I just finished reading “The Hockey Stick Illusion”, by A.W.Montfort (Bishop Hill) and I would recommend it to anyone.
The first question I have for science is, “Does a tree’s growth rate respond to temperature?” and a corollary to that is, “Is the science of dendrochronology advanced enough to pick up temperature changes of 0.7C per century?”
In searching the internet (Googling) for “tree growth rate” my first selection was www.arborday.org/treeguide/growth.cfm. They quoted from “Manual of Woody Landscape Plants, by Michael Dirr” that “Rate of growth refers to the vertical increase in growth unless specified differently. Rate, as is true for size, is influenced by numerous variables such as soil, drainage, water, fertility, light, exposure, ad infinitum.” No mention made here of temperature.
Professor Kim D. Coder of the University of Georgia, in and article at, http://warnell.forestry.uga.edu/service/library/index.php3?docID=131&docHistory%5B%5D=2 gives a description of how photosynthesis works in the crown of the tree and the roots absorb water and nutrients and together the crown and roots enable the tree cells to grow.
Photosynthesis is the process in which chlorophyll absorbs light in the visible range, except for green, and uses that energy to convert carbon dioxide and water to a carbohydrate and oxygen.
The basic physics behind carbon dioxide action as a greenhouse gas is as follows: Carbon dioxide has the ability to capture long wave infrared radiation of two specific wave length bands corresponding to vibrational frequencies of its molecular bonds. Incoming solar infrared radiation is of a higher frequency, or shorter wavelength than that absorbed by carbon dioxide so it is not absorbed. The earth is warmed by the solar infrared radiation and gives off infrared radiation of a longer wavelength, some of which can be absorbed by the carbon dioxide in the atmosphere. This is all physics that can be readily measured, except I am not sure of one thing. I do no know how they measure the vibrational frequency of the carbon dioxide molecule-that may be theoretical.
The temperature measurement data has shown that night-time temperatures have increased more than day-time temperatures. This can be due to greenhouse gasses preventing loss of heat at night, increased humidity or urban heat island effect, or a combination of all of these factors.
From what we know so far, is it logical that warming would cause increased growth? Growth is a result of photosynthesis which is dependent on visible light. Warming from greenhouse gas is a result of infrared radiation. Does that impact photosynthesis. Special fluorescent light bulbs are used for indoor plants as they do not put out the heat that an incandescent bulb does. So apparently heat from a light bulb does not stimulate growth. Other tests have shown that photosynthesis in some plants is susceptible to heat stress while other plants, such as corn, are not. The tests have also shown that increased temperature increases a plant’s transpiration rate, which could result in depletion of the plant’s water supply, which would have a negative affect on photosynthesis.
Warming, on the other hand has increased the number of frost-free days so it is possible that a lengthened growing season would increase the growth rate. Early warm weather in the spring has been mentioned in news reports as an issue for fruit growers as it stimulates blooming of fruit trees, and when these trees are later hit by frost, the fruit production is negatively impacted. Leaf growth in the fall is, to my knowledge, halted by production of a leaf bud for the following season, not by the first fall frost. Then again, many of the trees selected for analysis were pines and other evergreen trees. What is the impact of the length of growing season on them?
In the studies by Mann et al, tree ring sequences were selected (some may say cherry-picked) by their correlation to local temperature. Is that adequate? Shouldn’t the growth correlation be related to the length of the growing season, the maximum daily temperature relative to the optimum growing temperature for that species and the amount of rainfall during the growing season?
Can we trust the results of a superficial statistical analysis of tree ring data without a thorough understanding of the science behind the data?
UPDATE 7/6/10 New posts by Pierre Gosselin and on Whats up with that discuss new research at the Max Plank Institute on the role of ecosystems in the global carbon system. The research relates to some of the issues that I discuss above. Of particular interest is point 1 in P. Gosselin’s posting, , “In most ecosystems, the photosynthesis rate at which plants fix carbon dioxide from the atmosphere changes relatively little as the temperature varies.” To me this is a bombshell that could blow up the effort to relate tree rings to temperature.
My second question will remain unanswered for the time being.
COMMENTS
2 Comments
Feet2theFire
July 7th, 2010 12:35 AM
FYI, I followed your link from Anthony’s site.
All in all, the questions you raise are legitimate, IMHO. They are at varying levels, but most seem to be asking the fundamental questions that should be among the first asked. I come from an engineering background; in engineering the philosophy is usually that no question is a stupid question except the ones we fail to ask. I worked in R&D for over 6 years, so I do have a bit of a background in inquiry and accumulating data.
When there are multiple forcings/causes for any phenomenon being studied, my limited scientific background has always said the first thing to do is to create a matrix – under controlled conditions – of the effects of the various forcings. Only with such a matrix can one see the relative influences. In engineering and design, that data is then used to consciously control some result in a current ongoing process. How anyone can use the same matrix statistically on proxy data from tree rings is beyond my ability to fathom. Singling out any one of the forcings out of simple tree ring widths or densities – I agree with you: It is assigning certainty where none can possibly exist.
Basically, every question you ask should have been independently addressed and nailed down before any of the data was even handed over to CRU. That CRU then took it and massaged it all one has to ask the further questions:
1. Did CRU teach themselves or ask questions about what part temperature played among the various forcings?
2. Did CRU then determine what would be the proper homogenization factors/values to apply?
3. Did CRU run these values by the original dendros?
4. Did CRU run these values by anyone else among dendros and climatologists, to see if outside minds would vet their process?
This is all outside the fact that CRU didn’t have a real statistician working with them to make sure of their statistical methodologies. They processed their own numbers (as shown in HARRY_READ_ME.txt) and faked it.
So, who are we to tell them how to do science, anyway?…lol
steveta_uk
July 7th, 2010 05:02 AM
Don’t forget the real “greenhouse effect” (i.e. the one that has nothing whatsoever to do with CO2.
A real greenhouse traps heats, mainly my allowing in short-wave radiation, warming the soil, warming the air by conduction, and trapping this warm air by being loosely sealed against convection to the outside.
So why are greenhouses used? Because plants grow considerably faster when warm. So much so in fact that a gardener has to ensure that plants destined to be grown outdoors are not left in the greenhouse for too long as they can ‘bolt’ resulting in excessively tall but weakened plants.
In summary, most vegetable plant growth reacts dramatically to temperature, so it seems unlikely that trees are unaffected.