Archives par mot-clé : Trees

climate-debate

Sheenjek, Alaska: A Jacoby-MBH Series

by S. McIntyre, Dec13, 2023 in ClimateAudit

MBH98 used three Jacoby tree ring chronologies from Alaska: Four Twelve (ak031) – discussed here, Arrigetch (ak032) and Sheenjek (ak033). Sheenjek will be discussed in this article.

In our compilation of MBH98 in 2003, we observed that the Sheenjek chronology archived at NOAA Paleo was not the same as the “grey” version used in MBH98.   While we used the MBH98 version to benchmark our emulation of the MBH98 algorithm, we used the version archived at NOAA in our sensitivity analysis, both in our 2003 article and in our early 2004 submission to Nature.  In his reply to our submission, Mann vehemently protested that the “introduc[tion of] an extended version of another Northern Treeline series not available prior to AD 1500 at the time of MBH98” “introduce[d] problems into the important Northern Treeline dataset used by MBH98”:

Finally, MM04 introduce problems into the important Northern Treeline dataset used by MBH98. Aside from incorrectly substituting shorter versions of the “Kuujuag” and TTHH Northern Treeline series for those used by MBH98, and introducing an extended version of another Northern Treeline series not available prior to AD 1500 at the time of MBH98, they censored from the analysis the only Northern Treeline series in the MBH98 network available over the AD 1400-1500 interval, on the technicality that it begins only in AD 1404 (MBH98 accommodated this detail by setting the values for AD 1400-1404 equal)

The other “Northern Treeline series” referred to here was Sheenjek chronology ak033.crn.  I checked Mann’s assertion alleging that the data was “not available prior to AD1500 at the time of MBH98”. This was contradicted by NOAA, who confirmed that the chronology that we had used had been available since the early 1990s.

In the figure below, I’ve compared three Sheenjek chronology versions:

  • the MBH98 version from 1580-1979 (plus 1980 infill);
  • the ModNegExp chronology (dplR) calculated from measurement data (ak033.rwl), which, in this case, has been available since the 1990s. It covers period 1296-1979.
  • the archived chronology at NOAA (ak033.crn). Also covering the period 1296-1979.

The issues relating to Sheenjek are different than observed at Four Twelve.

Continuer la lecture de Sheenjek, Alaska: A Jacoby-MBH Series →

better to know...?, climate-debate

Warmth Limits For Tree Growth Affirm Austria Was 4-7°C Warmer Than Today 2000 Years Ago

by K. Richard, Jan 23, 2023 in NoTricksZone

Robust evidence from bison remains recovered from the Austrian Alps in 2020 and 2021 invalidate claims modern Alpine temperatures are unusually warm.

A new study suggests that from about 6000 to 1200 years ago European bison fed on deciduous tree/vegetation that grew at Alpine altitudes reaching around 800 m higher than they do today.

Known beech and oak tree growth warmth thresholds – the required number of days per year above a minimum temperature limit – thus affirm Austria needed to be 4-7°C warmer than now during this period (~2000 years ago).

“[T]he beech limit but also the forest line during the »wisent time« (6,000 to 1,200 years before today) was much higher and the average summer temperature had to be at least 3 to 6 °C higher than today. Remarkable is a palynological record (Ressl, 1980) from the shaft cave Stainzerkogelschaft near Lunz am See. Remains of wisent were found in the shaft (1,463 m, see Tab. 3). The clay with a skull fragment with horncores inside was examined palynologically. The dominating pollen were from alder (Alnus), oak (Quercus) and linden tree (Tilia). The oak boundary (boundary between colline and montane vegetation stages) today lies between 400 and 800 metres in the Northern Alpine Alps (Grabherr et al., 2004). Oaks (Quercus) at an altitude of 1,450 metres around 2,000 years ago also indicate a climate approximately 4 to 7 °C warmer than today.”

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better to know...?, climate-debate

Phantom Forests: Why Ambitious Tree Planting Projects Are Failing

by Fred Pearce, Oct 6, 2022 in YaleEnvironment360

High-profile initiatives to plant millions of trees are being touted by governments around the world as major contributions to fighting climate change. But scientists say many of these projects are ill-conceived and poorly managed and often fail to grow any forests at all.

It was perhaps the most spectacular failed tree planting project ever. Certainly the fastest. On March 8, 2012, teams of village volunteers in Camarines Sur province on the Filipino island of Luzon sunk over a million mangrove seedlings into coastal mud in just an hour of frenzied activity. The governor declared it a resounding success for his continuing efforts to green the province. At a hasty ceremony on dry land, an official adjudicator from Guinness World Records declared that nobody had ever planted so many trees in such a short time and handed the governor a certificate proclaiming the world record. Plenty of headlines followed.

But look today at the coastline where most of the trees were planted. There is no sign of the mangroves that, after a decade of growth, should be close to maturity. An on-the-ground study published in 2020 by British mangrove restoration researcher Dominic Wodehouse, then of Bangor University in Wales, found that fewer than 2 percent of them had survived. The other 98 percent had died or were washed away.

“I walked, boated, and swam through this entire site. The survivors only managed to cling on because they were sheltered behind a sandbank at the mouth of a river. Everything else disappeared,” one mangrove rehabilitation expert wrote in a letter to the Guinness inspectors this year, which he shared with Yale Environment 360on the condition of anonymity. The outcome was “entirely predictable,” he wrote. The muddy planting sites were washed by storms and waves and were otherwise “ecologically unsuited to mangrove establishment, because they are too waterlogged and there is no oxygen for them to breathe.”

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better to know...?, sciences-general

Tree rings may hold clues to impacts of distant supernovas on Earth

by University of Colorado at Boulder, Nov 11, 2020 in ScienceDaily

Massive explosions of energy happening thousands of light-years from Earth may have left traces in our planet’s biology and geology, according to new research by University of Colorado Boulder geoscientist Robert Brakenridge.

The study, published this month in the International Journal of Astrobiology, probes the impacts of supernovas, some of the most violent events in the known universe. In the span of just a few months, a single one of these eruptions can release as much energy as the sun will during its entire lifetime. They’re also bright — really bright.

“We see supernovas in other galaxies all the time,” said Brakenridge, a senior research associate at the Institute of Arctic and Alpine Research (INSTAAR) at CU Boulder. “Through a telescope, a galaxy is a little misty spot. Then, all of a sudden, a star appears and may be as bright as the rest of the galaxy.”

A very nearby supernova could be capable of wiping human civilization off the face of the Earth. But even from farther away, these explosions may still take a toll, Brakenridge said, bathing our planet in dangerous radiation and damaging its protective ozone layer.

To study those possible impacts, Brakenridge searched through the planet’s tree ring records for the fingerprints of these distant, cosmic explosions. His findings suggest that relatively close supernovas could theoretically have triggered at least four disruptions to Earth’s climate over the last 40,000 years.

The results are far from conclusive, but they offer tantalizing hints that, when it comes to the stability of life on Earth, what happens in space doesn’t always stay in space.

“These are extreme events, and their potential effects seem to match tree ring records,” Brakenridge said.

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Tree rings (stock image).
Credit: © CrispyMedia / stock.adobe.com
climate-debate

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

by Postdam Institute, Sep 10, 2020 in WUWT

“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.

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climate-debate

Longest-Ever S. Hemisphere Tree-Ring Reconstruction Finds The 1700s-1800s Were Warmer Than Today

by  K. Richard, February 3, 2020  in NoTricksZone

A new 5680-year tree-ring temperature reconstruction for southern South America (Lara et al., 2020) reveals (a) no clear warming trend in recent decades, and (b) the 18th and 19th centuries (and many centennial-scale periods from the last 5680 years) had much warmer temperatures than today.

In addition to finding modern temperature changes in southern South America fall well within the range of natural variability in the context of the last 5680 years, Lara et al. (2020) assess solar forcing to have contributed to climate variations for this region of the Southern Hemisphere.

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climate-debate

3000-Year-Old Trees Excavated Under Icelandic Glacier

by P. Homewood, December 12, 2019 in NotaLotofPeopleKnowThat

Ancient tree stumps found under Breiðamerkurjökull glacier in Southeast Iceland are confirmed to be roughly 3,000 years old. RÚV reports.

A specialist believes the remarkably well-preserved stumps were part of a massive forest that disappeared after a long period of a warm climate.

One of the tree stumps was found in Breiðamerkursandur a couple of months ago, and once it was being salvaged a second, larger one was found. The smaller one was sent for examination while the larger will be examined at a later time.

Examinations revealed that the tree stump died very quickly at 89-years-old in the month of June. Nearby sediments and data suggest that the glacier itself was the culprit.

The tree stumps are from a period when Iceland was covered in forests. Even though 9th century Norse settlers reported vast forests across the country, it is believed that 3,000 years ago, the forests were much larger, even reaching the highlands. Approximately 500 BC, the climate became colder and glaciers began to form, destroying parts of the forests.

The 3,000-year-old remains of the forest are very well preserved and will be researched thoroughly. “It is absolutely incredible just how well preserved this tree stump is, having been buried under a glacier and that it still looks so whole, as opposed to being all wrinkled up like many of the specimens we have found.” Once examinations conclude, the water will be extracted from the tree stump and it will be filled with wax instead, allowing it to be exhibited.

https://www.icelandreview.com/news/3000-year-old-trees-excavated-under-glacier/

Discovering ancient forests under receding glaciers is not confined to Iceland. Remains of trees dating back to the Middle Ages have been found under the Juneau and Exit Glaciers in Alaska, as well under glaciers in Patagonia.

Tree stumps have also turned up under Swiss glaciers, carbon dated to about 4000 years ago.

The simple reality is that glaciers worldwide expanded enormously during the Little Ice Age, arguably to their greatest extent since the Ice Age. Despite decades of retreat since the 19thC, they are still abnormally large by historical standards.

climate-debate

Reforesting is a good idea, but it is necessary to know where and how

by Charles the moderator, October 20, 2019 in WUWT

An international group of ecologists contests an article published in Science, which among other cardinal errors proposed ‘reforestation’ of the Cerrado, Brazil’s savanna biome

Fundação de Amparo à Pesquisa do Estado de São Paulo

An article recently published in Science, entitled “The global tree restoration potential”, presents what it calls “the most effective solution at our disposal to mitigate climate change”. The lead author is Jean-François Bastin, an ecologist affiliated with the Swiss Federal Institute of Technology (ETH Zurich).

The article attracted enormous media attention. It reports the results of a study in which Bastin and collaborators used remote sensing and modeling techniques to estimate that forest restoration in areas totaling 900 million hectares worldwide could store 205 gigatonnes of carbon.

The study was contested by a large international group of ecologists led by Joseph Veldman, a professor in Texas A&M University’s Department of Ecosystem Science and Management (USA). At the invitation of the editors of Science, the group formulated a reply, now featuring on the October 18th edition of Science under the title “Comment on ‘The global tree restoration potential’..

Its authors include William Bond, Emeritus Professor in the University of Cape Town’s Department of Biological Sciences (South Africa) and considered the world’s foremost expert on savanna ecology. Several Brazilian researchers also co-authored the reply, such as Giselda Durigan, affiliated with the São Paulo State Forestry Institute’s Ecology and Hydrology Laboratory.

“The plan proposed by Bastin et al. is based on flawed calculations and is actually a threat to the planet’s savannas, meadows and water resources,” Durigan said.

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better to know...?, climate-debate

Why California burns — its forests have too many trees

by T.M. Bonnicksen, November 12, 2018 in San FranciscoChronicle

The reason wildfires are burning California with unprecedented ferocity this year is because our public forests are so thick. It is our fault. We don’t manage our forests, we just let them grow. That is the simple truth. However, it is easier to deny the truth and blame a warming climate instead of admitting our guilt and taking action to prevent wildfires.

Hot, dry weather doesn’t cause catastrophic wildfires. It only makes them worse. In order for any fire to burn, it must have fuel. To spread wildly, it must have abundant fuel. Efforts in the 20th century to prevent fire and preserve forests have been too successful — they have disrupted the ecological balance and allowed more and more trees to grow.

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climate-debate

PAGES2K: North American Tree Ring Proxies

by Steve McIntyre, October 24, 2018 in ClimatAudit

The PAGES (2017) North American network consists entirely of tree rings. Climate Audit readers will recall the unique role of North American stripbark bristlecone chronologies in Mann et al 1998 and Mann et al 2008 (and in the majority of IPCC multiproxy reconstructions).  In today’s post, I’ll parse the PAGES2K North American tree ring networks in both PAGES (2013) and PAGES (2017) from two aspects:

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Conclusions

  • ex post screening based on recent proxy trends necessarily biases the resulting data towards a Hockey Stick shape – a criticism made over and over here and at other “ske;ptic” blogs, but not understood by Michael (“I am not a statistician”) Mann and the IPCC paleoclimate “community”;

  • the PAGES 2017 North American tree ring network has been severely screened ex post from a much larger candidate population: over the years, approximately 983 different North American tree ring chronologies have been used in MBH98, Mann et al 2008, PAGES 2013 or PAGES 2017. I.e. only ~15% of the underlying population was selected ex post – a procedure which, even with random data, would impart Hockey Stick-ness to any resulting composite

  • despite this severe ex post screening (in both PAGES 2013 and PAGES 2017), the composite of all data other than stripbark bristlecones had no noticeable Hockey Stick-ness and does not resemble a temperature proxy.

  • …
climate-debate

Hunger Stones and Tree Ring evidence suggests solar cycle influence on climate

by Francis Tucker Manns Ph.D., September 30, 2018 in WUWT

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Conclusions

Extreme weather events, mostly drought are considered, but floods as well, correspond to solar minima in more than 75% (18 out of 24 of the cases known).

Current concentrations of carbon dioxide cannot be invoked for extreme weather in the historical past.

The sun controls the climate of the Earth.

During summer it is inevitable that lightning storms ignite fires and produce heavy rain. The intensity of what we have come to call extreme weather is magnified by standing Rossby waves.

Sunspot research tends to emphasize sunspot peaks and sunspot numbers; more may be gained by evaluating trough events and peak and trough frequencies.

climate-debate, press and newspapers

Global Tree Cover Has Expanded More Than 7 Percent Since 1982

by  Ronald Bailey, September 4, 2018 in Reason

Global tree canopy cover increased by 2.24 million square kilometers (865,000 square miles) between 1982 and 2016, reports a new study in Nature.

Researchers using satellite data tracked the changes in various land covers to find that gains in forest area in the temperate, subtropical, and boreal climatic zones are offsetting declines in the tropics. In addition, forest area is expanding even as areas of bare ground and short vegetation are shrinking. Furthermore, forests in montane regions are expanding as climate warming enables trees to grow higher up on mountain.

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climate-debate

Carbon emissions in African savannas triple previous estimates

by Edinburgh University, August 24, 2018 in ScienceDaily

The findings highlight the extent to which humans are impacting one of the world’s major ecosystems — the Miombo woodlands, which cover 2.5 million square kilometres, across countries including Angola, Zambia, Tanzania and Mozambique.

At the same time, however, the growing number of trees in remote parts of these woodlands is helping to offset the emissions, researchers say.

The study is the first to provide an in-depth analysis of areas gaining carbon while also losing it through degradation — a process where some, but not all, trees are removed, usually as a result of logging and fire.

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See original article in Nature

better to know...?, climate-debate

Scientists discover that the world contains dramatically more trees than previously thought

by Chris Money, September 2, 2015 in TheWashingtonPost

In a blockbuster study released Wednesday in Nature, a team of 38 scientists finds that the planet is home to 3.04 trillion trees, blowing away the previously estimate of 400 billion. That means, the researchers say, that there are 422 trees for every person on Earth.

However, in no way do the researchers consider this good news. The study also finds that there are 46 percent fewer trees on Earth than there were before humans started the lengthy, but recently accelerating, process of deforestation.

“We can now say that there’s less trees than at any point in human civilization,” says Thomas Crowther, a postdoctoral researcher at the Yale School of Forestry and Environmental Studies who is the lead author on the research. “Since the spread of human influence, we’ve reduced the number almost by half, which is an astronomical thing.”

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climate-debate

Trees and climate change: Faster growth, lighter wood

by Technical University of Munich (TUM), August 14, 2018

Wood density of European trees decreasing continuously since 1870

Trees are growing more rapidly due to climate change. This sounds like good news. After all, this means that trees are storing more carbon dioxide from the atmosphere in their wood and hence taking away the key ingredient in global warming. But is it that simple? A team analyzed wood samples from the oldest existing experimental areas spanning a period of 150 years — and reached a surprising conclusion.

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But the most important finding for practical and political aspects is that the current climate-relevant carbon sequestration of the forests is being overestimated as long as it is calculated with established but outdated wood densities. “The accelerated growth is still resulting in surplus carbon sequestration,” says Pretzsch. “But scaling up for the forests of central Europe, the traditional estimate would be to high by about ten million metric tons of carbon per year.”

climate-debate

Once again, climate scientists use a single tree to define global change

by A. Watts, February 19, 2018 in WUWT

From Keele University and the “It’s like deja vu all over again”  department with the leader of the “ship of fools” thrown in for comic relief. Long-time WUWT readers surely remember the single “Most influential tree in the world” from the Yamal fiasco, where the “signal” in one tree (YAD06) biased an entire paper with a hockey stick shape, making it worthless. Well, here we are again with another single tree used to define the entire globe. Obviously they’ve learned nothing, then again, it’s Chris Turney.