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.”
=================================================================
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.
All leaves from 900AD to 1400AD are automatically “adjusted” to a coller temperature since we know they are deniers.
There’s also the variation in stomata in leaves to consider, but that relates directly to CO2 availability. More CO2 = smaller/fewer stomata, and hence reduced water transpiration/loss/use = higher productivity.
I think I’ll stick to old bones and chicken blood to divine past temperatures …
I swear sometimes it seems witch doctors have better scientific methods …
and they are calibrating these leaf temperatures against what………………
http://onlinelibrary.wiley.com/doi/10.1111/j.1469-8137.2010.03615.x/abstract
It seems like it is in the May issue not the April issue.
REPLY: Thanks. That would make the press release from Baylor wrong then, as they say “April”. – Anthony
Sensitivity of leaf size and shape to climate: global patterns and paleoclimatic applications
REPLY: thanks for the link! – Anthony
Another big problem is dating the leaves from disparate species and regions. Carbon 14 dating has a limited resolution. You’d time smear any serious signal resolution. At least tree rings have accurate temporal resolution, even if that’s the only thing you know is accurate.
Have you checked the May issue? There appears to be an article about paleobotany called “Sensitivity of leaf size and shape to climate: global patterns and paleoclimatic applications (pages 724–739)”
http://onlinelibrary.wiley.com/doi/10.1111/j.1469-8137.2010.03615.x/abstract
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’m skeptical how one dates leaves? If we are talking eras and paleo-earth layer zones, what is the point? Resolution seems impossibly poor.
This one isn’t it, but it is free:
http://onlinelibrary.wiley.com/doi/10.1111/j.1469-8137.2011.03725.x/pdf
I assume this is it:
Sensitivity of leaf size and shape to climate: global patterns and paleoclimatic applications (pages 724–739)
paywall: http://onlinelibrary.wiley.com/doi/10.1111/j.1469-8137.2010.03615.x/pdf
Latitude at 1:33 pm: “and they are calibrating these leaf temperatures against what…”
Mannian treemometers, of course.
Maybe some readers with more time than I can figure it out and leave a comment.
The paper is on Royer’s website
http://droyer.web.wesleyan.edu/Peppe_et_al_2011.pdf
I take back what I said earlier as this study and method is looking at much longer time periods than I realized where C14 dating would be completely appropriate.
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?
All that and with Decimal Degree Precision!
So why they didn’t put the leaves in various true greenhouses with different temperatures they should show something different…
So how do you acount for changes in trace gas levels (including CO2) light levels (yes, oddly enough plants depend on sunlight, a bit like ourselves) and other variables, such as rainfall, air pollution (or didn’t they have volcanoes and forest fires back then?) mineral changes, animal and insect population changes (yep, they eat leaves) and deseases.
But hey, lets use these ever so accurate measurements to base the spending of countless trillions of dollars on, after all that’s what we are doing with tree rings. Not that using that money to acutally clothe, feed, medically care for and educate folk might actually be a better idea (duh!).
As interesting as these studies are, should public money really be funding them? Haven’t we got more serious things to do with our limited academic funds?
The claimed reason for not updating tree ring proxies to cover modern times is that it is too hard.
What will be the excuse for not collecting leaf samples to update the proxies?
Isn’t there a problem here? Nine ‘well studied fossil flora’ may not adequately represent flora of the past at all. This might be the equivalent of self chosen responders to surveys.
Oh for crying out loud. As they get more desperate, they start grasping for ever more subjective ways to validate their hypothesis.
I read the summary of Peppe’s paper and when I came to this … “This work also illustrates the need for better understanding of the impact of phylogeny and leaf habit on leaf–climate relationships.” … I became aware of what was at the root of the initial study.
They want more money to continue looking at the remnants of old vegetation.
If I was the financier, I’d just say “Endex!”
(Those with a background in any disciplined service will understand that!)
For example tree A1 is in a wet environment tree A2 is in a dry environment. The trees are the same species but have different leaf characteristics.
How are they going to separate out climate effects and simple genetic differences?
Have the paleo-community considered constructing a temperature history from fossilized straw?
(Though, I am sure that even the least clairvoyant among us can guess the shape that such a temperature chronology would possess.)
Not only will they have to figure out climate impacts on leaf growth, they will also have to sort out climate variables that affect fossilization.
My hypothesis is that cooler weather/climate makes preservation more likely. Therefore the sample of fossilized leaves will have to be recongnized as being biased toward one climate extreme and somehow corrected.
The word model is frightening me . A climate model based on past paleo-records of leaves ? It is sounding to me like indian hocus-pocus . Do these researchers , who are most probably paid by governmental donations , make their basic materials available for other scientists or will they also block FOI – requests as usual with alarmists ?
I think leaves from deciduous trees would make much better proxies than trunks. A tree grows it’s leaves in relation to that spring/summer climate.
Their biggest problems will be figuring out which year the leaf fossil is from and of course calibration. But it looks promising.