Archives par mot-clé : MWP

climate-debate

In Climatology, Whatever Happened To Evidence-Based Science?

by J. Hellner, Nov 21, 2023 in ClimateChangeDispatch

Isn’t it time that journalists and students are taught to do research and ask questions about the climate instead of just regurgitating talking points pushing the green agenda?

We are constantly told that storms, floods, droughts, and other natural disasters are growing in frequency and intensity—so why don’t we see specific examples? [emphasis, links added]

Like the severe drought and warm period in Europe in 1540 when temperatures were 9–13 degrees above today’s averageduring the Little Ice Age?

For eleven months, there was practically no rain, and temperatures were five to seven degrees [Celsius] [9–13°F] above the normal values of the 20th century; in many places, summer temperatures must have exceeded 40°C (104°F).

Many forests in Europe went up in flames, choking smoke darkened the sun, and not a single thunderstormwas reported in the summer of 1540.

Water was already scarce in May, wells and springs dried up, mills stood still, people starved, and livestock was slaughtered. Estimates are that in 1540, half a million people died, mostly from dysentery.

Or what about the massive fires in the United States in 1871? In 1871, the Midwestern United States had a severe drought and warm weather, clearly not caused by humans and our use of natural resources.

As a result of this heat and drought, there were severe fires throughout the Midwest, including the Great Chicago Fire.

The temperature was 85 degrees on October 8, 1871. This year the high was 55 degrees, or thirty degrees cooler.

Why isn’t Chicago warmer, after 152 years, with all the cement, people, and gas vehicles and equipment if they all cause warming?

The Chicago fire alone caused $200 million in damages, which is the equivalent of over $5 billion today.

I am 70 years old, and I don’t recall serious fires during my lifetime in the Midwest.

The narrative that humans and our use of natural resources are to blame for warming temperatures, in turn creating an existential threat to our survival, is contrary to the data and facts; scientific honesty would be forming a narrative based on the evidence, instead of forcing “evidence” to fit a story.

What about the Medieval Warm Period 1,000 years ago where temperatures were similar to today? What caused that warming since it clearly wasn’t man’s use of natural resources?

…

climate-debate

New Reconstructions From Brazil, China, Europe Indicate No Net Warming In Recent Centuries

by K. Richard, Oct 26, 2023 in NoTricksZone

Paleoclimate studies continue to undermine claims of “unprecedented” global warming in the modern era.

A new temperature reconstruction (Oliveira Silva Muraja et al., 2023) for Brazil reveals there has been no net modern warming since the 1400s.

…

…

 

Another new temperature reconstruction (Yue et al., 2023) indicates there has been no net modern warming in Central China since the 1400s.

…

climate and geology

New Study: Roman And Medieval Warm Periods Were 2.8°C Warmer Than 1970-2000 In Central China

by K. Richard, Mar 13, 2023 in NoTricksZone

A series of paleoclimate lake reconstructions across China in recent years have failed to support the global-scale warming narrative.

Per a new lake temperature reconstruction (Li et al., 2023) from Central China, there were distinct “warm intervals during the RWP [Roman Warm Period] (403–413 CE), with a temperature 2.89°C higher than that of the mean for 1970–2000 CE, and during the MWP [Medieval Warm Period] (864–882 and 965–994 CE), when the temperature was 2.81°C higher.”

There are 8 other lake sediment reconstructions from the region (Qinghai, Gahai, Sugan, Kusai, Tiancai, Heiahi, Lugu, Cuoqia) documented in the study. None of the 8 are shown to have a modern temperature uptick that would support the claims of an unusually warm modern climate relative to past millennia.

better to know...?, climate-debate

Russian Temperature Records Are Not Cooperating With The CO2-Driven Climate Narrative

by K. Richard, Nov 14, 2022 in NoTricksZone

Two new studies indicate there has been no modern warming in the last centuries in western (Urals) and eastern (Kolyma) Russian mountain ranges.

A new 27,000-year temperature reconstruction assesses it was ~2.5 to 4.8°C warmer than today from 8.9-5.2 ka BP in the Ural Mountains, or when CO2 is said to have hovered in the 265 ppm range.

Summer temperatures were also warmer during the Medieval Warm Period, or from 1.2-0.7 ka BP. After a post-Medieval cool-down fostering in the Little Ice Age, the reconstructed record suggests there has been no warming since 0.5 cal ka BP, or for the last several centuries.

The smoothed temperature record shown in the study indicates there was only one brief period in the last 10,000 years that was not warmer than today.

“The reconstructed TJuly [8.9-5.2 cal ka BP] are the highest recorded, reaching up to 4.8 °C higher than today’s air temperature. … Present day T July have persisted since 0.5 cal ka BP.”

…

climate-debate

New Study: In Northern Poland The Medieval Warm Period Was 3°C Warmer Than Today

by K. Richard, Feb 17,2022 in NoTricksZone

The temperature record for this region also shows today’s temperatures are not much different than they were during the Little Ice Age.

Another chart contained in the study (Pleskot et al., 2022) shows North America’s and Europe’s mean annual temperatures are nearly the lowest of the last 4,500 years.

…

better to know...?, climate-debate

4 More New Reconstructions Affirm The Medieval Warm Period Was ‘Warmer Than Today’

by K. Richard, Oct 14, 2021 in NoTricksZone

From Russia to the Indian Ocean to Antarctica, surface temperatures were much warmer than  they are today during Medieval times.

1. The Eastern Russia region was 1.5°C warmer than now during the Medieval Warm Period. The modern warm-up began centuries ago and temperatures have declined in the last few centuries. Relative sea levels were 1 m higher than now 1,000 years ago.

Nazarova et al., 2021

….

 

2. Scientists use coral fossil evidence to suggest mean sea surface temperatures (SST) during the Medieval Climate Anomaly were “warmer than today”. At the two Indian Ocean study sites, there has been no obvious SST warming since 1982.

Yudawati Cahyarini et al., 2021

…

3. The modern (1994-2004) surface temperatures in the South China Sea are colder now than any time in the last 6000 years. Except for a brief interval ~500 years ago, SSTs have been consistently 2-4°C warmer than today since the middle Holocene.

Zhou et al., 2021

….

4. Modern sea ice extent for Antarctica’s Ross Sea is more extensive today (and temperatures cooler) than nearly any time in 6000 years.  It was warmer with less sea ice 1.6 to 0.7k years ago. Penguin numbers decline with cooling/increased sea ice.

Xu et al., 2021

…

better to know...?, climate-debate

New Study: 2000-Year Precipitation Reconstructions Expose Climate Models Still Of Junk Grade

by Atwood et al., Aug 18, 2021 in NoTricksZone

A new study by Atwood et al (2021) published in the journal of Paleoceanography and Paleoclimatology found there’s “poor agreement” between precipitation reconstructions and model simulations over the past 2000 years. This means future projections made by current models are unreliable. 

…

 

Models and reconstructions don’t agree

These comprehensive reconstructions show that from 800 to 1000 CE there was a pronounced drying event relative from the eastern Pacific and parts of Mesoamerica.

Also the period “1400–1700 CE is marked by pronounced hydroclimate changes across the tropics, including dry and/or isotopically enriched conditions in South and East Asia, wet and/or isotopically depleted conditions in the central Andes and southern Amazon in South America, and fresher and/or isotopically depleted conditions in the Maritime Continent.”

The study’s abstract also notes how there’s a glaring disagreement between the simulations done by models and what the reconstructions show: “We find notable dissimilarities between the regional hydroclimate changes and global-scale and hemispheric-scale temperature reconstructions, indicating that more work needs to be done to understand the mechanisms of the widespread tropical hydroclimate changes during the LIA.”

unclassified

Greenland Ice Core CO2 during the past 1,000 years

by R. Hannon, July 2, 2021 in WUWT

Introduction
This post compares CO2 ice core measurements from Greenland to those from Antarctica over the last millennium. Paleoclimate studies typically use only Antarctic ice cores to evaluate past CO2 fluctuations. This is because the entire Greenland CO2 datasets were deemed unreliable due to chemical reactions with impurities in the ice and therefore have not been used in studies since the late 1990’s. This post will demonstrate that CO2 data from Greenland ice cores have scientific value and respond to key paleoclimate events such as the Little Ice Age and Medieval Warm Period.

Antarctic Ice Core CO2 Trends
Antarctic ice CO2 data is readily available and has been studied extensively (Bauska, 2015, Ahn, 2012, Siegenthaler, 2005 and Rubino, 2019). Most of the focus of recent studies has been on high snow accumulation sites which tend to have higher resolution and less smoothing of the trapped gas age in ice bubbles due to the firn to ice transition. Gas age width and resolution ranges from 10 years in Law Dome ice cores to 65 years in Dronning Maud Land DML. Figure 1 shows CO2 data from Antarctic high-resolution ice cores over the past millennium.

Ahn et al, 2012, compiled CO2 records from the West Antarctic Ice Sheet (WAIS) and compared them to other key datasets such as Dronning Maud Land (DML), and Law Dome. Their study recognizes and discusses elevated CO2 during the Medieval Warm Period (MWP) at 1000 AD, decrease of CO2 around 1600 AD during the Little Ice Age (LIA) and the subsequent rapid increase beginning around 1850 AD.

…

…

climate-debate

Study: Medieval Climate Change Existed in Africa

by A. Watts, Feb 24, 2018 in WUWT

Mapping Medieval Climate Change in Africa:

Continental warming, coastal cooling and shifting rainbelts 1000 years ago

Global climate is currently undergoing major change. Experts agree that this change is driven by a combination of man-made and natural factors. However, full quantification of the anthropogenic and natural components is still a matter of debate. In order to better understand the contribution of natural climate variability and distinguish this from man-made influence, researchers worldwide have gone out to the field to study Earth’s pre-industrial climate history. Of particular interest are the past thousand years, which in Europe and North America have seen the transition from a rather warm medieval period to major cooling of the Little Ice Age, followed by the temperature rebound of the Current Warm Period which was further intensified by human greenhouse gas emissions. Our understanding of medieval climate outside this well-studied North Atlantic region is unfortunately still poor.

An international team led by geoscientist Sebastian Lüning wants to change this. Lüning is a professional resources geologist who in his sparetime works on paleoclimatological studies with the Switzerland-based Institute for Hydrography, Geoecology and Climate Sciences. Together with colleagues from Poland, Nigeria, Turkey and Germany they embarked on a journey through the scientific literature to shed light on the so-called ‘Medieval Climate Anomaly’, a period comprising of the years 1000-1200 AD. The initial focus region of their study was Africa. Lüning and his team crawled through hundreds of publications and mosaiced together a fascinating picture of African medieval climate change that tracks ancient heat waves, local cooling, drought and phases of amplified rainfall. Using modern database and visualization technology, the team managed to synthesize astonishing trends from the large amount of filtered data. Lüning explains the challenge:

….

better to know...?, climate-debate

Climate Change Causation: Was The Medieval Warm Period ‘Regional?’

by F. Menton, Jan 5, 2021 in ClimateChangeDispatch

Some commenters yesterday noted that the climate establishment has not just completely ignored the threat to their orthodoxy posed by the Medieval Warm Period and other similarly-warm pre-human-emissions eras.

Initially, there was a recognition that this issue could be important, and there was definitely some attempt to deal with it.

However, over time, the accumulation of evidence, particularly as to the existence Medieval Warm Period as a global phenomenon, gradually became overwhelming.

So — in the face of evidence that, under the normal precepts of the scientific method, would be deemed to invalidate the hypothesis that only human CO2 emissions could be causing current warming — how can the orthodoxy be kept alive?

The answer, almost entirely, has been to resort to the hand-waving of “detection and attribution” studies, and hope nobody notices. And, to a remarkable extent, nobody notices.

Readers may be interested in a short history of this issue.

…

…

See also  A prequel to the Dantean Anomaly: the precipitation seesaw and droughts of 1302 to 1307 in Europe

climate-debate

New Study Effectively Eliminates Confidence In Human Attribution For Modern Global Warming

by K. Richard, Nov 5, 2020 in NoTricksZone

The forcing uncertainties and lack of observational measurements in the top-to-bottom global ocean preclude an assessment that modern warmth is due to anthropogenic activities.

Key points from a new paper (Gebbie, 2021):

• 93% of the changes to the Earth’s energy budget, manifested as warming of the Earth system, are expressed in the global ocean. Just 1% of global warming is atmospheric.

• Even with the advent of “quasi-global” temperature sampling of the ocean since 2005 (ARGO), these floats “do not measure below 2,000-m depth.” This means that temperature changes in “approximately half the ocean’s volume” are still not being measured today.

• To detect the effects of anthropogenic forcing, it would require energy budget imbalance measurement precision of 0.1 W/m² at the top of the atmosphere (TOA). Uncertainty in the forcing changes affecting climate are ±4 W/m², meaning that uncertainty is about 80 times greater than an anthropogenic signal detection.

• Past changes in global ocean heat content, such as the last deglaciation, have been 20 times larger than modern changes.

• Ocean heat storage during the Medieval Warm Period (Medieval Climate Anomaly, or MCA) was much greater than modern. Modern global ocean heat uptake is “just one-third” of what is required to reach the levels attained during Medieval times.

climate-debate

New Study: East Antarctica Was Up To 6°C Warmer Than Today During The Medieval Warm Period

by K. Richard, Oct 15, 2020 in NoTricksZone

As recently as 2000 to 1000 years ago, spanning the Roman to Medieval Warm Periods, East Antarctica was 5-6°C warmer than it is today. The consequent ice melt resulted in >60 meters higher water levels in East Antarctica’s lakes.

East Antarctica has been rapidly cooling in recent decades, with magnitudes reaching -0.7°C to -2.0°C per decade since the mid-1980s (Obryk et al., 2020).

…

A new study (Myers et al., 2020) reports that until about 15,000 years ago and throughout the Last Glacial Maximum, East Antarctica was 4-9°C colder than it is today.

Antarctica then abruptly warmed 15°C within centuries. From 12,000 to 6,000 years before present, East Antarctica was about 5°C warmer than it is today.

…

…

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.

…

climate-debate

Chinese Scientists: It Was Warmer In China During Medieval Warm Period Than Today

by Hao et al. , January  2, 2020  in GWPF

For China as a whole, the longest warm period during the last 2000 years occurred in the 10th–13th centuries’

Abstract: The Medieval Climate Anomaly (MCA, AD950-1250) is the most recent warm period lasting for several hundred years and is regarded as a reference scenario when studying the impact of and adaptation to global and regional warming. In this study, we investigated the characteristics of temperature variations on decadal-centennial scales during the MCA for four regions (Northeast, Northwest, Central-east, and Tibetan Plateau) in China, based on high-resolution temperature reconstructions and related warm-cold records from historical documents. The ensemble empirical mode decomposition method is used to analyze the time series. The results showed that for China as a whole, the longest warm period during the last 2000 years occurred in the 10th–13th centuries, although there were multi-decadal cold intervals in the middle to late 12th century. However, in the beginning and ending decades, warm peaks and phases on the decadal scale of the MCA for different regions were not consistent with each other. On the inter-decadal scale, regional temperature variations were similar from 950 to 1130; moreover, their amplitudes became smaller, and the phases did not agree well from 1130 to 1250. On the multi-decadal to centennial scale, all four regions began to warm in the early 10th century and experienced two cold intervals during the MCA. However, the Northwest and Central-east China were in step with each other while the warm periods in the Northeast China and Tibetan Plateau ended about 40–50 years earlier. On the multi-centennial scale, the mean temperature difference between the MCA and Little Ice Age was significant in Northeast and Central-east China but not in the Northwest China and Tibetan Plateau. Compared to the mean temperature of the 20th century, a comparable warmth in the MCA was found in the Central-east China, but there was a little cooling in Northeast China; meanwhile, there were significantly lower temperatures in Northwest China and Tibetan Plateau.

climate-debate

Melting Glaciers Uncover Medieval Artefacts In Norway

by P. Homewood, April 16, 2020 in NotaLotofPeopleKnowThat

Melting glaciers in Norway have revealed ancient artefacts dropped by the side of a road more than 1,000 years ago.

Clothes, tools, equipment and animal bone have been found by a team at a lost mountain pass at Lendbreen in Norway’s mountainous region.

A haul of more than 100 artefacts at the site includes horseshoes, a wooden whisk, a walking stick, a wooden needle, a mitten and a small iron knife.

The team also found the frozen skull of an unlucky horse used to carry loads that did not make it over the ice.

The objects that were contained in ice reveal that the pass was used in the Iron Age, from around AD 300 until the 14th century.

Activity on the pass peaked around AD 1000 and declined after the black death in the 1300s, due as well to economic and climate factors.

The researchers say the melting of mountain glaciers due to climate change has revealed the historical objects, with many more to come.

https://www.dailymail.co.uk/sciencetech/article-8224817/Melting-ice-reveals-lost-Viking-mountain-path.html

 

Unfortunately neither the journalist nor the scientists seem to be capable of adding 2+2!

 

The existence of the Medieval Warm Period in Norway, followed by glacial advance in the Little Ice Age has been long known about, as HH Lamb wrote in 1982:

…

climate-debate

New Studies: Europe Is No Warmer Today Than It Was During Medieval Times

by K. Richard, April 13, 2020 in NoTricksZone

Two new papers use tree ring proxy evidence to suggest modern European temperatures are neither unusual nor higher than they were during the Medieval Warm Period.

Esper et al. (2020) have produced a new temperature reconstruction for Southern Europe to complement past reconstructions for Northern and Central Europe.

They find “the warmest 30-year period since 730 CE occurred during high Medieval times (876–905 CE=+0.78 °C w.r.t. 1961–1990) and has been slightly warmer than the recent period from 1985–2014 (+0.71 °C)“.

The proxy evidence and instrumental record also show there has been no obvious net warming in Southern Europe since the 1940s.

Past reconstructions for Northern and Central Europe also show no unusual warming has occurred over the last century, with as-warm or warmer temperatures during the 1940s.

Ljungqvist et al., 2020  cite tree ring temperature studies from Scandinavia, Scotland, Continental Europe, and the Pyrenees that also show the 1930s and 1940s were as-warm or warmer than recent decades.

…

climate-debate

Greenland Ice Core CO2 Concentrations Deserve Reconsideration

by Renee Hannon, January 7, 2020, in WUWT

Introduction
Ice cores datasets are important tools when reconstructing Earth’s paleoclimate. Antarctic ice core data are routinely used as proxies for past CO2 concentrations. This is because twenty years ago scientists theorized Greenland ice core CO2 data was unreliable since CO2trapped in air bubbles had potentially been altered by in-situ chemical reactions. As a result, Greenland CO2 datasets are not used in scientific studies to understand Northern and Southern hemispheres interactions and sensitivity of greenhouse gases under various climatic conditions.

This theory was put forward because Greenland CO2 data were more variable and different than Antarctic CO2 measurements located in the opposite polar region about 11,000 miles away. This article re-examines Greenland ice cores to see if they do indeed contain useful CO2 data. The theory of in-situ chemical reactions to explain a surplus and deficit of CO2, relative to Antarctic data, will be shown to be tenuous. The Greenland CO2 data demonstrates a response to the Medieval Warm Period, Little Ice Age, Dansgaard-Oeschger and other past climate change events. This response to past climate changes offers an improved explanation for why Greenland and Antarctic CO2 measurements differ. Further, Greenland CO2 measurements show rapid increases of 100 ppm during warm events in relatively short periods of time.

Atmospheric CO2 is More Variable in Northern Latitudes

Figure 1, from NOAA, shows atmospheric CO2 concentrations measured from the continuous monitoring program at four key baseline stations spanning from the South Pole to Barrow, Alaska. CO2 has risen from about 330 ppm to over 400 ppm since 1975 and is increasing at approximately 1-2+ ppm/year. Many scientists believe that rapidly increasing CO2 is mostly due to fossil fuel emissions.

Figure 1. Atmospheric CO2 concentrations from NOAA
…
climate-debate

NEWLY PUBLISHED SCIENTIFIC PAPER TEARS GLOBAL WARMING AND THE IPCC TO SHREDS

by Cap Allon, December 11, 2019 in Electroverse

A scientific paper entitled “An Overview of Scientific Debate of Global Warming and Climate Change” has recently come out of the University of Karachi, Pakistan. The paper’s author, Prof. Shamshad Akhtar delves into earth’s natural temperature variations of the past 1000 years, and concludes that any modern warming trend has been hijacked by political & environmental agendas, and that the science (tackled below) has been long-ignored and at times deliberately manipulated.

The published paper –available in full HERE— sets out its intent:

Climate change is NOT a new phenomenon. The palaeo-climatic studies reveal that during the Pleistocene and Holocene periods several warm and cold periods occurred, resulting in changes of sea level and in climatic processes like the rise and fall of global average temperature and rainfall.

…

climate-debate

Another New Study Finds The Canadian Arctic Was About 1-2°C Warmer During Medieval Times

by K. Richard, December 16, 2019 in NoTricksZone

Four reconstructions from the central and western High Arctic reveal July temperatures were about 1-2°C warmer than today during most of the 1st millennium and Medieval period (Tamo and Gajewski, 2019).

A few years ago, a chironomid reconstruction of Boothia Peninsula in the Canadian Arctic (Fortin and Gajewski, 2016) revealed not only were today’s temperatures the coldest of the last 7000 years, but the last 150 years “do not indicate a warming during this time.”

…

 

climate-debate

Three Graphs

by Kip Hansen, November 30, 2019 in WUWT

…

…

Now an annotated version of the second graph:

Here we have the second graph 1850-2015, with the global Average Surface Temperature anomaly (again — baseline 15 CE)  but I have dropped in a smaller window, on the left, bringing forward  the Roman Warm Period and the Medieval Warm Period (MWP) — the years 100-800 CE (same scale) — to illustrate the difference between the peak Global Average Surface Temperature (GAST)  of the Medieval Warm Period to the most current GAST on the graph (2015).

This exposes the ubiquitous trick of the Climate Debate, in which Global Temperatures are [almost] always shown only from the depths of the Little Ice Age (clearly marked on the first graph by Gebbie), resulting in images similar to Gebbie’s Figure 2 — despite the fact that most 2 millennia reconstructions clearly show the Roman and Medieval Warm Periods as generally in the same range as the Modern Warm Period.   Given the acknowledged range of error  in any temperature reconstruction and in modern estimates of global surface temperatures (today, in absolute temperatrures,  around +/- 0.5ºC  or a range of 1ºC)  — there may be little, if any,  significant-to-the-global-environment difference  between the two periods.

The Medieval Warm period did not result in a “Climate Catastrophe”  and the [iffy] little additional 0.2°C  seen today  is very unlikely to spark a modern Climate Catastrophe either.

climate-debate

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.

…

climate-debate

Mann, Hayhoe Try To Erase To The Pesky Medieval Warm Period

by J. Taylor, October 3, 2019 in ClimateChangeDispatch

Climate alarmists Michael Mann and Katharine Hayhoe have been caught using dubious, revisionist temperature data in their attempt, as one Climategate email author put it,  to “deal a mortal blow” to the extensively documented Medieval Warm Period.

Before climate change became a political issue, it was scientifically well-established that a significant global warming event occurred between approximately 900 AD and 1200 AD.

For example, the United Nations Intergovernmental Panel on Climate Change (IPCC) First Assessment Report presented a temperature history and visual graph documenting that the Medieval Warm Period existed and that it brought temperatures at least as warm as today (at pg. 7).

Multiple peer-reviewed studies provided additional confirmation of the Medieval Warm Period.

The warming climate of the Medieval Warm Period spurred abundant crop production, fewer extreme droughts and floods, a growing human population, and improving living standards.

The Little Ice Age terminated the Medieval Warm Period and brought devastating weather extremes, widespread crop failures, famines, plagues like the Black Death, and a contracting human population.

For a good summary of the extensive benefits of the Medieval Warm Period and the devastating harms of the Little Ice Age, see the excellent book, “In the Wake of the Plague: The Black Death and the World It Created.”

…

climate-debate, to keep an eye on...

Protesting Warmth? Greta’s Home, Sweden, Is 3°C COLDER Today Than Nearly All Of The Last 9000 Years

by K. Richard, September 26, 2019 in NoTricksZone

Greta Thunberg lives in Sweden. According to peer-reviewed science, Sweden was at least 3°C warmer than it is today about 6000 to 9000 years ago, when CO2 concentrations lingered around 265 ppm. At 410 ppm CO2, 21st century Sweden is colder now than almost any time in the last 9000 years.

…

A Much Warmer Northern Hemisphere

During the Medieval Warm Period, wine vineyards flourished in Scandinavia and Russia at the same latitude (55°N) where polar bears roam today.

…

…

climate-debate

Medieval Warmth Was GLOBAL…Confirmed By Over 1,200 Papers At Google Maps

by P. Gosselin, Sep. 3, 2019 in ClimateChangeDispatch

More than 1,200 publications show the Medieval Warm Period (MWP) was global – an embarrassment to global warming alarmists who claimed it was regional.

Global-warming-alarmist scientists like claiming that the well-documented Medieval Warm Period (MWP) was mostly a regional, North Atlantic phenomenon, and was not global, and so we should just move along and stop questioning man-made global warming.

For example, the online Britannica entry on the Medieval Warm Period written by John P. Rafferty writes that it occurred “predominantly in the Northern Hemisphere from Greenland eastward through Europe and parts of Asia.”

Britannica does state that the claim of a global extent is highly controversial, though it really isn’t as we are about to see.

More than 1,200 papers evidence it was global

Indeed the claim that it was global is now backed up by a huge body of scientific studies meticulously compiled by Dr. Sebastian Lüning of Die kalte Sonne and presented at Google Maps here.