Anthony Watts has a tendency to put his foot in his mouth any time he lets his fingers touch his keyboard. (Ha ha - do you like the contortionist imagery?) This time he's showing off his ignoramus side again in a WUWT article with the headline: Bad news for Michael Mann’s ‘treemometers’ ? (Archived here.)
Implications for paleoclimatology and Mann's hockey stick?
Anthony introduced his copy and paste press release by writing this (my bold italics):
From the “trees aren’t linear instruments and the Liebigs Law department” and the Smithsonian Tropical Research Institute, comes this story that suggests the older trees are, the less linear their tree ring growth might be, which has implications for “paleoclimatology” and Mann’s hockey stick temperature reconstructions from tree rings.
I found Anthony's quote all over the internet - but only in copy and pastes from WUWT! I'm guessing Anthony is about the only person whose first thought was that this has implications for “paleoclimatology” and Mann’s hockey stick. Wishful thinking on the part of science deniers. (It's probably worth mentioning that nowhere in the remainder of Anthony's article or the sciencedaily.com press release or the abstract of the paper he was referring to was there any mention of tree ring growth, it's linearity or otherwise.)
The new paper Anthony was introducing wasn't about dendrochronology at all. It was a paper about how for "most species, the biggest trees increase their growth rates and sequester more carbon as they age".
Anthony quoted himself in his introduction, with his reference to Liebigs (sic) Law. (See below for some "paleo" curiosities about Liebig's Law and its successors.) Back in 2009 Anthony Watts wrote an article about how plant growth is limited by the least available nutrient or requirement for growth. It was one big logical fallacy article. What he was trying to argue was dendrochronologists "don't know nuffin'" about tree growth. He was suggesting that world-leading scientists who have spent most of their careers examining and analysing signals in tree growth, don't understand that there are multiple factors that affect plant growth. He wrote:
I make no claims of being an expert in either forest growth or dendroclimatology. I’m simply presenting interesting information here for discussion.
But, I am amazed at the nonlinearity and interactivity of all limiting growth factors, and especially the parabolic response to temperature.
...If you see a wide tree ring, you can safely conclude the tree had a good year. If you see narrow rings you can conclude a poor growth year. But was that poor year a product of an unfavorable temperature range alone? Or was it due to lack of moisture or lack of sunlight or both? Not having local records for those, how would you know?
It seems to me that dendroclimatology has a lot of uncertainty.
Anthony Watts: "scientists don't know nuffin'"
Anthony Watts was in effect saying that "scientists don't know nuffin'". His logical fallacy was his "argument from personal incredulity". In this 2003 paper by Keith Briffa, Tim Osborn and Fritz Schweingruber, the very first paragraph in the introduction is (my bold italics):
A large amount of tree-ring research is concerned with very localised site studies (Dean et al., 1996), necessarily reflecting the complex ecological processes that operate on small scales in forest ecosystems. Depending on the specific situation, dendrochronology can focus on the study of many different factors that influence tree growth. Examples include the following: the frequency of insect defoliation, the occurrence of severe frosts or fire, or the general competitional interactions in forest dynamics. The challenge for the tree-ring researcher is to establish an optimal representation or reconstruction of the past variability of the particular factor under study. This should involve providing realistic estimates of uncertainty, given that in practice many factors can act together to produce the changing patterns of tree growth that are measured.
Anthony's specialty is not dendrochronology but doubt and disinformation. So he can't be expected to know the main points, let alone the finer points, of any subject let alone one as highly specialised as dendrochronology. And if, in some parallel universe, an Anthony Watts did know anything about trees or the study of their cross-sections, do you think he would present it honestly?
Trees keep growing
Anthony Watts is barking up the wrong tree. The study to which Anthony's introduction purportedly related is published in Nature. Stephenson et al conducted an analysis of 403 tropical and temperate tree species around the world and found that for most species, mass growth rate increases continuously with tree size. In other words, trees keep growing as they age. The press release states that trees "grow more quickly the older they get". I don't have the paper so I don't know by how much growth rate accelerates with age. The abstract does state that this doesn't conflict with observations of (presumably) old growth forests having declining leaf level and productivity:
The apparent paradoxes of individual tree growth increasing with tree size despite declining leaf-level and stand-level productivity can be explained, respectively, by increases in a tree’s total leaf area that outpace declines in productivity per unit of leaf area and, among other factors, age-related reductions in population density. Our results resolve conflicting assumptions about the nature of tree growth, inform efforts to understand and model forest carbon dynamics, and have additional implications for theories of resource allocation and plant senescence.For some reason this notion of increasing growth as trees get older makes me think of fractals. The bigger the tree the bigger the trunk, the more branches it has and the more it can sprout new branches. So even if individual branches grow at the same rate as branches did when the tree was younger (or even more slowly), there are more of them as the tree ages so the total mass of the tree accelerates over time. I'll be interested to read the paper itself.
Supplementary data can be accessed here. It's a list of all the species studied. The fattest tree they recorded was Picea sitchensis, a conifer from North America, with a diameter of 270 cm. According to Wikipedia the trunk diameter at breast height can exceed 5 m. The supplementary data doesn't include height.
The press release at ScienceDaily.com specifically mentions trees that grow around these parts, the mountain ash - Eucalyptus regnans. These trees have a phenomenal growth rate - Sadly many of the largest and oldest specimens got chopped down in times past.
About Liebig's Law
I came across another early paper, "Limitations of Blackman's Law of limiting factors and Harder's concept of relative minimum as applied to photosynthesis" by B. N. Singh and K. N. Lal published in Plant Physiology. It was published in 1935 and the newest reference is dated 1925. The paper points out that no resource acts in isolation, so it's not as simple as saying that growth is limited by the scarcest resource. (For example, think of how plants respond to increased atmospheric CO2 concentrations and the response of stomata, which allows them to lose less water.)
Stephenson, N. L.et al. "Rate of tree carbon accumulation increases continuously with tree size." Nature (2014), http://dx.doi.org/10.1038/nature12914
Briffa, K. R., T. J. Osborn, and F. H. Schweingruber. "Large-scale temperature inferences from tree rings: a review." Global and planetary change 40, no. 1 (2004): 11-26. doi:10.1016/S0921-8181(03)00095-X
Singh, B. N., and K. N. Lal. "Limitations of Blackman's law of limiting factors and Harder's concept of relative minimum as applied to photosynthesis." Plant Physiology 10, no. 2 (1935): 245.
From the WUWT comments
@njsnowfan is still jumping up and down trying to get Michael Mann to listen to his "ice age cometh" argument and says:
January 15, 2014 at 12:01 pm
That will have to be filled under the category” Oh Mann” with all the rest.
P.S Dr M. Mann
If you read my post, Just want to know if you are seeing signs of the sun freezing your hockey stick in the ice yet? Remember my first tweet to you when you blocked me 2 years ago. Yup this is I, so many blocked how could you remember me?
arthur4563 doesn't know much about factors that can affect tree rings and says "scientists don't no nuffin'":
January 15, 2014 at 12:07 pm
The biggest mstery is why anyone who claims intelligence in these matters would ever buy into the idea that temperature determines tree growth. I would think that any farmer would consider Mann a city-bred fool.
Donald Mitchell's mind works in strange ways - he says:
January 15, 2014 at 12:14 pm
I really do not see a problem for the alarmists. If the public finally realizes that the increased carbon dioxide increases the rate of growth, they can always claim that increasing temperatures cause increasing carbon dioxide. This not only wraps things up in a nice circular argument, but certainly would not affect their credibility in my estimation.
Theo Goodwin decides he likes this work, but rather oddly implies that he doesn't think dendrochronology is empirical when he says:
January 15, 2014 at 12:35 pm
Finally, someone is doing empirical research on treemometry. It comes only seventeen years after The Team ignored the obligation to do it. Once this work gets rolling, prepare to be amazed. Science will replace wishful thinking. Should be broadcast to all secondary school students.
And Theo Goodwin follows it up with another blunder when he says:
January 15, 2014 at 12:41 pm
Cam_S says: January 15, 2014 at 12:20 pm “Wow! This story has made it to The Guardian.”
I bet it gets disappeared. They do not yet understand its implications.
Alec aka Daffy Duck says "everybody knew that":
January 15, 2014 at 1:23 pm
??? They think this is new? I’m a layman but logged wood in Maine in my youth AND know the equation for the volume of a cylinder … I thought everyone knew tree faster and faster as they grow
Rud Istvan says "it's not universally true" - just look at the tree rings!:
January 15, 2014 at 1:35 pm
Another way to see that this is not universally true is simply to look at growth rings of a boll cross section. My wife and I just harvested two, a white pine and an oak, for proposes of making furniture at the cabin in Georgia. For both the hardwood and the softwood, the annual ring spacing starts large, and shrinks as the tree matures. Inner rings are more widely spaced, outer rings are quite narrow. One can measure this differential over time, and using the change over time in pi* delta r^2 (since volume is just times height, and trees reach their species typical maximum height long before maximum mass (explained by the hydraulic limitation hypothesis) can actually use calculus to work out optimum harvesting times depending on the wood sought-sawtimber or pulpwood (or, in the case of hardwood with extensive crowns, both).
While Gary Pearse says the opposite to Russ Istvan and this isn't "a new discovery" :
January 15, 2014 at 1:40 pm
A little arithmetic would have saved the researchers all that trouble:
(Circumference of year 20 ring / Circumference of year 10 ring) >2
given, on average, rings are similar in thickness plus there is growth upwards and outwards of the canopy. Certainly if you measured 100 trees the relation would be pretty firm. Sheesh what are they teaching in botany and forestry these days that this is a new discovery.
“…growth accelerates as they age suggests that large, old trees may play an unexpectedly dynamic role in removing carbon from the atmosphere.” Suggests? It is a certainty! Sheesh, what arithmetic are they teaching botanists and foresters these days. No 95% certainty among these folks.
KNR decides that specialist dendrochronologists know nothing about tree growth:
January 15, 2014 at 1:48 pm
One thing for me that stood out was in ‘the team’ there was not one person who was well qualified in consider what actual effects tree growth, considering how important was to their claims . But then one thing climate ‘scientists’ have never been short of its ego and a extreme belief, against all evidenced, if their own intelligence. So perhaps they felt they did not need one.
M Courtney had the same thought as I did when he said:
January 15, 2014 at 3:13 pm
When talking of volume growth it is worth remembering that trees are fractal.
The growth in tree volume can be a twig from a branch. An increase in the external sixe of the tree may not be necessary.
So the limits of growth may not be reached on the lifetime of a tree.