Archives par mot-clé : Holocene

Emmanuel Le Roy Ladurie A (re)lire absolument…

by Alain Préat,  3 octobre 2019 inScienceClimatEnergie


S’il est un livre, et un des premiers, à s’être penché de manière aussi détaillée sur l’évolution (récente) du climat, c’est celui d’Emmanuel Le Roy Ladurie ‘Histoire du climat depuis l’an mil’, publié en 1967.

Rappelons cependant le livre précurseur de Joseph-Jean-Nicolas Fuster publié en 1845 et récemment analysé ici même à SCE (et toujours disponible, voir ici).

 

1/ Introduction

A lire ou relire ce livre de 366 pages (Figure 1), on ne peut qu’être stupéfié par l’analyse rigoureuse qui met en évidence la variabilité naturelle du climat aux échelles pluriséculaire et décennale, qui décortique et privilégie  avec finesse le caractère local du climat par rapport à un climat global et fournit à partir d’indicateurs fiables des fourchettes de températures pour les variations climatiques observées à l’échelle pluriséculaire.

 Figure 1. Histoire du climat depuis l’an mil, Flammarion, publié en 1967

Avant d’aborder ce sujet en détail, il semble qu’aucun modèle sorti des ‘computers’ (GIEC) n’ait été jusqu’à présent capable de rendre compte des évolutions rapportées dans le livre d’ Emmanuel Le Roy Ladurie, ces modèles se prétendent ‘globaux’, contrairement à la conclusion du livre en question qui insiste particulièrement sur le caractère local des climats. Enfin il s’agit d’un livre de 366 pages bien illustré (photographies, cartes et graphiques) dans lequel il n’est pas mentionné une seule fois ‘le poison’ des temps modernes, à savoir le CO2. L’auteur, en 1967 (faut-il le rappeler …), propose ou explore quand  même des pistes pour rendre compte de la succession d’épisodes ‘froids’ et ‘chauds’, tout au long de ces 1000 années d’histoire, qui en fait  débutent il y a 3500 ans (mais pour ces temps historiques plus reculés, les données fiables sont moins nombreuses).

 

2/ Alors que dit Emmanuel Le Roy Ladurie ?

Anthropocene: “it will be the rocks that have the final say” about this fake word.

by David Middleton, August 7, 2019 in WUWT


The fake geologic epoch known as the “Anthropocene” just won’t die… It’s like a zombie from a bad science fiction movie.

Despite being populated with activists like Naomi Oreskes, it has taken the AWG ten years to vote on what their conclusion will be and to start looking for evidence to support their conclusion… And the vote wasn’t unanimous.

Here’s where the Anthropocene dies…

 

Figure 4 from Finney & Edwards.  “Workflow for approval and ratification of a Global Standard Stratotype Section and Point (GSSP) proposal. Extensive discussion and evaluation occurs at the level of the working group, subcommission, and International Commission on Stratigraphy (ICS) Bureau. If approved at these successive levels, a proposal is forwarded to the International Union of Geological Sciences (IUGS) for ratification. This process is also followed for other ICS decisions on standardization, such as approval of names of formal units, of revisions to the units, and to revision or replacement of GSSPs.”

For Most Of The Last 10,000 Years, Greenland Ice Sheet and Glacier Volume Was Smaller Than Today

by K. Richard, August 5, 2019 in NoTricksZone


A new paper (Axford et al., 2019) reveals NW Greenland’s “outlet glaciers were smaller than today from ~9.4 to 0.2 ka BP” (9,400 to 200 years before 1950), and that “most of the land-based margin reached its maximum Holocene extent in the last millennium and likely the last few hundred years.”

The authors conclude:

“We infer based upon lake sediment organic and biogenic content that in response to declining temperatures, North Ice Cap reached its present-day size ~1850 AD, having been smaller than present through most of the preceding Holocene.”

Furthermore, the authors assert Greenland was 2.5°C to 3°C warmer than modern on average during the Holocene Thermal Maximum, and peak temperatures were 4°C to 7°C warmer.

 

 

Image Source: Mikkelson et al., 2018

1980s Science: Ice Cores Show CO2 Naturally Rose 200 ppm (65 ppm/100 Years) During The Early Holocene

by K. Richard, July 22, 2019 in NoTricksZone


A few decades ago it was “consensus” science that CO2 levels had reached 400 ppm (and even up to 500 ppm) during the Early Holocene, with rising amplitudes of greater than 200 ppm and rates of 65 ppm in less than a century. Then the “consensus” opinion changed.

In 1982 it was still quite acceptable for Dr. Flohn, a climate scientist, to acknowledge that changes in CO2 concentration changes are significantly determined by temperature “rather independent of” fossil fuel emissions, but also that Holocene CO2 concentrations reached 350 to 400 ppm between 8,000 to 6,000 years ago (Flohn, 1982).

Why the discrepancy between “consensus” CO2 and historically recorded CO2?

Polish physicist Dr. Zbigniew Jaworowski (1997) was a fierce critic of the means by which ice core data have been collected to assign CO2 concentration values to past epochs.

His criticisms center around the post-1985 tendencies for fellow scientists to openly employ selection bias in making pre-determined decisions about what measurements are “right” and which ones are “wrong” – effectively rendering their results meaningless.

He cites Pearlman et al. (1986), for example. These authors collected 74 Antarctic ice core CO2 samples. Of those, 32 (43%) were rejected because they had values that were too high or too low to match with the agreed-upon pre-determination.

In what other branch of science is it acceptable to discard measured data we don’t agree with?

 

Antarctica was warmer one thousand years ago — and life was OK

JoNova, July 11, 2019


Remember when polar amplification was the rage? So much for that theory

Antarctica is twice the size of the US or Australia. Buried 2 km deep under domes of snow, it holds 58 meters of global sea level to ransom. The IPCC have been predicting its demise-by-climate-change for a decade or two.

A new paper looks at 60 sites across Antarctica, considering everything from ice, lake and marine cores to peat and seal skins. They were particularly interested in the Medieval Warm Period, and researched back to 600AD.  During medieval times (1000-1200 AD) they estimate Antarctica as a whole was hotter than it is today.  Antarctica was even warmer still  — during the dark ages circa 700AD.

Credit to the paper authors: Sebastian Lüning, Mariusz Gałka, and Fritz Vahrenholt

Feast your eyes on the decidedly not unprecedented modern tiny spike:

The little jaggy down after 2000 AD is real. While there was rapid warming across Antarctica from 1950-2000, in the last twenty years, that warming has stalled. Just another 14 million square kilometers that the models didn’t predict.

We already knew the Medieval Warm Period was a global phenomenon, thanks to hundreds of proxies, and 6,000 boreholes. But this new paper is a great addition.

With an awesome dedication to detail, the team put all the big oceanic and other factors into one big graph. It is nice to see them side by side so we can see the connections between them.

Dry Hot North German Summers Were More Common 1000 Years Ago, Scientists Report

by P. Gosselin, June 19, 2019 in NoTricksZone


Dry Summers Like 2018 Were Common in the Middle Ages

Central Europe temperature constrained by speleothem fluid inclusion water isotopes over the past 14,000 years

by Affolter et al., June 5, 2019 in ScienceAdvance


Abstract

The reasons for the early Holocene temperature discrepancy between northern hemispheric model simulations and paleoclimate reconstructions—known as the Holocene temperature conundrum—remain unclear. Using hydrogen isotopes of fluid inclusion water extracted from stalagmites from the Milandre Cave in Switzerland, we established a mid-latitude European mean annual temperature reconstruction for the past 14,000 years. Our Milandre Cave fluid inclusion temperature record (MC-FIT) resembles Greenland and Mediterranean sea surface temperature trends but differs from recent reconstructions obtained from biogenic proxies and climate models. The water isotopes are further synchronized with tropical precipitation records, stressing the Northern Hemisphere signature. Our results support the existence of a European Holocene Thermal Maximum and data-model temperature discrepancies. Moreover, data-data comparison reveals a significant latitudinal temperature gradient within Europe. Last, the MC-FIT record suggests that seasonal biases in the proxies are not the primary cause of the Holocene temperature conundrum.

The Holocene Sea Level Highstand

by David Middleton, June 6 , 2019 in WUWT


What is a highstand?

A highstand is one phase of the sea level cycle (AAPG Wiki)

  • Rising
  • Highstand
  • Falling
  • Lowstand

The highstand is the maximum sea level achieved during the cycle.

The Holocene Epoch

The Holocene Epoch was recently formally subdivided into three stages:

  1. Greenlandian Stage = Lower or Early-Holocene. 11.70 ka to 8.33 ka
  2. Northgrippian Stage = Middle or Mid-Holocene. 8.33 ka to 4.25 ka
  3. Meghalayan Stage = Upper or Late-Holocene. 4.25 ka to present

The abbreviation “ka” refers to thousands of years ago. Lower, Middle and Upper are generally used when referring to rock-time units. Early, Mid and Late are generally used when referring to time units (Haile, 1987). Prior to the formal subdivision, Lower/Early, Middle/Mid and Upper/Late were commonly used; however there was no formal nomenclature. The fake word, “Anthropocene” is not used by real geologists.

There is also an informal climatological subdivision of the Holocene:

  • Preboreal 10 ka–9
  • Boreal 9 ka–8 ka
  • Atlantic 8 ka–5 ka
  • Subboreal 5 ka–2.5 ka
  • Subatlantic 2.5 ka–present

Source: Wikipedia

Why would there have been a Mid- to Late-Holocene highstand?

Figure 1. Holocene sea level curves from Moore & Curray, 1974.

New Paper: Arctic Sea Ice Was Far Less Extensive Than Today During The ‘Ice Free’ Early Holocene

by K. Richard, May 23, 2019 in NoTricksZone


Biomarker evidence for Arctic-region sea ice coverage in the northern Barents Sea indicates the most extensive sea ice conditions of the last 9,500 years occurred during the 20th century (0 cal yr BP). In contrast, this region was ice free with open water conditions during the Early Holocene (9,500-5,800 years ago).

New Study: The Tropical Atlantic Was 7.5°C Warmer Than Now While CO2 Was 220 ppm

by K. Richard, May 9, 2019 in NoTricksZone


Another new paper published in Paleoceanography and Paleoclimatology casts further doubt on the paradigm that says CO2 has historically been a temperature driver.

Evidence from the tropical Atlantic indicates today’s regional temperatures (15.5°C) are 7.5°C colder than a peak temperatures (23°C) between 15,000 to 10,000 years ago, when CO2 hovered around 220 ppm.

Less Ice In Arctic Ocean 6000-7000 Years Ago

by Geological Survey of Norway, October 20, 2008 in ScienceDaily


Recent mapping of a number of raised beach ridges on the north coast of Greenland suggests that the ice cover in the Arctic Ocean was greatly reduced some 6000-7000 years ago. The Arctic Ocean may have been periodically ice free.

”The climate in the northern regions has never been milder since the last Ice Age than it was about 6000-7000 years ago. We still don’t know whether the Arctic Ocean was completely ice free, but there was more open water in the area north of Greenland than there is today,” says Astrid Lyså, a geologist and researcher at the Geological Survey of Norway (NGU).

Scientists Document No Clear Warming Role For CO2 During The Last Deglaciation – Or The Last 10,000 Years

by K. Richard, April 4, 2019 in NoTricksZone


A new paper indicates the rise in CO2 concentration occurred well after the Northern Hemisphere’s ocean circulation changes drove the abrupt warming (~11,700 years ago) that ended the last ice age – a lag that effectively leaves no causal role for CO2 during deglaciation.

 

Nature Unbound III: Holocene climate variability (Part A)

by Javier, April 30, 2017 in ClimateEtc.


First in a two part series on Holocene climate variability.

Summary: Holocene climate is characterized by two initial millennia of fast warming followed by four millennia of higher temperatures and humidity, and a progressively accelerating cooling and drying for the past six millennia. These changes are driven by variations in the obliquity of the Earth’s axis. The four millennia of warmer temperatures are called the Holocene Climatic Optimum which was 1-2°C warmer than the Little Ice Age. This climatic optimum was when global glaciers reached their minimum extent. The Mid-Holocene Transition, caused by orbital variations, brought a change in climatic mode, from solar to oceanic dominated forcing. This transition displaced the climatic equator, ended the African Humid Period and increased El Niño activity.

 

 

Figure 36. Holocene temperature profile. A. Summer (July-August) Central England temperature reconstruction from multiple proxies and sources by H. H. Lamb.Crosses represent dating and temperature uncertainty. Black dots are centennial averages. Red dot is 1900-1965 average. Source: Lamb, H.H. 1977. Climate: Present, past and future. Volume 2. B. Greenland temperature reconstruction based on an average of uplift corrected δ18O isotopic data from Agassiz and Renland ice cores. This average has been corrected for changes in the δ18O of seawater and calibrated to borehole temperature records. Some historical periods are indicated. Source: B. Vinther et al., 2009.

New Paper: Widespread Collapse Of Ice Sheets ~5000 Years Ago Added 3-4 Meters To Rising Seas

by K. Richard, March 11, 2019 in NoTricksZone


During the Mid-Holocene, when CO2 concentrations were stable and low (270 ppm), Antarctica’s massive Ross Ice Shelf naturally collapsed, adding the meltwater equivalent of 3-4 meters to sea levels.

Because CO2 concentrations changed very modestly during the pre-industrial Holocene (approximately ~25 ppm in 10,000 years), climate models that are predicated on the assumption that CO2 concentration changes drive ocean temperatures, ice sheet melt, and sea level rise necessarily simulate a very stable Holocene climate.

In contrast, changes in ocean temperatures, ice sheet melt, and sea level rise rates were far more abrupt and variable during the Holocene than during the last 100 years.

Modern ocean changes are barely detectable in the context of natural variability

Image Source(s): Rosenthal et al., 2013Climate Audit