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
The LIA happened when and if it can be explained away. It takes powerful editorial forcings to keep that balance in place.
Next they’ll explain that supervolcano eruptions are clustered every 1,000 years.
(Minoan warm time, Roman, Medieval…)
Maybe they’re even stupid enough to believe it themselves.
A general question: TerryS mentioned carbon dating. That looks at Carbon 14 and its ratio to “normal” Carbon from atmospheric CO2 being incorporated into living things. We know that CO2 levels have fluctuated throughout history. Does carbon dating take these fluctuations into account?
“I guess it must be a coincidence that solar minimums and colder weather happen at the same time.”
Powerful enough volcano could influence the sun, right?
The (btw very good) Eruptions blog has this to say about the last study about this subject:
http://www.wired.com/wiredscience/2012/02/the-mysterious-missing-eruption-of-1258-a-d/
The volcanists does not seem to be on the CAGW bandwagon.
Don’t forget, regulars here, you need to not believe this, because you already “know” that the LIA was caused by solar forcing.
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.”
___________________________________
HUH?
Are you talking about this graph: http://lasp.colorado.edu/sorce/images/instruments/sim/fig01.gif
It shows the wavelengths that penetrate to 10 meters below the ocean surface.
The problem with volcanic eruptions as also the paper states is that the aerosol forcing is relative short lived. It could of course create some triggering mechanism, theoretically.
Another factor which I guess the paper didn’t mention is that the cooling of the early 14 century happened to coincide with what is called the Wolf solar minimum.
Hey could the sun have something to so with it?
No, not according to the prevailing wisdom of today’s climate science, which seem to believe that climate forcing during the Holocene can only be explained by changes in the composition of the atmosphere, aerosols and nothing else.
Sitting here reading this in the UK, from where I have also seen recent mention that Katla is showing signs of life in Iceland … hmmm.
Resourceguy says: (10:00 am) … powerful editorial forcings …
I like that! 🙂
I will add this other study to the discussion. Study of Dust in Ice Cores Shows Volcanic Eruptions Interfere with the Effect of Sunspots on Global Climate
Seems Sunspots DO correlate with climate…. Unless volcanic action interferes according to this study of dust in Greenland ice cores, sunspots, and volcanoes. Combining the studies you end up with the Sun (solar insolation + magnetic field), Ocean and Volcanoes influencing the climate just as Joe Bastardi and many of the rest of us have been saying all along.
The research, published in a paper in the May 15 [2002] issue of Geophysical Research Letters, provides striking evidence that sunspots — blemishes on the sun’s surface indicating strong solar activity — do influence global climate change, but that explosive volcanic eruptions on Earth can completely reverse those influences.
It is the first time that volcanic eruptions have been identified as the atmospheric event responsible for the sudden and baffling reversals that scientists have seen in correlations between sunspots and climate…
“By carefully studying the timing of other volcanic eruptions, we found that they coincided with all of the correlation reversals between sunspots and climate,” said Ram.
A chart in the paper shows how six major volcanic eruptions between 1800 and 1962 occurred during precisely the same years when there were reversals in the correlation between sunspot activity and climate….
According to Donarummo, it long has been known that volcanoes add more dust and more sulfates to the atmosphere.
The UB team discovered that these additional sulfates cause cosmic rays to have a more pronounced effect on Earth by spurring the formation of small droplets in the atmosphere that, in turn, cause the formation of a type of cloud that does not produce rain.
“During these times of high volcanic activity, the sunspot/climate correlation reverses and dust levels rise, even in the absence of high sunspots,” explained Stolz.
I carried out a very detailed reconstruction of temperature from 1538 and in doing so compared the reconstrctions of Dr Mann and Hubert Lamb
http://judithcurry.com/2011/12/01/the-long-slow-thaw/
This covered a large period of the Little Ice Age. The name is a misnomer as although it might have included some extended cold periods there were many warm years also. Many of the summers were notably warm, it was the cold winters that often brought the averages down.
Volcanos could well have had a sporadic and significant effect, combined no doubt with changes in the position of the jet stream and for some reason the weather patterrns often became ‘stuck’. (long periods of winter easterlies in the UK)
However volcanos are only going to be one of a number of causes of the LIA periods and at times likely had little effect during the half millenium cited as the time scale of this event
tonyb
Original paper available here …
w.
rgb @ur momisugly duke
I saw a graph of volcanic / earthquake activity, I think it might have been Landscheidt, but I can’t remember where.
Anyway, it showed regular marked increases of activity during solar minimums. The two seem to go together, a double whammy for climate.
I don’t buy it. We’ve seen the effect on climate from large volcanic eruptions. Remember Mount St. Helens, Mt. Pinatubo. The climatic effect from these were only 1-2 years. This is just another attempt at negating the effect of solar output on climate. There has been an ongoing effort in this area for about a year now. In a few months you’ll see a new paper from “The Team” pointing to this paper as proof that solar irradiance has no effect on climate.
Interesting data, screwed up interpretation. That Miller et al. have been able to date expansions of the ice cap is a significant advance, but notice that the dates of these advances match neatly with sharp declines in solar-magnetic activity:
Below is a graph of solar proxies from Usoskin 2003. It shows solar activity levels halving from 1200 to 1250, with an uptick before continuing to plummet after 1300, and it shows solar activity bottoming out around 1450:
Yet Miller et al. pretend that their findings militate against a solar explanation, arguing that, thanks to their volcanic-amplification theory, “large changes in solar irradiance are not required.” This is just what the CO2 alarmists say about their CO2 driven models today. By adjusting a hundred parameters they can tweak their CO2 driven model to very roughly fit a hundred and fifty years of temperature data, so why should they bother to look at the evidence for other explanations when they are “not required”?
Miller claims that “natural forcings are either weak or, in the case of volcanism, short lived.” But this depends on the unstated assumption that the only natural solar forcing is solar irradiance, when he has actually provided substantial evidence that solar activity has a stronger effect than can be accounted for by solar irradiance alone.
Yes, it COULD be that volcanism induces feedback effects that amplify its cooling effects, and it could be that there is an amplification mechanism for solar effects, as Svensmark’s GCR-cloud theory predicts. Miller has actually provided substantial evidence in support of Svensmark’s theory, yet he refuses to note it, and actually presents his paper as an argument against a solar explanation. Another example of how every piece of data has to be twisted to favor the “consensus” anti-CO2 narrative and against the competing solar theory.
Mad Scotsman says:
April 12, 2012 at 9:08 am
So the LIA did happen. Someone should tell Mann & Jones fast.
———————————————————-
And what is the name of what happened before the LIA
They seem anxious to avoid looking at the Wolf and Spoerer grand solar minima, which occured at the same time as their cooling initiation events.
Looks like the html for showing the Usoskin figure does not work in the comments. You can view the graph here:
http://i191.photobucket.com/albums/z36/AlecRawls/SolarproxiesUsoskinetalPRL2003FIG260.png
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.
Oh, good. Some more model results. And this model has proven accuracy? And references to these proofs of accuracy?
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.
**************************************
This garbage again? Why do people keep repeating this?
Wuups, wrong link above. Should have been this:
http://www.wired.com/wiredscience/2012/01/volcanoes-and-the-little-ice-age-not-the-smoking-gun/
The other fun part of connecting massive / multiple volcanic eruptions with cold snaps is mapping their frequency against solar cycles. There are a few who suggest periods of low solar activity have more eruptions. Pushback against this notion has been significant, as corellation does not suggest causation. Worse still, eruptions are not all that easy to find or date as you go back into the past. For example, the cause of the 535 AD event cooling down into the Dark Ages is unknown. There is an ongoing argument between advocates of a Krakatau eruption around then and advocates of a cometary impact somewhere. All in all, a fascinating mystery to unravel; one in which more data, more observations is always better than less. Cheers –
Willis Eschenbach says:
April 12, 2012 at 11:07 am
Original paper available here …
w.
Thanks, what I’d really like to see is the SI, can you or Lief make that available? Thanks
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.
Willis Eschenbach, thank you for the link to the original.
The authors’ last sentence seems sufficiently modest: 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.
A belief in their result requires a belief in the accuracy of their model. But their paper highlights the fact that disentangling solar and volcanic “forcings” will not be easy, and multiple models (with conflicting interpretations) will likely be found to be equally accurate for the last 1,000 years’ temperature history.
“Does not require” is complementary to the AGW proponents’ claim that any accurate model for the 20th century does require CO2. But multiple models have been produced that are as accurate as the IPCC models without “requiring” CO2. I think a fair assessment at this time is that the effects of the “forcings” can not be disentangled by complex modeling of the historical records because the forcings are “coincident”; and the anthropogenic CO2 effect is not very strong, at best, in the recent historical record.
The paper adds valuable empirical evidence.