Claim: Historical climate fluctuations in Central Europe overestimated due to tree ring analysis

Present warming is extraordinary


Research News

“Was there a warm period in the Middle Ages that at least comes close to today’s? Answers to such fundamental questions are largely sought from tree ring data,” explains lead author Josef Ludescher of the Potsdam Institute for Climate Impact Research (PIK). “Our study now shows that previous climate analyses from tree ring data significantly overestimate the climate’s persistence. A warm year is indeed followed by another warm rather than a cool year, but not as long and strongly as tree rings would initially suggest. If the persistence tendency is correctly taken into account, the current warming of Europe appears even more exceptional than previously assumed.”

To examine the quality of temperature series obtained from tree rings, Josef Ludescher and Hans Joachim Schellnhuber (PIK) as well as Armin Bunde (Justus-Liebig-University Giessen) and Ulf Büntgen (Cambridge University) focused on Central Europe. Main reason for this approach was the existing long observation series dating back to the middle of the 18th century to compare with the tree ring data. In addition, there are archives that accurately recorded the beginning of grape and grain harvests and even go back to the 14th century. These records, as well as the width of tree rings, allow temperature reconstructions. A warm summer is indicated by a wide tree ring and an early start of the harvest, a cold summer by a narrow tree ring and a late start of the harvest. The trees studied are those from altitudes where temperature has a strong influence on growth and where there is enough water for growth even in warm years.

“Medieval archives confirm modern climate system research”

“It turned out that in the tree ring data the climatic fluctuations are exaggerated. In contrast, the temperatures from the harvest records have the same persistence tendency as observation data and also the computer simulations we do with climate models,” says co-author Hans Joachim Schellnhuber of PIK. “Interestingly, medieval archives thus confirm modern climate system research.”

To eliminate the inaccuracies of the tree ring data, the scientists used a mathematical method to adjust the strength of the persistence tendency to the harvest data and the observation data. “The adjustment does not change the chronological position of the respective cold and warm periods within the tree rings, but their intensity is reduced,” explains co-author Armin Bunde from the University of Gießen. “The corrected temperature series corresponds much better with the existing observations and harvest chronicles. In its entirety the data suggests that the medieval climate fluctuations and especially the warm periods were much less pronounced than previously assumed. So the present human-made warming stands out even more.”


Article: Josef Ludescher, Armin Bunde, Ulf Büntgen und Hans Joachim Schellnhuber (2020): Setting the tree-ring record straight. Climate Dynamics, DOI:

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September 10, 2020 at 04:44PM

Radical Actions to Fight Climate Change Are Worthless (Guest: Benjamin Zycher)

By Jim Lakely -September 9, 2020

Nobel prize winning economist William Nordhaus has come under sustained attack from the environmental left because the integrated model he developed to consider the economic and environmental impacts of climate change and policies proposed to prevent it doesn’t endorse radical restrictions on fossil fuels.

Nordhaus’ model indicates policies like the Green New Deal, endorsed by the Democratic presidential nominee Joe Biden and his running mate Kamala Harris, will impose huge costs on the economy while preventing little if any future temperature increase. Heartland Daily Podcast · Radical Actions to Fight Climate Change Are Worthless (Guest: Benjamin Zycher)

The post Radical Actions to Fight Climate Change Are Worthless (Guest: Benjamin Zycher) appeared first on Climate Realism.

The Truth About Wildfires that Gov. Newsom ‘Has No Patience For’

California Gov. Gavin Newsom is in the news today, proclaiming wildfires in his state have left him with “no patience for climate change deniers.” That is too bad. If Newsom had the patience to spend 2 minutes reviewing wildfire facts, he wouldn’t be advancing a fake climate scare.

DeadlinePolitico, and many other media outlets are reporting on Newsom’s comments today. Politico’s story, “Newsom: ‘No patience for climate change deniers’ amid historic wildfires,” was typical of the coverage, with Newsom linking the ongoing horrific wildfires and heat California is suffering under to supposed human cause climate change. The problem is the data undermine his and the headlines’ assertions that the heat and wildfires are “historic.”

Research shows massive wildfires have regularly swept through California. Indeed, a 2007 paper in the journal Forest Ecology and Management reported that prior to European colonization in the 1800s, more than 4.4 million acres of California forest and shrub-land burned annually. That is far more than the area of California that has burned cumulatively since 2000. As compared to the 4.4 million California acres that burned each year prior to European colonization, only 90,000 acres to 1.6 million California acres burn in a typical year now.

Wildfires have declined sharply over the course of the past century in the United States. As reported in Climate at a Glance: Wildfires, long-term data from the U.S. National Interagency Fire Center (NIFC) show wildfires have declined in number and severity since the early 1900s. Assessing data on U.S. wildfires from as far back as 1926, NIFC reports the numbers of acres burned is far less now than it was throughout the early 20th century, with the current acres burned running just 1/4th to 1/5th of the amount of land that typically burned in the 1930s (see the figure, below).

Figure 1: Total wildfire acreage burned by year in the United States, 1926 to 2019. Data from
Graph by meteorologist Anthony Watts

Globally, the data on wildfires are just as clear. In his book False Alarm, Bjorn Lomborg observes:

“There is plenty of evidence for a reduction in the level of devastation caused by fire, with satellites showing a 25 percent reduction globally in burned area just over the past 18 years … In total, the global amount of area burned as declined by more than 540,000 square miles, from 1.9 million square miles in the early part of last century to 1.4 million square miles today.”

Gavin Newsom has announced he has lost patience for practicing science and discovering the truth. Fortunately, climate realists still have the patience to do so.

The post The Truth About Wildfires that Gov. Newsom ‘Has No Patience For’ appeared first on Climate Realism.

The Media Lies About Meat Production and Climate Change!

By Heartland Institute -September 9, 2020

You’ll regularly hear in the media that meat production is a major source of greenhouse gas emissions. How true is this? Is methane released from cow farts and burps really contributing to a climate crisis? The Heartland Institute’s Andy Singer presents data from the EPA to answer this question.

For more, check out this link.

The post The Media Lies About Meat Production and Climate Change! appeared first on Climate Realism.

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New York Times debunks climate-caused California wildfires

California can either manage its forests better or watch them burn for another 200 years — according to the New York Times.

All you need to know about California drought and wildfires:

BEGINNING about 1,100 years ago, what is now California baked in two droughts, the first lasting 220 years and the second 140 years. Each was much more intense than the mere six-year dry spells that afflict modern California from time to time, new studies of past climates show. The findings suggest, in fact, that relatively wet periods like the 20th century have been the exception rather than the rule in California for at least the last 3,500 years, and that mega-droughts are likely to recur.

As there were no SUVs or coal-fired power plants 1,100 years ago, California may want to start thinking now about some serious forest management before nature takes her own devastating course.

The full text of the NYTimes article is below.


BEGINNING about 1,100 years ago, what is now California baked in two droughts, the first lasting 220 years and the second 140 years. Each was much more intense than the mere six-year dry spells that afflict modern California from time to time, new studies of past climates show. The findings suggest, in fact, that relatively wet periods like the 20th century have been the exception rather than the rule in California for at least the last 3,500 years, and that mega-droughts are likely to recur.

The evidence for the big droughts comes from an analysis of the trunks of trees that grew in the dry beds of lakes, swamps and rivers in and adjacent to the Sierra Nevada, but died when the droughts ended and the water levels rose. Immersion in water has preserved the trunks over the centuries.

Dr. Scott Stine, a paleoclimatologist at California State University at Hayward, used radiocarbon dating techniques to determine the age of the trees’ outermost annual growth rings, thereby establishing the ends of drought periods. He then calculated the lengths of the preceding dry spells by counting the rings in each stump.

This method identified droughts lasting from A.D. 892 to A.D. 1112 and from A.D. 1209 to A.D. 1350. Judging by how far the water levels dropped during these periods — as much as 50 feet in some cases — Dr. Stine concluded that the droughts were not only much longer, they were far more severe than either the drought of 1928 to 1934, California’s worst in modern times, or the more recent severe dry spell of 1987 to 1992.

In medieval times the California droughts coincided roughly with a warmer climate in Europe, which allowed the Vikings to colonize Greenland and vineyards to grow in England, and with a severe dry period in South America, which caused the collapse of that continent’s most advanced pre-Inca empire, the rich and powerful state of Tiwanaku, other recent studies have found.

Does Tiwanaku’s fate await modern California?

Dr. Stine, who reported his findings last month in the British journal Nature, says that California, like Tiwanaku, presents “a classic case of people building themselves beyond the carrying capacity of the land,” which is determined not by wet times but by dry ones. “What we’ve done in California is fail to recognize that there are lean times ahead,” said Dr. Stine, “and they are a lot leaner than anything we’ve come up against” in the modern era.

How far ahead that reckoning might lie is, of course, uncertain. But one ominous sign may be that the earth’s climate as a whole is now warming up, whether from natural causes or because of heat-trapping atmospheric gases emitted by industrial society. Any significant global warming would probably cause changes in atmospheric circulation and precipitation patterns, and the new findings suggest that “during much of medieval time the planetary ocean-atmosphere system operated in a mode unlike that of modern time,” Dr. Stine wrote in Nature.

This alteration of the system could well have been caused by a natural global warming, he said. He believes that one long-term effect was to steer storm tracks and rainfall away from California. If this pattern was indeed brought about by a medieval global warming, he said, a future global warming — whether natural or human-induced — might bring back the decades-long droughts of yore.

Dr. Stine’s findings, combined with similar evidence he turned up in Patagonia, strengthen the case of those who believe that the earth experienced a general warming at the time of the Middle Ages, Dr. F. Alayne Street-Perrott, a paleoclimatologist at Oxford University in England, wrote in a commentary accompanying Dr. Stine’s report in Nature. Other experts maintain that the medieval warming was not global but instead affected only some parts of the world.

“I’m not prepared to believe that the whole world was warmer,” said Dr. Malcolm K. Hughes, a paleoclimatologist who directs the Laboratory of Tree Ring Research at the University of Arizona in Tucson. Nor is it possible to say for sure that future global warming would bring back the large-scale droughts of the past. “We’ve not done the work on the actual mechanisms,” he said.

But he said that Dr. Stine’s findings, coupled with similar conclusions that can be drawn from other tree-ring studies by scientists in his laboratory, are a “serious cause for concern.” There appears to be little doubt that the epic dry spells of the past did occur, he said, adding that “what has happened can happen.”

The findings also emphasize the importance of precipitation changes, rather than simply changes in temperature, when weighing the potential impact of future global climate change, Dr. Stine wrote in Nature. Periods of ‘Epic Drought’

The Sierra Nevada, where Dr. Stine conducted his study, is California’s most important area for the collection of water. Runoff from the Sierras provides two-thirds of the state’s surface-water supply for cities and farms. The study involved trees at four places: Mono Lake, Tenaya Lake, the West Walker River and Osgood Swamp. Dr. Stine’s tree-ring analysis found that live trees had covered dry beds of lakes, streams and swamps for overlapping periods of 50, 100, 141 and 220 years and that these “lowstand” periods were clustered in two major dry spells separated by a century-long wet period. “Epic drought,” he wrote in Nature, is “the only plausible explanation for the site-to-site contemporaneity of the stumps.”

In the period separating the two long droughts, Dr. Stine said, the water in Mono Lake rose to a level higher than any in the last 150 years, suggesting that the California climate was even wetter then than it is today. The last century and a half, Dr. Stine found, has been the third wettest period in the last three millenniums. But, he said, “the vast majority of years during the past 3,500 years have been much drier than what we’ve come to expect to be normal in California.”

The evidence for the medieval drought periods is especially strong, Dr. Hughes said, because the lake basins are closed, with no natural outlets; consequently, their water levels are influenced only by inflow and evaporation, making them ideal gauges of drought. And even though radiocarbon dating is somewhat imprecise, he said, it is good enough “to show two major phases of tree growth and lowstands; there’s no doubt about that.” This, he said, shows that “often, for sure, there have been periods of 100 years or more” that have been “markedly drier” than the 20th century.

The 10th to the 14th centuries, encompassing the prolonged droughts reported by Dr. Stine, saw “dramatic changes” in Western Hemisphere civilizations, Dr. Street-Perrott wrote in Nature, and some have been attributed by archeologists to changes in rainfall. One example is the sudden decline of the Anasazi cliff-dwellers in the American southwest at about the year 1300. Another, even more striking, is the collapse of Tiwanaku.

Tiwanaku was a flourishing empire that lasted seven centuries and reached its zenith near the end of the first millennium A.D. It commanded an area about the size of California, extending from the Andean plateau around Lake Titicaca to the Pacific Coast and covering parts of present-day Bolivia, Chile and Peru.

The empire’s economy was based on intensive agriculture carried out on raised fields: acres of end-to-end rectangular platforms created by digging the dirt from areas between them. The dug-out areas became canals from which silt was taken to provide fertilizer. This highly productive and environmentally sound system dominated Latin American agriculture for centuries. Death of a Civilization

But several lines of evidence, including analyses of fossilized pollen grains and isotopes of oxygen in lake sediments, make it clear that an extended drought afflicted the region starting between A.D. 950 and A.D. 1000 and continuing, with fluctuations, until 1410, concluded a study last year by Charles R. Ortloff, a fluid-mechanics specialist at the FMC Corporate Technology Center at Santa Clara, Calif., and Dr. Alan L. Kolata, an archeologist at the University of Chicago. That period mostly overlaps the one in which the California mega-droughts occurred.

The South American drought was of “horrendous proportions,” said Dr. Kolata, and it destroyed Tiwanaku’s agricultural base. The empire’s cities were abandoned by about 1000. Dr. Kolata believes that the raised fields could no longer support the cities, and archeological evidence shows that the fields were abandoned between 1000 and 1100. The political state collapsed, the population dispersed and, with agriculture no longer possible, the people relied on raising alpacas and llamas.

Tiwanaku’s agricultural system had been able to adjust to the less drastic cycles of drought and inundation that were thought to be normal, but “Tiwanaku agro-engineers were incapable of responding to a drought of unprecedented duration and severity,” Mr. Ortloff and Dr. Kolata wrote in a 1993 paper in The Journal of Archeological Science.

Like Tiwanaku’s engineers, those who draw up California’s water-management plans do so on the basis of what are believed to be normal droughts but in fact are not nearly as severe as what has occurred in the past and can occur again, said Dr. Stine.

“The assumption they’ve made for a long time — that California is subject to droughts of a maximum of seven years — could be harmful in the long run,” he said, because “they have doled out water on that assumption.

“This could be destructive if you get hit with a 9th or a 10th or a 15th year of severe drought.”

In gauging the length and frequency of droughts for planning purposes, California officials rely on a tree-ring study extending back to about 1560. Over that period, the 1928-1934 drought was the longest and worst. The problem, said Dr. Stine, is that the study period includes not only the wet 19th and 20th centuries, but also the even wetter 16th and 17th centuries. “They’re using the wettest period of the last 3,000 years to define the duration and severity of the droughts we can expect in the future,” he said.

Maurice Roos, the chief hydrologist of the California Department of Water Resources, said he had not read Dr. Stine’s report in Nature. But he did acknowledge that a mega-drought of the kind described in the report would probably cause much of the state’s lush irrigated cropland to cease producing. The cities would probably have the money and political power to appropriate enough water to get by, he said, adding, “There will always be some water; there is not going to be no water.” He said he would not expect farming to cease altogether, or cities to be deserted.

Modern California has at least one coping weapon that Tiwanaku did not: the ability to turn sea water into fresh water. The 1987-92 drought did, in fact, prompt Santa Barbara to build a desalinization plant, Mr. Roos said, though he was quick to point out that this solution at present would be “enormously expensive.”

At the very least, Dr. Stine wrote in Nature, a recurrence of the medieval droughts “would be highly disruptive environmentally and economically.” Planning for a mega-drought now, while heads are a little cooler, would help, he says. The planning might include, for example, deciding which crops are to be taken out of production first, what restrictions to place on the pumping of groundwater and how cities are to obtain water.

But in the end, he said, a reprise of the medieval droughts would simply overwhelm California’s efforts to cope. And he said: “We don’t need 200 years of drought to bring us down. At some point, in the 9th year, or the 15th year or the 19th year, the damage is done and it doesn’t matter any more.”


September 10, 2020 at 03:16PM

They Know How to Prevent Megafires. Why Won’t Anybody Listen?

The sitation in California is just like the one in Australia

Tim Ingalsbee has been fighting fires or trying to prevent them since 1980. He founded Firefighters United for Safety, Ethics, and Ecology.

They know how to prevent megafires

Elizabeth Weil, ProRepublica

So what’s it like? “It’s just … well … it’s horrible. Horrible to see this happening when the science is so clear and has been clear for years. I suffer from Cassandra syndrome,” Ingalsbee said. “Every year I warn people: Disaster’s coming. We got to change. And no one listens. And then it happens.”

The pattern is a form of insanity: We keep doing overzealous fire suppression across California landscapes where the fire poses little risk to people and structures. As a result, wildland fuels keep building up.

This week we’ve seen both the second- and third-largest fires in California history. “The fire community, the progressives, are almost in a state of panic,” Ingalsbee said. There’s only one solution, the one we know yet still avoid. “We need to get good fire on the ground and whittle down some of that fuel load.”

Modern Californians are burning 0.1% of what […]Rating: 10.0/10 (1 vote cast)

via JoNova

September 10, 2020 at 03:09PM

Potsdam Does a New Hockey Stick Trick

The paper is Setting the tree-ring record straight byJosef Ludescher, Armin Bunde, Ulf Büntgen & Hans Joachim Schellnhuber. 

The title is extremely informative, since the trick is to flatten the tree-ring proxies, removing any warm periods to compare with the present.  Excerpts below with my bolds.


Tree-ring chronologies are the main source for annually resolved and absolutely dated temperature reconstructions of the last millennia and thus for studying the intriguing problem of climate impacts. Here we focus on central Europe and compare the tree-ring based temperature reconstruction with reconstructions from harvest dates, long meteorological measurements, and historical model data. We find that all data are long-term persistent, but in the tree-ring based reconstruction the strength of the persistence quantified by the Hurst exponent is remarkably larger (h≅1.02) than in the other data (h= 0.52–0.69), indicating an unrealistic exaggeration of the historical temperature variations. We show how to correct the tree-ring based reconstruction by a mathematical transformation that adjusts the persistence and leads to reduced amplitudes of the warm and cold periods. The new transformed record agrees well with both the observational data and the harvest dates-based reconstructions and allows more realistic studies of climate impacts. It confirms that the present warming is unprecedented.


Figure 1a shows the tree-ring based reconstruction (TRBR) of central European summer temperatures (Büntgen et al. 2011), together with its 30 year moving average that reveals the long-term temperature variations in the record. Particularly large temperature increases occurred between 1340 and 1410 and between 1820 and 1870 that even are comparable in amplitude with the recent warming trend since 1970, indicating that the recent (anthropogenic) warming may not be unprecedented.

Tree ring-based reconstruction of the central European temperatures in the last millennium. a The reconstructed June-August temperatures in units of the records standard deviation. The red line depicts the moving average over 30 years. b, c The DFA2 fluctuation functions F(s) and the WT2 fluctuation functions G(s), respectively, for the reconstructed data from a, for monthly observational data (Swiss temperatures from Berkeley Earth, station data from Prague) and the MPI-ESM-P-past1000 model output for central European summer temperatures, from top to bottom. For the TRBR and model data, the time scale s is in years, while for the two observational records, it is in months. Note that in the double logarithmic presentation, the asymptotic slopes (Hurst exponents h) for the reconstruction data (h≅1) and the observational and model data (h≅0.6) differ strongly

To correct the enhanced long-term persistence in the TRBR, we are interested in a mathematical transformation of the data, which lowers the natural long-term persistence while leaving the gross features of the record, the positions of the warm and cold periods, unchanged. We performed the following mathematical transformation to change the original TRBR Hurst exponent h0=1.03 to h1=0.60 and thus to be in line with the observational, harvest and model data. Since this transformation is only suitable for altering a record’s natural long-term persistence, i.e., in the absence of external trends, we transformed the TRBR data between 1000 and 1990, before the current anthropogenic trend became relevant.

Figure 4a compares the transformed TRBR data (blue) with h1=0.6 with the original TRBR data (black). The bold lines are the 30-year moving averages. The figure shows that by the transformation the structure of the original TRBR data is conserved, but the climate variations characterized by the depths of the minima and the heights of the maxima are reduced.

Original and transformed tree-ring proxy temperature record. a Compares the original TRBR record for the period 1000–1990, where the Hurst exponent h is 1.03 (black), with the transformed TRBR record, where h≡h1=0.6 (blue). For better visibility, the transformed TRBR record has been shifted downward by 5 units of its standard deviation. b How the magnitudes of the cold periods in the transformed TRBR record decrease with decreasing Hurst exponent h1. The magnitudes are quantified by the differences of the 30 year moving averages between the beginning and the end of the respective periods. c Compares the 30-year moving averages of the original and the transformed TRBR record (h=0.6) with the 30-year moving average of the observational temperatures from Switzerland. The comparison shows that the transformed TRBR record fits quite nicely with the observational data

To see how the strength of the long-term variations in the transformed TRBR data depends on their Hurst exponent h1h1, we have determined, in the 30-year moving average, the temperature differences in 4 periods (1415–1465, 1515–1536, 1562–1595, 1793–1824) where the greatest changes between 1350 and 1950 occur. The result is shown in Fig. 4b. The figure shows that the temperature difference between the beginning and the end of each period decreases continuously with decreasing h. For h around 0.6, the temperature differences are roughly halved.


Since tree ring-based reconstructions play an important role in the understanding of past temperature variability, we suggest the use of the Hurst exponent as a standard practice to assess the reconstructions’ low-frequency properties and to compare the determined values with the Hurst exponents of other respective time series (observational, harvest dates, models). If deviations from the expected values are detected, the data should be transformed to adjust the Hurst exponent. This will lead to a more realistic reconstruction of the record’s low-frequency signal and thus to a better understanding of the climate variations of the past.

My Comment

Wow!  Just Wow!  The Mann-made Hockey Stick was found bogus because it was produced by grafting a high-resolution instrumental temperature record on top of a low-resolution tree ring proxy record.  Now climatists want to erase four bumps in the Medieval period lest they appear comparable to contemporary temperatures sampled minute by minute.  A simple tweaking of a formula achieves the desired result.  Fluctuations which were decadal are now centennial and cannot compete with modern annual and monthly extremes.  Well done! (extreme snark on)

Background:  See Return of the Hockey Stick

via Science Matters

September 10, 2020 at 02:07PM

AEP Solves The Climate Emergency!

By Paul Homewood

h/t Robin Guenier

The usual repetitive nonsense from AEP;


Once again he trots out fairy tale that wind and solar will soon start ‘to undercut the marginal running costs of existing coal plants’, without any facts to back it up and based on propaganda from the renewable lobby.

Even the most recent offshore wind CfDs are currently priced at £48/MWh, well above the wholesale price of £30/MWh. They will all be index linked, so that difference will continue to grow. Even under pre-pandemic costs of gas, the BEIS reckoned that the marginal cost of CCGT plants was only £38/MWh.

And that is before we add on all of the other costs associated with intermittent renewables.

But far more fundamental is the fact that no modern economy can run on a predominantly intermittent energy source, making discussion of costs irrelevant.

Both China and India have expressly acknowledged this fact, which is why they continue to build coal power plants.

Despite lockdown, China for instance have installed 16 GW of new thermal power capacity in the first half of this year alone. 1.3% of existing capacity. In comparison, only 6 GW of wind power has been added, equivalent to only about 1 GW once intermittency is factored in:


Remember too that coal is dirt cheap in China, which is why they favour it to gas power.

Of course, if AEP is really right, we can immediately do away with any further CfD auctions, as energy businesses will be queuing up to build wind farms, without the need for subsidies.

There will also be no need for carbon taxes, which are designed purely to make fossil fuels uncompetitive.

Above all there will be no more need for climate summits, starting with next year’s in Glasgow.

AEP writes exactly the same drivel month after month. I recall a similar piece about Greta last year. You might have thought the Telegraph would expect more for their money!!


September 10, 2020 at 01:06PM