There’s a new article at Nature News where they report on an amazing new paleoclimatology breakthrough with temperature reconstructions using clamshells. The Nature article reports on a new paper in PNAS from William Patterson at the University of Saskachewan. Here’s a short excerpt:
The study used 26 shells obtained from sediment cores taken from an Icelandic bay. Because clams typically live from two to nine years, isotope ratios in each of these shells provided a two-to-nine-year window onto the environmental conditions in which they lived.
Patterson’s team used a robotic sampling device to shave thin slices from each layer of the shells’ growth bands. These were then fed into a mass spectrometer, which measured the isotopes in each layer. From those, the scientists could calculate the conditions under which each layer formed.
Unlike counting tree rings which have varying widths due to all sorts of external influences such as rainfall, sunlight, temperatures, available nutrients, and available CO2, this method looks at the levels of different oxygen isotopes in their shells that vary with the temperature of the water in which they live. One simple linear relationship.
The data resolution from isotope counts is incredible.
“What we’re getting to here is palaeoweather,” Patterson says. “We can reconstruct temperatures on a sub-weekly resolution, using these techniques. For larger clams we could do daily.”
The reconstruction is shown below. We see familiar features the little ice age, the medieval warm period and the downturn which led to the extinction of Norse settlements on Greenland.
And the feature of this reconstruction to surely stick in the craw of many who think we are living in unprecedented times of warmth is the “Roman Warm Period”. Have a look:
From Nature: Shellfish could supplant tree-ring climate data
Temperature records gleaned from clamshells reveal accuracy of Norse sagas.
Richard A. Lovett
Oxygen isotopes in clamshells may provide the most detailed record yet of global climate change, according to a team of scientists who studied a haul of ancient Icelandic molluscs.
Most measures of palaeoclimate provide data on only average annual temperatures, says William Patterson, an isotope chemist at the University of Saskatchewan in Saskatoon, Canada, and lead author of the study1. But molluscs grow continually, and the levels of different oxygen isotopes in their shells vary with the temperature of the water in which they live. The colder the water, the higher the proportion of the heavy oxygen isotope, oxygen-18.
The study used 26 shells obtained from sediment cores taken from an Icelandic bay. Because clams typically live from two to nine years, isotope ratios in each of these shells provided a two-to-nine-year window onto the environmental conditions in which they lived.
Patterson’s team used a robotic sampling device to shave thin slices from each layer of the shells’ growth bands. These were then fed into a mass spectrometer, which measured the isotopes in each layer. From those, the scientists could calculate the conditions under which each layer formed.
“What we’re getting to here is palaeoweather,” Patterson says. “We can reconstruct temperatures on a sub-weekly resolution, using these techniques. For larger clams we could do daily.”
It’s an important step in palaeoclimatic studies, he says, because it allows scientists to determine not only changes in average annual temperatures, but also how these changes affected individual summers and winters.
“We often make the mistake of saying that mean annual temperature is higher or lower at some period of time,” Patterson says. “But that is relatively meaningless in terms of the changes in seasonality.”
For example, in early Norse Iceland — part of the 2,000-year era spanned by the study — farmers were dependent on dairy farming and agriculture. “For a dairy culture, summer is by far the most important,” he says. “A one-degree decrease in summer temperatures in Iceland results in a 15% decrease in agricultural yield. If that happens two years in a row, your family’s wiped out.”
Technically, the molluscs record water temperatures, not air temperatures. But the two are closely linked — specially close to the shore, where most people lived. “So, when the water temperatures are up, air temperatures are up. When water temperatures are down, air temperatures are down,” Patterson says.
Read the complete article at Nature News
Kelyfoclimatology?
I will never see a raw clam (only way to eat ’em) in the same light, as it gets washed down my gullet with a cold brew. I will send a prayer of thanks for each little morsel. On a serious note, this is absolutely brilliant! Who knew?????
mmmmmmm…slurp slurp….mmmmmmmmmmmm
The graph is missing ….
[Reply: until it’s fixed, just click on the blank box and the embiggened chart will appear. ~dbs, mod.]
Someone just needs to graft the instrumental record on the tail end of that puppy, and the clams can play hockey, too!
Sorry sir, but this, sounds too much like science. I believe computer models, scientific papers where the raw data is unavailable and conspiracy of big oil is more logical.
Mann puts it perfectly. “The side that is issuing these attacks, our detractors, are extremely well-funded, they are extremely well-organized. They have basically had an attack infrastructure of this sort for decades. They developed it during the tobacco wars. They honed it further in efforts to attack science that industry or other special interests find inconvenient. So they have a very well-honed, well-funded, organized machine they are bringing to bear now in their attack on climate science.”
Forget about the science, forget about my emails, let me tell you a story of big greasy oil, sending professional squad teams against good scientists like me. Be afraid, woOoohhh.
I don’t get a reconstruction image on screen, for some reason.
[Reply: click on the blank box, you’ll get it. ~dbs, mod.]
“If he can find the funding, that is exactly what Patterson would like to establish next. “We have what may be the world’s oldest clam,” he says, “that might give a continuous record going back 400 years.””
So, we have a “demonstration” that covers the period up to 1650 and if Patterson gets the funding we will get the clam record of the past 360 years!
It looks promising, mabe this is money well spend!
“So, when the water temperatures are up, air temperatures are up. When water temperatures are down, air temperatures are down,” Patterson says.
Dunno. Ever swim in a ocean inlet or bay? The surface water down to about three feet is nice and toasty. Get below that, where there are plenty of bivalves, and water temps drop rapidly.
I’m with Pamela, prefer eating on half shell than reading paleoclamate.
The image doesn’t seem to show.
[Clicky in box, image appear. ~dbs, mod.]
“The study used 26 shells obtained from sediment cores taken from an Icelandic bay. Because clams typically live from two to nine years, isotope ratios in each of these shells provided a two-to-nine-year window onto the environmental conditions in which they lived.”
So they are after a 2,000 year timespan of sedimentary layers to examine oxygen isotopes in clamshells. This will yield temperatures in a sub-weekly resolution. That is placing a lot of confidence in the accuracy of the dating of the stratigraphy in the cores. That is putting all your clams in one basket!
I foresee an undending series of Clam jokes coupled with Climate science. “Climate scientists clam up on Warm periods’. Seriously, given the ability to both carbon date any remaing organic matter in a clamshell and analyse the corresponding water temperature makes dendrochronology a dead end for climate reconstruction. There are the limitations that it can only give the shallow water temperatures but that never stopped the dendro’s.
This theory is way wrong. The water temps vary in different spots that are not far apart.
Let’s turn loose about 6 teams and see if their results are identical.
“For a dairy culture, summer is by far the most important,” he says. “A one-degree decrease in summer temperatures in Iceland results in a 15% decrease in agricultural yield. If that happens two years in a row, your family’s wiped out.”
I will take the one degree increase in summer temperatures over an increase in energy and food costs through carbon rationing, any day!
“Decrease,” that is. Or increase!
[Clicky in box, image appear. ~dbs, mod.]
Nothing happens.
[I get it with no problem. But I’ll look into it ASAP. In the mean time, you can get the same image from the link in the last sentence of the article. ~dbs]
Error bars! What are these . . . error bars?!
Clamy…how I love ya…how I love ya…my dear ol’ Clamy!”
…and so the Mann says to the clam, “Have you heard the one about the hockey stick…..”
This will fill in the gaps in the SH record regarding the MWP. Researchers down under should jump on this. Lots of data is needed to build confidence, so nothing will be wasted. Australia (both ends), NZ, Chile, S. Africa, etc. should each fund a couple of studies.
If you want the graph, click on the link to the article itself, then click on the thumbnail image within the article.
I tried clicking in the box but nothing happens.
REPLY: Yes the pinheads at Nature don’t allow image sharing links. I’ve fixed their problem. -A
PS: A miracle has happened.
Use this link to the image in the above text:
http://www.nature.com/news/2010/100308/images/800px.chart.2010.Fig3_mussels.jpg
Geoducks have a lifespan up to 150 years.
Nothing could be finer than to spend a Sunday morning at the Acme Oyster House in New Orleans, slurping down oysters and drinking a bloody Mary!
Looks like the video is correct,
Unstoppable Solar Cycles (Video) (10min)
The Roman Warm Period did not exist because Wikipedia felt fit to delete a well resourced article on it.
PNAS,
not Nature,
and here is the actual article
http://www.pnas.org/content/early/2010/03/02/0902522107.full.pdf+html
REPLY: Nature News covered the PNAS paper. That news article is what is referenced. – A
The full paper, much longer than the report in Nature is at http://www.pnas.org/content/early/2010/03/02/0902522107.full.pdf
I would recommend these folks not release any of their data or methods to any member of the “Hockey Team”. After all they’ll just want to find something wrong with it.
The Arctic sea ice is at NORMAL levels in nearly all areas, except the sea area (South and West of Greenland) that has been readily affected by natural processes easily shown.
This is just begging for me to don furry underwear and insulated outwear to dig for clams around the entire edge of the Arctic basin. We just might find correlations between clams and ice. Bring beer and binoculars. We can laugh at yonder insurance company researchers trying to get their equipment to work.
Maurice Newman, Chairman of ABC Australia (BBC equivalent – tax-payer funded) has created a huge furore 0 especially with his own staff – with a speech he made to ABC journalists yesterday:
Maurice Newman’s address to ABC staff
Climate change is a further example of group-think where contrary views have not been tolerated, and where those who express them have been labelled and mocked. In his ABC Online blog last October Chris Uhlmann wrote a piece called In praise of the sceptics. ‘“Climate science we are endlessly told is “settled”’ he wrote. “But to make the, perfectly reasonable, point that science is never settled risks being branded a “sceptic” or worse a “denier”…one of those words, like “racist”, which is deliberately designed to gag debate…You can be branded a denier if you accept the problem and question the solutions.”
This collective censorious approach succeeded in suppressing contrary views in the mainstream media, despite the fact that a growing number of distinguished scientists were challenging the conventional wisdom with alternative theories and peer reviewed research.
Then came the sensational revelations of unprofessional conduct by some of the world’s most influential climatologists exposed by the hacked or leaked emails from the University of East Anglia’s Climatic Research Institute. This was followed by more evidence of dubious research and politicised advocacy contained in scientifically unsupported claims and errors in the IPCC 4th Assessment, including in the carefully vetted Synthesis Report. Questionable methods of analysis resulting in spurious temperature data have added further doubts on the underlying credibility of the science.
The lack of moral and scientific integrity shown by the IPCC serves only to reduce clarity and increase confusion, disappoint believers and give fuel to doubters. It has frustrated policy makers, and as polling now shows, it has clearly weakened public belief in climate change and devalued respect for science in general.
In defending the indefensible, Mr Gore, university vice-chancellors and those in the media, do a disservice to the scientific method and miss the point that no matter how noble your work, your first responsibility must always be to the truth.
As you would expect, as Chairman of a public broadcaster, I followed with interest the announcement by the BBC Trust that it would carry out a review of the accuracy and impartiality of the BBC’s coverage of science. It came after a year in which online science bloggers continued to raise concerns about mainstream media coverage.
A contributing factor for the review was the revelation that the CRU emails were known to Paul Hudson, the BBC climate correspondent one month before the story broke – but not reported at the time. While disturbing, it is heartening to know that the BBC takes quality control seriously.
The Guardian noted “The moment climatology is sheltered from dispute its force begins to wane.” Which raises an important question for a media organisation: who, if anyone, decides what to shelter from dispute? And when? Should there be a view that the ABC was sheltering particular beliefs from scrutiny, or failing to question a consensus, I would consider it to be a dangerous perception that could lead to the public’s trust in us being undermined…
http://www.theaustralian.com.au/business/media/maurice-newman-speech/story-e6frg996-1225839427099
this is hopefully the beginning of some changes at the ABC.
We’ll see how well this pans out. In the meantime, everybody keep clam.
The clams do not lie.
This is old hat. Even Wikipedia has an entry on 18Oxygen:
http://en.wikipedia.org/wiki/Delta-O-18
Emiliani figured all this out: Emiliani, C. 1955. Pleistocene temperatures. J. Geol. 63:538-578.
This data is obviously wrong! The peer review process has failed, clearly the data must undergo homogenisation and adjustment.
Looking at the chart and the caption beneath, which you did not post, I would conclude that parts of the little ice age were as warm as the medieval warm period.
Others mileage may vary, but more clam shells need to be processed in order to give a complete and robust temperature reconstruction, don’t you think.
REPLY: try a refresh. I did indeed post it, but Nature News doesn’t like to share. – Fixed now -A
The history of this method can be found here: http://www.leif.org/EOS/12-740Spring2002.pdf
Come on Leif. I’ve had a really rough day at “group-think” central today and I need to let off a little steam…steam…mmmmmm.
So does Mann NOT read Wiki? Why on Earth would he go around goring poor defenseless trees that he does not intend to eat, when he can measure clams and then eat the contents? This seems a no brainer to me. Trees – Clams. Trees – Clams.
But then I didn’t know about temperature and clams either. In fact, don’t know squat other than my first bite of oysters on the half shell at the Oyster Bar in Portland, OR, which caused me to ring my waiter and complain that my food wasn’t cooked. He graciously (without a word) took my plate away and brought steamed oysters. I then caught his eye again and said I wanted the other oysters back, that I had changed my mind.
You know what? He brought out another plate of raw oysters, telling me he hadn’t had a chance to dump the plate. Now that I am older, I will have to admit that I was a dumb-ass then and that good waiters are hard to find. I have found only one worthy of his clams. Who probably still thinks I’m a dumb-ass.
Leif Svalgaard (18:48:03) :
What’s not old hat is the confirmation of the Medieval Climate Optimum and the falsification of the treering data.
So will the “mainstream” clam-media finally open up and cover this story?
No. Don’t ya know that you have to cook clams to get them to open up without using a pry bar?
So now we can get our clams read after dinner?
If this catches on, M Manns job is chowder.
Pamela Gray (19:00:06) :
But then I didn’t know about temperature and clams either.
The 18Oxygen stuff has been know for more than half a century. See the historical notes I provided. But every so often people has to be reminded of the known knowns.
I’m not certain I’m buying this. According to the study some of those clams would have been dead for hundreds of years. Those were HOLLOW clams. Robust claims can only come from robust clams, and these ones were hollow. There’s no way to cut them open and count the rings which is the only way to get a robust clam claim. And this business of shaving them? CLAMS DONT SHAVE THEY DONT EVEN HAVE HAIR! And this clown claims the clams aren’t clamming up about climate?
Wasn’t there an old BC comic about clams talking?
The automated, fine-tuned shell-shaver seems to be a new advance. It promises much more detailed and reliable results. This alone ought to promote increased use of this technique.
LOL! Great job with the Mann/clam photoshop.
I should think you would have to nail down with great resolution when the clams being tested were alive in order to use the data on a timeline showing sub-weekly temperatures. How accurate are the sediment dating methods? Or, are they determining the age of the mollusks individually using an isotope, carbon or other dating method?
Is my thinking off-kilter here?
Thousand Foot Krutch — Clam It Up lyrics
Chorus:
I’ve got a bad case of clammin it up
It’s getting cold in here so clam it up
I’ve got a bad case of clammin it up
It’s getting cold in here so somebody clam it up
Come on and clam it up
Verse 1:
I’m in love with the feeling
Of temps to the ceiling
We come with intention
To face my opposition
Get raw when it’s time
To lay it on the line
To the walls where we’re taking it
Let your tree shine, like
Let your tree shine, like
Let your tree shine
[Chorus]
Take it higher, take it higher
Til the roof is on fire
Take it higher, take it higher
Let’s burn it up
We throw down
When it’s time for the action
Make it happen, and the sound
That you’re feeling like lead
Might just happen
When you’re warm
You might not
Get a warning or a sign
To the walls where we’re taking it
Let your tree shine, like
Let your tree shine, like
Let your tree shine
Mann’s least liked movie? The Silence of the Clams.
I am reminded of the early papers on tree ring data and see some of the same localized problems. However I hope to see development of more data from all over the world.
On viewing the graph I see that it is worse then I thought, we are already heading into the next Iceage. The AGCC people better get ahead of this because we are all doomed, and I left Alaska because I was tired of the cold and snow. ;-[
Leif Svalgaard (18:59:21)
Old hat? Done before? Foraminifera are not a type of clam. I dont think they are claiming to have invented O16-O28 aging.
YES…there was a MWP
YES…there was a LIA
NO….Methane is not building up in the atmosphere. Read here World climate Report
Note the spikes during El Nino years.
Re: the above post. I thought I could help Mann out by providing him with a good PR song for promoting his tree.
Fried clams, steamed clams, clams in Portugee stew – there’s as many ways to eat a clam as there are clams.
So, does this prove that clams got legs?
phlogiston (19:22:16) :
Old hat? Done before? Foraminifera are not a type of clam.
So what? this works with any kind of shell with oxygen in it.
E.g. 2009 Portland GSA Annual Meeting (18-21 October 2009)
USING MOLLUSK SHELL SHUTDOWN TEMPERATURE TO CONSTRAIN OXYGEN ISOTOPES OF WATER
GILLIKIN, David P., et al.
“It is well known that mollusk shell oxygen isotopes (δ18O) are a function of both water temperature and δ18O value of water in which they grew.”
or http://www.geo.arizona.edu/ceam/GoodwinPalaios.pdf
[from 2003]
Have to agree with Henry here.
This paragraph is full of fail:
Technically, the molluscs record water temperatures, not air temperatures. But the two are closely linked — specially close to the shore, where most people lived. “So, when the water temperatures are up, air temperatures are up. When water temperatures are down, air temperatures are down,” Patterson says.
First off, it would be “especially”, not “specially”. And secondly, we’ve seen that melting of ice around Greenland recently has been demonstrated to be due to warmer currents moving north, not warmer air temps. It would take a very long time and a complete lack of currents and wind for local water and air temps to locally homogenize.
Just keep that shaver thing away from the Rocky Mountain Oysters.
@davidmhoffer (19:15:44) :
It wasn’t clams mate, but we won’t go into that here…
http://s396.photobucket.com/albums/pp47/clamsgotlegs/
Moderator: Tips and Notes doesn’t seem to be working. My browser freezes when I click the link. I wanted to pass on the information that the crisis in climate science made it onto the PBS Newshour tonight with an entire segment titled, “Criticism of Climate Science Heats Up.” The segment was apparently provoked by the announcement of the “independent” IPCC investigation, and features Stephen Schneider, Pat Michaels, and Judith Curry. It has some flaws, to be sure, but all-in-all quite balanced I thought. Judge for yourself (The link starts with a short commercial):
http://www.pbs.org/newshour/bb/weather/jan-june10/climate_03-10.html
REPLY: Whatever the problem is, it is with your computer setup/browser.
This appears to be a promising method. I think this article is just scratching the surface though – no pun intended.
Pamela Gray
Thank you for the posts. You make the wait between syndicated episodes of “Family Guy” much more bearable.
I love it when something like this paper turns up… after I was criticised in private.
Here is evidence the LIA did apply to Alaska too. There will be much more there for finding if you look in the data. What this might do is give a clue on where to look.
Compare with the graph in the full clam paper.
http://daedalearth.wordpress.com/
Please don’t tell Pachauri about shaving climate clams, he’ll start a sequel to “Return to Almora”!!
Synopsis: Slices from layers of shell growth bands fed into a mass spectrometer = palaeoweather.
Hmmm… seems as if the grouping of shell growth bands into “layers” might be arbitrary.
Anyway, the spectrometry of slices of shell growth bands = spectrometry of slices of shell growth bands. I am certain that “palaeoweather” is linearly independent of the spectrometry of slices of shell growth bands.
What a crock of excrement.
phlogiston (19:22:16) :
Old hat? Done before? Foraminifera are not a type of clam.
The clams were done before the Foraminifera, Epstein [1951], on suggestion from Urey [discoverer of Heavy Water] back in 1947:
http://geology.rutgers.edu/~jdwright/JDWWeb/2000/Wright2000.pdf
Emiliani did it on a large scale and takes credit for the systematic exploitation of the idea.
R. de Haan (18:03:27) :
“If he can find the funding, that is exactly what Patterson would like to establish next. “We have what may be the world’s oldest clam,” he says, “that might give a continuous record going back 400 years.””
So, we have a “demonstration” that covers the period up to 1650 and if Patterson gets the funding we will get the clam record of the past 360 years!
It looks promising, mabe this is money well spend!”
Sounds like it is time to take up a collection…. Where oh where is all that OIL MONEY
Seriously, if I were not dead broke I would very much like to help fund this research….
Think they need a free lab assistant???
Lazarus Long (19:27:57) :
So, does this prove that clams got legs?
they got feet… or foot, at least.
Sorry.
I got as far as sub-weekly resolution & my BS detector hit the pins
I’m a sceptic but I reject this
DaveE.
I’m so sorry…
I can’t help myself..
Playing this U Tube will reveal that, YES, we “skeptics” are very, Very, VERY…
SICK!
Leif Svalgaard
Now you’re shifting from plankton to molluscs. That is the whole point. The growth of a mollusc shell at a given location will vary year-to-year much less than that of plankton (bloom and bust) at any location. A K rather than an r strategist. This makes measurement of O16-18 ratio in the mollusc shells a statistically stronger (I’ll avoid the other “r”-word) measurement than planktonic foraminifera.
Going from smaller molluscs to clams just continues this improvement in data quality – bigger, more mineralised tissue for more accurate mass spec.
“Because clams typically live from two to nine years, isotope ratios in each of these shells provided a two-to-nine-year window onto the environmental conditions in which they lived.”
By contrast your average foraminiferan lives only for a few months.
pat (18:46:06) :
“Maurice Newman, Chairman of ABC Australia (BBC equivalent – tax-payer funded) has created a huge furore 0 especially with his own staff – with a speech he made to ABC journalists yesterday:….”
Thank you very much for this. I can not believe a journalist is actually showing this much integrity. …. Now I have to go pick my jaw up from off the floor.
phlogiston (19:58:23) :
Now you’re shifting from plankton to molluscs.
That is still old hat as I showed with some cites. And for ‘climate’ studies, the lifetime of weeks, month, years, etc doesn’t make much difference. What makes a difference is how often the claims are sampled, and from the Figure shown that leaves a lot to be desired. Looks like centuries to me.
seems most here today are in a humourous mood. Good.
The shaver thingy? it’s been around for years. That’s how we get nice thin slices of ham.
So there were warmer and cooler periods going back thousands of years? Oh well, there goes another nice theory murdered by a brutal gang of facts.
(Duc de La Rochefoucauld)
Leif Svalgaard (19:43:42)
OK I read you second post – fair enough. The paper you referenced looked at Belemnites – sort of extinct Mesozoic cuttlefish; Planulina, an abyssal snail; and … more foraminifera. All smaller than clams.
I’m not sure there is anything actually new here. This is not global in scope. The argument remains as to if the Holocene Optimum and the MWP were regional or global remains.
I guess I’m unclear how examining just 26 clams with a lifespan of a mere 9 years gives a reliable estimate of temperatures over more than 2,000 years. Seems like there would be a lotta lotta gaps in coverage that would have to be estimated.
And it’s only related to temps at that particular spot in Iceland.
Now if they get their hands on a few thousand clams from a couple hundred sites around the globe…
It will be interesting to see if the use of “a robotic sampling device to shave thin slices from each layer of the shells’ growth bands.” to the accuracy claimed in this article can be duplicated.
Lief I think the “robotic sampling device ” capable of following the clam’s growth rings accurately was the actual break through and not the isotope ratio analysis by mass spec.
mann will just flip the series
The tastiest and juiciest oysters in the world come from the south of the South Island, New Zealand – Foveaux straight, nearest port Bluff.
Gotta come on down and try some in season.
Shuck & slurp – yum.
But not certain if they can tell the temperature.
OK our clams are very average but surely they can tell the temp.
phlogiston (20:16:56) :
All smaller than clams.
http://www.pcas.org/documents/PagesfromV39N4-5.pdf
Figure 3. Is that a clam? big enough for you? This has been a standard technique for many years, on clams and many other shelled animals. And contrary to many other situations in life, size doesn’t matter in this.
Leif @ (19:15:29) :
“The 18Oxygen stuff has been know for more than half a century. See the historical notes I provided. But every so often people has to be reminded of the known known”.
I guess the question that then has to be asked then is why the others have persisted with the problematic tree ring proxies for so long, and why it has been afforded such unjustified credence, when there are more accurate ways of doing it. Blinkers, arrogance, funding, or just ignorance….I dunno.
OK – everyone on this list please KEEP CLAM!
What bothers me about such reports is the little phrase “reveal accuracy of Norse sagas.” The Norse “sagas” don’t need verifying with respect to depictions of climate and travels that are already known to have happened based on finding the settlements. It is the “scientific” studies that are in question. That is, can they or can they not reproduce the known conditions of that day. For example, if a roman historian makes a side remark about the army taking a certain mountain pass, and if that pass is IMPASSABLE today – any temp. proxy must conform to that description of the climate of the time. To read a lot of these studies you would think it is the history that needs verifying when it is the other way around, the proxies must conform to known history!
Granted that not all literature was to be taken as fact, but it is usually easy to pick out the mythology tales from accounts of travel and normal prose literature.
Gail Combs (20:29:24) :
“robotic sampling device ” capable of following the clam’s growth rings accurately was the actual break through
Could be, and opens the door for a much more extensive campaign.
For some reason, when I think Big Clam I think of Pam Anderson.
Off topic, but is NORSEX fiddling the data ?
Yesterday NORSEX showed Arctic sea ice right on the average line, now its been dropped half an SD below it.
http://arctic-roos.org/observations/satellite-data/sea-ice/ice-area-and-extent-in-arctic
Dave Wendt (18:42:28) :
That was very funny
One pile of clams from one bay in Iceland does not falsify any of the hockey sticks. However, if a whole lot of bays in a whole of lot of places in both hemispheres is sampled for piles of clams there might be something to say regarding hockey sticks.
Then of course there are errors that need to be addressed, as in sampling protocols, lab procedures, species of clams, etc.
I think as proxies go though, this clam thing has promise. And then there’s the clam feast – baked is my favorite, but fried works too. Raw is just plain wrong though (except oysters that is).
I’m sure Michael Mann can show how this is all just oil funded research. One of the oil companies is even named “Shell.” See?
KC (20:37:14) :
Not funny! Now CLAM UP! 😐
@ Leif Svalgaard: I don’t understand why tree rings were used then. Just for the shell of it? 😐
Ok, I guess I am out of steam. 😐
Pamela Gray (19:20:35) :
Thousand Foot Krutch — Clam It Up lyrics
LOL! Wow you’re over the top – what have you been drinking today? Hopefully a Bloody Caesar – although you are a ‘USA-an’ and Americans do not properly appreciate this Canadian concoction! It’s like a Bloody Mary only much better. Use clamato juice – a blend of clams and tomato juice – plus a shot or two of vodka, a few drops of tobasco, a splash of Worcestershire sauce, and a squirt of lemon juice, all over ice, and with a stick of celery in a celery-salt rimmed glass. Yum. (Thanks for the entertainment here and recipes in past threads).
—————————–
Though I’m partial to clams I’m skeptical about how useful they are as clamometers: currents and upwellings and the like can dramatically affect water temperature quite apart from atmospheric temperature readings. Why oh why didn’t those pesky medievals invent thermometers while they were going about inventing other useful things like mechanical clocks?
Love the Mann-clam pic at the top!
CLAMATOlogy. Clamato is a heresy. If it isn’t, it should be.
Is there a way they measure how long the clam was alive? How do they know it was two years, and not nine years?
@ Joe: Quote of the year goes to you my friend
“Sorry sir, but this sounds too much like science. I believe computer models, scientific papers where the raw data is unavailable and conspiracy of big oil is more logical.”
Leif Svalgaard (21:12:55) :
The hard part is not the temperature when the clams lived [that is old hat as I said], but to know the age of the clam and to find old clams that can be dated. Kitchen middens
—
I guess there were too many jokes about clam claims…
Does anyone mind if I mussel in on this thread?
joe (18:00:17) :
Forget about the science, forget about my emails, let me tell you a story of big greasy oil, sending professional squad teams against good scientists like me. Be afraid, woOoohhh.
In this instance, they’d need to send professional squid teams…
Looks like there was a lot of cold-weather famine during the so-called “Medieval Warm Period” ( 950 – 1250 AD ). Huh.
But not to worry, now there is a “Roman Warm Period” to speculate about. Too bad they didn’t include datapoints from the last 350 years or so on this graph:
http://wattsupwiththat.files.wordpress.com/2010/03/clamatologyfig3_mussels.jpg
The GISS temperature anomalies are +/- with respect to 13.9 deg C.
( http://pubs.giss.nasa.gov/docs/1999/1999_Hansen_etal.pdf )
Jan 2010 had a temperature anomaly of 0.71 deg C:
http://data.giss.nasa.gov/gistemp/tabledata/GLB.Ts+dSST.txt
Hence, their calculated temperature for the planet was 14.61 deg C.
Even the “Roman Warm Period” in this Icelandic bay was about 13.5 deg C.
Is this Nature News paper trying to hide the increase with proxy data ?
That’s pretty dangerous, people call for you to be fired over such things.
Technically, the molluscs record water temperatures, not air temperatures. But the two are closely linked — specially close to the shore, where most people lived. “So, when the water temperatures are up, air temperatures are up. When water temperatures are down, air temperatures are down,” Patterson says.
This will have to be spelled out clearly.
The study used 26 shells obtained from sediment cores taken from an Icelandic bay.
This is an interesting technique for getting temperature proxy data, but they will need to find mollusc shells all over the world in ocean sediment to get a sampling of global paleoclimate. 1000 locations all over the world’s coasts should probably be a good spatial sampling.
The Idso group at co2science has done a lot of work on the MWP —
http://www.co2science.org/data/mwp/description.php
The MWP was mostly warmer than the current period, and it was global.
this data will all have to be thrown out because it is not suitable for all audiences.
WARNING: this news bit contains clams being shaved. Shaving may cause things to heat up. viewer discretion is advised.
26 Shells? Really? Should I cry or is this an impressive sample size?
From one location? Really?
Err…are 26 clam shells sufficient? Didn’t I see scorn pored upon the absurdity of using a dozen or so trees to derive the “hockey stick”? Are we falling into the oft repeated AGW trap of believing a thing because it tells us that which we wish to confirm? Just asking!
An interesting name. “Klamat” means to “fool” somebody, or to “cheat”, so “clamatology” (klamatologie) is a science how to fool others. 😉
Turbo (19:18:35)
Here’s the original …
w.
So how long before the data is “corrected” and “homogenized” and the original data is lost?
Bets?
Leif Svalgaard (20:34:47) — And contrary to many other situations in life, size doesn’t matter in this.
Female clams may beg to differ.
Leif — What makes a difference is how often the claims are sampled, and from the Figure shown that leaves a lot to be desired. Looks like centuries to me.
So why do you think this type of study has been eschewed for dendro work? Is there a known error or otherwise huge “gotcha” that makes studying shelled critters less desirable than trees?
I get the feeling I’m missing something here, but what, I’m unsure. It seems asinine to think that one can easily get reliable paleotemp data worldwide easily — and it’s been known for ages! — and yet… the entire climate community relies on highly subjective dendro work replete with questionable statistical manipulations needed to tease any sort of signal at all? Something ain’t right here.
Frederick Michael (20:56:48) : “I’m sure Michael Mann can show how this is all just oil funded research. One of the oil companies is even named “Shell.” See?”
Ahhh, baloney.
Dr A Burns (20:50:34) :
Off topic, but is NORSEX fiddling the data ?
Yesterday NORSEX showed Arctic sea ice right on the average line, now its been dropped half an SD below it.
http://arctic-roos.org/observations/satellite-data/sea-ice/ice-area-and-extent-in-arctic
———–
Maybe they changed the date for which they calculate the average.
Look at NSIDC, they use the average for 1979-2000, and it’s higher ice levels:
http://nsidc.org/images/arcticseaicenews/20100303_Figure2.png
If NORSEX used an average from 1979-2007, or 2008, or 2009, the average would be dragged down even more, since these years were all pretty warm and had low Arctic ice extent compared to 1979-2000:
http://www.ijis.iarc.uaf.edu/en/home/seaice_extent.htm
2003 had the most Arctic ice for these years, but its already included in the 1979-2006 average.
“But molluscs grow continually, and the levels of different oxygen isotopes in their shells vary with the temperature of the water in which they live. The colder the water, the higher the proportion of the heavy oxygen isotope, oxygen-18.”
Is the abundance of oxygen-18 isotopes in sea water really that stable for centuries, and in different parts of the world? What if 18O was highly variable in the past? Then the clam would not have been in warmer water, he would have just had less 18O in his habitat.
Just a question. I know it looks like it corresponds well with the MWP & the LIA, but I would like to avoid eating any half-baked ideas, they make me sick later. A little more raw data would be good. But pass on the raw moluscs. I’ll just go straight to the chaser!
“Mann puts it perfectly. “The side that is issuing these attacks, our detractors, are extremely well-funded, they are extremely well-organized. They have basically had an attack infrastructure of this sort for decades. They developed it during the tobacco wars. They honed it further in efforts to attack science that industry or other special interests find inconvenient. So they have a very well-honed, well-funded, organized machine they are bringing to bear now in their attack on climate science.”
Who would have thought that cuddly clams are such sentient beings to be involved in a ” well-honed, well-funded, organized machine”? Is there no end to the malevolent ingenuity of deniers?
The spike in the mid-1500s is interesting: Europe had some very hot summers at this time, especially 1540 (see e.g. http://www3.interscience.wiley.com/journal/112100473/abstract?CRETRY=1&SRETRY=0).
Leif Svalgaard (21:12:55) :
“The hard part is not the temperature when the clams lived [that is old hat as I said], but to know the age of the clam and to find old clams that can be dated. Kitchen midden
I guess there were too many jokes about clam claims…”
Is the good solar physicist branching out into a new realm of research I presume….to that of paleoCLAMatology?
Chris
Norfolk, VA, USA
It will be interesting to see how clams may be used to document changes in temperature due to:
(1) Changes in ocean currents;
(2) Nearby underwater vents and other geothermal activity like the birth of the island, Surtsey;
(3) Changes in nearby freshwater runoff;
etc.
Clamatology indeed!
The work of this group will be silenced by the IPCC and media.
Because the data litherally comes from Shell(s).
Just like this paper here;
http://www.phys.huji.ac.il/~shaviv/Ice-ages/GSAToday.pdf
Because this is inconvenient research, done by inconvenient scientists, showing inconvenient data.
“Paleoweather”…hmmm.
I haven’t read the paper, so I don’t know if the precision they’re claiming is real or not, but I do see one problem they won’t be able to get around even if they do possess this phenomenal precision, and that is a limit on the dating accuracy. Presumably, the clams have to be dated using carbon dating, so even if they get single-day precision for 2-9 years, they won’t know when that 2-9 year period falls to any better than 1% or so (which is still pretty good, but definitely not as accurate as “Paleoweather” implies).
Still, I find it nice to see some recent reports confirming the previously well-known, but recently re-written, MWP and LIA.
-Scott
“The study used 26 shells obtained from sediment cores taken from an Icelandic bay. Because clams typically live from two to nine years, isotope ratios in each of these shells provided a two-to-nine-year window onto the environmental conditions in which they lived.”
I just can’t see how it possible to draw any major conclusions from such a small sample covering such a small amount of time, and possibly (I haven’t read the actual paper) unknowns such as water depth. Count me sceptical.
OTOH : R. de Haan</b? (18:03:27) : “We have what may be the world’s oldest clam,.. that might give a continuous record going back 400 years.”
So is the “two-to-nine year window” correct, or should it be in hundreds of years???
Darn I see that pun was nabbed hours ago so I can’t claim it here!
Or …can’t CLAM it here, so to speak. So I just try to try hide things in a clamdestine and clamtic fashion so nobody will be able to underclam what I clam saying.
Was trying to talk about the great and tragic clamity that occurred when the tide came in and they all got eaten by bigger clams….and somehow THEY concocted [or conclammeded to be correct] clamdyia and a severe case of the clam….and that was all she wrote. The end.
Chris the Clam
Norfolk, VA, USA
Hmmm, over two thousand years of climate history deduced from 26 2-9 year intervals from one icelandic bay. I’m sorry but I’m a little skeptical.
A pity the study only looked at clams in one very small area of the world. A more global study would be interesting. And has anybody ever doubted that Iceland (and the North Atlantic) had a MWP? There is plenty of historic evidence of that.
And I seem not to be able to see any data on clams after 1700AD? Did they all die out then?
Anu (21:33:47) :
Even the “Roman Warm Period” in this Icelandic bay was about 13.5 deg C.
A quick Google indicates the present annual mean temp for Iceland is about 5 deg C
LIA & MWP: Yes – there’s some pearls in that data !
The aboringinals all around Australia have left middens which are large mounds of used oyster shells which will date back thousands of years which can be used to identify the mediavel warming and Roman warming periods.
If the clam doesn’t fit, you must acquit.
CLAMS ‘MUSSEL’ IN ON CLIMATE DEBATE!
This looks a LOT more dependable in principle – as everyone else has said, we need more studies in different regions to confirm this method and build up a body of evidence.
Leif Svalgaard is right here. There is nothing new in using oxygen isotope ratios in biogenic carbonates be they forams, clams, snails or any other mollusc. Neither is there anything new in using a micromilling technique to achieve very fine resolution. Bill Patterson has been a pioneer of micromilling biogenic carbonates and produced some very excellent work.
Similar work, if memory serves me correctly at sub monthly resolution using the quahog Arctica islandica, a benthic marine species. Check out the studies of Schoene on North Sea temperature reconstructions.
As with all studies of the 18-O partitioning between carbonate and water there are two key unknowns: (i) the temperature of growth, and (ii) the 18-O isotope composition of the water. In shallow water bays we may expect the water isotope composition to vary, albeit within narrow margins, depending on amounts of surface run-off, river inputs, ice melt etc. This places limits on the precision with which we can estimate temperature.
I haven’t read the paper yet and it’s provoking a lot of interest so I’ll go to it today and have a good look.
I do think that isotope studies offer us our best opportunity for recovering past temperatures and there are some new systems coming on stream that allow us to decouple the water isotope composition and temperature. This is a method known as clumped isotopes and pioneered at CalTech. The technique is so new that In one months time we have the first international workshop on clumped isotopes and their applications.
I’ll post my comments on the Patterson paper on my blog. I’ve been conspicuously quiet in posting due to an illness so apologise to those who may have been returning over the past month to find no new posts.
Can’t help thinking of the Walrus and the Carpenter talking about Cabages and Kings…..
Hairy clams, shaved clams….
Why can nobody keep on topic here?
What a crock. 26 from one location to suddenly show global climate shifts.
What is does prove is how readily scientists are ready to jump up and publish half-baked stuff when it comes to climate.
Come back and tell us when you have sampled 100 shells in each of 100 global locations.
CBut then perhaps this secures their future funding….
Leif said that sometimes people have to be reminded of the known unknowns.
How true. I often get a sense of deja vu when reading articles, whilst saying to myself ‘but I already know that’!
Myself and many others have posted numerous times regarding the Roman Warm Period and the MWP as well as more distant warm periods in the Bronze age and before. This was all common knowledge and very well documented before Dr Mann rewrote history. The ironic thing is that Al Gore refers to these warm periods in his 1992 book ‘Earth in the Balance’.
There is simply nothing extraordinary about our present age and it verges on the most absurd Monty Python type script when we need to use clams to demonstrate (again) what we already know.
Is there a restaurant delivery service near Manns office from where we can send him a sea food dish containing clams with our compliments?
Tonyb
If Lovelock thinks it, can the rest of the UK’s climate scientists be far behind?
***************************************************************************
HOW CARBON GASES ‘HAVE SAVED US FROM A NEW ICE AGE’
Daily Express
http://www.express.co.uk/posts/view/162506/How-carbon-gases-have-saved-us-from-a-new-ice-age-
Thursday March 11, 2010
By Donna Bowater
MAN-MADE carbon emissions are staving off a new ice age, says a leading environmental scientist. Climate-change expert Dr James Lovelock says the greenhouse gases that have warmed the planet are likely to prevent a big freeze that could last millions of years.
In a talk at London’s Science Museum Dr Lovelock said the balance of nature was in charge of the environment. He said: “We’re just fiddling around. It is worth thinking that what we are doing in creating all these carbon emissions, far from being something frightful, is stopping the onset of a new ice age. If we hadn’t appeared on the earth, it would be due to go through another ice age and we can look at our part as holding that up. I hate all this business about feeling guilty about what we’re doing. We’re not guilty, we never intended to pump CO2 into the atmosphere, it’s just something we did.”
Dr Lovelock’s comments come in the wake of the scandal at the University of East Anglia where leaked emails suggested climate change data had been manipulated. The 90-year-old British scientist, who has worked for Nasa and paved the way for the detection of man-made aerosol and refrigerant gases in the atmosphere, called for greater caution in climate research.
He compared the recent controversy to the “wildly inaccurate” early work on aerosol gases and their alleged role in depletion of the ozone layer. He said: “Quite often, observations done by hand are accurate but all the theoretical stuff in between tends to be very dodgy and I think they are seeing this with climate change. We haven’t learned the lessons of the ozone-hole debate. It’s important to know just how much you have got to be careful.” According to Dr Lovelock’s Gaia theory, the earth is capable of curing itself. “A planet that is effectively alive can regulate itself and its composition and climate,” he said.
Thomas Crowley, professor of geoscience at Edinburgh University, responded: “People have thought about the possibility of an ice age but it wouldn’t be for many thousands of years. Dr Lovelock might be right in the abstract but this does not necessarily mean that CO2 is good now.”
Another “global warming” scientist:
Who is Professor Crowley?
Professor Thomas J. Crowley BA, MS, PhD
Professor of Geosciences
Research Group: Global Change
Room: 343
Grant Institute
The King’s Buildings
West Mains Road
Edinburgh
Scotland
EH9 3JW
0131 650 5339
Email: Thomas.Crowley@ed.ac.uk
Web Page: http://www.geos.ed.ac.uk/homes/tcrowley
Research Groups: 1. Global Change (Primary) http://www.geos.ed.ac.uk/research/globalchange/
Research Interests: History and modelling of past climates: effect of climate change on the biosphere; past carbon cycle variations; utilisation of palaeoclimae data to validate climate models and as a reference scale for future climate change projections; Pleistocene oceanography; palaeo-ocean modeling; decadal-centennial scale climate variability; climate projections for nuclear waste disposal sites; climate change in Texas and the Gulf Coast; effect of sea level rise on coastal processes.
Further Information: Personal Home Page http://www.geos.ed.ac.uk/homes/tcrowley
http://www.geos.ed.ac.uk/people/person.html?indv=1612
Nature is a clearing house for political science. They offer full editorial access for fraudulent climate alarmists. Can anyone recommend a science magazine that checks it’s facts and has a healthy scepticism ? It is time to write off these alarmist MS propaganda media.
Right, I think that’s what’s needed. It would be tedious, but it shouldn’t be terribly expensive.
The whole study sounds very interesting if it can be broadened enough to make worldwide judgments.
If Patterson used mussels from ancient docks, would this qualify as “pier” reviewed work? Just wondering.
@jorge (22:00:13) :
————————————————————
Frederick Michael (20:56:48) : “I’m sure Michael Mann can show how this is all just oil funded research. One of the oil companies is even named “Shell.” See?”
————————————————————
From: “Mick Kelly”
To: m.hulme@xxxxxxxxx.xxx, t.oriordan@xxxxxxxxx.xxx
Subject: Shell International
Date: Mon, 11 Sep 2000 13:05:29 +0100
Reply-to: m.kelly@xxxxxxxxx.xxx
“Mike and Tim
Notes from the meeting with Shell International attached.
Sorry about the delay.
I suspect that the climate change team in Shell International is probably
the best route through to funding from elsewhere in the organisation
including the foundation as they seem to have good access to the top
levels.
Mick”
http://www.climate-gate.org/email.php?eid=185&s=kwshell
Search Results:”shell”:
http://www.climate-gate.org/search.php?keyword=shell&submit=Search
The reason tree rings are attractive is that each tree lives much longer than the typical clam. It will be very helpful of giant clamshells can be located. Is there some way that ground-penetrating radar can be used on the seafloor to detect such large shells?
oops — “if”, not “of”.
Leif Svalgaard (19:29:49) :
So there should be lots of data in old papers to extend this?
Okay, I’ve got to be equally skeptical with this report as with Mann/Jones/et al. They got all this from 26 shells? 26? You’ve got to be kidding me. And they’re trying to project GLOBAL temps using specimens taken from a single geographic locale? I think the science of determining the LOCAL temperature is better than than the tree ring data but I can’t give this any more credence at this stage than I gave to Briffa’s tree rings.
I’m worried about that Roman Warm Period. Didnt the Roman Empire collapse?
Lief Svalgaard
G.L. Alston (21:58:18)
It seems indeed there is “nothing new under the sun” – here’s a nice one from 1966
Australian Tertiary paleotemperatures, FH Dorman – The Journal of Geology, 1966
http://www.jstor.org/pss/30075176
Most previous O16-18 papers using clams looked at salinity and river flow-rates but this one also reconstructed past climate.
All of this is quite interesting and will hopefully help more correctly establish temperature histories. Nevertheless, I like my clams in a good New England-style chowder.
Why the picture of Mann? If it is old hat Mann could have used it if he had wanted to, instead of tree rings. The tree rings are far better and more reliable for reverse science – to get support for the pc results
pat (18:46:06)
“the revelation that the CRU emails were known to Paul Hudson, the BBC climate correspondent one month before the story broke ”
I think this has been covered many times before, and that Paul Hudson received a single email that contained a few other quoted emails, but not the entire Climategate emails.
On 11 Oct 2009 there was a flurry of emails about Paul Hudson “BBC has significant influence on public opinion outside the US. Do you think this merits an op-ed response in the BBC from a scientist?” from these people:
Stephen H Schneider 11 Oct 2009
Kevin Trenberth 12 Oct 2009
Michael Mann 12 Oct 2009
Tom Wigley 14 Oct 2009
Kevin Trenberth 14 Oct 2009
Michael Mann 14 Oct 2009
Michael Mann 14 Oct 2009
Tom Wigley 14 Oct 2009
Tom Wigley 14 Oct 2009
Gavin Schmidt 14 Oct 2009
A couple people have complained about the study making broad generalizations, viz:
Actually, what this proves is how readily people are ready to jump up and make half baked claims when they haven’t read the paper. It says nothing about the global climate. The word “global” doesn’t appear anywhere in the paper. In their own words, what they are doing is “demonstrating the impact of seasonal climatic extremes on the establishment, development, and, in some cases, collapse of societies in the North Atlantic.” Nothing global in the slightest.
Another verse to add to the climategate song that did the rounds on the internet.
Picking clams one at a time,
Shaving them and slicing fine,
measuring the years in their lines
temperature’s fine…
:Chorus:
Clambakegate,
you know the clams just taste so great,
Would be better with some wine,
But the temperature’s fine…
We found the decline…..
There are literally hundreds of studies showing the MWP, the LIA and not a few the Roman Warm Period as well. All those proxies tell much the same story: MWP as warm or warmer than today; Roman Warm period, warmer still. Only the tree-proxy results beloved of Mann and Briffa show a different picture, and more so when cherrypicked and improperly analyzed. My view based on that is that Mann’s results are a heap of junk. They can’t even get correlation between surface temperatures and the tree proxies within living memory (the ‘divergence’ problem), and that is the final nail in the coffin.
Considering that tree-proxies are clearly the outliers in the data, one needs to ask why such unreliable data and methods would be used to adorn the IPCC report and become the poster boy of the AGW brigade. Clearly this is manipulation of the worst kind. I think the only fit response to anyone who insists that tree proxies should be used for paleoclimatology should be ridicule.
The methodology is nothing new. There are a range of other studies on clams that live longer that are already out there, try this one, or this one (from 1993).
Arctica islandica is long lived. The one in the study above is 374, and I recall that there was one aged 600…..
Al Gore’s Holy Hologram: “The Roman Warm Period did not exist because Wikipedia felt fit to delete a well resourced article on it.”
The really dim-wit thing about the idiots who edit climate articles on Wikipedia, is that they really can’t see that the public are less likely to swallow their BS if they remove every piece of evidence contrary to their view. Most sceptical editors want nothing to do with articles that are so POV and perhaps have realised that the best way to let the public know how much this is all propaganda dressed as science, is to let them fill wikipedia as much as they like with their propaganda and hope the public can read between the lies.
Rather odd that this particular paper hasn’t raised much interest within the WUWT community. Temperature reconstructions using clamshells may become the primary method in coming years considering the level of data resolution it offers. I am no scientist but it seems to me we are looking at Hubble Space Telescope of paleoclimatology. I wonder whether the technique may be expanded further to other shell types, even if theoretically. Is it possible to reconstruct temperatures from other shell creatures lakes and rivers further inland? Will it be possible to one day to take snapshot of global climate in particular periods using shell re-constructions from all around the world?
Leif Svelgard says that this is “old hat”. Well, that may be so for some scientific specialists but it is fairly fresh news for the rest of us. I note that Dr. Svelgard gave the link to the basic science behind the technique. What makes this particular paper unique is that it not only demonstrates a new line of evidence for past climate but it matches climatic variations with the anecdotal evidence with great precision as well. The paper validates the events depicted in Norse Sagas but more so it verifies the reliability of the technique used to identify the periods in which the events took place. One may see the Medieval Warm Period and the Little Ice Age in tree rings as well but it seems not at the same zoom range and focus as clamshells. This looks like a new hat.
There are two other interesting bits in the paper. The first one is that it doesn’t shy away from declaring “reconstructed water temperatures for the Roman Warm Period in Iceland are higher than any temperatures recorded in modern times.” While the current debate is whether the MWP was warmer than the modern times, the new paper claims that the Roman period was even warmer than both the Medieval and the modern era. The second, temperature reconstruction from clamshells extend only to late 18th Century. Why they did not extend the study to the 19th and 20th Centuries and/or whether there will be a fresh paper covering the modern period are questions that perhaps ought to be asked to the authors of the paper.
Now, with the business end of my comment is over, I’d like to express my LOLs to yet another witty ‘re-construction’ of that famous Mann photo. While many other commenters also tried their hands at clam jokes, Doctor Zoidberg tried his claws: On Earth, you enjoy eating a tasty clam. On my planet, clams enjoy eating a tasty you.”
Willis Eschenbach (01:29:14) :
Yes. That point is worth repeating. Moreover, this particular paper is ostentatiously about establishing the accuracy of Norse Sagas, but it establishes the reliability of a new method for study of climate in the past as well. Other papers studying the global climate from clamshells will probably come months and years from now.
I find this quite an exciting piece of research. The point that is obvious to me is that whilst alive, a particular clam species will move so as to remain within a particular narrow environment, described by parameters such as water depth, depth in the sediment column, salinity level etc. The same cannot be said for trees or more benthic oceanic species.
Studies on the descendants of these clams (or their close relatives) might enable one to delineate this near shore zone, define its temperature history and then perform a study to determine the relationship between temperatures within this zone and the overlying atmosphere.
Cheers
Jim
Re Pamela Gray (19:00:06) :
“…So does Mann NOT read Wiki? Why on Earth would he go around goring poor defenseless trees…”
Pamela, did you mean goreing?
I do second what Willis stated above. I spent at least two hundred hours of reading climate audit before beginning to form any opinion on AGW.
I also second, or is it third or fourth, the question of why, if this method was available for 50 years and has less noise then tree ring data, was this not used in the climate history proxy studies?
I also am curious on how water depth is quantified. I guess I will have to follow what Willis suggested, and read the paper. Until then I will just “clam up”
Willis Eschenbach (01:29:14) : “A couple people have complained about the study making broad generalizations, […]
Actually, what this proves is how readily people are ready to jump up and make half baked claims when they haven’t read the paper. It says nothing about the global climate. The word “global” doesn’t appear anywhere in the paper.”
I’m one that made such a complaint, but I was careful not to overstate anything. What I said was “I just can’t see how it [is] possible to draw any major conclusions from such a small sample covering such a small amount of time, and possibly (I haven’t read the actual paper) unknowns such as water depth. Count me sceptical.”.
The WUWT article says “We see familiar features the little ice age, the medieval warm period and the downturn which led to the extinction of Norse settlements on Greenland.
And the feature of this reconstruction to surely stick in the craw of many who think we are living in unprecedented times of warmth is the “Roman Warm Period”.” and “Oxygen isotopes in clamshells may provide the most detailed record yet of global climate change”
I have now read a bit of the paper, and checked that it matches the quoted sample size and clam lifespan. While it is very interesting that the study does provide evidence [NB. evidence not proof] of the MWP etc, I still don’t think that it can be used for any major conclusions.
But it is reasonable to suppose – as one poster has – that it may be a valuable line of research if a large number of samples from many locations can be analysed.
“That is placing a lot of confidence in the accuracy of the dating of the stratigraphy in the cores. That is putting all your clams in one basket!”
Not really, because they have cross-checked the stratigrpahy by carbon-dating the clams as well. So then they have cross-checked points of reference that tell them that some of the strata are where they think they should be, so using the strata in between those cross-checked reference points to interpolate the years between the carbon dated reference points is not at all unreasonable.
This is so much better science than the ridiculous tree-ring density nonsense. Oxygen isotope ratios are known to be a reasonable proxy for temperature, but tree ring densities are affected by so many factors, not just temperature – CO2, for instance, can have a big impact!
Anyway, this looks like promising research. It shows periods in the historical record that the tree ring data did not, suggesting it probably is a better proxy than the tree-ring data as we might expect.
Interesting is the Roman warm period. It has long been suspected that Britain was warmer during the Roman occupation, and interesting that by the end of the roman occupation it has become significantly cooler (the Roman empire had shifted south by then and renamed itself the Byzantine empire – did they do that to get out of the cold?).
If it isn’t scientific enough for anyone, I’m sure somebody can weave it into a story about capitalist imperialist sexist white suprematist privileged oppression of the last tribes of the world.
This “science” appears to run contrary to established consensus by the IPCC and as such, raises questions about the motivations of the people promoting this “clam” claim and their funding…
… shell company funding.
Willis, you hit the nail on the head. Further than that, it does not say anything about the ocean currents and the runoff from land ice. In Florida that may not mean a lot. But if you are melting ice on the main part of Iceland, its going to cause some pretty cold water flow down into some of the near coast. A change in currents such as the gulf stream would effect stuff too. Certainly this is and should be taken for what it is, but no more. It is an accurate measure of the water temperature at one place over time. As you said, nothing global in the slightest. If they extend the isotope analysis to other places over the globe we can get a more accurate picture. Hopefully they do that.
A few graps from CO2-Science showing MWP in Iceland:
Lake Haukadalsvatn, West Iceland
http://www.co2science.org/data/mwp/studies/l2_haukadalsvatn.php
See also this interesting article: A 2000 year record of climate variations reconstructed from Haukadalsvatn, West Iceland.
http://www.springerlink.com/content/2305471k06745398/fulltext.pdf
–
Lake Stora Viðarvatn, Northeast Iceland
http://www.co2science.org/data/mwp/studies/l1_lakestora.php
–
Northern Icelandic Coast
http://www.co2science.org/data/mwp/studies/l1_northiceland.php
–
Northern Icelandic Shelf, North Atlantic Ocean
http://www.co2science.org/data/mwp/studies/l1_icelandicnshelf.php
–
(The above is from my blog http://agbjarn.blog.is/blog/agbjarn/entry/896498/ )
April fools? This is a joke, isn’t it? Hasn’t Mann only recently been strung up from one of his own trees specifically because of his use of minuscule and localized test-samples to reach a global conclusion? I think a little more scepticism is needed here.
Leif: I think the new thing here is not the dating method but the slicing. By slicing growth rings you can get a much more detailed picture of the temperature changes.
A C (00:43:43) : said
“I’m worried about that Roman Warm Period. Didnt the Roman Empire collapse?’
Yes, as the climate cooled.
tonyb
I’ve not read the paper or through all the comments so don’t know if someone has already mentioned this but …… the graph stops at 1800 so we don’t know what those other periods are like relative to our own. Also, the temperature on the graph only goes up to around 13C and the current “global” average is around 15C isn’t it?
I’m a sceptic, but I don’t see what there is in this that suggests we aren’t in a period of human induced warming.
However, the fact that I’m sitting here in the UK freezing my a*** off in the middle of March does!
“Hasn’t Mann only recently been strung up from one of his own trees specifically because of his use of minuscule and localized test-samples to reach a global conclusion? I think a little more scepticism is needed here.”
I think this was just a feasibility study. The researcher is asking for more funds to have a proper crack at it. But the results so far look more promising than the tree-ring nonsense which gave results that didn’t correlate with known historical facts.
This could be the most important climate paper ever written. A sticky should be put on this paper. Its a wonderful piece of work.
Kate (00:18:43) :
If Lovelock thinks it, can the rest of the UK’s climate scientists be far behind?
(…)
Thomas Crowley, professor of geoscience at Edinburgh University, responded: “People have thought about the possibility of an ice age but it wouldn’t be for many thousands of years. Dr Lovelock might be right in the abstract but this does not necessarily mean that CO2 is good now.”
(…)
——————
Reply:
I’m not aware of any other “professor of geoscience” that has the same view as Thomas Crowley regarding the next ice age. The past four interglacials are of equivalent duration; this current interglacial has lasted as long as the average so the Earth is due for another ice age; I don’t believe it is “many thousands of years” away. There is no reason why our current interglacial should be of longer duration than prior interglacials.
I also wouldn’t give much credibility to the idea that CO2 is delaying the next ice age—since we’re seeing that the Medieval Warm Period and the Roman Warm Period are both warmer than today, it doesn’t give his hypothesis of an ice age delayed by CO2 much credibility because I doubt the last two warming periods were caused by CO2.
However, I think current elevated CO2 level do indeed have benefits completely avoided by the AGW crowd. Their argument is pretty shaky just based on their “science” alone; applying a cost/benefit analysis that includes CO2 upside would certainly put it all in perspective and nobody in their right mind could consider AGW viable.
Pat @ 18:46: Don’t kid yourself. The same day he lectured the ABC troops about even-handed coverage, The Drum published another unhinged rant about the evils of “deniers”. As a five-part series from Clive “Crazy Cat” Hamilton wasn’t enough!
Just for laughs and to see where our tax dollars are going:
http://www.abc.net.au/unleashed/stories/s2842091.htm
Actual temperatures might vary from one location to another – but surely the trends could be expected to be the same where ever. These graphs show the various warm periods cold periods etc which the IPCC seek to obliterate.
roger samson – make that a hockey sticky
Clams got legs!
(Old BC comics reference…)
It’s somewhat disappointing to read the sarcastic attempts at humor reflected in many of the comments regarding an analytical method which shows great promise compared to what passes as present day accepted climatological methodology. The application of chemometrics and ANNS (Artificial Neural Networks) has provided insights into areas that were previously untenable via the accepted methodologies. The methods described here may provide an extremely valuable insight into climate history that is sensitive, precise and reproducible. This approach represents a definite improvement over dendroclimatological methods.
AlexB (22:53:31) :
Hmmm, over two thousand years of climate history deduced from 26 2-9 year intervals from one icelandic bay. I’m sorry but I’m a little skeptical
Must agree with this – it is a VERY small sample, in a rather odd area of the world.
Iceland is warmed by the THC. A minor variation in this could change the icelandic temperature with little global effect.
Also don’t clasms live in water? So we are measuring water not air temp.
I would propose the term Chrematology, from the greek “Χρεμα”=money, for describing the activity of selling one’s own convictions in exchange of money.
I wonder what homogenized clam tastes like?
Makes me happier than a clam with Misssissippi mud in his beard.
Here is a similar one http://www.timesonline.co.uk/tol/news/weather/article7056875.ece
In about the 9th century the Vikings invaded Orkney, which became a colony of Norway until the islands were annexed by Scotland in 1472. The Vikings thrived on farming and fishing, but what was the climate like in those days?
On a sandy beach at Quoygrew on the island of Westray, Orkney, waves have scoured a bank and revealed a Viking rubbish tip of seashells from limpets, possibly used as bait by Viking fishermen between AD800 and AD1200. And those shells have yielded a fascinating archive of ancient climate.
Shellfish grow all year round, and each year of their growth shows up as very thin lines in their shells, giving their age. The temperature of each season can also be read from the proportions of two different forms of oxygen that were in the seas when the limpets were alive — cold seas are rich in one type of oxygen and warmer seas have more of the other type. And the Orkney shells taken from the 9th and 10th centuries show that sea temperatures, and hence the climate, were similar to today. However, detailed analysis revealed that summer temperatures were slightly warmer than today, and winter slightly cooler. Why the seasons were more exaggerated in Viking days is not clear, though.
In fact, the climate of modern Orkney and Shetland is remarkably mild all year round and has the smallest daily temperature range over the year in the UK. This is thanks to the mild waters of the North Atlantic Drift, the extension of the Gulf Stream, which keeps the islands warm in winter but cool in summer. That said, local people say that they have nine months of winter and three months of bad weather.
Hit the road, Manniacs!
A new way to fabricate the past is at hand.
I’m very sceptical of the clam proxy. Studies like this reinforce to me the unsoundness of using paleoclimatology as a basis for public policy.
What distinguishes paleoclimatology from a soothsayer reading animal entrails?
A scientific study would offer a falsification against known temperature records, i.e. cutting down more trees in modern times for dendro, or in this case, grow the clams in a salt water aquarium and see what effect known and controlled temperatures have on a double-blind proxy reconstructions (and any “divergence problems”).
Until then you may as well be slaughtering aurochs to find out paleo temps.
This clam proxy reconstruction, using only 23 clams, seems not to offer a falsifiable comparison to known temps, and ends well before 1800.
Perhaps it’s proto-science, and clam proxy reconstructions will in the future be tested against known temperatures. But it’s instructive that such a falsification test seems to be considered unnecessary in the “science” of paleoclimatology, where “divergence problems” are treated as mysteries rather than falsifications. That are disappeared by Yamal style sample selection, rather than held up as scientific success through experimental failure (a la Michelson-Morley and luminiferous aether).
@ Al Gore’s Holy Hologram (18:36:30) :
“The Roman Warm Period did not exist because Wikipedia felt fit to delete a well resourced article on it.”
The Wikipedia deletion log shows the article being deleted on 11 December 2008 at the request of the author. See:
http://en.wikipedia.org/wiki/User_talk:Andrew_c#Roman_Warm_Period
This deletion log also says the article was merely a pointer to a non-existent article on Roman Age Optimum.
So, do you have any more detail on the deleted article?
So could this be the final confirmation that “clam ate” change is real?
Okay, I’ve had a chance to read the paper and look at one or two of the cited references. I want to make just one point here with regard to the water isotope composition.
The paper states that for the salinity range 33.99 to 35.15 parts per thousand the oxygen isotope composition of the water will vary by 0.16 per mille corresponding to an environmental temperature uncertainty of +/-0.6 degrees C. They cite Smith et al 2005 for the data on salinity – water isotope composition. This latter study looked a t very few samples and found a gradient between oxygen isotope composition and salinity of between 0.25 and 0.32. Applying this to the Patterson et al salinity estimates suggests an actual water composition variation of closer to 0.29 to 0.37 per mille. This translates to an error in temperature of close to 1.4 to 1.8 degrees C.
However, there is some doubt as to the validity of the Smith et al mixing line. My own work (Freer, Dennis, Heywood and Boswell, 2001) has a North Atlantic shallow water oxygen isotope – salinity gradient of 0.59. raig and Gordon (1965) found a gradient of 0.61 and Fairbanks (1982) a gradient of 0.63. All these later studies are using much more extensive North Atlantic water data sets. If we use the average gradient of 0.6 taken from these studies then we find the range of water oxygen isotope compositions in the Patterson et al study to be 0.7 per mille. This equates to a range in temperature of 3.3 degrees C.
This is close to the range of temperatures reported in the Patterson et al study.
The moral is that one has to have a deep understanding of the water oxygen isotope composition to be able to interpret carbonate derived temperatures. Even for marine systems this is not an easy task.
references
Craig and Gordon, 1965, Deuterium and oxygen-18 variations in the ocean and the marine atmosphere in Stable Isotopes in oceanographic studies and palaeotemperature, Spoleto Conference Proceedings (ed. Tongior, E) 9-130
Frew, Dennis, Heywood, Meredith and Boswell, 2000, The oxygen isotope composition of water masses in the northern North Atlantic, Deep Sea Research, 47, 2265-2286
Fairbanks, R, 1982, The origin of continetal shelf and slope water in the New York Bight and Gulf of Maine….., J. Geophys Res., 87, 5796-5808
Smith et al., 2005, Temperature reconstructions for SW and N Iceland waters over the last 10ka……., Quaternary Science Reviews, 24, 1723-1740
The Tree versus Clam wars. I can see it now. Giant trees versus giant clams in a conflagration to out ring each other. Might there be some clams or other shave-able entity near the area where Mann got his trees? Now that is a temperature comparison I would pay many clams to see.
Errr – was it political correctness that prevented them displaying any clam data more recent than 200 years old as per the graph? It would have been nice to see the paleo data compared to the supposed anthro-carbon era.
What controls the formation of O18? I don’t remember. I think it is unlikley that it is some perfect proxy for temp.
Why does the graph stop at year 1800?
Anybody find it odd that the graph stops at year 1800? Are they holding back the recent data because it shows no warming? Maybe it shows a hockey stick?
What we’re getting to here is palaeoweather,” Patterson says. “We can reconstruct temperatures on a sub-weekly resolution, using these techniques. For larger clams we could do daily.”
The bogus alarm is going off!
I don’t know about his other reconstructions, I just flat do not believe the above statement.
from the number watch
Langmuir’s Laws of bad science
1 .The maximum effect that is observed is produced by a causative agent of barely detectable intensity, and the magnitude of the effect is substantially independent of the intensity of the cause.
2. The effect is of a magnitude that remains close to the limit of detectability, or many measurements are necessary because of the low level of significance of the results.
3. There are claims of great accuracy.
geez, and here I was thinking I’m the biggest troll around.
C’mon, is’t that hard to read 5 pages with pictures, before commenting?
“Roger Knights (00:31:40) :
The reason tree rings are attractive is that each tree lives much longer than the typical clam. It will be very helpful of giant clamshells can be located. Is there some way that ground-penetrating radar can be used on the seafloor to detect such large shells?”
Doubtful. Radar doesn’t work underwater, and has limited penetration through water from above. Sonar would be problematic as well. My last tour in the navy was in mine warfare. Even large (500-1000kg) mines buried in mud and sand can be a challenge to find using the best sonar equipment.
It is implicit in this study that there are and there will be a big and increased production of anthropogenic CLAMS due to the increase in anthropogenic CO2, which these creatures capture without receiving any carbon credits in exchange!!!
SInce water temp is affected by depth, how is water depth accounted for? Clams do move , there are drop offs on the ocean floor. Where they were found does not mean that that was where they had been living. n=26?
David Byrd (04:52:44) :
It’s somewhat disappointing to read the sarcastic attempts at humor reflected in many of the comments regarding an analytical method which shows great promise compared to what passes as present day accepted climatological methodology. The application of chemometrics and ANNS (Artificial Neural Networks) has provided insights into areas that were previously untenable via the accepted methodologies. The methods described here may provide an extremely valuable insight into climate history that is sensitive, precise and reproducible. This approach represents a definite improvement over dendroclimatological methods.
——————————
My problem is that I am not aware of any studies that correlate surface temperatures with ocean temperatures. For example, during the warming temperatures that we experienced in the late 1980s and early 1990s (remembered anecdotally by experiencing some brutal heat waves in Eastern Canada) the sea temperatures on the Grand Banks dropped substantially – to the point that fisheries scientists at the Department of Fisheries and Oceans are convinced that this temperature drop, rather than over-fishing, was the main contributor to the collapse of the groundfish stocks. The only coincidence with surface temperatures would have occurred in 1992, when world temperatures dropped due to the Mount Pinatubo explosion, and a moratorium was put on the Western Atlantic cod fisheries because by then there were virtually no fishable populations.
Remember, too, that last year we experienced a year without a summer, but sea surface temperatures reached record highs. I would just like to see a clearer linkage between surface climate and oceanographic phenomena (aside from major phenomena like the El Nino and La Nina). At best, what these clam studies could reveal, surely, would be trends at the multidecadal level. Not sure what exactly a weekly resolution would actually reveal about climate, whether local (which is the only claim made in this study, as Willis Eschenbach points out) or globally.
Nothing new. To Mann, AGW has always been a shell game.
During the Great AGWarming Period, 1989-2009, Science and Nature were frozen tight, during the Great AGCooling Period, 2009-TBD, Science and Nature are warming up.
The rate at which Science and Nature publish real scientific information is inversely proportional to the perceived temperature of the data submitted.
Does anyone else perceive a change in the “whether” at Science and Nature?
A new earthquake in Chile, a few minutes ago:
http://earthquake.usgs.gov/earthquakes/recenteqsww/Quakes/us2010tsa6.php
1: nothing new here [move on 🙂 or rather go find some old clams, see below]
2: the real difficulty [and why clams have not been used so much as trees] is that it is very hard to find clams that can be dated as well as trees [on a time scale of centuries].
3: I said people need to be reminded about known knowns, not known unknowns.
@jaymam (01:02:19)
————————————————————-
I think this has been covered many times before, and that Paul Hudson received a single email that contained a few other quoted emails, but not the entire Climategate emails.
————————————————————-
Paul Hudson | 13:07 UK time, Monday, 23 November 2009
I was forwarded the chain of e-mails on the 12th October, which are comments from some of the worlds leading climate scientists written as a direct result of my article ‘whatever happened to global warming’. The e-mails released on the internet as a result of CRU being hacked into are identical to the ones I was forwarded and read at the time and so, as far as l can see, they are authentic.
http://www.bbc.co.uk/blogs/paulhudson/2009/11/climategate-cru-hacked-into-an.shtml
Moderators, why was my post deleted? I see someone used the same joke later on. What gives?
@ Ryan Stephenson (03:02:00)
“tree ring densities are affected by so many factors, not just temperature – CO2, for instance, can have a big impact”
Indulge me in a thought experiment, if you please.
Logically speaking, temperature (A) is estimated by looking at tree ring density (B) because the two are correlated. However, tree ring density (B) also correlates to CO2 (C). As a result, using tree ring density as a proxy for temperature will necessarily correlate temperature and CO2, it’s tautological. A therefore B, B therefore C logically results in A therefore C, true by definition, no research required. If you wish to link temp to CO2, this is guarantee to do it every time.
In other words, you’ve already stacked the deck, and my question is: would it not be reasonable for a research in this field to be aware of this, and know the outcome in advance? And if so, what conclusions can be drawn about the research/researchers in question?
What is needed is a combining of many proxies which should provide a good general description of historic climate. The peaks and troughs when viewed overall would help distinguish a timeframe consistency. Why just look at individual proxies? Multiple proxies should reduce noise as outliers would be eliminated.
Sorry, found it. Please ignore David Ball (07:22:00) : Must open eyes and insert coffee !!! I should know that you guys wouldn’t let me down.
This appears to be a good reconstruction. Typical of climate reconstructions I’ve seen over the past 50 years, before paleoclimate was hijacked by political hacks. My only complaint is using this line:
And the feature of this reconstruction to surely stick in the craw of many who think we are living in unprecedented times of warmth is the “Roman Warm Period”. Have a look:
Which is specious as the chart ends in 1700, there is no comparison to modern climate depicted.
There are 26 ‘brackets’ at the bottom of the chart above with the chart spanning from approx. -400 AD through to 1800 AD; do these brackets represent the 26 sample clams in this study (I think they do, but, I must phrase this in the form of a question and make no assumptions)?
If so, the longest period encompassed by one of the last brackets would seem to depict a period of approx. 250 years.
Why, then, is this statement in the introduction: “Because clams typically live from two to nine years …”
(No, I have not read the paper; the answer probably lies therein.)
.
.
I imagine WUWT advises people like the author of this article that you’re putting their work up for comments and that they’re welcome to drop by and comment if they wish. I further assume that the good author of this piece has decided to remain mum for various personal and professional safety/security reasons that do not have to do with us, or WUWT, but rather with his colleagues and his professional associations. Are we such lepers?
“Author: vigilantfish”
About the water temperature.
We are not interested in the water temperature but in the fractionation which occurs as a result of air temperature. Your comment more of less proved something: brutal heat at the same time as cold water… evaporation and guess what changes the isotope ratio?
Shell growth is irrelevant provided there is some, it is the composition of the shell which matters, ie. if they grow slowly in cold water that doesn’t matter.
Wondering Aloud (06:12:50) :
What controls the formation of O18? I don’t remember. I think it is unlikley that it is some perfect proxy for temp.
The fundamental process is that when water evaporates, the lighter isotopes 16O evaporates more than the heavier 18O, and conversely when rain precipitates, so there will be fractionation depending on temperature because temperature controls the equilibrium between vapor and condensed phases.
Not to be overly critical and take this as a friendly suggestion, but why are there a lot of people commenting before they’ve read the paper? That seems a bit strange to me. C’mon, folks… READ!
A bunch of the comments posted here wouldn’t have been posted had reading come before SWAGs.
An elegant technical approach whose ramifications may become clear through the next 20 years.
I do think it critical though, to examine really carefully quite a few assumptions stated in the article to be sure they are actually true.
Without doubt though, if you can accurately data samples by another means, then the fine mapping will now become possible.
A spur to more accurate interannual dating technologies, perhaps??
Actually, what this proves is how readily people are ready to jump up and make half baked claims when they haven’t read the paper. It says nothing about the global climate.
Erm, no. I said I had to be equally skeptical of the REPORT – not the scientific paper. In other words, the quoted article which says, “Oxygen isotopes in clamshells may provide the most detailed record yet of global climate change, according to a team of scientists who studied a haul of ancient Icelandic molluscs.”
As I said, the science behind this appears to be much stronger than for tree ring data but they really need to broaden the data collected and verify the technique that worked in an Icelandic bay works equally well across the world and establish the air/water temperature correlation before it becomes a good tool for assessing GLOBAL climate conditions.
Perhaps I should have been clearer (proof that one should reconsider hitting “Submit” when typing something an hour after normal bedtime) but what I was reacting to was the immediate reaction I saw of “see, this proves the AGW proponents are wrong”. It proves nothing of the sort — what it DOES prove is that there may be a better way to extract paleoclimate information than tree rings and a broader study using this technique may therefore prove the AGW proponents are wrong.
savethesharks (22:50:28) :
Darn I see that pun was nabbed hours ago so I can’t claim it here!
Yeah, those damn clam-jumpers!
As an environmental biologist by training, I’m highly skeptical of this technique. Mollusc shell growth and structure is dependent upon many factors besides temperature including water chemistry, adequate diet, predation etc. The seabed is a very unstable environment due to sedimentation, toxin accumulation etc.
I guess I’m skeptical about clam change.
<blockquote A C (00:43:43) :
I’m worried about that Roman Warm Period. Didnt the Roman Empire collapse?
That’s why several in the climate science community are trying to push to call the current period the Skeptics Warm Period.
PS. Michael Mann’s least favorite musical – “Clamity Jane”!
One has to wonder why the recent clam data post 1660 was not included, were they asked to remove it?, didn’t do it? or thought they wouldn’t get it published if they included it? I wish the authors would state why the more recent period wasn’t included.
The picture of Mann, above, is very revealing. I –for some reason– always thought he was taller. The clams give better perspective and proportion I guess.
Dr A Burns (20:50:34) :
Off topic, but is NORSEX fiddling the data ?
Yesterday NORSEX showed Arctic sea ice right on the average line, now its been dropped half an SD below it.
http://arctic-roos.org/observations/satellite-data/sea-ice/ice-area-and-extent-in-arctic
REPLY:
Look at the graphs again. What they did was add in the average (black) and error (grey) for some other data probably the usual 1950 to 1980 time period when the ice was at maximun and the temp at the lowest for the modern era.
I did a search on the research proposal and it seems it was supposed to be until the present, so the question is why isn’t the present data… present?
here is the proposal
http://www.sciencestorm.com/award/0326776.html
and a clip
“Seasonal to annual temperature estimates will be achieved through analysis of 60 individuals, with life spans of two to ten years, that lived during modern times, through the Settlement of Iceland (AD 871) and beyond the interval of human impact to c. 2000 years ago. The use of the micromilled molluscs in marine cores is the only way, at present to obtain seasonally- to-annually resolved climate data from Iceland, beyond the instrumental and documentary record. The short, but annually resolved records are placed within an environmental framework through analysis of other traditional proxy records. Drawing on earlier analyses of these cores, major environmental changes of the past are identified. These include a prolonged “cold” interval between 70 and 400 yr B.P. (ca. AD 1930 back to 1600), an interval with lower ?18O (CaCO3) (warmer) values around AD 1000, and a cool interval centered at AD 670. The project will select molluscs for analysis within these .warm. and .cold. intervals. In order to study the human dimensions of these changes, emphasis will be placed on the period from the Settlement of Iceland (c. AD 871) to the present.
David Ball (07:33:39) :
Please post (a link to) a photo of you inserting coffee as described.
@_Jim
The 26 samples are mentioned to be -representative- of the different time periods.
EJ (21:45:44) :
26 Shells? Really? Should I cry or is this an impressive sample size?
A minimum of thirty would have been better and that is if the samples all belong to the same distribution. However given cost of testing you generally do not get to look at the desired sample number. What this study does is show it is worth while to continue to pursue this line of scientific enquiry.
here is the entire thesis that the paper came from, seems nothing more recent than 1660
http://library2.usask.ca/theses/available/etd-01252007-101516/unrestricted/K.Dietrich_thesis.pdf
The data set stops at ~1650AD. Question, why didn’t he continue on the data set to the current century? I would like to see the correlation of the clam data set to the current data set of temperature readings.. I can envision an offset between air temp and water temp. But if there is measurement data for the water temp where the clams were harvested, then wouldn’t it show a closer correlation than the tree ring data?
Just playing the part of a skeptic, posing questions to the information provided.
Everyone, remain clam!
This IS interesting work. I hope similar studies are being pursued using clams from other marine estuaries around the planet. If the precision purported holds up, a reliable measure of local/regional temperature and climate may be achieved.
As some have already stated, but it would be interesting to see clamatology done up to today with an proportionally amount of clams, so one can easily ad hoc it to their current plot.
Oh and did you lovely loonies truncate one of my ever so witty lines or did the text parser manage to auto-magically do that by it self? [The whole geez blah blah hilarious religious funny reference.]
Paul Dennis (23:47:42) :
I’ll post my comments on the Patterson paper on my blog. I’ve been conspicuously quiet in posting due to an illness so apologise to those who may have been returning over the past month to find no new posts.
Reply:
Where is your blog and perhaps you could do a guest post here at WUWT.
Dear Sirs,
You realize that were one to try, one could find 10,000 Quaternary Research papers covering aspects of the above results (which seem like good work by the way). The on-going mystery is why an entire sub-discipline was in essence ignored in the period of AGW hypothesis formation. You realize of course that Kenneth of CRU email fame would exclude the above molluscan isotope study from consideration out-of-hand because dating control is not at an annual level (thus the preference for dendro.). What the dendrochronologists (with the exception of Jan Esper and a few others) do not usually admit is that the mathematical function of detrending (in essence, the math used to construct wiggle-matches between tree ring seuences) itself removes low frequency (long-term) climate change signals. Along the lines of the above study, D. Geography at U. Cardiff (Wales) is presently collecting a mollusc series that will comprise an absolute (annual level resolution chronology) in the eastern North Atlantic that will match the above study with respect to indicative value strength, as well as being chronologically very precise.
Yours sincerely,
Bruce M. W. Albert, Ph.D., PDRA, Durham University
Paul Dennis (05:35:04) :
Thanks Paul for dropping in. its always fun to read the “mix” of comments, from the low to the high, from the curious to the close minded, from the uninformed to the informed. ( you and leif’s always being top shelf of course )
Pascvaks (07:47:28) :
Are we such lepers?
Some of my colleagues express the thought that there is enough pseudo-science peddled on WUWT to keep them away [or rather not admitting in public that they lurk]. So, we are lepers. Luckily, the nuts are only a handful and are well-known, so we live with them with only an occasional swipe.
Leif Svalgaard (07:07:36) — 2: the real difficulty [and why clams have not been used so much as trees] is that it is very hard to find clams that can be dated as well as trees [on a time scale of centuries].
Why is it necessary to locate methusaleh clams? Perhaps I misunderstand this stuff, but it seems one could dig up a buried clamshell sample, carbon date it, and then do the magical/mystical oxygen isotope process and have a number. Dig up enough buried shells — rinse/lather/repeat — and you would have the same data as with a death defying ageless clam.
Where did I go wrong?
There is an obscure record by Arlo Guthrie (I don’t think it was ever released as a CD) that has an “Alice’s Restaurant” style song called “The Ballad of Rueben Clamzo and His Strange Daughter”. This is the story of early American settlers having to kill the giant, humungous, Mann-eating clams that threatened the Atlantic coast. I’ve GOT to dig that one out of my vinyl collection and render it to digital.
So it would appear that the Lord of the Tree Rings needs to clam up.
Mann and RC are going to respond with “local/regional anomaly – not global” in 5… 4… 3… 2…
These temperature variations are also present in the Greenland ice cores, but does anyone know if they show up in the Vostok (Antarctica) cores? I’ve tried a few times to dig up information on it with no luck.
G.L. Alston (09:04:49) :
but it seems one could dig up a buried clamshell sample, carbon date it, and then do the magical/mystical oxygen isotope process and have a number.
There are contributions from atmospheric carbon dioxide, fermentative CO2 from bottom muds, and from carbonates from dissolving limestones, making errors of shell radiocarbon dates as large as several thousand years.
I’m sorry but my computer model of clam life does not verify any of this. It merely shows a (surprisingly agile) clam traversing a maze, eating plankton. Several cephalopods chase it until excess CO2 causes them to turn blue at which point the clam begins to prey on the weakened cephalopods. The model is called Pac Mann.
Paul Dennis (05:35:04) :
Thank you for taking the time to address 18O variability in the water! I could not get the right search on google to find that. Terrific.
Oxygen 18 abundance in sea water does not just vary with air and water temperatures.
Yes/No
We all know that if the carbon date does not match the supposed order of the sedimentary layers, they throw out the carbon date.
If you fuss about that, you become a carbon date denier and a flat earther.
I rather doubt that this interesting approach can accurately measure hotter and colder paleo-weather at a weekly scale of resolution, for a few reasons:
1. Clams don’t actually live in the water. They live buried beneath the sea floor sediment (some species at depths of a foot or more). Here temperature variations will be moderated by insulation, due to the sediment layer above them and lack of water circulation around them (though granted they do ingest, circulate and expel sea water through a siphon that reaches up to the water/sediment interface)
2. Many live in the inter-tidal zone, where at low tides the sediment above them may be warmed directly by the sun, chilled by evaporation, particularly on windy days, etc. Though of course part of the point of being buried is that it protects them from the greatest extremes at low tide, when they also cease to ingest water from above.
3. As anybody who swims regularly in shallow ocean waters can experience, the wind direction along a shallow shoreline can make a huge difference to the shoreline water temperature:
In summer, when there is a cool onshore sea breeze at our local beach, here in Western Australia (Cottesloe, which incidentally has very small tides), water from the topmost, warmest surface layer of the indian ocean is driven onshore and piles up against the beach, so that you feel like you are stepping into a warm bath.
Conversely, when there is a searingly hot, dry, offshore easterly breeze blowing, it skims off the warmest uppermost layer of surface water, driving it out to sea, leaving chilly deeper water to well up in its place along the the shoreline, so that by contrast you feel like you are stepping into an icy pond.
CLAMS GOT LEGS!
Johnny Hart – B.C. Comic
http://wattsupwiththat.com/2010/03/10/paleo-clamatology/#more-17233
““Roman Warm Period”. Have a look”
Perhaps explained by ?:
The data is from:
“The study used 26 shells obtained from sediment cores taken from an Icelandic bay. ”
http://www.ncdc.noaa.gov/paleo/globalwarming/holocene.html
“These orbital changes can be easily calculated and predict that the northern hemisphere should have been warmer than today during the mid-Holocene in the summer AND colder in the winter. The paleoclimatic data for the mid-Holocene shows these expected changes”
Dr Leif S. — There are contributions from atmospheric carbon dioxide, fermentative CO2 from bottom muds, and from carbonates from dissolving limestones, making errors of shell radiocarbon dates as large as several thousand years.
OK, thanks, radiocarbon seems out. There are other dating technologies out there; are you aware of the application of any of these to this type of study or are these used exclusively by paleontologists and/or archaeologists?
(I don’t know enough about dating tech, obviously.)
Oh, and is radiocarbon really out? I read where a new curve was being applied that allowed better archaeological dating, although it seems you’re saying that the samples are too contaminated for *any* corrections.
Thanks,
Regarding my previous, wrong time period.
I have ever been tempted to believe a clam over a mann. The lowly clam has no reason to lie and is not subject to human enticements. The lowly mann is many reasons to lie and is subject to many enticements.
Would that the clam will ever out number the mann and the harmony and balance of the universe be forever maintained.
Zeke the Sneak
The 18-oxygen composition of seawater is not temperature dependent per se. If we look at the North Atlantic the surface waters plot on a mixing line with the freshwater end member very similar to Arctic runoff. i.e. the isotope composition depends on the relative proportion of the sea water end member and the admixed freshwater.
Anthony, many thanks for the valuable service to the truth in climate research that your blog provides.
After lurking here for about two years or so, this is the first time I posted a comment to any topic at your blog. The reason for doing that is that the many clam-jokes pertaining to the article this discussion thread is based on detract considerably from the message of the study report interpreted by the article.
As interpretations go, usually much gets lost in them in successive stages, so much so that eventually much of any relationship to the reality offered in the original story hopelessly loses itself in a wild tangle of assumptions, many of those being expressions of misinformed humor and often unsubstantiated assumptions.
In the process of the discussion of the message getting lost like that, wattsupwiththat.com loses credibility. That is not good but not so much the fault of the moderators as it is caused by the many attempts at uninformed humor and jumps to preconceptions that are based on wrong assumptions, not facts.
The study report (http://www.pnas.org/content/early/2010/03/02/0902522107.full.pdf) is only 5 pages long (including the 39 bibliographical references that put the study into context). Reading those few pages would have precluded many of the comments made in this discussion thread.
The study points to the resolution and accuracy of “reconstructions of North Atlantic atmospheric and oceanic conditions [that] have focused mainly on the ice core records of Greenland but more recently have also been derived from marine sediment records.” Those sedimentary records, as the study quite properly identifies, are, as Leif Svalgaard chose to call them, “old hat”, but that is not what the study by Patterson et al. called them, for good reasons. Instead the study took 26 high-resolution snapshots in the form of isotope-ratio analyses of individual clam shells that could individually be placed (within the limits of the error bars identified) in the time progression of the marine sediment cores in which the shells had been found.
The study does not claim to be a replacement for any climate reconstructions that were used for the study.
I am a little confused by what is happening in this discussion thread. Jokes about clams, jokes that are widely off-target, drown out the important message of the Patterson et al. study report. It seems to me that those jokes should have been judged off-topic, especially those about clams being shaved. The original study report states nothing about shaving of any clams. It is apparent in this discussion thread that the jokers do not seem to be serious about using academic standards to be able to seriously challenge climate hype and hysteria.
–Walter
IMO there is a telling clue, reading between the lines, the reason for this article that nobody has spotted…
Pascvaks (07:47:28) : I imagine WUWT advises people like the author of this article that you’re putting their work up for comments and that they’re welcome to drop by and comment if they wish. I further assume that the good author of this piece has decided to remain mum for various personal and professional safety/security reasons that do not have to do with us, or WUWT, but rather with his colleagues and his professional associations. Are we such lepers?
roger samson (08:28:26) : I did a search on the research proposal and it seems it was supposed to be until the present, so the question is why isn’t the present data… present?
Bruce M. Albert, Ph.D., PDRA [Durham University] (08:47:37) : Dear Sirs, You realize that were one to try, one could find 10,000 Quaternary Research papers covering aspects of the above results… The on-going mystery is why an entire sub-discipline was in essence ignored in the period of AGW hypothesis formation…
Dr Albert bears out Leif Svalgaard, and points to what has really happened.
My hunch is that Nature is, so to speak, dipping their toes to test the temperature of the water: that it would be far too much for them at this moment to run an article that shows evidence right up to the present time… Do a drip feed instead… acclimatize… and eventually claim they discovered the evidence for no AGW. Forget about the skeptics. Nature did it. People have short memories.
If the good ship Nature is slowly turning now, the sea change we want is surely happening – perhaps the best we can hope for – but slowly enough for all the rascals to fade and change their tunes without being hauled in front of the enquiries like Jones.
Leif Svalgaard (20:14:49) :
phlogiston (19:58:23) :
Now you’re shifting from plankton to molluscs.
That is still old hat as I showed with some cites. And for ‘climate’ studies, the lifetime of weeks, month, years, etc doesn’t make much difference. What makes a difference is how often the claims are sampled, and from the Figure shown that leaves a lot to be desired. Looks like centuries to me.
Leif, the clamshells were sampled from sediment cores, the 26 reported were selected from the core in regions of forminifera δO18 extrema. Dating was apparently by C14.
Steve in SC (06:16:34) :
…and now we have:
4. Clams of great accuracy!
ErnieK (06:49:10) :
Nothing new. To Mann, AGW has always been a shell game.
Well done.
Dave Wendt (23:04:17) :
Anu (21:33:47) :
Even the “Roman Warm Period” in this Icelandic bay was about 13.5 deg C.
A quick Google indicates the present annual mean temp for Iceland is about 5 deg C
———-
A similar datapoint during the “Little Ice Age” shows 12 deg C, so I doubt temperatures at the bottom of the Bay were similar to those at the surface, which is also mentioned in the paper.
Also, different clams show different temperatures – Astarta, Macoma, Nuculana, Talina and Thyasira. What’s up with that ?
And why do the datapoints arrange in vertical lines with 8 to 12 deg C spreads ?
Anyway, interesting start. I’d like to see data on other parts of the world using this technique.
_Jim (07:36:25) :
The study used 26 shells obtained from sediment cores taken from an Icelandic bay. Because clams typically live from two to nine years, isotope ratios in each of these shells provided a two-to-nine-year window onto the environmental conditions in which they lived.
There are 26 ‘brackets’ at the bottom of the chart above with the chart spanning from approx. -400 AD through to 1800 AD; do these brackets represent the 26 sample clams in this study (I think they do, but, I must phrase this in the form of a question and make no assumptions)?
If so, the longest period encompassed by one of the last brackets would seem to depict a period of approx. 250 years.
Why, then, is this statement in the introduction: “Because clams typically live from two to nine years …”
It lies in the figure reproduced above, the error bar shows the ±1sd uncertainty in the carbon dating of the clamshell.
G.L. Alston (10:06:36) :
the samples are too contaminated for *any* corrections.
Radiocarbon is not *out*, but must be applied carefully and all contamination estimated or compensated for. I’m just saying that it is not *simple* to get the dating correct. There may also be other methods of dating, like counting annual rings in the clam, etc. Not impossible, but not simple, is all.
Cletus Wilbury.
Was just going to post about wrong time period, but you beat me to it!
Phil. (10:54:35) :
Leif, the clamshells were sampled from sediment cores, the 26 reported were selected from the core in regions of forminifera δO18 extrema. Dating was apparently by C14.
Or by sedimentation rate supported by C14? As long as all clams come from the same general location the 14C uncertainties are smaller. The issue was about using clams from all over the world, so from many different environments and their ages would be very uncertain.
Phil. (10:54:35) :
Dating was apparently by C14.
It doesn’t say that anywhere. If I missed it show me where.
Now, there is a statement in the paper [which I have read] that is a bit troubling:
“bivalves were selected from cores at stratigraphic intervals from notable warm and cold periods, as evidenced by the chemistry and sedimentology of cores.”
So there is some selection going on. Apparently they use ‘chemistry and sedimentology’ as temperature indicators too. I wonder how?
“”” Technically, the molluscs record water temperatures, not air temperatures. But the two are closely linked — specially close to the shore, where most people lived. “So, when the water temperatures are up, air temperatures are up. When water temperatures are down, air temperatures are down,” Patterson says. “””
Well according to John Christy et al; technically the water temperature and the air temperature are not closely linked. They showed in Jan 2001 that they are not correlated. Why the hell would they be, with ocean currents of a few knots, and wind speeds of tens to hundreds of km per hr. Air over Hawaiian waters today, may be over California next week; how would the two ever establish equilibrium.
So last time I checked, clams are agressive diggers. How energetically they dig, depends on how determined their predators are to get at them.
So who’s to say just what layer of sedimentary muck those living clams were in when they grew their shells, compared to where the dead empty shells ended up.
Well for me, I’ll take the New Zealand Green Shelled Mussels any day over any Icelandic clam, any day, whether ancient or modern.
But it is interesting to see the lengths they can go to, to try and establish knowledge of the growth cirumstances of something that lived eons ago, about which we know nothing of their metabolic processes, or how they lived.
But I’m eager to learn about their techniques anyway; I still say “It’s the water; silly !”
RockyRoad (07:53:38) : “Not to be overly critical and take this as a friendly suggestion, but why are there a lot of people commenting before they’ve read the paper? That seems a bit strange to me. C’mon, folks… READ!”
Fair enough, but … as soon as I saw sample size 26 and short lifespans, I lost interest in reading the whole paper. I did read enough to confirm those stats, and yes the paper could be showing the way to greater things, but of itself it surely cannot deliver much of relevance to global climate.
Derek H (08:07:31) puts it well : “[…] the science behind this appears to be much stronger than for tree ring data but they really need to broaden the data collected and verify the technique that worked in an Icelandic bay works equally well across the world and establish the air/water temperature correlation before it becomes a good tool for assessing GLOBAL climate conditions.
[…] what I was reacting to was the immediate reaction I saw of “see, this proves the AGW proponents are wrong”. It proves nothing of the sort — what it DOES prove is that there may be a better way to extract paleoclimate information than tree rings and a broader study using this technique may therefore prove the AGW proponents are wrong.”
There have been a lot of good posts on this thread. It’s no big deal skipping the jokes.
For those who are interested in the approach of micromilling molluscs to determine sea temperatures I suggest you read up on some of the work of Bernd Schone in Mainz. The bio-increments group have been working on long lived Arctica islandica in the North Sea and have even published data on daily growth increments. I think they now have a 500 year record of North Sea temperatures. Heres a URL to a short news item article:
http://www.physorg.com/news134892774.html
sHx (02:22:16) :
There are two other interesting bits in the paper. The first one is that it doesn’t shy away from declaring “reconstructed water temperatures for the Roman Warm Period in Iceland are higher than any temperatures recorded in modern times.” While the current debate is whether the MWP was warmer than the modern times, the new paper claims that the Roman period was even warmer than both the Medieval and the modern era. The second, temperature reconstruction from clamshells extend only to late 18th Century. Why they did not extend the study to the 19th and 20th Centuries and/or whether there will be a fresh paper covering the modern period are questions that perhaps ought to be asked to the authors of the paper.
The paper quotes a max measured water temperature in the region since 1938 as 11ºC, only about 3 or 4 shells from the Roman period exceed that value (from their main core, 2266). Other samples from another core (341) which seems generally warmer also reach that value but no data is given for present day temperatures there (it’s more sheltered).
The other finding is that the MWP was a rather erratic period as far as T was concerned: “Unlike the Roman Warm Period, however, this interval featured more variability in minimum annual temperatures that had ranges that were more than twice as large as the maximum temperature variability.”
“”” Leif Svalgaard (07:53:10) :
Wondering Aloud (06:12:50) :
What controls the formation of O18? I don’t remember. I think it is unlikley that it is some perfect proxy for temp.
The fundamental process is that when water evaporates, the lighter isotopes 16O evaporates more than the heavier 18O, and conversely when rain precipitates, so there will be fractionation depending on temperature because temperature controls the equilibrium between vapor and condensed phases. “””
Well in all the papers I ahve read on Oxygen isotope based temperature proxies, this is the first thing I have ever seen on the theory behind the proxy.
So now I am even more confused.
Evaporation, as I understand it is controlled entirely by the temperature of the water (surface), as to whether a molecule evaporates or not.
Precipitation on the other hand can easily take place thousands of km away, from where the evaporation occurred, and the condensation into a water droplet, and or subequently an ice crystal, would seem to depend entirely on the conditions in whatever altitude atmospheric layer, that droplet or ice crystal forms, and the resulting precipitation might never again for geological time scales, ever end up in the same body of water, from which the evaporation occurred.
So what am I missing; just WHAT TEMPERATURE is it that is being enshrined forever in some water/ice/clamshell sample.
Is there some definitive text that describes in detail exactly how oxygen isotope thermometry is to be carried out, and the governing theory behind it ?
Leif Svalgaard (11:56:31) :
Phil. (10:54:35) :
Dating was apparently by C14.
It doesn’t say that anywhere. If I missed it show me where.
Bottom rhs of fig 3.
George E. Smith (12:31:42) :
Is there some definitive text that describes in detail exactly how oxygen isotope thermometry is to be carried out, and the governing theory behind it ?
Yes and no. This is such standard method that many things are just stated in modern papers. But here are some pointers:
http://www.coloradocollege.edu/DEPT/GY/Fricke__Wing_AJS2004.pdf
http://web.viu.ca/earle/geol-412/oxygen%20Isotope%20fractionation.pdf
http://ethomas.web.wesleyan.edu/ees123/isotope.htm
The operative concept is “Rayleigh Fractionation”.
Craig and Gordon laid the foundations back in 1965.
Here is some on that:
http://iahs.info/conferences/CR2006/2006-Pisa.pdf
http://www.plantphysiol.org/cgi/content/full/120/4/1165
George E. Smith (12:31:42) :
Precipitation on the other hand can easily take place thousands of km away, from where the evaporation occurred, and the condensation into a water droplet, and or subequently an ice crystal, would seem to depend entirely on the conditions in whatever altitude atmospheric layer, that droplet or ice crystal forms, and the resulting precipitation might never again for geological time scales, ever end up in the same body of water, from which the evaporation occurred.
So what am I missing; just WHAT TEMPERATURE is it that is being enshrined forever in some water/ice/clamshell sample.
It is the water temperature which controls the precipitation of the COOO18, the paper states that the water O18 levels aren’t as important in this location: “The influence of variable δ18O(H2O) values on δ18O(CaCO3) is much less significant than that of temperature.” (bottom page 1 and page 2)
Charles:
Took out my reference to Elvis in “Do the Clam”.
Pity!
Max
Reply: Wasn’t me. lot’s of moderators. ~ ctm
Phil. (12:35:29) :
Bottom rhs of fig 3.
Thanks for spotting this.
You can also see that most of the dates are interpolated [not 14C], so my suspicion “Or by sedimentation rate supported by C14?” seems on the mark. Note the rather large uncertainties [and those are 1 sigma] of typically a century. This is probably not a problem within the same core, but the dating problem can become severe when widely scattered cores are used. I wonder why they only selected a few clams. I would have analyzed all I could find.
Leif Svalgaard (13:21:28) :
Phil. (12:35:29) :
You can also see that most of the dates are interpolated [not 14C], so my suspicion “Or by sedimentation rate supported by C14?” seems on the mark.
In fact, of the 26 clams, 21 have an interpolated age and only 5 a 14C calibrated age [and none of those were in the oldest half of the data].
Freshwater clams might be a better proxy for climate than marine ones. They are found in lakes and rivers and would generally live in an environment more subject to weather than marine clams. They are not as robust, but temperate climate ones should have well-defined growth lamin