Archives par mot-clé : Hockey Stick

L’Optimum Climatique Médiéval : ce Grand Oublié !

by A. Préat, 29 novembre 2019 in ScienceClimatEnergie


1/ Introduction

Comme rappelé dans un précédent article (ici) les événements hyperthermiques sont fréquents tout au long de l’histoire de la Terre. Bien que fréquents et étudiés avec détail, force est de reconnaître que le ‘fin’ mot de leur origine n’est toujours pas connu, sauf à leur attribuer à tous un lien de parenté avec l’un ou l’autre des gaz dits à effet de serre, sans qu’une démonstration en bonne et due forme soit présentée. C’est ce que décortique l’article paru dans SCE (ici) pour un des événements hyperthermiques les plus intenses (événement PETM pour Paleocene-Eocene Thermal Maximum) s’étant déroulé au début de l’ère Cénozoïque il y a environ 56 millions d’années.

Rappelons la succession de ces événements au Cénozoïque, d’abord l’événement PETM, ensuite E-O (Eocene-Oligocene transition with climatic shift), MMCO (Mid-Miocene Climatic Optimum), MPTO (Mid-Pliocene Thermal Optimum) et depuis environ 10 000 ans l’Optimum Holocène. Ces événements montrent tous que la Terre a régulièrement connu de longues périodes chaudes avec des ‘températures moyennes globales’ plus élevées que l’actuelle (voir par exemple Cronin 2010, également mentionné sur de nombreux sites web). L’indicateur climatique communément utilisé , la température moyenne globale est loin d’être parfait (ici et ici). Il ne faut donc pas prendre au pied de la lettre cette notion de ‘température moyenne globale’ car déjà pour aujourd’hui elle est plus que discutable, et pour le passé elle est plus qu’inconnue. Mais il n’en reste pas moins vrai que lors des événements hyperthermiques ou des optima climatiques la température était plus élevée qu’actuellement, nous le savons grâce à de nombreux indicateurs ou ‘proxies’ (voir plus loin). Ces événements ne concernent pas uniquement le Cénozoïque (y compris l’Holocène) mais l’ensemble de l’échelle des temps géologiques au-delà du Cénozoïque, avec parfois des températures fort supérieures à celles du Cénozoïque, comme par exemple au Permien (ici).

2/ L’Optimum Climatique Médieval

Revenons aux temps actuels, c’est-à-dire aux temps historiques. Plusieurs Optima Climatiques se succèdent depuis environ 6000 ans, avec pour la période la plus proche de nous, c’est-à-dire environ 3500 ans, la succession des Optima Climatiques Minoen, Romain, Médiéval et Actuel (Figure 1). Le plus récent est l’Optimum Climatique Médiéval (OCM) dont l’acmé se situe aux alentours de l’an mil. S’agissant de températures à peine plus élevées (1,5°C cfr ici et Le Roy Ladurie, 1967, également 1.0-1.4°C in Easterbrook, 2011), la délimitation précise de cet intervalle par rapport aux périodes encadrantes est difficile et l’OCM est finalement compris du 8ème au 13ème siècle (= le ‘petit optimum du Moyen Age’ d’environ 700 à 1350 sensu Le Roy Ladurie, 1967).

Figure 8 (cfr. Figure 5 in Préat, 2019). Capture d’écran de la Figure 8 de Scafetta (2019) : On the reliability of computer-based climate models. IJEGE, 19, 49-70. En comparant les deux courbes on peut se demander si l’on parle de la même chose! (RWP Roman Warm Period, DACP Dark Age Cold Period ou période froide post-romaine, MWP Medieval Warm Period, LIA Little Ice Age, CWP Current  Warm Period). Pour rappel la courbe A du haut, est la fameuse courbe en forme de hockey de Mann et al. 1998 du GIEC.

Michael Mann Refuses to Produce Data, Loses Case

by P. Homewood, August 26, 2019 in NotaLotofPeopleKnowThat


Some years ago, Dr. Tim Ball wrote that climate scientist Michael Mann “belongs in the state pen, not Penn State.” At issue was Mann’s famous “hockey stick” graph that purported to show a sudden and unprecedented 20th century warming trend. The hockey stick featured prominently in the IPCC’s Third Assessment Report (2001), but has since been shown to be wrong. The question, in my view, is whether it was an innocent mistake or deliberate fraud on Mann’s part. (Mann, I believe, continues to assert the accuracy of his debunked graph.) Mann sued Ball for libel in 2011. Principia Scientific now reports that the court in British Columbia has dismissed Mann’s lawsuit with prejudice, and assessed costs against him.

What happened was that Dr. Ball asserted a truth defense. He argued that the hockey stick was a deliberate fraud, something that could be proved if one had access to the data and calculations, in particular the R2 regression analysis, underlying it. Mann refused to produce these documents. He was ordered to produce them by the court and given a deadline. He still refused to produce them, so the court dismissed his case.

 

Hockey Stick Groundhog Day

by P. Homewood, August, 1, 2019 in NotaLotofPeopleKnowThat


Some ancient history

Fifteen to twenty years ago, Michael Mann and colleagues wrote a few papers claiming that current warming was unprecedented over the last 600 to 2000 years.  Other climate scientists described Mann’s work variously as crap, pathetic, sloppy, and crap.  These papers caught the interest of Stephen McIntyre and this led to the creation of his Climate Audit blog and the publication of paperspointing out the flaws in these hockey stick reconstructions. In particular, Mcintyre and his co-author Ross McKitrick showed that the method used by Mann and colleagues shifted the data in such a way that any data sets that showed an upward trend in the 20th century would receive a stronger weighting in the final reconstruction.  With this method, generation of a hockey-stick shape in the temperature reconstruction was virtually guaranteed, which M&M demonstrated by feeding in random numbers to the method.

12 New Papers Provide Robust Evidence The Earth Was Warmer During Medieval Times

by K. Richard, July 29, 2019 in NoTricksZone


Claims that modern temperatures are globally warmer than they were during Medieval times (~800 to 1250 A.D.) have been contradicted by a flurry of new (2019) scientific papers.

Southern Ocean/SE Pacific (SSTs)

The Medieval Warm Period (1100 years BP) was 1.5°C warmer than today (14°C vs. 12.5°C) in the SE Pacific or Southern Ocean.

 

 

See also here

No Hockey Sticks: Studies Reveal Long-Term Lack of Warming

by Vijay Jayaraj, May 16,2019 in WUWT


A new temperature reconstruction, using proxy temperature measurements from locations in central Asia, has revealed that there has been no warming in the past 432 years.

The Global Warming “Hiatus” or Pause

The word “hiatus” became popular in recent years after the discovery of a pause or hiatus in global warming. There has been a lack of warming in the atmosphere since 1999, despite the predictions of computer climate models.

Busted Hockey Sticks: 35 Non-Global Warming Papers Have Been Published In 2019

by Kenneth Richard, March 22, 2019 in NoTricksZone


Could a transition in paleoclimate reconstruction be underway? More and more, scientists aren’t hiding statements or graphical depictions of the lack of modern warming or the much-warmer Holocene past.

 

A compilation of 35 papers from across the globe indicate that modern climate is not unusual, remarkable or unprecedented, and that large regions of the Earth were as warm or warmer than now when CO2 concentrations were much lower (260 to 350 ppm).

This development continues apace with the trends from the last two years, when 253 non-hockey stick papers were published.

ClimateGate continues – the Mann Hockeystick University of Arizona emails are now public

by Anthony Watts, March4, 2019 in WUWT


After years of trying to suppress their release, and finally being ordered to be released by a judge, they are now public, and we have them here. This will remain as a “top post” for a day, new stories will be below this one.

There’s quite a treasure trove, but also some duplications from previous releases.

A Fabricated ‘Uptick’? Marcott’s 2013 Hockey Stick Graph Debunked By Marcott’s Own 2011 Ph.D Thesis

by K. Richard, December 13, 2018 in NoTricksZone


Almost immediately after it was introduced to the public, the lead author of Marcott et al. (2013) squelched the narrative that said the hockey-stick-shaped reconstruction he and his colleagues produced is a robust representation of modern global-scale temperature changes.

In an interview with Marcott published by RealClimate.org, it was acknowledged that the “uptick” does not represent a global-scale reconstruction, as it is based on only a few proxy records and lacks statistical significance. 

Despite this admitted lack of supporting evidence for the 20th century’s “uptick”, the Marcott et al. (2013) “hockey stick”-shaped graph has nonetheless been unskeptically cited by other authors nearly 700 times.

View From German Scientists On The U Of Arizona’s Coming Release Of The Hockey Stick Chart E-Mails

by P. Gosselin, October 26, 2018 in NoTricksZone


A Piece Of Climate Science History: Hockey Stick Emails Soon To Be Published

By Dr. Sebastian Lüning and Prof. Fritz Vahrenholt
(Text translated by P Gosselin)

The hockey stick controversy over a temperature reconstruction of the past 2000 years represents an important stage in the climate debate. At around the turn of the millennium, the authors of the “hockey stick chart” suggested that the pre-industrial climate was monotonous and uneventful. The Medieval Warm Period and Little Ice Age described in many parts of the world climatically must have been very similar. But that’s hard to understand if you look at the wide variety of case studies.

Cover-up absurdity, then forced to correct

Later, the authors improved and presented a corrected version, which again showed stronger climatic fluctuations. Quite a science story. You can read about it here.

In addition to this scientific rush job, the debate about the hockey stick also showed that climate data really must be made publicly available. This is all the more important if the science is used for far-reaching policies. Data and results obtained thereof must be verifiable. At the time no one wanted the data to be released. Today in retrospect that was quite an absurdity — similar to smoking in a large open office.

108 Graphs From 89 New Papers Invalidate Claims Of Unprecedented Global-Scale Modern Warmth

by K. Richard, August 2, 2018 in NoTrickZone


During 2017, there were 150 graphs from 122 scientific papers published in peer-reviewed journals indicating modern temperatures are not unprecedented, unusual, or hockey-stick-shaped — nor do they fall outside the range of natural variability.  We are a little over halfway through 2018 and already  108 graphs from 89 scientific papers undermine claims that modern era warming is climatically unusual.

For the sake of brevity, just 13 (15%) of the 89 new papers are displayed below.

The rest of the non-hockey-stick scientific papers and graphs published thus far in 2018 can be viewed by clicking the link below.

81 Graphs From 62 New (2018) Papers Invalidate Claims Of Unprecedented Global-Scale Modern Warming

by K. Richard, May 10, 2018 in NoTricksZone


During 2017, there were 150 graphs from 122 scientific papers published in peer-reviewed journals indicating modern temperatures are not unprecedented, unusual, or hockey-stick-shaped — nor do they fall outside the range of natural variability.  We are a little over 4 months into the new publication year and already 81 graphs from 62 scientific papers undermine claims that modern era warming is climatically unusual.

After 20 Years, The ‘Hockey Stick’ Graph Behind Waves Of Climate Alarmism Is Still In Dispute

by M. Bastach, April 30, 2018 in ClimateChangeDispatch


Roughly 20 years ago, climate scientist Michael Mann published his famous “hockey stick” graph that he says “galvanized climate action” by showing unprecedented global warming.

Mann used the 20-year anniversary of the graph to opine on the “industry-funded” attacks “to discredit the iconic symbol of the human impact on our climate,” which Mann claimed had withstood criticism.

“Yet, in the 20 years since the original hockey stick publication, independent studies, again and again, have overwhelmingly reaffirmed our findings, including the key conclusion: recent warming is unprecedented over at least the past millennium,” Mann wrote in Scientific American on April 20.

However, the two Canadian researchers who found serious flaws in the “hockey stick” study’s data and methodology disputed Mann’s characterization of the graph’s legacy.

(…)

FLASHBACK: Twenty years ago today, the infamous “hockey stick” was published in Nature

by Anthony Watts, April 23, 2018 in WUWT


Twenty years ago today: The infamous “hockey stick” graph that crystalized global warming and ignited the climate wars was published, and became known as MBH98. The science in it was so bad, it is credited with spawning the modern climate skeptic movement.

Original “hockey stick” temperature graph in Nature, 1998. The Y axis shows the Northern hemisphere mean temperature, in degrees Celsius; the zero line corresponds to the 1902 – 1980 mean. Credit: “Global-scale Temperature Patterns and Climate Forcing over the Past Six Centuries,” by Michael E. Mann et al. in Nature, Vol. 392, April 23, 1998

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.

Update: The 2017 Explosion Of Non-Hockey Stick Graphs Continues

by K.  Richard, September 28, 2017 in NoTricksZone


It was four months ago that an article entitled  80 Graphs From 58 New (2017) Papers Invalidate Claims Of Unprecedented Global-Scale Modern Warmingappeared on this website.  The article received international attention and was “shared” tens of thousands of times.

In the last 4 months,  40 more graphs taken from 30 more new peer-reviewed scientific papers have made their way into the ever-growing volume of evidence that today’s climate is not only not unprecedented or unusual in the context of the last millennium, but modern temperature values are still among the coldest of the last 10,000 years.

Autopsy Of An Excuse

by Willis Eschenbach, July 22, 2017 in WUWT


Well, Dr. James Hansen, the man who invented the global warming scam and our favorite failed serial doomcaster, recently addressed the cratering of a 30-year prediction he made in 1988.

Back then, he said the globe would warm up by one full degree by 2018 under the “business as usual” rubric … not. Here’s the story as written up in “Spin” magazine in 1988.

Alarm about alarmism

by Judith Curry, July 15, 2017 in ClimateEtc.


In understanding climate change risk, and deciding on the ‘if’ and ‘what’ of ‘action’,  we need to acknowledge that we don’t know how the climate of the 21st century will play out (Deep Uncertainty, folks).  Four possibilities:

  1. It is possible that human-caused climate change will be swamped by much larger natural climate variability.

  2. It is possible/plausible  that the sensitivity of the climate is on the low end of the IPCC envelope (1.0-1.5C), with a slow creep of warming superimposed on much larger natural variability.

  3. It is possible/plausible that the IPCC projections are actually correct (right for the wrong reasons; too much wrong with the climate models for much credibility, IMO).

  4. It is possible that AGW and natural variability could conspire to cause catastrophic outcomes