“In Europe, for example, the average temperature between AD 21 and 80 was warmer than during AD 1971-2000.”
From Northern Arizona University
Regional insights set latest study of climate history apart
As climate studies saturate scientific journals and mainstream media, with opposing viewpoints quickly squaring off in reaction and debate, new findings can easily be lost in the noise.
But in the case of Northern Arizona University Regents’ professor Darrell Kaufman and a study appearing in Nature Geoscience, obscurity is an unlikely fate.
What Kaufman—the lead co-author of “Continental-scale temperature variability during the last two millennia”—and 78 experts from 24 countries have done is to assemble the most comprehensive study to date of temperature change of Earth’s continents over the past 1,000 to 2,000 years.
By looking regionally, the researchers found considerable complexity hidden within a global average.
“We wanted a new and ambitious effort to reconstruct past climate,” Kaufman said of the PAGES 2k network of researchers. “One of the strongest aspects of the consortium study is that it relies on regional expertise.”
Members of the consortium represent eight continental-scale regions. They lent their insights about the best proxy records—such as tree-ring measurements—to use for a particular region, and how to interpret the data based on regional climatology.
While the study does not attempt to attribute temperature changes to natural or human-caused factors, Kaufman said the finding of a long-term global cooling trend that ended late in the 19th century is further evidence that increased greenhouse gasses have had an influence in later years.
“The pre-industrial trend was likely caused by natural factors that continued to operate through the 20th century, making 20th century warming more difficult to explain if not for the likely impact of increased greenhouse gasses,” Kaufman said.
While that sounds like a familiar theme, the study’s findings of regional variations are less well known. Because of extensive participation by scientists working in the Southern Hemisphere, Kaufman said, data from those regions broadened what had been a view previously centered on Europe.
“We know the most about the long-term temperature history in Europe, but we find that not every region conforms with that pattern,” Kaufman said. He noted that temperatures varied by region against the backdrop of the long-term cooling identified by the study.
The regional focus on the past 2,000 years is significant for two reasons, Kaufman said. First, climate change at that scale is more relevant to societies and ecosystems than global averages. And second, “regional scale differences help us to understand how the climate system works, and that information helps to improve the models used to project future climate.”
Kaufman’s own research team added to the strong regional input. His research in Alaska and elsewhere formed part of the dataset.
“The questions that my team hopes to address involve the larger climate system, and our research contributes one piece of the global puzzle,” he said.
Kaufman’s role as lead co-author came about partly from good timing—he was on sabbatical as a visiting scientist at the Bern, Switzerland, headquarters of Past Global Changes (PAGES) organization, as the data were being assembled, so he took the lead in writing the manuscript.
Later, as the paper underwent a substantial reworking to address the scrutiny of peer review, co-author Nick McKay, a post-doctoral researcher at NAU, “did the heavy lifting,” Kaufman said. “He analyzed the data from each of the regions to uncover the most important similarities and differences, which we needed for the synthesis.”
In another of the study’s major contributions, the entire database on which it was based has been tabulated and will be made available publicly for further analysis. Kaufman and his co-authors have posted the data along with frequently asked questions about the study on the PAGES project website.
“My co-authors and I look forward to seeing the data used by others in future analyses because science moves forward with well-informed alternative interpretations,” Kaufman said.
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Andrew Revkin has an interview with the author.
I found this part very interesting:
We also found that temperatures in some regions were higher in the past then they were during the late 20th century and that, the longer the individual site record, the more likely it was to show prior warm intervals, which is consistent with the long-term cooling trend. In Europe, for example, the average temperature between AD 21 and 80 was warmer than during AD 1971-2000. But temperatures did not fluctuate uniformly among all regions at multi-decadal to centennial scales. For example, the transition to colder regional climates between AD 1200 and 1500 is evident earlier in the Arctic, Europe and Asia than in North America or the Southern Hemisphere.
More here: http://dotearth.blogs.nytimes.com/2013/04/22/study-charts-2000-years-of-continental-climate-changes/
‘“The pre-industrial trend was likely caused by natural factors that continued to operate through the 20th century’
The give away word is ‘likley ‘ so they don’t know what natural forces caused past cooling or indeed warming, but they know for a fact that recent warming has to be man made becasue …..?
In reality what they know is what brings in further research grants and what it is that organisations like the IPCC need , and its not anything that suggests that current warming cannot be the fault of man .
@Village Idiot
“The Vikings grew potatoes on Greenland, for goodness sake!”
Not the Vikings, but watch this:
http://www.real-science.com/potato-farming-in-greenland
And do an internet search for contemporary agriculture in Greenland.
You might be amazed! 😉
Total carbon emissions from fossil-fuels (million metric tons of C) go from 3 in 1751 to 8 in 1800 to 188 in 1875 to 534 in 1900 to 6750 in 2000 to 8749 in 2008 (end of data).
http://cdiac.ornl.gov/ftp/ndp030/CSV-FILES/global.1751_2008.csv
So, over the last decade or so, in spite of fossil fuel emissions running at 15-30 times the late 19thC rate, global warming has stalled. The idea put forward in this paper that “the finding of a long-term global cooling trend that ended late in the 19th century is further evidence that increased greenhouse gasses have had an influence in later years.” is completely ludicrous.
No flies on WWUT readers! Silly me – it’s now that they grow commercial crops of potatoes (plus other vegetables) in Greenland. Plus record amounts of lamb.
http://climategreenland.gl/udfordringer_og_muligheder/landbrug/&new_language=1
“They lent their insights about the best proxy records—such as tree-ring measurements ….”
What ?! The best proxy records are tree-ring measurements ?! Classical climate change theory says that temperature changes are most pronounced at night and during the winter. Trees grow during the daytime and in the summer. Rates of growth are influenced not only by temperature but also by sunlight (cloudiness), the availability of nutrients, competition from other trees/plants for sunlight and nutrients, precipitation, disease / fungus / insect attack and, last but definitely not least, atmospheric CO2 levels. I seriously doubt that it is possible to filter out any temperature signal from all these confounding factors. Indeed, the “hide the decline” scandal where proxies (predominantly tree-rings) indicated declining temperatures when thermometers showed temperatures were rising confirms that tree-rings are utterly useless as temperature proxies.
There are much better proxies such as oxygen isotopes in ice cores or studies of the historical height of tree lines.
But Richard Verney has really hit the nail on the head in his comment above, “All proxy studies contain huge error margins and uncertainties and it is important that they should be considered in tandem with written historical record…”
http://www.co2science.org has a directory of published studies from around the world relevant to the Medieval Warm Period. These studies confirm that the MWP was global and they are roughly 4:1 in favour of the MWP being warmer than the modern warm period. I wonder how many of these studies made it into the Pages2K paper.
“Kaufman said the finding of a long-term global cooling trend that ended late in the 19th century……” Someone ought to tell Kaufman that the low point of the Little Ice Age occurred around 1690. The world has been warming since, though with cool interludes such as the Dalton Minimum. The LIA is considered to have ended around the mid/late 19th century but the world wasn’t on a long-term cooling trend up until then.
“The pre-industrial trend was likely caused by natural factors that continued to operate through the 20th century, making 20th century warming more difficult to explain if not for the likely impact of increased greenhouse gasses.” The upward trend in temperatures during the 20th century was pretty similar to the upward trend in the 18th and 19th centuries. Given that the natural factors continued to operate, this means the influence of an increase in greenhouse gases must be pretty small. This is being confirmed today as 21st century temperatures flatline. And with a quiet sun, we can expect another Dalton-type cooling for a couple of decades.
“How can anybody take the European reconstruction seriously ? MWP almost gone. in Europe !”
About 15 years ago I visited a vineyard in the south of England, they had a poster up showing where vineyards had historically existed, it was as far north as Leeds. It must have been significantly warmer than it is now, for a long enough period for people to have considered planting the vines, for this to have been the case.
@Nial
“About 15 years ago I visited a vineyard in the south of England, they had a poster up showing where vineyards had historically existed, it was as far north as Leeds. It must have been significantly warmer than it is now, for a long enough period for people to have considered planting the vines, for this to have been the case.”
And what is with this vineyard?
http://www.visitleeds.co.uk/thedms.aspx?dms=13&feature=2&venue=2193741
“We know the most about the long-term temperature history in Europe, but we find that not every region conforms with that pattern,” Kaufman said. He noted that temperatures varied by region against the backdrop of the long-term cooling identified by the study.”
Well I guess that rules out calibrating and comparing high frequency regional proxies to global averages then.
“The pre-industrial trend was likely caused by natural factors that continued to operate through the 20th century…”
Show your work.
Correlation cannot be used to establish causation, so the temperature rise from the late 1800s cannot be ascribed to CO2 simply because the temperatures rose.
I liked the like button
cn
@richard verney
“We know from written record that, in Northern Europe, there was a Roman warm period. We know from written accounts that vines were grown around the Scottish boarder. This cannot be done today. We therefore know that it was warmer at those latitudes than it is today. For vines to grow in the Scottish boarders, the region most probably would have had to enjoy a similar temperature/climate to that enjoyed today bySouthern England, ie., about 3 to 4 degrees warmer.”
Is Cumbria close enough to the Scottish border?
http://www.highcupwines.co.uk/site/
“We know from archaelogical evidence that the Vikings settled in Greenland during the Viking warm period. Again, bearing in mind farming technology available, Greeenland would most probably have to have enjoyed a temperature between 3 to 6 degrees warmer than it is today to enable Viking settlements to have flourished for several centuries.”
http://en.wikipedia.org/wiki/Economy_of_Greenland#Agriculture_and_forestry
http://www.independent.co.uk/environment/climate-change/greenland-reaps-benefits-of-global-warming-8555241.html
It may be that at those times and places it was warmer than it is now. However, quite some less than 3 degrees would be enough.
The instructive “further study” step would be to attempt a reconstruction of the atmospheric and oceanic oscillations that could have brought about these regional trends. It would then behoove climate scientists to determine whether or not these same conditions could be present today (and they would have to prove these same conditions could not cause similar warming). The rest of the story will be written in history books about the chicken little CO2 scare.
Reich.Eschhaus says:
April 23, 2013 at 6:05 am
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Modern varieties of grape which have bben genetically modified through selection to be more hardy cannot be compared to those varieites available in Roman times.
Likewise modern day farming techniques cannot be compared to the technology and facilities available to the Vikings in the Viking warm period. Not only is crop variety more hardy, sometimes grown under grass or poly-tube, but also cattle and the like are wintered in heated barns. One only has to see how much live stock was lost this winter in Wales and Scotland due to a reasonably harsh winter to see the problems that the Vikings would have faced with much harsher conditions in Greenland. No tractors or diggers to help them out and/or to distribute feed etc.
As far as Greenland is concerned, some of the Viking homesteads are still in areas where there is permafrost such that farming is not possible.
All these studies going back a few millenia are getting boring. They all have a feeling of desperation and pleading that you MUST believe that it wasn’t as warm in the past and carbon dioxide MUST be the devil incarnate. When all is said and done they simply say that it’s a tiny bit warmer today than when the Little Ice Age came to a close. None offer any solid proof that man has anything to do with the climate variations. Every time I read one of these pitiful studies my conclusion of their conclusions is always, BIG F….ING DEAL! What a waste of taxpayer dollars.
As the Schnidejoch glacier in the Swiss alps recedes, it has revealed a mountain pass once used by men, forests which once grew there and evidence of human activities. Over 300 human artefacts have been found. The dating of these artefacts is interesting. There are intervals to which artefacts can be dated: neolithic, bronze age, Roman period and medieval times, interspersed with intervals with no artefacts whatsoever.
What this tells us is that (a) current temperatures cannot be unprecedented – they have happened before, and (b) there is a cycle of warming and cooling which has occurred a number of times in the past, each time reaching current temperatures. (Or exceeding them – we don’t know what is still below the glacier.) Any proxy temperature indicator which fails to reflect these episodes is worthless.
These earlier warming episodes occurred without any assistance from CO2 and they did not result in thermal Armageddon. On the contrary, they were beneficial to mankind. As the laws of nature have not changed, it is most likely that whatever caused these earlier warmings is the prime suspect for most of the current warming too. The alternative is to believe that these natural factors have been switched off and coincidentally (temporally and in their effect) almost exactly replaced by CO2.
Arrhenius claimed that warming from a doubling of atmospheric carbon dioxide would be greatest in the north of the NH (i.e. northern Scandinavia) and that it would be most expressed in winter and at night. So we can take this area as the “canary in the coalmine” to determine whether CAGW is real or not. Looking at the Koppen-Geiger climate zone maps we see that Greenland, where all the Gore ice melt is meant to happen, is in the same zone as northern Norway, where a recent paper presented here at WUWT shows that the end of the 20th century was distinctly cooler than in the MWP. One can find similar data for other climate zones – note that the USA region used in Pages2K is made up of several climate zones so confounding proxy and temperature data. The same is true of their other regions. This study owes more to agriculture than science – picking cherries.
http://hockeyschtick.blogspot.fi/2012/08/paper-finds-medieval-warm-period-in.html
Medieval Warm Period in Arctic was much warmer than the present
Divine, D., Isaksson, E., Martma, T., Meijer, H.A.J., Moore, J., Pohjola, V., van de Wal, R.S.W. and Godtliebsen, F. 2011. Thousand years of winter surface air temperature variations in Svalbard and northern Norway reconstructed from ice-core data. Polar Research 30: 10.3402/polar.v30i0.7379.
A paper published in Polar Research finds that temperatures at two sites in the Arctic were much warmer than at the end of the 20th century. At one site, Longyearbyen, the 11-year running-mean peak winter temperature was a remarkable 9C warmer than at the end of the record in 2000. At the 2nd site, Vardo, the 11-year running-mean peak winter temperature was about 3.3C warmer than at the end of the record in 2000.
Later, as the paper underwent a substantial reworking to address the scrutiny of peer review, co-author Nick McKay, a post-doctoral researcher at NAU, “did the heavy lifting,” Kaufman said. “He analyzed the data from each of the regions to uncover the most important similarities and differences, which we needed for the synthesis.”
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Yet another wet-behind-the-ears pseudo-scientist armed with the latest Marxist world-view manipulating data in defense of the agenda. NAU, might as well be Portland State. Pablo Freire would be proud!
The split from natural to anthropogenic determinants, of coming out of the LIA “naturally” and then continuing the change by the contribution of anthropogenically generated CO2 is the fundamental and key component that has none, nada, zilch, zero observational evidence. It is all theoretical. Wherever or whenever the split is, it is built on argument by ignorance, by models that leave a hole to be filled by CO2 by the non-observed but intellectually argued limitations of the natural factors put into their equations.
What will be the response when the solar cycle induced cooling kicks in strongly and the observational records fall completely from the IPCC scenarios? I’m hoping that the academic world begins to lose credibility. I know this is a blasphemy to many, but if you think of the Friedman economic theories, the stock market and money-supply theories, the DDT/GMO/Vaccination, linear-no-threshold theories, green technology and how subsidies will create new economies and wealth, and how all these peer-reviewed ideas have messed up lives in the late 20th century, when you recall how prediction of this and that from specialized, wired activists have failed to come true due to basic errors in assumptions, you wonder how much we really should be paying more than concept-service to those with more educational letters after their names than their parents gave them initials for financial paperwork.
With more time I’d tell you what I really think about those without their feet on the ground telling me where and when to walk.
Apparently history forgot that vikings used to trade with Scotland, Ireland and wales. There is actual documented accounts that the Americas were explored centuries before the Portuguese and Spanish began their relationship with Ireland and wales, by this time there were accounts of Celtic monks (holy men) who had traveled the western Atlantic, 10’s of thousands of years worth of history has always been ignored or even manipulated by later generations, the ridiculousness of history really does sink in when you objectively study it, its fascinating. What the Vikings would have grown in Greenland would have been similar to what they were growing in Scandinavia, Ireland and northern Britain, which was various swedes, turnips and a variety of hardy crops to feed cattle, but I’m open minded that exploration and trade had been advanced enough for the possibility that other exotic vegetables were farmed, Sea fearing nations have been around for 10’s of thousands of years after all.
The warm historical temperatures mentioned in many posts above seem to support this paper’s conclusions, rather than show they are wrong. The paper is all about the variations across regions (continental scale). Of course specific locations, whether in Greenland, UK or wherever, should have even more variation. Some have been warm at times when other places were average or cool.
The synthesis part is looking at all their regional data together to see what is common and what’s not. Anecdotes can’t address that, but the scientists’ analysis seems to agree with other recent studies: there was a long global cooling trend reversed by recent warming.
Is there a geological reference frame in these studies related to the Earths position and precession of regional areas, I understand that glaciers which have melted have all become easterly facing during sunrise and westerly during sun set, unsheltered valleys surrounded by mountains and hills, where as if they were northerly facing during sun rise and southerly facing during sun set they would be sufficiently sheltered to accumulate. A curious scientific fact.
Me too. Two positive qualities: It could allow readers to express appreciation for quiet, sensible, but otherwise unremarkable comments. And it could indicate the absence of general WUWT support for wackier comments, undermining their usefulness as horrible examples of our thinking to be cited by alarmists.
OTC:
Roger, do you think those two quotations contradict? I mentioned a global trend and dcfl51mentioned one glacier in Switzerland. The PAGES 2k paper graphs four different NH reconstructions (along with their own semi-global) showing where the LIA fits. All but Hegerl (2006) show cooling since at least 1000 AD. Globally, Marcott (2013) does too.
A lot of confusion seems to come from mixing up local, regional and global descriptions.
‘“The pre-industrial trend was likely caused by natural factors that continued to operate through the 20th century, making 20th century warming more difficult to explain if not for the likely impact of increased greenhouse gasses,” Kaufman said.’
The quotation above contains what is very likely the best example of horrendous reasoning by a scientist that I have encountered.
The first howler is that he confuses natural variability with drivers of climate. Natural variability is the range, from top to bottom, of all of our data points for temperature or whatever we are measuring. Natural variability is not a driver of climate or of anything. It is simply a range of numbers. So, in reality, to say that the “natural factors continued to operate through the 20th century” is to say that our range of temperatures remained the same. It is nonsense based upon a confusion that is crucial to AGW climate dogma.
The second howler is that he treats natural variation as on a par with his favorite causative agent, increased greenhouse gases. As he sees it, because the pre-industrial causes continued to operate then a new cause, increased GHGs, is needed to explain rising temperatures. But natural variation is not a cause or a system of causes. It is simply our record of temperatures from top to bottom.
We do not know all the causes that make up natural variation. To pretend that we do is foolishness beyond belief. Treating natural variation as a set of causes introduces an ambiguity into the phrase ‘natural variation’ that makes nonsense of all claims about natural variation.
At the bottom of all the nonsense coming from AGW climate scientists is the assumption that all discussion of climate must be a discussion of one or more causes of climate change. Take away that assumption, as skeptics have done by insisting on the importance of natural variation (which is not a cause), and the whole global warming/…/climate extremes edifice crumbles.