Since Princeton’s Dr. Michael Oppenheimer conflated weather with climate last week, proclaiming a short lived heat wave as “This is what global warming really looks like” in a media interview, it seems only fair to show what real science rather than what he and Dr. Trenberth’s government funded advocacy looks like. I can’t wait to see how Dr. Michael Mann tries to poo-poo this one. – Anthony
From Johannes Gutenberg-Universität Mainz: Climate in northern Europe reconstructed for the past 2,000 years: Cooling trend calculated precisely for the first time
Calculations prepared by Mainz scientists will also influence the way current climate change is perceived / Publication of results in Nature Climate Change
An international team including scientists from Johannes Gutenberg University Mainz (JGU) has published a reconstruction of the climate in northern Europe over the last 2,000 years based on the information provided by tree-rings. Professor Dr. Jan Esper’s group at the Institute of Geography at JGU used tree-ring density measurements from sub-fossil pine trees originating from Finnish Lapland to produce a reconstruction reaching back to 138 BC. In so doing, the researchers have been able for the first time to precisely demonstrate that the long-term trend over the past two millennia has been towards climatic cooling.
“We found that previous estimates of historical temperatures during the Roman era and the Middle Ages were too low,” says Esper. “Such findings are also significant with regard to climate policy, as they will influence the way today’s climate changes are seen in context of historical warm periods.”
The new study has been published in the journal Nature Climate Change.Was the climate during Roman and Medieval times warmer than today? And why are these earlier warm periods important when assessing the global climate changes we are experiencing today? The discipline of paleoclimatology attempts to answer such questions. Scientists analyze indirect evidence of climate variability, such as ice cores and ocean sediments, and so reconstruct the climate of the past. The annual growth rings in trees are the most important witnesses over the past 1,000 to 2,000 years as they indicate how warm and cool past climate conditions were.
Researchers from Germany, Finland, Scotland, and Switzerland examined tree-ring density profiles in trees from Finnish Lapland. In this cold environment, trees often collapse into one of the numerous lakes, where they remain well preserved for thousands of years.The international research team used these density measurements from sub-fossil pine trees in northern Scandinavia to create a sequence reaching back to 138 BC. The density measurements correlate closely with the summer temperatures in this area on the edge of the Nordic taiga.
The researchers were thus able to create a temperature reconstruction of unprecedented quality. The reconstruction provides a high-resolution representation of temperature patterns in the Roman and Medieval Warm periods, but also shows the cold phases that occurred during the Migration Period and the later Little Ice Age.In addition to the cold and warm phases, the new climate curve also exhibits a phenomenon that was not expected in this form.
For the first time, researchers have now been able to use the data derived from tree-rings to precisely calculate a much longer-term cooling trend that has been playing out over the past 2,000 years.
Their findings demonstrate that this trend involves a cooling of -0.3°C per millennium due to gradual changes to the position of the sun and an increase in the distance between the Earth and the sun.”This figure we calculated may not seem particularly significant,” says Esper. “However, it is also not negligible when compared to global warming, which up to now has been less than 1°C. Our results suggest that the large-scale climate reconstruction shown by the Intergovernmental Panel on Climate Change (IPCC) likely underestimate this long-term cooling trend over the past few millennia.”
===========================================================
Orbital forcing of tree-ring data
Jan Esper, David C. Frank, Mauri Timonen, Eduardo Zorita, Rob J. S. Wilson, Jürg Luterbacher, Steffen Holzkämper, Nils Fischer, Sebastian Wagner, Daniel Nievergelt, Anne Verstege & Ulf Büntgen
- Received 27 March 2012 Accepted 15 May 2012 Published online 08 July 2012
Solar insolation changes, resulting from long-term oscillations of orbital configurations1, are an important driver of Holocene climate2, 3. The forcing is substantial over the past 2,000 years, up to four times as large as the 1.6 W m−2 net anthropogenic forcing since 1750 (ref. 4), but the trend varies considerably over time, space and with season5. Using numerous high-latitude proxy records, slow orbital changes have recently been shown6 to gradually force boreal summer temperature cooling over the common era. Here, we present new evidence based on maximum latewood density data from northern Scandinavia, indicating that this cooling trend was stronger (−0.31 °C per 1,000 years, ±0.03 °C) than previously reported, and demonstrate that this signature is missing in published tree-ring proxy records. The long-term trend now revealed in maximum latewood density data is in line with coupled general circulation models7, 8 indicating albedo-driven feedback mechanisms and substantial summer cooling over the past two millennia in northern boreal and Arctic latitudes. These findings, together with the missing orbital signature in published dendrochronological records, suggest that large-scale near-surface air-temperature reconstructions9, 10, 11, 12, 13 relying on tree-ring data may underestimate pre-instrumental temperatures including warmth during Medieval and Roman times.
===============================================================
I’m sure Steve McIntyre will give this paper a thorough examination for the same sorts of issues we’ve seen before in MBH98. Hopefully he won’t have to beg for years to get the data for replication like he did with Mann.
h/t to WUWT readers “Typhoon” and Dr. Leif Svalgaard
Discover more from Watts Up With That?
Subscribe to get the latest posts sent to your email.
A problem is that if we don’t believe treemometers for warming trends they should hold as much weight for cooling trends.
You have a good point but if they release ALL their data and methods then it’s up to others to try to find fault with it. I too am sceptical about tree rings being thermometers.
Will Warmists accept this with open arms? If tree rings from Briffa and Mann was good enough for them then what about this study? Just questions.
They will call this “just regional.” I may be wrong but I recall that Mann and Briffa’s hockey sticks studies were also regional. The recent US heatwave was also regional.
The Medieval Warm Period was global.
http://www.co2science.org/data/mwp/mwpp.php
climatereason says:
July 10, 2012 at 12:54 am
……. this chart shows summer temperatures. which reduces the studies usefulness somewhat. It was the winters that dragged the overall mean temperature down-many LIA summers were very hot
tonyb
Hi Tony
Summers are always warm enough for growth, I think it is rainfall which is reflected in the tree rings. My regular excursions to the Wimbledon common shows that everything grass, shrubs and the established trees have gone absolutely exuberant, not to mention a rhododendron and fatsia japonica in my garden.
Good score for the ‘magnetics’ on the solar thread, not a ‘nonsense’ any more just based ‘on the flimsiest grounds’. ( It looks like as ‘where vukcevic boldly goes, NASA cautiously follows’)
Almost a Laplander says:
July 9, 2012 at 11:37 pm
@R Barker
I have read previous studies using trees from lapland as a temperature proxy. Why these are so good proxies is that unlike many other trees, the only limiting factor for their growth is the temperature….
Nope. People really do need to get their head around the concept that a single tree lives in its own complex ecosystem which may share many similar variables with its neighbours. No one tree or small sample of trees is a proxy for anything. Geographic variation imposes large, mostly unreconcilable, constrants on sample homogeneity for statistical purposes.
The treeline in the scandinavian mountains was much higher during the MWP, so the temperature certainly was much higher than today.
Now this is a pursuable goal for the purpose of climate interpretation on a local basis, but again you have the problem of isolating climate from weather geography and other factors over the long term. Treelines will wax and wane with climatic and geographic influences – this is true of most terrestrial species at their environmental limits. However, the issue of isolating climate as the limiting factor is complex. The experimental scale is beyond most research methodology and budgets that I’ve seen so far. At best, the conclusions are mostly only anecdotal, notwithstanding the number of “names” on the citation.
Scottish Sceptic says:
July 10, 2012 at 1:04 am
SteveSadlov “In a relatively moisture rich environment in the mid latitudes treemometers sort of work. Elsewhere, not so much.”
Trees respond to the dominant controlling factor. If that is not water, then it allows more influence of temperature, but we are still left with the problem of “canopy adaptation”. The problem is that trees will grow until no more trees can grow. …
Overly simplistic and not necessarily true. You are conflating trees with forests. Canopy is but one chaotic variable controlling the life of a tree in a forest. What is true is a tree will grow until it can grow no more. The limits to growth of an individual tree are not the same as the limits to growth of trees in a forest, but they are chaotically interconnected. A forest is the net sum of an almost unresolvable number of component ecosystems, each contributing to the other, but each standing alone on its own merits. The relationship is not synergistic, however. “Climate” scientists that don’t understand this and persist on dabbling with cores have little hope of resolving climate….
“as they will influence the way today’s climate changes are seen in context of historical warm periods.”
I highly doubt it.
Just playing Devil’s Advocate here, and it may have already been addressed, but if we don’t believe the previous 1000 year reconstructions from tree rings showing warming because tree rings make lousy thermometers, why should be believe this one showing cooling?
Very difficult proxy to use…
I can’t shake the feeling that this paper is a strawman for the treehuggists to attack and try to vindicate their own tree ring noise plots.
Tree rings are affected by rainfall, humidity, disease, soil composition, sunlight and other factors. Identifying the growth attributable to temperature is not a straightforward task. Call me skeptical.
The good news: The authors have not grafted thermometer measurements onto proxy data.
Objection: tautological.
This long term cooling due to orbital effects is I believe correct. I found it to be about 0.2 deg C/1000 yrs in my 2004 paper:
Loehle, C. 2004. Climate Change: Detection and Attribution of Trends from Long Term Geologic Data. Ecological Modelling 171:433-450
and frequent evidence of similar cooling in more extensive data sets:
Loehle, C. and S.F. Singer. 2010. Holocene Temperature Records Show Millennial-Scale Periodicity. Canadian J. Earth Sciences 47: 1327-1336
It has even been found in Mann’s work.
Note that 0.3 deg/1000 projected back to the Holocene warm peak gives 0.3×7000 = 2.2 deg C warmer, which matches various estimates I have seen (for at least northern hemisphere temps). Since polar bears and most everything else did just fine then, and that is when human agriculture began, it is hard to argue that a similar warming today will be catastrophic, unless you hold a Panglossian view of the world (what is can not be improved upon).
kirkmyers said:
The good news: The authors have not grafted thermometer measurements onto proxy data.
In the actual published article in Nature Climate Change, they did overlap the instrumental data.
Now all of a sudden tree rings are great predictors with fine resolution? And from a single place in Finland they predict the temperatures of all of Europe?
Properly statisticked tree rings show long term cooling, archived ice cores show long term cooling, glacial erratics stub the plow; folks, that’s an iceberg ahead, not the Promised Warmer Land.
Even kim can’t get a good rangefinding for the mountain of cold, but it is surely out there. All the confusing echoes confirm its reality, but not its location.
======================================================
Scottish Sceptic writes:
The problem is that trees will grow until no more trees can grow. It does not matter whether it is the middle of the tropical jungle, or the sparse canopy of the north, the fact is that if more trees could grow, they would. So, if conditions “improve” the result may be a spurt in growth for individual trees, but it is also likely that more trees can grow, and fairly rapidly (a few decades), there will be more trees, these trees then compete reducing growth for other trees so that any individual tree will tend towards its optimum growing conditions.
But it occurs to me, looking at the the photos of the trees in their paper, leaning over the lake, that the effect of competition for sunlight with other trees may be mitigated by the trees being lakeside–basically always having a clearing. This may imply other sampling problems: is the open space created by the lake on the north side, south side (or does it matter since they are far north and the sun is shining nearly from every direction in summer?). Is there a sampling bias by taking the trees that fell in–the ones that stuck their neck out farthest?
AndyG55 says:
July 9, 2012 at 3:58 pm
Doesn’t ice core data show a gradual cooling over the whole Holocene?
Yes.
10,000 yrs Vostok: GRAPH
10,000 yrs Greenland: GRAPH
As far as this study goes, I still dislike tree ring data. There are just too many factors that influence growth in “tree-ring density measurements ” All that can be said is the local conditions were favorable/not favorable for growth. Heck we have not had rain since June 23 until last night, my grass looks like hay but fifty miles north of me or fifty miles south got hit by thunderstorms and got at least three or four rain storms over the same period and their grass looks just fine.
So I will wait until I hear what Steve M. has to say about the study. If the amount of data is large enough and spread over a wide enough area you might be able to squeeze some general climate data out of it but I am not holding my breath.
On the other hand where plants will or will not grow seems to me to be a better indicator. You will not find orange trees or even poison ivy growing in northern Canada for example.
If I were just a little bit excited by temperatures than I am, I would surely conjecture that the Decline of the Roman Empire was sparked by the Decline of the temperatures.
Sorry, Anthony. This looks like another attempt to find a hockey stick where one doesn’t exist. Wait until they graft the instrumental record on the end and then use it to say it’s even worse than we thought because man is ending an inexorable period of global cooling. Fact is lots of scientists believe the warming is NATURAL and that the earth has been warming gradually since the last ice age! The Roman and Medieval Climatic Optimums were blips on a long-term warming, caused by increased solar and cosmic flare activity as well as a predominantly warm-phase of oceanic oscillations.
So we are trending towards an over due interglacial period. Makes Sense
But wait, where’s the Little Ice Age? This graph actually looks very much like the Hockey Stick, just without the blade (which I suppose was the most important part). Let’s not get prematurely excited about this.
Babsy says:
July 9, 2012 at 5:12 pm
Bob Tisdale says:
July 9, 2012 at 4:14 pm
Hey, Bob! I thrilled beyond description it hasn’t been 120 so far this summer in North Texas. It’s raining today and *COOL* LOL!!
___________________________
OT looks like the East Coast Heat Wave broke. Temps are back down into the 80’s F for the rest of the week – tomorrow is supposed to have a high of 82F (77F in mid N. Carolind at 10:30 AM)
After reading Dr. Tim Ball’s comment my distrust of treeometers is now complete. Thanks Dr. Ball especially for pointing out trees only record the growing season and not the winter temperatures where annual cooling shows the most. If it is the winter temperatures that are critical then the whole annual global temperature idea is bogus and it is the NH November through February temperatures where we should be looking and where the signal for ‘climate change’ is strongest. (SH doesn’t show as much change either because of the amount of ocean.)
@Tim Ball
“Theodor Landscheidt later developed the relationship between solar activity and midlatitude droughts. http://www.john-daly.com/solar/US-drought.htm”
This is going to be interesting: Landscheidt predicted a mega-drought in the US in 2018 not long before he died. If it happens, it will be trumpted (of course) by the warmistas as ‘proof of global warming and expect more of this’. The fact that he was able to predict it more than a decade before by studying the acceleration of the sun around the barycentre is going to cause some serious cognitive dissonance because they will be claiming it is human-sourced CO2 which Landscheidt didn’t factor in at all.
No doubt the Executive Summary of AR 7/8/9 will have some ‘explanation’ for the ‘coincidence’ and Theodor’s ‘lucky guess’. Maybe by then Peirs will have confessed he uses Tarot Cards and his long range weather forecasts are just ‘lucky guesses’ too. Interesting how people who study solar events and cycles are always such lucky guessers.
Vuk
As you may have seen elsewhere, I do believe that tree rings are a reasonably good proxy for moisture but even in a small country like the uk rainfall varies greatly from place to place and year by year. So although rings might show moisture it is very localised. Look forward to seeing some of yoir studies in print.
Whilst everything may be vey green things havent set-i havent been able to grow outdoor tomatios for 5 years, which when you look at the cet decline over the last decade speaks volumes that we need a plan b (cooling) as well as a plan a (Warming)
tonyb
Craig Loehle says:
July 10, 2012 at 7:05 am
……
Dr. Loehle
An unexpected vindication of strong correlation of your temperature reconstruction and the Earth’s magnetic field, as I presented here
http://www.vukcevic.talktalk.net/LLa.htm
is coming from an unexpected source, no less than JPL/NASA
http://phys.org/news/2011-03-earth-core-climate-insights.html
evidence is overwhelming from data by: Wang &Lean, Svalgaard, Arctic temperature records, Arctic magnetic flux, data from Jackson & Bloxham and at least another half a dozen other sources. I am looking forward to the day when the Loehle’s temperature reconstruction becomes the science’s standard.
George says:
July 9, 2012 at 5:16 pm
While tree rings by themselves may not represent temperature, the combination of tree rings and the isotopes contained in the wood together can be a pretty good indication.
_______________________________
I was thinking the same thing (Shackleton’s isotope work on deep-sea sediment cores) However that was not what was done here.
One wonders why isotopes are not used since these are sub-fossil. Anyone know?
It also does not negate Dr. Tim Ball’s observation about winter temperatures.
did anybody comment on the fact that the reconstruction is for Northern Scandinavia only?