Ancient shellfish remains rewrite 10,000-year history of El Niño cycles
Hannah Hickey University of Washington
The planet’s largest and most powerful driver of climate changes from one year to the next, the El Niño Southern Oscillation in the tropical Pacific Ocean, was widely thought to have been weaker in ancient times because of a different configuration of the Earth’s orbit. But scientists analyzing 25-foot piles of ancient shells have found that the El Niños 10,000 years ago were as strong and frequent as the ones we experience today.
The results, from the University of Washington and University of Montpellier, question how well computer models can reproduce historical El Niño cycles, or predict how they could change under future climates. The paper is now online and will appear in an upcoming issue of Science.
“We thought we understood what influences the El Niño mode of climate variation, and we’ve been able to show that we actually don’t understand it very well,” said Julian Sachs, a UW professor of oceanography.
The ancient shellfish feasts also upend a widely held interpretation of past climate.
“Our data contradicts the hypothesis that El Niño activity was very reduced 10,000 years ago, and then slowly increased since then,” said first author Matthieu Carré, who did the research as a UW postdoctoral researcher and now holds a faculty position at the University of Montpellier in France.
In 2007, while at the UW-based Joint Institute for the Study of the Atmosphere and Ocean, Carré accompanied archaeologists to seven sites in coastal Peru. Together they sampled 25-foot-tall piles of shells from Mesodesma donacium clams eaten and then discarded over centuries into piles that archaeologists call middens.
While in graduate school, Carré had developed a technique to analyze shell layers to get ocean temperatures, using carbon dating of charcoal from fires to get the year, and the ratio of oxygen isotopes in the growth layers to get the water temperatures as the shell was forming.
The shells provide 1- to 3-year-long records of monthly temperature of the Pacific Ocean along the coast of Peru. Combining layers of shells from each site gives water temperatures for intervals spanning 100 to 1,000 years during the past 10,000 years.
The new record shows that 10,000 years ago the El Niño cycles were strong, contradicting the current leading interpretations. Roughly 7,000 years ago the shells show a shift to the central Pacific of the most severe El Niño impacts, followed by a lull in the strength and occurrence of El Niño from about 6,000 to 4,000 years ago.
One possible explanation for the surprising finding of a strong El Niño 10,000 years ago was that some other factor was compensating for the dampening effect expected from cyclical changes in Earth’s orbit around the sun during that period.
“The best candidate is the polar ice sheet, which was melting very fast in this period and may have increased El Niño activity by changing ocean currents,” Carré said.
Around 6,000 years ago most of the ice age floes would have finished melting, so the effect of Earth’s orbital geometry might have taken over then to cause the period of weak El Niños.
In previous studies, warm-water shells and evidence of flooding in Andean lakes had been interpreted as signs of a much weaker El Niño around 10,000 years ago.
The new data is more reliable, Carré said, for three reasons: the Peruvian coast is strongly affected by El Niño; the shells record ocean temperature, which is the most important parameter for the El Niño cycles; and the ability to record seasonal changes, the timescale at which El Niño can be observed.
“Climate models and a variety of datasets had concluded that El Niños were essentially nonexistent, did not occur, before 6,000 to 8,000 years ago,” Sachs said. “Our results very clearly show that this is not the case, and suggest that current understanding of the El Niño system is incomplete.”
The research was funded by the U.S. National Science Foundation, the U.S. National Oceanic and Atmospheric Administration and the French National Research Agency.
Other co-authors are Sara Purca at the Marine Institute of Peru; Andrew Schauer, a UW research scientist in Earth and space sciences; Pascale Braconnot at France’s Climate and Environment Sciences Laboratory; Rommel Angeles Falcón at Peru’s Minister of Culture; and Michèle Julien and Danièle Lavallée at France’s René Ginouvès Institute for Archaeology and Anthropology.
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New data shows modern El Ninos are the same intensity/severity as they were 10,000 years ago… and the best ‘climate models’ don’t emulate this at all. The ‘climate models’ are shown to be significantly in error, yet again. GIGO.
if the world warmed by 35C that would be CAGW.
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let us know when it goes up 34.9 so we can take action.
Another one bites the dust, yeah
no one of serious thought doubts that 3.5C rise wouldn’t have many many serious negative consequences for mankind.
but how do we have any control over that when CO2 sensitivity is likely ~1deg C? 285 ppm x 2^3.5 = 3220 ppm. If man’s total combustion of fossil fuels to date is an additional 120ppm CO2, we run out of all fossil carbon sources before we get to 1800 ppm. And that in at least 250 years from now.
oh yeah, it GCMs all the way down. silly me. It’s more likely in 200 years from now they’ll be thanking us from saving the world from the next Glacial cycle.
ENSO, AMO, etc.exist.
They are cyclical and we have absolutely not the vaguest idea if they are slowly ramping up or down because we lack the necessary multi-centennial observation data. Models that take them into account are not verifiable, therefore will not be validated for many generations to come.
Short term variations of the atmospheric temperature are linked to such cycles, but long term climate changes have nothing to do with them – multi-decadal is very short term in climate speak.
Steven Mosher says:
August 8, 2014 at 7:11 pm
“If it’s not catastrophic then who gives a toss?
1. people who live in areas likely to be effected
…
The EU supposes to reduce CO2e emissions 80% by 2030 compared to 1990. That would be a catastrophe – considering agriculture alone makes up most of the remaining 20%.
1. not really, who cares about the EU? not me
You care about people living in certain areas, but you don’t care about EU?
Funny.
what i don’t undestand is the reason why they could think el nino phenomenon is more or less understood….????
There’s actually been little discussion about this paper in comments so far.
Unfortunately it’s paywalled and we don’t get to see any of the data, graphs, or anything to assess the validity of the study.
If I understand the description, these are large dumps of shellfish remains caught, cooked and dumped. The dating comes, not from depth position ( which would be useless in this context ) but from carbon remains from the fire that cooked each sample.
Now you need to paper to see how they get samples that are not affected by cross-contamination.
The main problem I see is that C14 dating is not very accurate and is very sensitive to individual measure errors and calibration.
http://en.wikipedia.org/wiki/Radiocarbon_dating#Errors_and_reliability
Radiocarbon dates are generally presented with a range of one standard deviation (usually represented by the Greek letter sigma: σ) on either side of the mean. This obscures the fact that the true age of the object being measured may lie outside the range of dates quoted. In 1970, the British Museum radiocarbon laboratory ran weekly measurements on the same sample for six months. The results varied widely (though consistently with a normal distribution of errors in the measurements), and included multiple date ranges (of 1σ confidence) that did not overlap with each other. The extreme measurements included one with a maximum age of under 4,400 years, and another with a minimum age of over 4,500 years.[57]
How it is possible pick up variations on an inter-annual scale using dating with that kind of impression needs to be looked at very carefully.
On the face of it, it seems highly questionable.
Until I get to see how and whether they address this issues in the paper I won’t be regarding it as anything more substantial.
Don Easterbrook: (http://www.nipccreport.org/reports/ccr2a/pdf/Chapter-5-Cryosphere.pdf
Figure 5.9.6.3, page 689. I’ll plot up the rest of the data and compare it with the data of Carre et al.
Have you found a link to the Carre et al data?
Unfortunately Figure 5.9.6.3, page 689 is pretty illegible apart from the wiggle.
The early period in particular looks very cyclic, other eras, less so. Variation in the “period” seems to be about 1:2 . Still it would be interesting if there is some corroboration with Carré et al.
Lewis P Buckingham says:
August 8, 2014 at 8:28 pm
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Of course not.
All living proxies are simply a good proxy for the environmental conditions in general in which the proxy finds itself. Beneficial environmental conditions promotes growth, adverse environmental conditions stunt growth. Environmental conditions extend to cover extraneous factors such as competion and predators, so is wider that your list.
One cannot isolate any one specific criteria from the more general. All we can say is that at time X, it was very good, or good, or not so good, or poor, or bad, or very bad for the proxy. Why that is so, we can only speculate.
All proxy evidenc e carries with it huge error bars and should be taken with pinch of salt.
OK, I’ve found there is quite a lot in the SI. http://www.sciencemag.org/content/early/2014/08/06/science.1252220/suppl/DC1
Preparation of the shell samples looks very meticulous providing approx 1 month resolution time lines for each shell.
Oxygen isotopes from 25 foot piles of shells that are mixed with charcoal from fires that is carbon dated. It’s proxy on top of proxy on top of proxy and we’re expected to believe that the ‘signal’ relates to tiny changes in ocean temperatures from 10000 years ago.
The only sensible part of this is obvious – “we’ve been able to show that we actually don’t understand it very well” – now there’s a surprise.
I don’t care whether the output supports a sceptical viewpoint or an alarmist viewpoint, it’s nonsense to use proxies for anything other than a vague interpretation of anything. Because in reality you can’t possible know all the contributing factors.
This type of ‘science’ is the equivalent of Jazz (aka musical w@nking), fun for those taking part and maybe a few interested voyeurs, but contributing nothing to society as a whole.
Once again skeptics are correct: The current climate is not exceptional.
Steve Mosher makes an important point:
The world is held in thrall by a non-defined, and therefor non-falsfiable pile of crap.
The promoters make careers and fortunes off of hyping something that is undefined.
The politicians tax and regulate and call names based on something that is not defined.
*That*, however is a pretty good definition of *scam*.
no one of serious thought doubts that 3.5C rise wouldn’t have many many serious negative consequences for mankind.
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I serious doubt that it would have more negative consequences than positive. Every morning of every day temperature rises more than 3.5C where I live. The same is likely true for most people.
Humans are better adapted to warm than any other large mammal. 99% of the places where human beings live today are TOO COLD for an unprotected human to survive.
We have minimal fur, and our upright poster minimizes exposure to the sun and maximizes evaporation and cooling. Without technology (fire) we would still be living in the tropical jungles.
Warming will most certainly lead to increased food supply and increased rainfall, on average. There will be winners and losers for sure. But since most of the warming will take place in regions that are currently cold, on balance it will be largely positive.
From a technology point of view, it is much cheaper to cool an object than to warm it. All that you need for cooling is the evaporation of water. However, to heat an object requires an energy source such as fossil fuel. Water is much cheaper than fossil fuel.
We all know GCM equals garbage in, gospel out.
Mosher has been the perfect example of do not blog after 2nd bottle of wine.
Well, something has changed in Peru. The guy in the picture, standing on top of a huge midden, is surrounded by … nothing. Why have all the Peruvians left the area that was once, for many centuries, a good place to eat?
*lemiere jacques August 9, 2014 at 12:55 am says: “what i don’t undestand is the reason why they could think el nino phenomenon is more or less understood….????”
Quite so. All those “experts” know nothing about it. The reason is that the only true explanation is in my book “What Warming?” and these pseudo-scientists are too lazy to read scientific literature in their own field. Same about Arctic warming. I proved that it is not caused by the greenhouse effect but is produced by warm Gulf Stream water carried into the Arctic Ocean by currents. It was in my book and also in a journal article I wrote that you can download from Judith Curry’s blog. But these pseudo-scientists ignore it and keep babbling about global warming in the Arctic. And then they are puzzled why the Antarctic is cold and the Arctic is warming. It is very simple: if it wasn’t for the warm water carried into the Arctic by currents the Arctic would be just as cold now as the Antarctic is. If you want to know about the climate your best bet is to start with my book and ignore these blowhards.
Unlike the beginning of glacial eras or glacial /interglacial oscillations within these eras, at least the oscillation period el Niño probably is influenced by continental configuration.
Milankovitch holds one seat on the board of directors for glacial/interglacial oscillations (out of maybe 10).
Had no idea models believed ninos did not exist at the beginning of the current interglacial. Why would anyone think this? Because CO2 was low? Haha. Of course, CO2 causes el ninos, along with war, Ebola and famine.
In January 2013 Kim Cobb at UCSD published in SCIENCE a study of corals going back 7000 years. In that journal it was all about meme format, but her data revealed that the strongest ninos during that 7000 year period were during the little ice age…
ENSO is the heart of the Pacific ocean pumping equatorial heat poleward. Not surprising that it has operated throughout the Holocene. A more interesting question would be if and at what strength it operated during deep glacial periods.
Bill Illis on August 8, 2014 at 4:31 pm
The requirements for an ENSO are a wide deep ocean at the equator, a rotating Earth, and Trade Winds. That makes for an ENSO operating for about 80% of Earth history.
Plus – possibly – a western continental boundary to entrain upwelling
gymnosperm, could the strong El Ninos noted during the LIA be the result of volcanic interruption of Walker Cells? When these cells are working, there are sufficient pressure differences between East and West oceanic areas to set up a trade wind circulation that keeps El Nino in neutral to La Nina territory (IE surface winds are blowing from East to West, keeping clouds and the solar warmed pool on the West side of equatorial ocean areas. When these cell functions are disrupted (as they have been reported to in the literature related to equatorial volcanic events), and Walker Cell pressure differences become more equal, an El Nino is triggered, the ocean surface calms, and the top layers of the ocean become defined with less mixing, setting up evaporation of the top most layer.
I am skeptical about the procedure as a whole and whether it is a representative ENSO metric. El Nino occurs three to six months every four to six years. It takes quite a bit of skills to segregate shells and examine infinitesimal shell thickness to locate temperature rise fingerprint. I question the results altogether.
ENSO increasing trend is observed at this time and noted in the IPCC Fourth assessment Report. It is the present time and we know it is increasing.
To Billy Liar:
You wrote in part:
A lack of trendy new restaurants opening in the area. Does it every time.