From Penn State
Tree rings may underestimate climate response to volcanic eruptions
Some climate cooling caused by past volcanic eruptions may not be evident in tree-ring reconstructions of temperature change because large enough temperature drops lead to greatly shortened or even absent growing seasons, according to climate researchers, who compared tree-ring temperature reconstructions with model simulations of past temperature changes.
“We know these tree rings capture most temperature changes quite well,” said Michael Mann, professor of meteorology and geosciences and director of the Penn State Earth System Science Center. “But the problem appears to be in their response to the intense short-term cooling that occurs following a very large volcanic eruption. Explosive volcanic eruptions place particulates called aerosols into the stratosphere, reflecting back some fraction of incoming sunlight and cooling the planet for several years following the eruption.”
Tree rings are used as proxies for climate because trees create unique rings each year that often reflect the weather conditions that influenced the growing season that year. For reconstructing climate conditions, tree-ring researchers seek trees growing at the extremes of their growth range. Inferring temperature changes required going to locations either at the tree line caused by elevation or at the boreal tree line, the northern most place where the trees will grow.
For these trees, growth is almost entirely controlled by temperature, rather than precipitation, soil nutrients or sunlight, yielding a good proxy record of surface temperature changes.
“The problem is that these trees are so close to the threshold for growth, that if the temperature drops just a couple of degrees, there is little or no growth and a loss of sensitivity to any further cooling. In extreme cases, there may be no growth ring at all,” said Mann. “If no ring was formed in a given year, that creates a further complication, introducing an error in the chronology established by counting rings back in time.”
The researchers compared temperature reconstructions from actual tree-ring data with temperature estimates from climate models driven with past volcanic eruptions.
Comparing the model-simulated temperatures to the Northern Hemisphere temperatures reconstructed from tree-ring thickness, Mann, working with Jose D. Fuentes, professor of meteorology, Penn State, and Scott Rutherford, associate professor of environmental science, Roger Williams University, found the overall level of agreement to be quite good.
However, they report in the current issue of Nature Geoscience that “there is one glaring inconsistency; the response to the three largest tropical eruptions — AD 1258/1259, 1452/1453 and the 1809+1815 double pulse of eruptions — is sharply reduced in the reconstruction.”
Following the 1258 eruption, the climate model simulations predict a drop of 3.5 degrees Fahrenheit, but the tree ring-based reconstruction shows only about a 1 degree Fahrenheit dip and the dip occurs several years too late. The other large eruptions showed the same type of discrepancy.
Using a theoretical model of tree-growth driven by the simulated temperature changes, the team determined that the cooling response recorded by the trees after a volcanic eruption was limited by biological growth effects. Any temperature drop exceeding roughly 1 degree Fahrenheit would lead to minimal tree growth and an inability of trees to record any further cooling. When growth is minimal enough, it is likely that a ring will not be detectable for that year.
The potential absence of rings in the first one to three years following eruption further degrades the temperature reconstruction. Because tree-ring information is averaged across many locations to obtain a representative estimate of northern hemisphere temperature, tree-ring records with and without missing rings for a given year are merged, leading to a smearing and reduced and delayed apparent cooling.
The researchers also noted that aerosol particles forced into the air by volcanoes block some direct sunlight causing cooling and they produce more indirect, scattered light at the surface. Trees like indirect sunlight and grow better under those conditions. However, this effect is small compared to that of lower temperatures and shorter growing seasons.
By accounting for these various effects in the tree growth model, the researchers were able to reproduce the reduced and smeared cooling seen in the actual tree-ring temperature reconstruction, including the near absence — and delay — of cooling following the massive 1258 eruption.
“Scientists look at the past response of the climate to natural factors like volcanoes to better understand how sensitive Earth’s climate might be to the human impact of increasing greenhouse gas concentrations,” said Mann. “Our findings suggest that past studies using tree-ring data to infer this sensitivity have likely underestimated it.”
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I am not an expert on trees but agree with others that tree ring growth is in general more determined by precipitation rather than anything else. Growth can also be stunted by extreme cold.
Here in Spain, in my garden, I have a number of orange trees. All are of broadly similar age and yet they have grown very differently. Some are a few metres apart (therefore getting the same sun, rain, temperature and soil nutrients) and yet perhaps only 20 to25% as large as the best growing trees! WUWT?
My back garden is open to the mountain side covered by 100s of pine trees. No two trees appear obviously the same and yet many must have rooted at the same time and they are all experiencing broadly similar growing conditions and yet their height and width and branching and canopy distribution is quite variable.
I suspect that trees are over rated as a proxy for anything. Some broad extrapolation may be possible, but fine resolution I suspect is very difficult.
So Mann, with all his simulated theoretical models, has proven that trees grow better in warmth. Isn’t this the same guy the loves glaciers and laments a warm globe?
As Willis says, “It’s models all the way down.”
“We know these tree rings capture most temperature changes quite well,”
In reality Manns show that his ‘no expert’ in tree growth as well as statistics , while the hide the decline tells us how stupid this claim really is . There are people who are experts in tree growth , that is they spend years working and studying in this area , and they would laugh at Mann’s ideas . But I guess they don’t count as their not ‘climate scientists’
I can not believe some of the tweets coming out of him.. He retweeted Heide Cullens nonsense about a pissed off planet causing Volcanoes and Irene, and now has tweeted its journalistic malpractice not to report the non US winter as a climate change indicator, when the global temp has plummeted and is over -.18C for the year so far.
I always wanted to give him the benefit of the doubt, but he is going the way of Hansen, pure and simple
“…Following the 1258 eruption, the climate model simulations predict a drop of 3.5 degrees Fahrenheit, but the tree ring-based reconstruction shows only about a 1 degree Fahrenheit dip and the dip occurs several years too late. The other large eruptions showed the same type of discrepancy…”
With this statement, he shows that either the climate model simulation is wrong, or his tree ring-based reconstruction is wrong. Either the first simulation is too high, or the other simulation is too low.
“…Using a theoretical model of tree-growth driven by the simulated temperature changes, the team determined that the cooling response recorded by the trees after a volcanic eruption was limited by biological growth effects. Any temperature drop exceeding roughly 1 degree Fahrenheit would lead to minimal tree growth and an inability of trees to record any further cooling. When growth is minimal enough, it is likely that a ring will not be detectable for that year…”
So where are the peer-reviewed papers showing that his selected trees (or any trees) can have no rings for a drop of 1 degree F? And, then, according to his latest – since we’ve seen a rise of about 1 degree F since the start of the industrial revolution, does that mean there was no tree growth before then?
“…theoretical model of tree-growth driven by the simulated temperature changes…”
This study isn’t being done to see how actual trees respond to actual biological changes. It’s being done to try and salvage the “today is the warmest it’s been in a million years” papers.
“Following the 1258 eruption, the climate model simulations predict a drop of 3.5 degrees Fahrenheit, but the tree ring-based reconstruction shows only about a 1 degree Fahrenheit dip and the dip occurs several years too late. The other large eruptions showed the same type of discrepancy.”
Just wow. In other words, the model has no prediction power and does not tie into the data. Invalid model. And the model then actual refutes their own hypothesis.
“If no ring was formed in a given year, that creates a further complication, introducing an error in the chronology established by counting rings back in time.”
It creates a counting error of one year. This is a major complication?
Why a missing ring causes such issues for Mr. Mann is puzzling. Real dendrochronologists know how to deal with missing tree rings. They do happen occasionally along with other phenomena such as double rings in a year.
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MIT Professor Richard Lindzen
Global Warming: How to approach the science
(Climate Models and the Evidence?)
2pm-4pm 22nd February 2012
Grimond Room, Portcullis House
Westminster, London
(Ask for Sammy Wilson MP’s meeting
and allow 30 minutes for security)
Special guest speaker
Prof. Richard S. Lindzen
Program in Atmospheres, Oceans, and Climate
Massachusetts Institute of Technology
Chairman: Philip Stott Emeritus Professor
Emeritus Professor of Biogeography at the University of London,
and former Editor-in Chief of the International Journal of Biogeography.
RSVP Eventbrite ticket required
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Claude Harvey says:
February 6, 2012 at 3:28 am
I’m confused. Is Mann talking about “regular trees” or “temperature trees”? We know from his previous work that not all trees are “temperature trees”. It takes a highly trained expert like Mann to tell us which trees are telling the truth about temperature and which of their neighbors are lying like rugs in the forest. It’s an ART!
……………………………………..
I used to own an old log cabin in Central PA, built sometime around 1800. I wanted to pinpoint the year exactly so I measured the rings of the logs with an accurate optical reticule to create a tree ring series. I also measured the rings of freshly felled trees (same species of pine) on my property and a few others down the valley. I also got some official tree ring data for the region going back about 500 years. Performing cross correlations between all samples, I couldn’t get any tree to agree with any other tree to within a correlation coefficient of about 0.6 with an uncertainty in lag for about +/- 30 years.
It’s hard to get two neighboring trees to show great correlation in their ring width series. As one tree grows faster than the other it starts to rob it of sunlight, nutrients, etc. I can even see that in my own back yard from saplings I’ve planted. Mann’s worry about missing a year in the series is the least of his problems. The absolute least.
“But I guess they don’t count as they’re not ‘climate scientists’”
But they are the cardiologists of trees. And yet, Mann doesn’t want to listen to them. He wants to claim expertise in their area, as all areas, for himself. Was he part of that letter in the WSJ? What hubris!
HeHe, I just saw this at Tom’s Hardware This Record Player Turns Trees Into Music …
This is undoubtedly a better use of the wood than letting Mann continually vindicate the Peter Principle.
At some point you just have to acknowledge the plain truth that this guy’s PhD was a gift. There’s a reason he dropped out of the physics program. Unbelievable.
Mark
richard verney says:
February 6, 2012 at 3:47 am
I cannot believe that this man is this stupid.
_____________________________
I can.
We have his hockey stick, now developing a bent handle from too much misuse.
And we have him and his colleagues treating the Earth’s surface as if it is a blackbody totally insulated from the atmosphere and emitting all the radiation observed from space, so, when we make such stupid assumptions we can derive a very sensible (?) statement showing the surface would have been -18 deg.C but for carbon dioxide and its colleagues.
But then we realise we had better put back the conduction, convection, evaporation etc into the energy diagrams, plus all the radiation from the atmosphere, so it all looks about right. Hopefully the public will be even stupider and forget that we left it out to calculate the -18 deg.C. Yes, I think we can count on climatologists forgetting that so they will peer-review the new energy diagrams and yet still remember that -18 deg.C figure which they will now teach to all their up-and-coming climatologists – so the the public will indeed be even stupider, and anyone who denies all this (because he/she sees how stupid it is) will be even stupiderer.
It would seem Mann is on the back foot. He appears still to be trying to justify his hockey stick. At least if he continues to bang on about ‘treemometers’ he may not be up to too much mischief elsewhere. The desperation is palpable.
I believe dendrochronology has been found useful for dating stuff.
I think people are missing the point here. It appears that tree rings under estimate cold, which means they need to apply cooling corrections to past temperature data thus exposing the fact that temperature rise is much worse than we thought!
“there is one glaring inconsistency; the response to the three largest tropical eruptions — AD 1258/1259, 1452/1453 and the 1809+1815 double pulse of eruptions — is sharply reduced in the reconstruction.”
He has just disproved his own hypothesis and is too entrenched to realize it. Start doing science, Mike.
I think the answer to the problem is right there in the article. Clearly, instead of using actual tree ring measurements, Mann needs to use his theoretical model of tree ring grow. Just plug in the data for temps and precip. If that doesn’t get the results, use a model to get the temp and precip data.
Aren’t we in danger of misssing a trick here? In the interests of holding out an olive branch, should we not be congratulating Mr Mann for finally admitting to the world the Hockey Stick chart is a crock of sh!te?
@H.R. says: on February 6, 2012 at 2:01 am
I see I am not the only fan of that movie. 😉
While it is obvious that Mann’s science is weak or non existent his “cause” still controls government action.
Don’t worry MM y0u will be going down in history as a scientist, it just may not be a scientist anyone would want to follow in the foot steps of.
Phil Jones (Whos he?) will thank you though as he probably will not be remembered.
“model simulations of past temperature changes.” Well if tree rings don’t match the model, change the model. Oh what if tree rings don’t capture most temperature changes quite well? Then we will select one tree that matches the models fairly well and use that one tree for a proxy of global temperature, until we have to hide a decline.
OK, maybe it’s just me, but doesn’t this actually make the hockey stick even *more* unrealistic?
Mann is saying the old, pre-volcano-adjustment, tree-ring data was too *high* for temperatures, but wasn’t “Mike’s Nature Trick” designed to camouflage the fact that the post-1950 tree-ring data was too *low*? If I read this right, this adjustment will make the tree-ring data *lower*, and thus *exacerbate* his problem.
Am I missing something? Was there a tent in this tree-ring circus that I haven’t seen?
“Some climate cooling… may not be evident in tree-ring reconstructions of temperature change… (when) tree-ring temperature reconstructions (are compared) with model simulations of past temperature changes.”
Translation: “When data doesn’t match our model simulations, we conclude our model is right and the data is wrong.”
or as Mythbuster Adam Savage says: “I reject your reality and substitute my own.”
Only in ‘Climastrology’ get you away with this B.S. The scientific community should laugh them off of the stage!