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.”
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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.
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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
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I have been skeptical of the claim that tree rings are a reliable indicator of temperature and I still am.
What would be more credible is to suggest that tree rings are a reasonable indicator of the relative goodness of a sequence of growing seasons regardless of the combination of conditions that caused them.
The subject study results appear to be in accord with the anecdotal climate evidence accumulated over that period of recorded history, something the “hockey stick” fails to do.
A string of favorable growing seasons may be most important measure of the quality of a climate rather than just temperature alone because it would be an indicator of the abundance of the food supply for the time period. Of course this does nothing to make the case for catastrophic global warming due to fossil fuels.
Density measurements? How did they control for the other factors besides temperature that can influence tree ring density?
I wonder how many people like Mann back then were blaming Jesus for causing global warming. Bush got off easy…
In the top right of the second graph in this article, if one clicks to enlarge, the late 1930s are seen to be as warm as the final years in the graph extending up to 2006. That is also what is seen in http://earthobservatory.nasa.gov/Features/ArcticIce/Images/arctic_temp_trends_rt.gif
(Within the timeframe of the past century, in overall shape of the trends, such basically supports the Loethle reconstruction too, within its margin of error, which used only non-tree-ring proxies in contrast, which I graphed in http://www.freeimagehosting.net/newuploads/319xq.jpg using data from http://www.ncasi.org/programs/areas/climate/LoehleE&E2007.csv — which includes likewise seeing a major temperature decline in the mid 20th century to a bit afterwards).
A similar pattern is observed again, for the late 1930s being as warm as today, including 0.7 degrees Celsius decline 1930s->1960s for the entire northern hemisphere average, in the original National Academy of Sciences graph discussed at http://antigreen.blogspot.com/2012/05/rare-corporate-courage-and-common-sense.html
Contrast to how, for instance, the CAGW movement’s “official” Hadcrut 4 temperature reconstruction shows a totally different temperature trend for the northern hemisphere specifically just as it does for its global temperature reconstruction; due to convenient hockey stick type adjustments, it is wrong both in the northern hemisphere and globally. (If such is plotted for the northern hemisphere at http://www.woodfortrees.org/plot/hadcrut4nh/from:1880/to:2013/plot/hadcrut4nh/from:1880/to:2013/mean:60 there is not just a small deviation but a totally vastly different trend with the 1940s-1960s conveniently revised to be about flat to hide the decline).
Meanwhile, as an example of cross-checking with other considerations, the global cooling fear of the 1960s-1970s did not occur for just no reason. In other words, true temperature history is not even close to that seen on most widely publicized graphs today but rather is one where:
* Temperatures rose from the 1910s-1930s, to a level roughly as high as now.
* Temperatures then had a major decline in the 1950s-1960s, a decline about as much as the entire global warming of the more recent past several decades.
* Then temperatures rose in the 1970s-1990s up to current temperatures which have been at a temporary near-plateau but slightly declined 1997-2012 after the 1997 albedo change.
Such is a particularly big deal as it utterly effects whether there is any actual large deviation from overall solar-GCR forcing trends beyond the fluctuations reasonable to expect from ocean oscillations on top (60-year cycle AMO+PDO and shorter fluctuations such as El Ninos and La Ninas).
Combine true temperature data with true solar data showing major rise in solar activity since the Little Ice Age, as in http://www.appinsys.com/globalwarming/GW_Part6_SolarEvidence_files/image008.jpg where the open circles are even cross-checking with aurora incidence (one way to cross-check whether a particular numerical percentage adjustment of sunspot counts over time is reasonable or not), also as in http://www.appinsys.com/globalwarming/GW_Part6_SolarEvidence_files/image023.gif — and all fits in overall trends. The CAGW proponent claims that there is excessive mismatch actually rests on pillars of fudging the temperature and solar data in convenient revisions.
The first step in creating a true model of climate would be carefully sticking to non-fudged data alone to help avoid GIGO, which is tricky since the dishonest kind is so widely publicized today that few climate scientists fully know the real picture even amongst those honestly trying. Someday I’m going to try to find some non-fudged southern hemisphere temperature data too to further complete the picture, but the global average is going to approximately fit what the more reliable indirect proxy figures show, such as http://www.agu.org/pubs/crossref/2007/2006GL028492.shtml which notes:
“The rate of sea level change was found to be larger in the early part of last century (2.03 ± 0.35 mm/yr 1904–1953), in comparison with the latter part (1.45 ± 0.34 mm/yr 1954–2003). The highest decadal rate of rise occurred in the decade centred on 1980 (5.31 mm/yr) with the lowest rate of rise occurring in the decade centred on 1964 (−1.49 mm/yr).“
Y’all don’t suppose? – that these results are the real reason “the great ice melt” was cancelled?!
http://wattsupwiththat.com/2012/07/07/350-org-cancels-melting-hoax-ice-sculpture/
Could we actually be seeing some impact? GK
The temperatures “rose in the 1970s-1990s” in my immediately prior comment was minor mistyping; I mean from the end of the 1970s through up to the 1997 albedo shift and 1998 El Nino, before how since then there has been decline (slight decline so far but wait for beyond around 2014).
Reblogged this on The GOLDEN RULE and commented:
Many thoughts arise from this article.
Mainly that there are numerable ways of measuring or estimating the global temperature trend, numerable ways of interpreting such measurements,
In a relatively moisture rich environment in the mid latitudes treemometers sort of work. Elsewhere, not so much.
And Gutenberg cast down Mann’s hockey stick in the presence of the peers, and lo! it became a serpent!
Compared to GISP2, Alley 2000, the above temperature profile does not exactly match, but the GISP2 profile shows a greater rate of cooling than the trees, added here in black:
http://i49.tinypic.com/9prvqh.jpg
I loved Table S4 in the Supplemental Data, where they take their own shot at the 10 warmest years. The top 3 were 125 BC, 1937 AD, and 4 BC. I suspect this to be a bit tongue-in-cheek, but it’s a great play on the endless attempts to show that the hottest year is 1998, no it’s 2007, no, it’s 2010….
The truth is also best served cold.
T’was the Roman chariots that done it. Then Rome fell and cooling commenced…
Seriously, what happens now? Do all the warmists go back home from the battlefield after realising that the enemy was non-existent? No, they will invent another enemy….
All them horses, Alex..
And all that marchin’ about everywhere.. way to much CO2 and methane produced.
@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.
Those trees start growing only after the temperature stays above 5C and continue to grow until it doesn’t. There is more than enough water even in a dry year and the sun shines 24/7 throughout the exceptionally short growing season.
Winter temperatures do affect the the growth, since the depth of the permafrost, lake ice coverage etc. depends on the harshness of the winter.
The treeline in the scandinavian mountains was much higher during the MWP, so the temperature certainly was much higher than today.
Decreasing temperatures over the last 2000, 9000 and 12000 years are well known from high quality reconstructions such as
http://www.agu.org/pubs/crossref/2007/2006GL028600.shtml
http://www.essc.psu.edu/essc_web/seminars/spring2006/Mar1/Bond%20et%20al%202001.pdf
(figure 3, which is upside down in temperature)
Mr Watts You comment “I can’t wait to see how Dr. Michael Mann tries to poo-poo this one. – Anthony” If you look at RealClimate you’ll find out. In an article on tree ring data Mann, Schmidt and Steig ignore it totally.
As well as temperature, and moisture, and horse manure….trees like CO2 🙂
So I would like to put forward the hypothesis that tree ring evidence of the RWP and MWP was cause by horses.. one way or another.
Now I know we haven’t an abundance of horses at the moment, be have got lots more humans and more luvly CO2.
This paper is as suspect as those delivering the “we are all going to fry and drown” message. Only summer reconstruction, dodgy proxies. Meaningless.
As Dr. Ball points out, the trees at best measure summer changes, while warming/cooling affect winter temps first and most. Anyone got any brilliant suggestions for a winter temp paleo-proxy? Formanifora?
“Their findings demonstrate that this trend involves a cooling of -0.3°C per millennium”.
It may also show that the soil is leaching vital nutrients, it may also show that some kind of growth inhibitor (like insect disease) is increasing in the area. It may show the area is getting wetter/drier, that wind damage is increasing (hence less growth). It may show a slow decolonisation by something that used to keep the tree numbers down and so used to allow individual trees to grow more. (Have wolf numbers been increasing, so keeping grazing animals in check.
Indeed, the whole “temperature” series may be nothing more than a proxy for the population of wolves in the area.
As I’ve said before, what Mann’s hockey stick proves is that if you correlate series for their fit with modern temperature (the blade), there is next to no correlation historically – i.e. they show no historical temperature. In other words:
a) either temperature did not vary in the past (Mann’s false assertion)
b) Tree rings are not a temperature proxy (the proper conclusion of the hockey stick)
So, the idea that tree rings are a better proxy than other methods is laughable.
Almost a Laplander;
Those trees start growing only after the temperature stays above 5C and continue to grow until it doesn’t. There is more than enough water even in a dry year and the sun shines 24/7 throughout the exceptionally short growing season.
>>>>>>>>>>>>>>
Ever see what a late frost after initial leafing out does to tree growth for the season? Ever seen what pestilence (tent caterpillars in my neck of the woods, but I’m certain there’s something similar in Lapland) does to growth for a year? How about disease? What about foraging animals? How about other plants that come and go, like pine trees, that make the soil and groundwater in the area more acidic? What about migrating birds which may choose that spot as a way station for a period of time, causing the soil and the groundwater to become more basic (goose pooh! oooh!). And once we get beyond all of THAT, we still don’t have a clue if the winter was abnormaly cold, abnormaly warm, or abnormaly normal.
Two big problems with this paper.
1 It’s using tree rings as a proxy for temperature when other limiting factors (water, sunlight, nutrients, etc) are important.
2 It’s published in Nature Climate Change which has demonstrated no ability to organise legitimate peer review. So much junk science has got published in there that I doubt anything that it deems worthy of publication.
It is interesting that this did get published anywhere, though.
Perhaps peer review needs redefinitioin, again?
Wonder how gavin and joe will try to knock this into the long grass?