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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Here’s a start–Change the last line to:
“Shells shame shills.”
“According to Fig. 5, a series of intense El Nino events (high red color intensity) begins at about 1450 BC that will last for centuries. In that period normal (La Nina) conditions have but disappeared. For comparison, the very strong 1998 El Nino event scores 89 in red color intensity. During the time when the Minoans were fading, El Nino events reach values in red color intensity over 200.”
http://www.clim-past.net/6/525/2010/cp-6-525-2010.pdf
Steven Mosher says:
August 8, 2014 at 5:39 pm
Cagw isn’t even defined.
>>>>>>>>>>>>>>>>
Well of course it has been defined. That’s why Republicans have to be sent to re-education camps. Wait…. are you a Republican?
What data sets suggested no El Ninos?
1. read the paper.
And since when did models need data, when it’s so much more fun and easier just to make stuff up?
1. since they were first used.
2. GCM data is available. go look at it.
“If it’s not catastrophic then who gives a toss?
1. people who live in areas likely to be effected
2. people who are overly concerned about the future
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
2. you seem certain about the catastrophe? chicken little
If it’s just AGW and not CatastrophicAGW then a whole lot of feeble-minded “scientists” are on the dole.
Not really,
“Well of course it has been defined. That’s why Republicans have to be sent to re-education camps. Wait…. are you a Republican?”
1. no it hasnt.
2. No libertarian, republicans controlled the congress senate and white house under Bush.
never trust them again,
Mosh says
“Nothing to see here!”
Aren’t you getting tired yet. Sooner or later even you can’t keep it up.
dbstealey says:
August 8, 2014 at 6:19 pm
CAGW = Catastrophic Anthropogenic Global Warming.
That’s the definition.
#############
no, thats how the acronym is defined. But yes, if the world warmed by 35C that would be CAGW.
“Bill_W says:
August 8, 2014 at 6:00 pm
Mosh,
CAGW is clearly understood. AGW is warming of 0 degrees to 1.99 C. CAGW is 2.0 or higher. Life on earth will end if the temp. goes up 2C. Ebola most likely will kill all the humans before the plankton dying kills the rest of life on earth.”
########################
Actually, not it depends. of course you’ll find in the non scientific alarmist literature references to some effects that would be catastrophic at 3C, but in the science.. there isnt a well defined concept known as a “catastrophe”
I quote: “…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…”
And well they might question because these modelers don’t have the faintest idea of what El Nino is or how it got started in the first place.. Comes from not doing your homework because it is all there in my book “What Warming?” First, El Nino is part of ENSO, an harmonic oscillation of equatorial Pacific water from east to west. It has a natural period of about 5 years but oceanic conditions can shorten or lengthen it at times. Trade winds pile up the warm water into the Indo-Pacific Warm Pool, and the Pacific Warm Pool as well. When the water level in the Indo-Pacific Warm Pool is high enough reverse gravity flow starts. An El Nino wave forms, follows the equatorial countercurrent, runs ashore in South America, spreads out along the coast, and warms the air above it. Rising warm air interferes with trade winds, joins the westerlies, and we notice that an El Nino has arrived. But any wave that runs ashore must also retreat. When the El Nino wave retreats the water level behind it drops by half a meter, cold water from below wells up, and a La Nina has started. As much as the El Nino warmed the air the La Nina will now cool it and the global mean temperature is not changed. This has been going on as long as the present configuration of equatorial Pacific currents has existed, which is to day since the Panamaian Seaway closed. That is about two million years, far more than the ten thousand they have just discovered.
I believe anthropologists studying ancient Andean cultures have linked major periods of civil disruption and abandonment of ancient cities to periodic super El Niño events going back more than 5,000 yrs before present. Of course they might be looking to the possibility of such events as cultural drivers when other factors may have been the true cause.
Steven Mosher says:
August 8, 2014 at 7:08 pm
I can’t read it. Why don’t you want to say what they were.
GCMs are entirely fictitious. They don’t use actual data. They make assumptions straight down the line, about future CO2 levels, feedbacks, clouds, everything. They’re GIGO from the git-go. No wonder they have failed utterly to forecast, since they can’t even hindcast, having never been validated.
Models aren’t science. They’re rent seeking politics. You’re a party to fraud of global proportions, yielding titanic waste of lives and treasure.
Steven Mosher: talking in riddles, koans and haiku as per effing usual.
If AGW isn’t CatastrophicAGW then it’s guaranteed that most climastrologists would be on the dole.
CAGW. When AGW becomes catastrophic.
Which will be when?
Steven Mosher;
2. No libertarian
>>>>>>>>>>>>>>>>>>
Nope. You’ve asserted that CAGW hasn’t been defined. According to MSNBC, that makes you a Republican in need of re-education.
Answer
When governments use it for power and control and stupid people buy it.
Oh that’s now.
But to make it truly valid, it must also be shown the La Ninas were also as strong and frequent.
Then for it to be a possible challenge to the global climate models, it must be shown El Ninos and La Ninas had global effects back then comparable to what current ones yield. What proof is there they weren’t just regional effects? Without it, you might as well try showing rampant global warming from a single distressed tree in Yamal. Who would believe that?
Kadaka says
Well it’s a good thing that those quality global climate models don’t have anything to worry about yet.
The Bible has many stories of droughts prior to 500BC. Some were as long as 3.5 years, and then there was the big drought in Joseph’s time which lasted 7 years, around about 1875BC.
“… sites in coastal Peru. Together they sampled 25-foot-tall piles of shells from Mesodesma donacium clams eaten and then discarded over centuries …”
What they wouldn’t have given for a good rack of llama.
Or some Heinz 57 cocktail sauce.
Lewis P Buckingham says:
August 8, 2014 at 8:28 pm
How do we know that shells are a good proxy for temperature?
>>>>>>>>>>>>>
Completely different approach from tree rings:
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.
Not that this makes in infallible, but the technique is credible as the oxygen isotopes are known to vary with temperature. Tree rings on the other hand vary with temperature, precipitation, length of growing season, disease, insect infestation, competition from other trees, soil fertility (including if or when a bear when poop and where) and so on. Tree rings are a joke.
kadaka said Then for it to be a possible challenge to the global climate models, it must be shown El Ninos and La Ninas had global effects back then comparable to what current ones yield. What proof is there they weren’t just regional effects?
You must be blind or undereducated for your present position. The proof been out there found in geological and archaeological studies(mainly underwater archaeologic studies of settlements from todays English channel over the North Sea all way up to close to island studies in Alta region, Norway). Studies of settlements that within a short period(50 to 100 years) had to be abondoned.
You seem to be unaware of what happened. Here in Scandinavia every pupil of 12 should have heard of it in school. When a hugh amount of fresh water within days “slipped” into the ancient Atlantic’s salt water system it caused a tremendous sudden effect on sea streams, straiths and during a short period (same 50 to 100 years) the collision between non-salt cold water with high saltination straiths, some warm (up to 24/25 degrees Celcius) some less warm but with high saltination factor caused phenomena such as El Nino, La Ninas etc. around the globe to “occure”.
That’s easy to take into computer models had some of all the so called AWG believers who wrote what they call models taken the 43 most essential factors for sealevel calculation in the past. I had it in my C-essay back in -93. Oh you must of course know exactly when and why it all happened and have knowledge of what type of sediment/ground/soil analyses you need to prove the effect around the globe for. But you don’t seem to know. Do you?
Well what happened happened 11 500 years ago. Within a short time, 50 years the temperature over Northern Hemisphere tised 12 degrees Celsius causing among other things a large lake called Yoldia Sea to fill up in and over the land as well as sea area of today’s Baltic Sea. When the inland sea (that was what it was/had been for aproximate 600 years) emptied over land within 50 years 10 700 BP causing a quick landrise of 25 meters around the Baltic Sea was followed by the Ancylus sea/lake with even colder and less salt water than the Yoldia Sea had had.
Short before 10 000 BP the Ancylus sea broke way over newly landrised land. The place that in earlier days was belived to be the place where erosion caused the sea to brake thru to the Atlantic area is called Sveafallet. Today’s scientists specialisted in studying sediment and how to date them places the exact location west of today’s Lake Vaenern (at that time part of the Ancylus Sea). If you had known where to look for the special geologic studies you should have needed to be able to make models, I had worked two summers in my youth for the geologic dept of a Swedish firm almost dominating the world for that type of analyses, you should have been able to put these factors together with chemical formulas for what happens in open sea when cold straights meet warm and if you had you would have known that the Earth rotation, wobbling and effect of sun on warm sea (with over 27 degrees Celcius temperature) caused effects not only locally but all around the Northern Hemisphere.
It’s basic knowledge of University Mathematic that’s all one need for finding the answer. The answers have to be checked for each 1000 meter around the coasts of today in Northern parts of Northern Hemisphere. In other words matematic variables gives figures which you have to check using empiric knowledge around the Atlantic and the Pacific Ocean. Then you will find where phenomena like El nino can and probably will occure. If you have matematic variables for saltination distribution combined with variables for temperature over seasons for each studied “point” you also will find almost all factors needed to understand El nino variations.
All this is simple to understand. But of course you need to know where to look for empiric data to prove thesis in each “GSP”-point you study.
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Remedial assignment:
Review evidence showing the Medieval Warm Anomaly was regional, thus did not warrant inclusion into the informative “Hockey Stick” graph showing historical global temperatures by renowned climatologist and Nobel Prize laureate Dr. Michael Mann.
Mosher does not even know what an El Nino is meteorologically… It is a distortion of the boreal hemisphere circulation, so there are no reasons that this event would not have happened in the past, especially given the known climatic shifts (glaciations/deglaciations).
Interesting results. Some years ago, I plotted up the raw oxygen isotope data measured by Stuiver and Grootes (1997) from the GISP2 ice core and was surprised to find 40 recurring warm/cool periods since 1480 AD. The average of each warm or cool cycle was 27 years, essentially the same as the PDO (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.