grand solar minimum across that time frame was irrelevant. Or did it perhaps trigger volcanism?
rgb
Wow, no mention at all of solar influences. The Maunder Minimum coincides very well with the grand solar minimum at the time, with a similar correlation with the Dalton Minimum.
Those worthless models again—they still do not include solar cycles and the solar/cosmic wind connection.
robert barclay says: April 12, 2012 at 8:49 am
“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.”
Robert, this makes no sense, particularly the last statement.
No no. Don’t you guys read anything? Little Ice Age was caused by Columbus finding Americas and causing millions of natives to die from smallpox! Less people = less CO2 = cold.
I read it from a study that was peer reviewed so it must be true.
Does anyone know the reasoning behind postulating the four large erruptions? Was it that erruptions were recorded or do they just make the model work?
The article triggers a feeling of “deja vu”. I took Reid Bryson’s class on climatic history in the late seventies, and he was already then talking about there being periods when volcanoes are exceptionally active, and how these active periods are a significant factor in global temperature changes. Didn’t think much of Reid’s argument then, but the more I have been reading on historical climate, the more it begins to look like he was onto something. (Bryson’s view of human-caused global warming: “hogwash”.)
Can’t be true: according to the alarmists man made global weirding causes vulcanism, earthquakes etc./sarc
@Tony: the histograms are (from the paper, top to bottom):
(a) Relative kill rates of moss by expanding local icecaps on Baffin Island, determined by carbon-14 dating. (b) Global mass of volcanic sulfate aerosol in the stratosphere, estimated from sulfates in ice cores. (c) Temperature anomalies in southern Greenland (relative to the 1880–1980 mean), determined from borehole measurements. (d) Concentration of ice-loving microplankton in sediment cores from the shelf off Iceland’s north coast, a proxy for sea-ice accumulation there
“The CLOUD results show that a few kilometres up in the atmosphere sulphuric acid and water vapour can rapidly form clusters, and that cosmic rays enhance the formation rate by up to ten-fold or more”
-From CERN’s CLOUD press release
“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.”
-Abstract
Interesting…
Gaaah cancel above. Wrong diagram. The (partially) right labels are:
A – don’t know
B – Global mass of volcanic sulfate aerosol in the stratosphere, estimated from sulfates in ice cores
C – Relative kill rates of moss by expanding local icecaps on Baffin Island, determined by carbon-14 dating
D – not sure
E – Concentration of ice-loving microplankton in sediment cores from the shelf off Iceland’s north coast, a proxy for sea-ice accumulation there
F – Temperature anomalies in southern Greenland (relative to the 1880–1980 mean), determined from borehole measurements.
1) Didn’t Shakun claim you need global proxies, not just ones in a small region like the arctic?
2) Is the obverse true? Less volcanism causes warming.
Blind men and elephants.
I guess it must be a coincidence that solar minimums and colder weather happen at the same time. Why can’t it be that both solar and volcanic contributed to the situation? And what was the source for the volcanic eruption data? And the solar data? 600 to 700 years ago?
So their computer says white ice, reflecting light, is more important than there being less light or more cosmic rays. Nice computer. Nice imaginary world.
Using some skepticism on the LIA sunspot observations, however… Taking their volcanic activity at face value, might there have been enough stuff in the atmosphere to affect the observations of sun spots? I rather doubt that, as observing the sun deals with so much excess illumination that the sun spot counts are probably still correct.