Archives par mot-clé : MWP

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and Tibetan Plateau) in China, based on high-resolution temperature reconstructions and related warm-cold records from historical documents.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.

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.


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:

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.

Greenland Ice Core CO2 Concentrations Deserve Reconsideration

by Renee Hannon, January 7, 2020, in WUWT

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


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.

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.”


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.

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.

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.”

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.

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.

New Attempts To Erase The MWP & LIA

by P. Homewood, July 29, 2019 in NotaLotofPeopleKnowThat

There have been many attempts to get rid of the Medieval Warming Period and Little Ice Age, and here’s another one:

The science teams reconstructed the climate conditions that existed over the past 2,000 years using 700 proxy records of temperature changes, including tree rings, corals and lake sediments. They determined that none of these climate events occurred on a global scale.

As with the other failed attempts, this latest one claims that the MWP and LIA were only localised phenomena. But nothing could be further from the truth.

These three new studies rely on proxies, but time and again hockey stick studies based on proxies are proven to be fake, based on cherry picked proxies and dodgy statistics.

In fact, we have no need to rely on proxies, because the actual evidence of warm and cold periods is very real and substantial across the world.

We are all familiar with the evidence from Greenland ice cores, which clearly show both the MWP and LIA:


Anti science L. A. Times hypes propaganda denying global wide Medieval Warm Period and Little Ice Age

by Larry Hamlin, July 28, 2019 in WUWT

The Los Angeles Times is at it again hyping anti science climate alarmist propaganda trying to conceal the global wide Medieval Warm Period and the Little Ice Age that are supported and justified by hundreds of scientific studies.

This climate alarmist propaganda Times article cites a new “study” that ridiculously attempts to deny these clearly established warm and cool periods in our past.

This alarmist hyped new “study” is addressed in a superb article at the JoNova website demonstrating the complete lack of scientific veracity of this studies claims.

There is nothing I can add to show how politically contrived and inane the claims are from this new “study” beyond the excellent presentation in the JoNova article.

Provided below are excerpts from this excellent article which demonstrate the lack of scientific credibility of the new “study” as well as the politically driven anti science climate alarmism bias of the Times.


1970s: Earth Warmed 0.6°C From 1880-1940 And Cooled -0.3°C From 1940-1970. Now It’s 0.1°C And -0.05°C.

by K. Richard, July 25, 2019 in NoTricksZone

About 45 years ago, the “consensus” in climate science (as summarized by Williamson, 1975) was quite different than today’s version.

1. The Medieval Warm Period was about 1°C warmer than present overall while the “largely ice-free” Arctic was 4°C warmer, allowing the Vikings to navigate through open waters because there was “no or very little ice” at that time.
2. The island of Spitsbergen, 1237 km from the North Pole and home to over 2000 people, “benefited” because it warmed by 8°C between 1900 and 1940, resulting in 7 months of sea-ice free regional waters. This was up from just 3 months in the 1800s.
3. Central England temperatures dropped -0.5°C between the 1930s to the 1950s.
4. Pack-ice off northern and eastern iceland returned to its 1880s extent between 1958 and 1975.
5. In the 1960s, polar bears were able to walk across the sea (ice) from Greenland to Iceland for the first time since the early 1900s. (They had somehow survived the 7 months per year of sea-ice-free waters during the 1920s-1940s).



Image Source: National Academy of Sciences,  Understanding Climatic Change

Medieval Climate Anomaly Now Confirmed In Southern Hemisphere On All Four Continents

by Lüning et al., July  6, 2019 in NoTricksZone

For a long time it has been said that the Medieval Warm Period was a purely North Atlantic phenomenon. This has proved to be wrong.

On 29 June 2019, a paper by Lüning et al. 2019 on the Medieval Warm Period in Antarctica appeared in the trade journal Palaeogeography, Palaeoclimatology, Palaeoecology. Here is the abstract:

With the publication of this paper, the Medieval Climate Anomaly (MCA) has now been confirmed on all four continents of the southern hemisphere.

While the largest part of the southern hemisphere apparently experienced a warm phase during the MCA, there were also isolated areas that cooled down. To the latter regions belong, for example, coasts, where cold water from the depth rose increasingly. In other areas so-called climate seesaws or dipoles were active, as we know them from today’s climate. One end of the “seesaw” heats up, the other end cools down.

Another result of the studies is that the medieval climate history of huge areas in the southern hemisphere is simply unknown. A task force urgently needs to be set up to fill in this climatic “empty space” with information on pre-industrial temperature development. This information is urgently needed to calibrate the climate models on the basis of which far-reaching socio-political planning is currently taking place.

What follows are publications on the Medieval Period climate of the southern hemisphere as an overview:

Lüning, S., M. Gałka, F. Vahrenholt (2019): The Medieval Climate Anomaly in Antarctica. Palaeogeogr., Palaeoclimatol., Palaeoecol., doi: 10.1016/j.palaeo.2019.109251

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

The Little Ice Age: What Happened Around the World

by Marcia Wendorf, May 15, 2019 in InterestingEngineering

Between 1300 and 1850, the Earth experienced a Little Ice Age whose cause to this day is not known.

During the period 950 CE to 1250 CE, the earth experienced an unusually warm period, which became known as the Medieval Warm Period (MWP) or the Medieval Climatic Anomaly. At their height, temperatures during that period were similar to those experienced during earth’s mid-20th-century warming period.

Following the Medieval Warm Period came a period of intense cold, which has become known as the Little Ice Age (LIA). The term “Little Ice Age” was coined by Dutch-born American geologist F.E. Matthes in 1939. The LIA began around 1300 CE and lasted until about 1850 CE.

Within that stretch, NASA’s Earth Observatory has described three particularly cold periods: one around 1650, a second around 1770, and the third around 1850.

Geologic Evidence of Recurring Climate Cycles and Their Implications for the Cause of Global Climate Changes—The Past is the Key to the Future

by  Don J. Easterbrook,  2011 in ScienceDirect

The Medieval Warm Period (MWP) was a time of warm climate from about 900 A.D. to 1300 A.D. when global temperatures were apparently somewhat warmer than at present. Its effects were evident in Europe where grain crops flourished, alpine tree lines rose, many new cities arose, and the population more than doubled. The Vikings took advantage of the climatic amelioration to colonize Greenland, and wine grapes were grown as far north as England where growing grapes is now not feasible and about 500 km north of present vineyards in France and Germany. Grapes are presently grown in Germany up to elevations of about 560 m, but from about 1100 A.D. to 1300 A.D., vineyards extended up to 780 m, implying temperatures warmer by about 1.0–1.4 °C (Oliver, 1973).

Solar forcing and climate variability during the past millennium as recorded in a high altitude lake: Lake Salda (SW Anatolia)

by I.B. Bauhi & S. Akçer-Ön, August 30, 2018 in QuaternaryInternational


Climate variability is a well-known phenomenon and has been frequently, though complex, linked to solar forcing on different time scales. The importance of solar forcing related climate variability is crucial in our understanding of paleoclimate and future climate changes, as well as building climate models. Here in, we present the late Holocene (last ca 1400) climate records from Lake Salda in SW Anatolia using high-resolution micro X-ray Fluorescence (μ-XRF), magnetic susceptibility (MS), stable isotopes13C and δ18O) and TOC-TIC measurements. The age model is constructed by using radionuclide (210Pb, 137Cs and 14C) dating methods. The lake’s high-resolution multiproxy results revealed lake water level fluctuations associated with humid and dry spells during the last 1400 years. Periods of higher lake levels are consistent with solar maxima in total solar irradiance and vice versa. Moreover, the Lake Salda records clearly show dry Dark Ages Cold Period (DACP), humid Medieval Climatic Anomaly (MCA), dry Little Ice Age (LIA), and humid Modern Warm Period (MoWP). These records suggest that the solar forcing, through its influence on the atmospheric circulation, is the main mechanism of climate change during the DACP, MCA, LIA and MoWP in this region.

Climate Book By Japanese Physics Professor: “The Globe Isn’t Warming Anymore”…IPCC “Scientifically Immoral”

by Kirye, October 23, 2048 in NoTricksZone

Dr. Fukai also points out that global vegetation coverage increased by 11% in 29 years, from 1982 to 2010, as increasing CO2 has helped the greening of the Sahel and Sahara Desert. He contradicts the often heard media claims that drought is spreading globally, writing: “The media spread the word that desertification is progressing globally, but practically the desert is greening through CO2.” […] “Everyone should be aware that increasing CO2 concentrations in atmosphere is not in itself harmful, but it’s a good thing.”

No correlation

Dr. Fukai also shows that the earth’s temperature change is not simple and does not correlate at all with CO2. He shows graphs from D. M. Etheridge et al., Mauna Loa Observatory and the temperature data from Moberg et al. (2005).


The retired Japanese professor writes that at around 1000 A.D. — the Medieval Warm Period — there were no signs showing CO2 concentration was higher. A temperature graph using data from Moberg et al. (2005) shows the Medieval Warm Period appears clearly and that CO2 was in fact around 280 ppm at that time.

Evidence of the Medieval Warm Period in Australia, New Zealand and Oceania

by S. Lüning, January 9, 2018 in WUWT

The climate of the pre-industrial past is of greatest importance to the ongoing climate discussion. Current climate can only be understood when interpreting it in the paleoclimatological context of the past few thousand years. Until not too long ago it was thought that the pre-industrial climate was monotonous and constant. This idea was e.g. promoted by Mann et al. whose famous hockey stick curve featured prominently in the IPCC report of 2001. Over the last 15 years, however, a large number of studies changed this view by providing robust evidence for the existence of significant natural climate variability. Of particular interest are the past 1000 years which commenced with the generally warm ‘Medieval Climate Anomaly’ (MCA, aka ‘Medieval Warm Period’, MWP), that eventually passed into the ‘Little Ice Age’ (LIA), before returning to the warm climate of the current ‘Modern Warm Period’ of the 20th and early 21st centuries.

There have been controversial debates about the existence of the MWP, …

During The 800s-1300s AD, Wine Grapes Were Grown At Latitudes Where Polar Bears Now Roam

by K. Richard, April 2, 2018

Canada’s stable-to-increasing polar bear population extends its range slightly further south of the 55th parallel (York et al., 2016).

According to published geological evidence from the 1950s, remnants of wine grape vineyards have been unearthed in regions as far north as the polar-bear-inhabiting 55th parallel during the Medieval Warm Period (~800s to 1300s AD).