by Dr Roger Pielke, Sr.
With the McShane and Wyler paper examining and questioning the method, this look at the proxy data and its problems seems like a relevant issue to review.
Comment On Tree Ring Proxy Data and Thermometer Type Surface Temperature Anomalies And Trends
There was an interesting conclusion in a New York Times article on the relationship between tree ring proxy temperature trend analyses and thermometer type measures of temperature anomalies and trends. The article is
British Panel Clears Scientists by Justin Gillis published on July 7, 2010
The relevant text is on page 2 it is written
“But they were dogged by a problem: Since around 1960, for mysterious reasons, trees have stopped responding to temperature increases in the same way they apparently did in previous centuries. If plotted on a chart, tree rings from 1960 forward appear to show declining temperatures, something that scientists know from thermometer readings is not accurate.”
There are, however, problems with this conclusion. Since the thermometers are not coincident in location with the tree ring data (in the same local area), it would not be surprising that they are different. Indeed, this is yet another example that implies unresolved biases and uncertainties in the surface temperature thermometer type data as we discussed in several of our papers (see and see), as the thermometers are measuring elsewhere then where the proxy tree data is obtained. This obvious issue has been ignored in the assessment of this so-called divergence between the two methods to evaluate temperature anomalies and trends.
It is possible, of course, that the trees are responding differently due to the biogeochemical effect of added carbon dioxide and/or nitrogen deposition. Nonetheless, to accept the thermometer record as the more robust measurement of spatial representative temperatures is premature.
I have discussed this issue further in the posts
Comments On The Tree Ring Proxy and Thermometer Surface Temperature Trend Data
December 2007 Session ‘The “Divergence Problem’ In Northern Forests
Restating the obvious: since tree rings respond to lots of things, like sunlight and moisture, it seems odd to me that they matched temperature trends at all. Particularly in ‘previous centuries’. Just how in the {snip} did they measure temperature in ‘previous centuries’? (what made that proxy so good?)
Seems like a lot of assumptions, and facts not in evidence. Or just Bad Science.
Excellent snark sir. May I suggest that the supremacy of trees be vetted by an unbiased panel of Druids?
In retrospect, trees are terrible proxies. Many botanists have commented on the problem. Insect, fungus, bacteria, drought, flood, rock slides, avalanches, wind, are all unrelated to temperature. Frankly, the proxies are likely falsified through the entire course. It was when temperature and correlation became possible the panic started. It was all BS to begin with.
I fail to understand the great faith in tree rings as temperature proxies. Trees do better in warm years than in cool years. Trees do better in wet years than dry years. Do they do better in warm dry years than in cool wet ones?
A close look at the rings in Dr Mann’s glamour shot show that a core taken from different azimuths can give you very different ‘temperature’ readings. Or maybe different rainfall readings. They can even give you different ages.
Whatever they show, they show it only for daytime, and only for part of the year. And they sure didn’t mysteriously stop showing it in 1960.
“Nonetheless, to accept the thermometer record as the more robust measurement of spatial representative temperatures is premature.”
Interesting. Perhaps the tree ring results which show cooling in the area should be incorporated into the temperature record “from 1960 forward”.
As for changing the way they (trees) respond to temperature increases, I call upon the concept of uniformitarianism.
Yes, this isn’t pure geology, but I believe the concept is sound.
Trees like CO2 rather a lot. Next to a coal fired power station growth rate was found to triple. If the growth rate is x3 then the trees’ rings are thicker. Amazing!
Yes…yes…here we were, going merrily, merrily for thousands of years with the tree rings being the best of the best temperature proxies until in 1960 they weren’t. I blame the thermometers, and the mystery. It’s a mystery, my friends, so methinks a novel is in order. A climate change novel, with a movie based on it. Quite an idea!
“Since the thermometers are not coincident in location with the tree ring data (in the same local area)”
Boy, stunning that such close proximity calibration hasn’t been done. How hard would it be to puta thermometer in the woods and actually callibrate tree ring data to exact temp? Or do tree ring analysis in woods near a well-sited thermometer with a long term record?
Not glorious work, but how impotent to do.
I was born in 1960 and I deliberately caused the divergence problem because I thought it might be fun.
I will consider the possibility that dendroclimatology is worth even looking at when someone can provide me with a description of the exact physical mechanism by which a tree can encode a record of the ambient atmospheric temperature of the vicinity where it grows, which is even remotely plausible. Until then, if you come bearing tree ring proxies, just keep walkin’, cuz I ain’t interested.
Everyone knows the trees were there in the 60’s so no wonder thay can’t remember the temperature…..man.
Which is as supportable as any theory that tree rings are a useful proxy for temperature.
Uh…is that really what you meant to say?
The logical conclusion is that the tree ring calculations are flawed.
The religious faith based conclusion is that CO2 has changed the trees.
Wow, relevant comments with some humor mixed in. What a nice contrast to the hockey stick thread!
I’m amazed people still give any credence to tree rings as proxies for temp. As stated, there are so many variables that combine for the make up of a tree ring, it is impossible for me to believe anyone can reasonable discern what is temp in the tree rings and what is not. Of course, if I cared to figure out the mystery of divergence, I’d look for an event that occurred near 1960. I don’t buy the CO2 and/or nitrogen theory, because if they can indeed discern temps from the tree rings, surely they’d be able to discern known substances that directly effect tree growth. If they can’t do that, then it is just more evidence that tree rings as proxies are as reliable as reading tea leaves. Further, given the hyperbole surrounding CO2, I think if there were even a remote chance CO2 were the culprit, we’d all already heard about it.
“…..but they were dogged by a problem: Since around 1960, for mysterious reasons, trees have stopped responding to temperature increases in the same way they apparently did in previous centuries….”
Since around 1960, trees have stopped responding to ADJUSTED temperature increases.
fixed
Mike McMillan says:
A close look at the rings in Dr Mann’s glamour shot show that a core taken from different azimuths can give you very different ‘temperature’ readings. Or maybe different rainfall readings.
Not only is this tree trunk more “egg shaped” than round it also shows very asymetric growth patterns in some years. Especially when young. Can’t really see how either temperature or rainfall could account for this. An alternative possibility would be shading from other trees restricting where this tree can put its branches and leaves, this needing more mechanical support in the trunk. However as it became more mature factors such as pervailing wind and direction of sunlight became more important.
Bruce of Newcastle says:
Trees like CO2 rather a lot. Next to a coal fired power station growth rate was found to triple.
Not really much of a suprise. Given that market gardeners have discovered that putting carbon dioxide into greenhouses increases yields.
Yeah, but it was the sixties, flower power and The Beatles, and they were “cool”, no wonder the trees stopped growing.
Hide the decline?
“Since around 1960, for mysterious reasons, trees have stopped responding to temperature increases in the same way they apparently did in previous centuries.”
This sort of moebius lie is acceptable? ?
I call ‘loco como mierda de murcielago’
The idea that tree rings can be used as a temperature proxy is so preposterous it shouldn’t even be on the table.
And anybody who claims to be able to measure rings to a hundredth of a mm should be locked up…
The fact that anybody is still talking about this is a triumph of intellect over intelligence!
The most prominent input to tree ring growth is atmospheric CO2 content. It is also problematic that some scientists insist that global temperatures have increased as shown by thermometers (after much fiddling with the data) and now consider that tree rings are wrong for the last 50 years when temperatures have actually shown a leveling then slight fall. But we must not be diverted from our forward march by data we do not like.
Until there are thermometers co-sited with the trees to be examined we can make no reliable deductions at all Mr Goddard – concerning the so called DP. Once the divergence problem was identified I would have thought that placing thermometers beside subject trees for long term evaluation would have been the first and most obvious response. If it hasn’t been done, now would be a good time dear “scientists”, and a wee bit further down the line you can make your deductions on the divergence problem based on relevant and useful data analysis, and also of course on the long term record. But, surely, this process has already been started. If not then we should pull out all interested climatologists by their rotten roots and have them replaced by proper scientists, or even rational human beings . . . .
Until there is a full confirmation by experiment of a Theory for the divergence the only explanation for the divergence is that trees do not react to higher temps post 1960 and never have before 1960. So until this tested theory is available using trees as a temp proxy will not work as high temps are unrecorded hence the Hockey Stick.