From Baylor University, a suggestion that leaves are a better paleo-proxy than tree-rings:
New Baylor Research Shows Using Leaves’ Characteristics Improves Accuracy Measuring Past Climates
NSF-funded study shows high promise for new method to estimate temperature, precipitation for ancient ecosystems
A study led by Baylor University and Wesleyan University geologists shows that a new method that uses different size and shape traits of leaves to reconstruct past climates over the last 120 million years is more accurate than other current methods.
The study appeared in the April issue of the journal New Phytologist and was funded by the National Science Foundation.
“Paleobotanists have long used models based on leaf size and shape to reconstruct ancient climates,” said Dr. Daniel Peppe, assistant professor of geology at Baylor, College of Arts and Sciences, who is an expert in paleomagnetism, paleobotany and paleoclimatology. “However most of these models use just a single variable or variables that are not directly linked to climate, which obviously limits the models’ predictive power. For that reason, they models often underestimate ancient temperatures.”
Baylor geology researchers, along with 26 other co-authors from universities around the world, collected thousands of leaves from many different species of plants from 92 climatically-different and plant-diverse locations on every continent except Africa and Antarctica. Multiple linear regression models for mean annual temperature and mean annual precipitation were developed and then applied to nine well-studied fossil floras.
The results showed:
• Leaves in cold climates typically have larger, more numerous teeth, and are more dissected. Leaves in wet climates are larger and have fewer, smaller teeth.
• Leaf habit (deciduous vs. evergreen), local water availability and phylogenetic history all affect the relationships between climate and leaf size and shape.
• The researchers’ multivariate mean annual temperature and mean annual precipitation models offer strong improvements in accuracy and precision over single variable approaches. For example, the mean annual temperature estimates for most of North American fossil floras were considerably warmer and wetter and in better agreement with independent paleoclimate evidence. This suggests that these new models offer the potential to provide climate estimates that will help scientists better understand ancient climates.
“Our study demonstrates that the inclusion of additional leaf traits that are functionally linked to climate improves paleoclimate reconstructions,” Peppe said. “This will help us to better reconstruct past climates and ecosystems, which will allow us to study how ecosystems respond to climate change and variations in climate on local, regional and global scales.”
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Since they have not included the actual paper with the Baylor press release, and didn’t even give a title for the paper, I have not been able to figure out which paper it is in the April edition of New Phytology here. Maybe some readers with more time than I can figure it out and leave a comment.
Three things make me just as skeptical of this claim as of tree rings being a good proxy for past temperature:
- Liebigs Law, which I cover in detail here: A look at treemometers and tree ring growth
- The revelation that leaves seem to maintain a constant temperature: Surprise: Leaves Maintain Temperature, new findings may put dendroclimatology as metric of past temperature into question
- How do you calibrate such a thing? If using modern leaf response as a baseline, how do they know the response millions of years ago was the same?
I’m sure we’ll learn more in discussion.
Leif Svalgaard says:
April 18, 2011 at 1:41 pm
How do you calibrate such a thing? If using modern leaf response as a baseline, how do they know the response millions of years ago was the same?
Dana Royer has some good research on this:
http://droyer.web.wesleyan.edu/research.htm
Personally, I think the method is sound and has a lot of promise.
I thought you might, sir. What’s in a name, eh? 😉
This study sounds pretty reasonable. The typical morphology of angiosperm leaves is an indication of typical climate. Some species ( e.g. almost any Australian Acacia) even have different leaf forms dependent on weather (not climate).
crosspatch says:
April 18, 2011 at 2:10 pm
Oh for crying out loud. As they get more desperate, they start grasping for ever more subjective ways to validate their hypothesis.
Exactly. It’s all boiling down to model validation. Model this, model that, if the model says so, etc., etc. Oops!!! The MODEL was wrong, have to recalibrate! Let’s see: While we do that, let’s just add another decade to the predfiction date to buy us some time, and watch the cash roll in, because in our grant application, we mentioned “temperature”.
How collossally transparent and tiresome, all at the same time.
Some variables:
° Temperature
° Rainfall
° Nutrients (including CO2 [ ])
° Genetics
° Drought
I’ll stop listing at 5.
John von Neumann, the great, late physicist and meteorologist has two quotes that put the paper in best context:
“With four parameters I can fit an elephant, and with five I can make him wiggle his trunk”.
“There’s no sense in being precise when you don’t even know what you’re talking about.
So what we get are “precise,” “accurate” “improvements” on “measurements” of the past temperatures and rainfall; but of course the “measurements” are really estimates. And these improvements of accuracy in estimations of the past are actually in mean annual averages. All of this improvement of accuracy is as over against past estimates, which were less accurate.
And the best thing is you get “high promise” and a “new model.”
All these studies remind me of the “Stock Market Scam” (Paulos 1989)
In the scam, you send a predictions to 32,000 people, half predicting higher the other half lower. For those 16,000 where you guessed right, you do it again. Then there are 8,000 who believe you were right 2 for 2,
4,000 who think you were write 3 for 3,
2,000 who think 4 for 4
1,000 who think you are an amazing 5 for 5 and will believe anything you say.
Only in this case, we have 32,000 hypotheses, of which at least 1,000 will be “proven” after 5 successive tests. If you want to allow for experimental error, far more will still survive.
“The first principle is that you must not fool yourself—and you are the
easiest person to fool.” – Richard Feynman
http://www.entheology.org/library/winters/QUACK.TXT
Lonnie E. Schubert says: April 18, 2011 at 1:42 pm
I’m skeptical how one dates leaves?
Like a panda … who Eats, shoots and leaves!
Again: it’s Liebig
Any tea leaves in this new improved highly promising model, by chance? I like tea leaves.
jeez says:
April 18, 2011 at 1:38 pm
… Carbon 14 dating has a limited resolution. …
In fact, C-14 is useless over spans of more than 20 to 50 kya. The leaf morphology approach was pioneered to investigate the environment that polar dinosaurs experienced over 100 mya. The initial investigations correlated leaf shape and size with latitude. One of the significant facts is that “toothy” leaves correlate with cooler climates. The leafs of temperate and cooler climate plants have glands on the points of the leaf serrations to help maintain water pressure in the stems and leafs and prevent wilting in colder weather. In the tropics atmospheric temperature does this without needing any special adaptations by the plants. During the Mesozoic we find dinosaurs within about 5 degrees IIRC of the pole, much closer than there is land at present. The leafs from these deposits resemble the cooler temperate rain forests in Canada and southern Alaska. It goes without saying that this was during a “warmhouse” period without polar ice caps.
REPLY: see his later comment, saying the same thing – Anthony
Can I have some funding please?
“Visions of sugar plums danced in their heads,” along with rich grants and an appointment or two to the NAS … if the result is “correct.”
In perusing some of the more panicky, skeptical responses here, it seems pretty clear that some of us need to learn to read and watch that old knee-jerk response. It is also evident that a primer on alternative means of dating geological evidence would help some of us. Then there are “skeptical” responses that are strictly political when the persiflage is peeled away. While politics can insert itself into science, and scientists are often encouraged to be more “active” these days, there is simply no reason to presume that science, “paleoclimate” and politics are chained together at the ankles.
For example, only in “climate science” will you see “paleoclimate” attached to studies for time periods in which there are historical records available. Geologists would laugh at the idea, while archaeologists (prehistorians anyway) would tend to smirk. “Paleo-” simply isn’t applied to periods with written records. The article, and leaf geometry studies in general, looki at much longer periods than “the team” is interested in. In fact, even 8,000 years ago the word “unprecedented,” as employed by the team, loses any significance. When you are stomping around 120 mya, the present looks like what it is – an Ice Age. So, please, leave off the hysteria; “model” and “climate” are not necessarily bad words. Leave it for warmists. We are in a cold climate period and have been for a (geologically) long time.
You have to wonder whether conditions that create fossilised leaves bias results towards …well subsets of conditions under which leaves are fossilised.
What is needed as with all these claims is validation.
So give the researchers some leaves from trees where the temperature (and all other weather variables are known. Ensure that some leaves are from the top of the tree others from the bottom, some are from a tree at the top edge of the forest and others are from trees in the middle of the forest by a river etc etc. In other words standard validation testing technique. Then have them use their clever model to tell you what the weather conditions were in which the leaf grew. No ‘clever tricks’ just straightforward validation testing. Perhaps enhance the impact of the testing to include the loss of tenure for any results less than 50% correct – it would concentrate their minds before making claims that they have not tested themselves.
This is relatively basic undergraduate level experiment design – perhaps these people have forgotten what that is?
ZT says: “Have the paleo-community considered constructing a temperature history from fossilized straw?”
I’m partial to global temperatures derived from ancient batpoop laminae in three caves in Kuala Lumpur. Paleospeleochiropterocoproclimatology.
Ian W says:
April 18, 2011 at 4:21 pm
What is needed as with all these claims is validation.
So give the researchers some leaves from trees where the temperature (and all other weather variables are known. […]
This is relatively basic undergraduate level experiment design – perhaps these people have forgotten what that is?
What makes you think that the claim is not validated? See their Figure 2. Did you even read the paper?
“Ray says:
April 18, 2011 at 1:56 pm
As everyone know, the leaves at the bottom of a tree are usually different in size and thickness that those from the top of the tree. How do they know they have a bottom or top leaf fossil?”
And those juvenile leaves from Eucalyptus and Corymbia species in Australia are often much larger than adult leaves. Others have extremely variable shaped and sized leaves and have scientific names which include …variifolia.
I notice a correlation coefficient of 0.98 in Royer’s paper. It seems far too good to be true. Or am I just too skeptical?
http://droyer.web.wesleyan.edu/research.htm
“”””” For example, the mean annual temperature estimates for most of North American fossil floras were considerably warmer and wetter and in better agreement with independent paleoclimate evidence. “””””
Recommendation to Baylor researchers:-
Be safe stick with “”””” independent paleoclimate evidence . “”””””
It’s independent, and better too.
Another suggestion for Baylor researchers:-
Would you recommend using tree leaf size, and number of points as a Temperature proxy to control the operation of a Nuclear reactor; if not; Why not ??
Duster and Anthony,
Thanks for jumping in for me Anthony, but even in my take back I screwed up and Duster is right to call me on my error.
@jorge
Paleospeleochiropterocoproclimatology.
What a magnificent word!
Maybe a shorter version could find popular usage:
Coproclimatology.
Reminds me of a UN panel for some reason…
Anthony,
Scientist forget that EVERYDAY is different. NEVER the same due to the planet moving away and slowing down year from year. Tilting changes and the atmosphere WAS different back millions of years ago. Centrifugal force was faster meaning that the atmosphere was less dense than today. Oceans compensated by having more salt to change the density to be heavier. Following the salt trail trough time is a very interesting trek.
Quite some time ago in the “Tips and Notes” section, I left this link:
http://www.pbs.org/wgbh/nova/nature/arctic-dinosaurs.html
Robert Spicer
Paleobotanist, Open University, UK
cepsar.open.ac.uk/pers/r.a.spicer/p5.shtml
Dr. Spicer has done quite a bit of work on this