Wow, I had not idea the stats, er, data, went back that far!
Posted on 03/08/2010 10:02:04 PM PST by neverdem
Temperature records gleaned from clamshells reveal accuracy of Norse sagas.
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...
(Excerpt) Read more at nature.com ...
Lets say 100 results from 100 clam shells from same strata/time period are the raw data for them to finally say to me that it was 67 degrees Fahrenheit in 1012AD. You can then look at the error bars and give an opinion on that 67 degrees
BUT EVEN before that MY CONTENTION is that the scientists are over promoting the accuracy of translating O2 isotope distributions (ratios?) in ancient clam shells into ancient temperatures. My contention is you can get a rough idea but nothing like me looking at my outdoor thermometer today. When my outdoor thermometer says 67 degrees I know it is 67 degrees at that location. Not that it is somewhere in the range of 63-71 degrees which is the clam shell result. That’s my contention...I am not a scientist
Uhhh, yeah! That’s the ticket! See these shells here....they gonna tell us about global warming...yeah...
Yes. And I'm sure that for the 100 clamshells that there would be more than one measurement per clamshell, so assume 300 total data points. You can plug those into Excel (or any other modern spreadsheet) and have it calculate the all the relevant statistics. There is also specialized software that does the same thing, but "deeper". Or you can whip out your handy-dandy scientific calculater, and do it "manually". But PLEASE don't ask me to do on paper :^)
"BUT EVEN before that MY CONTENTION is that the scientists are over promoting the accuracy of translating O2 isotope distributions (ratios?) in ancient clam shells into ancient temperatures. My contention is you can get a rough idea but nothing like me looking at my outdoor thermometer today."
And I agree that they are over-selling their precision and accuracy.
"When my outdoor thermometer says 67 degrees I know it is 67 degrees at that location. Not that it is somewhere in the range of 63-71 degrees which is the clam shell result. That’s my contention...I am not a scientist."
Not really. Unless you have taken the time to calibrate your thermometer (say using a glass of melting ice cubes, and a pot of boiling water), you really have no idea that it is actually 67 degrees. And by taking several measurements at each temperature, you can determine how "fuzzy" your thermometer is inherently. And even if you "have" used the ice cubes and boiling water, you'll still not be as accurate as possible, because you need to correct those calibrations for atmospheric pressure at your specific altitude and weather conditions.
To give you an example. I just ran through the exercise of calibrating our shop measuring equipment (dial calipers). To do so, I needed a set of gage blocks, with certification traceable back to NIST. I did three determinations on each of three different gage blocks. For the certified "2 inch" block, for one caliper I got 1.9995, 2.0005, and 2.000. And even then I didn't do the MOST accurate check, because I should have measured and recorded the temperature in the lab at that point in time, because the gage blocks do have a coefficient of thermal expansion. So my "fuzziness" is more than is possible with the equipment I had.
Minimizing "fuzziness" (actually fuzziness is a very good descriptive term for statistical errors) is a LOT of work.
My outdoor thermometer gives fuzzy readings. True....but better than O2 isotope method. They are much fuzzier and in the past. Far better to get temperature readings in the here and now. Proxy readings from tree rings do not agree with real temperature readings from real weather stations. One infamous hockey stick chart went from proxy readings to actual readings when the proxy reading turned ....inconvenient.
And so called global warming scientists go ballistic over tenth of a degree temperature fluctuations. Those clam shells will not yield anything closed to tenth of degree accuracies
Yes, they are, the issue is knowing what year it starts and stops in.
This is my original anger. I see more grant grubbing, grant hungry scientists getting into the act. More taxpayer money squandered on global warming "research"
Doesn’t sound kosher to me....
Scientists shuck clam claims during calm.
I can promise you that you in no way even began to approach the sheer rage the encompassed me when I saw the magnitude of the fraud they were perpetrating. The damage that they have done to the vast majority of truly ethical practicioners of science is immense, and I can only hope that it can be reversed. These charlatans should be driven out of their labs with whips, and never be allowed near a grant proposal again.
Well,...you are more qualified than most of us...keep talking.
If using tree rings is valid,...this would seem to have a chance....
Agreed, with the caveat that we're talking about isotopes that are not only stable of themselves, but which are not daughters of something that is unstable. What also might not be so clear is whether there might be a reservoir unusually rich in a particular isotope of oxygen on this terrestrial ball, that sporadically leaks into the atmosphere and gets into the mix that we see on the surface. This could invalidate our assumptions about the average molecular weight of oxygen X number of years ago.
Yes...thanks, Ernest.
They're also overrated in my opinion but they keep the grants flowing and scientists and their grad student flunkies are kept employed.
My point with these clam shells is that they are not that accurate and are being over-promised and over-promoted by scientists who want grant money
One problem I see here is the water temperature is dependent on depth, water clearness, the amount of sun hitting the water (cloudy or clear), water currents, and of course climate above the water.
That's a lot of variables. I hate to say it, but I don't trust these people. I figure they will cherry pick data that matches what they want and ignore the effects of the other variables---just as they have been shown to have done before.
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Wow, I had not idea the stats, er, data, went back that far!
A while back someone mentioned varves as a dating (and I think paleoclimate study) method. Coral reefs have also been used for both, as have stalactites and stalagmites.
Weil, that's pretty much true for the lighter elements. The only light element that is a daughter of decay (sounds like a social commentary, doesn't it) is helium. Some VERY few of the heavier light elements might form from spontaneous fission of the very heavy elements like uranium (which DOES happen, but VERY infrequently), and such fissions tend to cluster around intermediate atomic weight elements like iron.
"What also might not be so clear is whether there might be a reservoir unusually rich in a particular isotope of oxygen on this terrestrial ball, that sporadically leaks into the atmosphere and gets into the mix that we see on the surface."
I'd have to put that in the "possible, but VERY unlikely category.
That's a very similar concept. You've got your bivalve method and since you usually get two layers a year your bivarve method.
< rimshot >
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