Archives par mot-clé : Holocene

climate-debate

Study: Sea Levels Rose 4.7 Centimeters Per Year 8200 Years Ago – 30 Times Faster Than Modern Rates

by K. Richard, Aug 26, 2024 in NoTricksZone

The modern rate of sea level rise is not even close veering outside the range of natural variability.

A new study reminds us that, 8200 years ago, near-global sea levels rose 6.5 meters in a span of just 140 years. This is 470 centimeters per century, 4.7 centimeters per year, during a period when CO2 levels were alleged to be a “safe” and stagnant 260 ppm.

Image Source: Nunn et al., 2024

To put this change rate in perspective, global sea levels rose at a rate of 1.56 millimeters per year from 1900 to 2018, including 1.5 mm per year rate during the more recent period from 1958-2014 (Frederikse et al., 2020, Frederikse et al., 2018). This is just under 16 centimeters per century or sixteen hundredths of a centimeter (0.16 cm) per year

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climate-debate

New Study: Central Europe Was ‘2-5°C Warmer Than Present’ Throughout Most Of The Holocene

by K. Richard, July 22, 2024 in NoTricksZone

There were millennia during the past glacial (when CO2 levels were under 200 ppm) that were as warm or warmer than today.

Four central Europe reconstructions, using collected evidence from disparate biomarkers, indicate there were periods (for example, 54,000 to 51,000 years ago, the Bølling–Allerød interstadial, 14,700 years ago) during the last glacial when temperatures were as warmer than (or similar to) today (Zander et al., 2024).

Temperatures throughout the Holocene (8,000 to 4,000 years ago), when CO2 hovered around 265 ppm, were 3.5°C (and up to 5°C) warmer than today. Modern temperatures are among the coldest of the last 10,000 years.

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climate-debate

High-frequency climate forcing causes prolonged cold periods in the Holocene.

by E. van Dijk et al., May 08 2024, in Nature (OPEN ACCESS)

Abstract

Understanding climate variability across interannual to centennial timescales is critical, as it encompasses the natural range of climate fluctuations that early human agricultural societies had to adapt to. Deviations from the long-term mean climate are often associated with both societal collapse and periods of prosperity and expansion. Here, we show that contrary to what global paleoproxy reconstructions suggest, the mid to late-Holocene was not a period of climate stability. We use mid- to late-Holocene Earth System Model simulations, forced by state-of-the-art reconstructions of external climate forcing to show that eleven long-lasting cold periods occurred in the Northern Hemisphere during the past 8000 years. These periods correlate with enhanced volcanic activity, where the clustering of volcanic eruptions induced a prolonged cooling effect through gradual ocean-sea ice feedback. These findings challenge the prevailing notion of the Holocene as a period characterized by climate stability, as portrayed in multi-proxy climate reconstructions. Instead, our simulations provide an improved representation of amplitude and timing of temperature variations on sub-centennial timescales.

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climate-debate

Hottest 12 Months for 125,000 Years Claim Lacks Any Scientific Evidence

by C. Morrison, Jan 7, 2023 in TheDailySceptic, 

Last year humanity lived through the hottest 12 months in at least 125,000 years, reported an hysterical CNN, a frame of mind replicated throughout much of the mainstream media. Scientists have compared 2023’s “climate change fallout” to a “disaster movie”, added the U.S. cable news channel. All poppycock, needless to say, with a political Net Zero motive, and little if any scientific evidence to back it up. Accurate temperature records barely started before the 20th century, and recent measurements by fixed thermometers have been heavily corrupted by growing urban heat. It is in fact possible using proxy measurements to get a good idea of general temperature movements over the last 125,000 years. All the evidence points to periods of much higher temperatures, notably between 10,000 to 5,000 years ago. The latest science paper examining this trend has just been published, and it points to summer temperatures at least 1.5°C higher around 5,000 years ago in the eastern Mediterranean, at a time when civilisation was developing rapidly.

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climate-debate

SE Asian Sea Levels Were 3-4 Meters Higher Than Today 7-4 Thousand Years Ago

by K. Richard, Dec 12, 2023 in NoTricksZone

Comprehensive data analysis shows relative sea levels were anywhere from 1 to 7 meters (~3.9 m) higher than present throughout the Mid-Holocene at 15 of 16 assessed sites across Southeast Asia.

A new study (Li et al., 2023) compiles highstand records from sites spanning Thailand, Vietnam, Singapore, Malaysia, Borneo, Sunda Shelf, Makassar Strait…and indicates that throughout southeast Asia there was a “peak RSL [relative sea level] highstand of ~3.9 ±1.1 m at ~6 ka BP or later.”

Of the 16 locations assessed, just 1 did not indicate sea levels were higher than present back when CO2 levels were alleged to be 265 ppm.

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climate-debate

Climatologist: Are We Really In An Unprecedented Time Of Warming?

by M. Wilelicki, Nov 7, 2023 in ClimateChangeDispatch

Dansgaard-Oeschger (D-O) events are one of the most striking discoveries in earth science related to past climate.

They are named after the two climatologists, Willi Dansgaard and Hans Oeschger, who were instrumental in their identification.

These events are rapid climate fluctuations that occurred frequently during the last glacial period, illustrating a planet capable of swift and dramatic temperature shifts. [emphasis, links added]

The discovery of D-O events can be traced back to the ice core drilling projects in Greenland in the late 20th century.

Analysis of the isotopic composition of ice cores, particularly the ratio of oxygen isotopes 18O and 16O, revealed evidence of abrupt climatic changes.

These isotopes served as proxies for past temperatures, with higher ratios indicating warmer periods.

The meticulous work of Dansgaard and Oeschger, along with their colleagues, in the 1980s led to the recognition that the Earth’s climate has not always changed at a steady pace but has seen dramatic swings, especially during the last glacial period around 115,000 to 11,700 years ago.

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climate-debate

Highlighting Climate Models’ Inability To Accurately Replicate Recent Climatic States

by Dr M. Wilelicki, AUG 31, 2023 in ClimateChangeDispatch

What is the Holocene Temperature Conundrum?

The Holocene Temperature Conundrum is a debate within the field of climate science regarding the patterns and variations in global temperatures during the Holocene epoch, which began around 11,700 years ago and continues to the present day.

The term refers to a discrepancy between the reconstructed global annual mean temperature and the simulated global annual mean temperature during the Holocene epoch, which spans from about 12,000 years ago to the present. [emphasis, links added]

Traditionally, reconstructions of Holocene temperatures were largely based on indirect data sources such as pollen, ice cores, lake sediments, and ocean sediment cores.

One prominent reconstruction suggested a pattern known as the Holocene Thermal Maximum (HTM) – a period between 9,000 to 5,000 years ago when temperatures were warmer than today, followed by a gradual cooling that lasted until the preindustrial era.

This cooling trend was particularly noticeable in the Northern Hemisphere and is the opposite of what would be expected from the effects of retreating ice sheets and rising greenhouse gases, which should cause global warming.

However, in the early 21st century, new reconstructions began to emerge based on a different set of proxies such as tree rings and stalagmites, which seemed to contradict the traditional view.

Instead of showing a gradual cooling over the Holocene, these reconstructions suggested that global temperatures remained relatively stable, or possibly increased slightly during this period, in agreement with the radiative forcing from ice sheets and greenhouse gases.

The contrasting interpretations of Holocene temperature patterns have sparked intense debate among scientists.

The discrepancies are thought to arise from differences in the geographical coverage of the proxies used, their seasonal biases, and other methodological differences.

Some experts suggest that the traditional view of a cooling trend might be influenced by a bias toward Northern Hemisphere summer temperatures, while others believe the newer reconstructions may underestimate past temperature variability due to various reasons such as the dampening effects of tree rings in capturing long-term trends.

This conundrum highlights the complexities involved in interpreting past climate change and the importance of refining methodologies and expanding datasets for a clearer understanding.

climate-debate

Untold Story of Climate’s Holocene Gift to Humanity

by V. Jayaraj, Jul 14, 2023 in CO2Coalition

News reports of summer heatwaves often perversely misrepresent a modern climate favorable to human flourishing in order to fearmonger the false narrative of catastrophic global warming.

The geological epoch of the Holocene, which roughly corresponds to the last 11,700 years, is a time of warmth that has been vital in fostering the diversity and adaptability of life on our planet – not a curse as popularly portrayed. The relevance of the Holocene interglacial period to humanity’s survival cannot be overstated.

The development and maintenance of life on Earth have been greatly aided by the Holocene – sometimes called the age of man.

Nearly 12 millennia back, the Holocene ended glacial stages known as the Wisconsin in North America and Weichselian in Europe, which had begun between 75,000 and 100,00 years ago. As previously ice-covered regions became accessible for colonization, plant and animal species expanded their geographical range and the Earth’s overall biodiversity.

This period saw the rise of ancient civilizations in Mesopotamia, Egypt, the Indus Valley and China, each of which made contributions to the advancement of human culture and numbers. There were a mere 170 million people on earth at the end of the first century, about half the population of the U.S. in 2023. Today the world has more than 8 billion people.

 

Continuer la lecture de Untold Story of Climate’s Holocene Gift to Humanity →

climate-debate

The Holocene CO2 Dilemma

by R. Hannon, June 2023, in WUWT

This post evaluates the relationship of global CO2 with regional temperature trends during the Holocene interglacial period. Ice core records show that CO2 is strongly coupled with local Antarctic temperature and slightly lags temperature over the past 800,000 years (Luthi, 2008). Whereas the emphasis has been on CO2 and temperature lags/leads, this study focuses on Holocene millennium trends in different latitude-bounded regions.

The Contrarian Antarctic

The Holocene is fortunate to have hundreds of proxy records analyzed by Marcott, 2013, and more recently Kaufman, 2020, to establish regional and global temperature trends. The Holocene interglacial occurs approximately during the past 11,000 years. In general, global temperature trends from proxy data show a Holocene Climatic Optimum (HCO) around 6000 to 8000 years ago and a subsequent cooling trend, the Neoglacial period, culminating in the Little Ice Age (LIA). The global mean temperature is comprised of regional trends that tend to have a concave down appearance during the Holocene shown in Figure 1a.

The exception is the Antarctic shown in red which has a concave up shape. The Antarctic reached an early Holocene Climatic Optimum between 9000 to 11000 years ago. While global and most regional temperatures were warming, Antarctic cooled to a minimum around 8000 years ago. While global and other regions show progressive cooling during the Neoglacial, the Antarctic was flat and erratic. This contrary Antarctic temperature behavior during the Holocene has also been noted by Andy May here.

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Observations

Climate change is routinely claimed to be largely controlled by greenhouse gases, especially CO2. This was concluded, in part, by the strong relationship between CO2 from Antarctic ice core bubbles and local Antarctic temperature trends. While CO2 mimics Antarctic temperatures very well, ninety percent of Earth’s surface temperature trends do not demonstrate a positive correlation to CO2 during the Holocene. Arctic and Northern Hemisphere temperatures become cooler during increasing CO2 levels. Tropical proxy temperatures don’t seem to be influenced by CO2.

Model simulated temperatures which are strongly influenced by CO2 do not accurately history match Holocene global proxy temperatures and tend to largely reflect Antarctic trends. The fact that CO2 correlates well to Holocene temperatures for only the Antarctic, or <10% of our planet’s surface, yet CO2 is considered as the dominant influence on climate change is a scientific dilemma.

Download the bibliography here.

climate-debate

Massive iceberg discharges during the last ice age had no impact on nearby Greenland, raising new questions about climate dynamics

by WUWT, Apr 24, 2023

CORVALLIS, Ore. – During the last ice age, massive icebergs periodically broke off from an ice sheet covering a large swath of North America and discharged rapidly melting ice into the North Atlantic Ocean around Greenland, triggering abrupt climate change impacts across the globe.

These sudden episodes, called Heinrich Events, occurred between 16,000 and 60,000 years ago. They altered the circulation of the world’s oceans, spurring cooling in the North Atlantic and impacting monsoon rainfall around the world.

But little was known about the events’ effect on nearby Greenland, which is thought to be very sensitive to events in the North Atlantic. A new study from Oregon State University researchers, just published in the journal Nature, provides a definitive answer.

“It turns out, nothing happened in Greenland. The temperature just stayed the same,” said the study’s lead author, Kaden Martin, a fourth-year doctoral candidate in OSU’s College of Earth, Ocean, and Atmospheric Sciences. “They had front-row seats to this action but didn’t see the show.”

Instead, the researchers found that these Heinrich events caused rapid warming in Antarctica, at the other end of the globe.

The researchers anticipated Greenland, in close proximity to the ice sheet, would have experienced some kind of cooling. To find that these Heinrich Events had no discernible impact on temperatures in Greenland is surprising and could have repercussions for scientists’ understanding of past climate dynamics, said study co-author Christo Buizert, an assistant professor in the College of Earth, Ocean, and Atmospheric Sciences.

“If anything, our findings raise more questions than answers,” said Buizert, a climate change specialist who uses ice cores from Greenland and Antarctica to reconstruct and understand the Earth’s climate history. “This really changes how we look at these massive events in the North Atlantic. It’s puzzling that far-flung Antarctica responds more strongly than nearby Greenland.”

Scientists drill and preserve ice cores to study past climate history through analysis of the dust and tiny air bubbles that have been trapped in the ice over time. Ice cores from Greenland and Antarctica provide important records of Earth’s atmospheric changes over hundreds of thousands of years.

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better to know...?, climate and geology, climate-debate

Scientists Say A 6°C Warmer-Than-Today Arctic Is ‘Optimal’ For Thermophile Species

by K. Richard, Apr 6, 2023 in NoTricksZone

Back in the Early Holocene, when CO2 levels were said to be ~255 ppm, Arctic Svalbard was warm enough to accommodate abundant numbers of thermophiles, or warmth-demanding species. Only “remnants” of these species and their habitat exist in today’s much-colder Arctic.

With the exception of a few centuries in recent millennia, today’s Svalbard (Arctic) is the most glaciated it has been in the last 10,000 years (see the blue trend line in the below chart from Brožová et al., 2023).

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This region is today about 6°C colder than it was during the early Holocene (~10,000 to 8,000 years ago), a climatic period scientists characterize as an optimum, or “most favorable,” for a “rich species pool” of thermophiles.

The sea surface temperatures (SSTs) in the western Barents Sea were as warm as 13°C and “sea ice-free during most of the mid-Holocene” (Łącka et al., 2019). In contrast, today’s SST in this region are as cold as they were during the last glacial (2-4°C), when CO2 hovered near 200 ppm. Rapid double-digit SST fluctuations, varying from 3 to 13°C, have been ongoing throughout the Holocene.

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climate-debate

New Study: Sea Levels Have Receded Over Last 1500 Years, Including Since 1800s, Along India’s Coasts

by K. Richard, April 3, 2023 in NoTricksZone

Contrary to alarmist claims, the seas have been retreating and the coasts have been expanding seaward along the coasts of southern India since the early 1800s.

Korkai was a port city, capital, and the principal trade center for India’s Pandya Kingdom from the 6th to 9th centuries CE.

While Korkai was situated on the sea coast during the early stages of the Medieval  Warm Period, the city center is now approximately 5 or 6 km from the coast. This confirms the sea has substantially receded since then.

Nautical maps from the 1805-1828 period clearly affirm the coast of southern India has continued expanding seaward in the last 200 years, despite the reported rise in relative sea level (Gupta and Bhoolokam Rajani, 2023).

In other words, much more coastal land area is above sea level today than during the Little Ice Age, or when CO2 levels were said to be 280 ppm.

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climate and geology, climate-debate

Nature Unbound I: The Glacial Cycle

by Javier, Oct 24, 2016 in ClimateEtc.

Insights into the debate on whether the Holocene will be long or short.

Summary: Milankovitch Theory on the effects of Earth’s orbital variations on insolation remains the most popular explanation for the glacial cycle since the early 1970’s. According to its defenders, the main determinant of a glacial period termination is high 65° N summer insolation, and a 100 kyr cycle in eccentricity induces a non-linear response that determines the pacing of interglacials. Based on this theory some authors propose that the current interglacial is going to be a very long one due to a favorable evolution of 65° N summer insolation. Available evidence, however, supports that the pacing of interglacials is determined by obliquity, that the 100 kyr spacing of interglacials is not real, and that the orbital configuration and thermal evolution of the Holocene does not significantly depart from the average interglacial of the past 800,000 years, so there is no orbital support for a long Holocene.

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climate-debate

New Studies Suggest Sea Levels Were 2-5 Meters Higher Than Today ~6000 Years Ago

by K. Richard, Oct 13, 2022 in NoTricksZone

From about 5000 to 7000 years ago, when Earth was several degrees warmer than it is today, there was more water locked up on land as ice. Consequently, relative sea levels were much higher and land areas now well above sea level were submerged beneath the sea.

None of these paleo indicators suggest warmth, ice melt, or relative sea level are consistent with claims CO2 is a climate driver.

1. Hapsari et al., 2022

2. Angulo et al., 2022

3. Watanabe Nara et al., 2022

4. Angulo et al., 2022

5. Angulo et al., 2022

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climate-debate

Arctic-Wide Glaciers And Ice Caps Were Absent Or Smaller Than Today From 10,000 To 3000 Years Ago By Kenneth Richard on 29. August 2022

by K. Richard, Aug 29, 2022 in NoTricksZone

A new study details how a much warmer climate than today led to the disappearance of glaciers and ice caps during the sub-300 ppm CO2 Early to Middle Holocene. The Arctic’s modern ice extent is among the largest of the last 10,000 years.

Glaciologists Larocca and Axford (2022) have synthesized a comprehensive record of Arctic-wide glaciers and ice caps (GICs) situated near lakes for Greenland, Alaska, Arctic Canada, Iceland, Scandinavia, Svalbard, and the Russian Arctic.

They compared the current volume and extent of GICs to past Holocene periods when they were either 1) smaller than present or 2) absent, with the latter characterizations signifying greater Arctic warmth.

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Contrary to the popular view that the modern glacier and ice cap extents are unprecedentedly small or on the verge of disappearing for the first time ever, the authors found more than half the Arctic’s GICs that exist today either did not exist or were smaller than today from 10,000 to 3400 years ago, when atmospheric CO2 ranged between 260 and 270 ppm.

Furthermore, most (“80% or more”) were smaller than today or absent from 7900 to 4500 years ago, which was the peak of this interglacial’s Arctic warmth – multiple degrees Celsius warmer than today.

The following images from the paper document the “Percent of GICs smaller or absent” for each region over the course of the last 10,000 years or more. Notice that between 80% to 100% of GICs were smaller than today or absent from about 8000 and 4000 years ago, and that even the Roman and Medieval Warm Periods had lower GICs extent than today.

The largest glacier and ice cap extent of the Holocene has been realized in the last millennium, suggesting any recession of GICs in the last few centuries is but a partial return to a former period of much greater warmth.

climate and geology

A Tropical Plant’s Warmth Threshold Affirms Mid-Holocene Temps Were ‘7.7°C Higher Than Today’

by K. Richard, July 25, 2022 in NoTricksZone

A warmth-demanding plant can provide us with solid evidence of a much warmer than today Mid-Holocene climate.

Growth of the tropical aquatic plant ceases when air temperatures fall below 10°C.

A new study says that from about 8000 to 5000 years ago it was warm enough in winter that could grow at the 40°N latitude in northern China. Today its warmth threshold growth limit is ~34°N.

Scientists can therefore deduce the Mid-Holocene winter temperatures needed to have been “7.7°C higher than today” at that time.

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better to know...?, climate-debate

New Study: Greenland ‘Must Have Been At Least 3°C Warmer’ Than Today During The Early Holocene

by K. Richard, Jul 4, 2022 in NoTricksZone

These much warmer Greenland temperatures imply that the elevation of the ice sheet was 400 meters lower than it is today from about 6,000 to 10,000 years ago.

Scientists (Westhoff et al., 2022) report that the two largest Greenland melt events in the last few hundred years occurred in 2012 and in 1889 CE – when atmospheric CO2 levels were still under 300 ppm.

The “melt events around the Holocene Climate Optimum were more intense and more frequent” than has been observed during the modern period. And the most prominent melt events of the last 10,000 years centered around the Medieval Warm Period, 986 CE.

Overall, the elevation of the Greenland ice sheet has grown by 0.4 km since the Early Holocene, as “summer temperatures must have been at least 3 ± 0.6°C warmer during the Early Holocene compared to today.”

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better to know...?, climate-debate

“We Live In The Coldest Period Of The Last 10.000 Years”

by P. Homewood, Jul 5, 2022 in NotaLotofPeopleKnowThat

Jørgen Peder Steffensen is an Associate Professor at the University of Copenhagen and one of the world’s leading experts on ice cores. Using ice cores from sites in Greenland, he has been able to reconstruct temperatures there for the last 10000 years. So what are his conclusions?

  • Temperatures in Greenland were about 1.5 C warmer 1000 years ago than now.

  • It was perhaps 2.5 C warmer 4000 years ago.

  • The period around 1875, at the lowest point of the Little Ice Age, marked the coldest point in the last 10,000 years.

  • Other evidence from elsewhere in the Northern Hemisphere confirms this picture.

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climate and geology

PERMAFROST AND CLIMATE CHANGE IN ICELAND

by B. Van Vliet-Lanoé & A. Gudmundsson, Feb 2020, in ResearchGate

Permafrost developed from Termination Ia (Bölling interstadial, 14.5 cal ka BP) in Northern Iceland, in answer to deglaciation. Permafrost persisted or even re-extended during the Preboreal cooling events (at 11.2, 10.3 and 9.3 cal ka BP) synchronic with pulsated glacial advances. It disappeared below 1000 masl during the Thermal Optimum (8-5 cal ka BP). The present-day re-extent was controlled with the cooling related with the Little Ice Age and particularily the Maunder solar Minimum. Continuous permafrost is stable above 1000 masl, but is today melting between 900 and 800 masl. Discontinuous permafrost is vanishing today with the recent climate warming (from 1970), especially in palsa bogs, and on valley slopes with thermokarstic mass wasting.

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climate and geology

Holocene ice-free strait followed by dynamic Neoglacial fluctuations: Hornsund, Svalbard

by A. Osaka et al., Apr 25, 2022 in TheHolocene

Keywords

Abstract

The recession of the Hornbreen-Hambergbreen glaciers (Hornsund, Svalbard) will lead to the formation of a strait between the Greenland and Barents Seas within a few decades. We provide evidence for the earlier existence of this strait, in the Early–Middle Holocene and presumably since 1.3 ka cal. BP until glacier advance 0.7 ± 0.3 ka or earlier. Radiocarbon dating of mollusc shells from the ground moraines in the Hornbreen forefield indicate the existence of the marine environment at the contemporary glacierized head of Hornsund since 10.9 ka cal. BP or earlier due to glacier retreat. The gap in the radiocarbon dates between 3.9 and 1.3 ka cal. BP and the published results of 10Be exposure dating on Treskelen suggest the strait’s closure after glacier advance in the Neoglacial. Subsequent re-opening occurred around 1.3 ka cal. BP, but according to 10Be dates from Treskelen, the strait has again been closed since ca. 0.7 ± 0.3 ka or earlier. The oldest known surge of Hornbreen occurred around 1900. Analysis of Landsat satellite images, morphometric indicators characterizing the glacier frontal zones and previous studies indicate one surge of Hambergbreen (1957–1968) and five re-advances of Hornbreen in the 20th century (after 1936, between 1958 and 1962, in 1986–1990, 1998–1999, 2011). While the warmer Holocene intervals might be a benchmark for the effects of future climate change, glacier dynamics in post-Little Ice Age climate warming seems to be an analogue of glacier retreats and re-advances in the earlier periods of the Holocene.

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climate and geology

Ancient Ice Reveals Scores of Gigantic Volcanic Eruptions

by C. Rotter, Mar 15, 2022 in WUWT/ClimPast

Magnitude, frequency and climate forcing of global volcanism during the last glacial period as seen in Greenland and Antarctic ice cores (60–9 ka)

Abstract

Large volcanic eruptions occurring in the last glacial period can be detected by their accompanying sulfuric acid deposition in continuous ice cores. Here we employ continuous sulfate and sulfur records from three Greenland and three Antarctic ice cores to estimate the emission strength, the frequency and the climatic forcing of large volcanic eruptions that occurred during the second half of the last glacial period and the early Holocene, 60–9 kyr before 2000 CE (b2k). Over most of the investigated interval the ice cores are synchronized, making it possible to distinguish large eruptions with a global sulfate distribution from eruptions detectable in one hemisphere only. Due to limited data resolution and large variability in the sulfate background signal, particularly in the Greenland glacial climate, we only list Greenland sulfate depositions larger than 20 kg km−2 and Antarctic sulfate depositions larger than 10 kg km−2. With those restrictions, we identify 1113 volcanic eruptions in Greenland and 737 eruptions in Antarctica within the 51 kyr period – for which the sulfate deposition of 85 eruptions is found at both poles (bipolar eruptions). Based on the ratio of Greenland and Antarctic sulfate deposition, we estimate the latitudinal band of the bipolar eruptions and assess their approximate climatic forcing based on established methods. A total of 25 of the identified bipolar eruptions are larger than any volcanic eruption occurring in the last 2500 years, and 69 eruptions are estimated to have larger sulfur emission strengths than the Tambora, Indonesia, eruption (1815 CE). Throughout the investigated period, the frequency of volcanic eruptions is rather constant and comparable to that of recent times. During the deglacial period (16–9 ka b2k), however, there is a notable increase in the frequency of volcanic events recorded in Greenland and an obvious increase in the fraction of very large eruptions. For Antarctica, the deglacial period cannot be distinguished from other periods. This confirms the suggestion that the isostatic unloading of the Northern Hemisphere (NH) ice sheets may be related to the enhanced NH volcanic activity. Our ice-core-based volcanic sulfate records provide the atmospheric sulfate burden and estimates of climate forcing for further research on climate impact and understanding the mechanism of the Earth system.How to cite. Lin, J., Svensson, A., Hvidberg, C. S., Lohmann, J., Kristiansen, S., Dahl-Jensen, D., Steffensen, J. P., Rasmussen, S. O., Cook, E., Kjær, H. A., Vinther, B. M., Fischer, H., Stocker, T., Sigl, M., Bigler, M., Severi, M., Traversi, R., and Mulvaney, R.: Magnitude, frequency and climate forcing of global volcanism during the last glacial period as seen in Greenland and Antarctic ice cores (60–9 ka), Clim. Past, 18, 485–506, https://doi.org/10.5194/cp-18-485-2022,

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better to know...?, climate-debate

Ancient El Niños reveal limits to future climate projections

by University of Texas at Austin, Mar 15, 2022 in ScienceDaily

The climate pattern El Niño varies over time to such a degree that scientists will have difficulty detecting signs that it is getting stronger with global warming.

That’s the conclusion of a study led by scientists at The University of Texas at Austin that analyzed 9,000 years of Earth’s history. The scientists drew on climate data contained within ancient corals and used one of the world’s most powerful supercomputers to conduct their research.

The study of the past, which was recently published in Science Advances, was motivated by the need to get a clearer picture of how climate change may affect El Niño in the future.

El Niño is the warm phase of the El Niño Southern Oscillation, a climate phenomenon that sets the stage every few years for weather patterns worldwide. Strong El Niño events, such as the ones in 1997 and 2015 that brought wildfires to the rainforests of Borneo in Asia and caused widespread bleaching to the world’s coral reefs, happened about once a decade.

Computer models, however, are unclear about whether El Niño events will become weaker or stronger as the world warms due to climate change.

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climate-debate

New Study Suggests The Early Holocene’s Baltic Sea Temperatures Were 5-11°C Warmer Than Present

by Weiss et al., 2022 in NoTricksZone

Baltic Sea surface temperatures may have reached 24°C 7,200 years ago compared to the current 12.7°C.

A new study (Weiss et al., 2022) indicates Baltic Sea regional surface temperatures ranged between 21-24°C from ~5.7 to 7.7 ka (thousand years ago). This period is referred to as the Baltic’s Holocene Thermal Maximum.

Temperatures dipped to 17.2°C at 1.373 ka. (The time span ranging from 0.0 ka to 3 ka is referred to in the study as the Modern Baltic, or M.B.)

The current (0.0 ka) surface temperature for the Baltic S is 12.7°C. This temperature is more than 11°C colder than the Baltic’s temperatures at 7.2 ka.

climate and geology

Climate Change in the Early Holocene

by University of Oxford, Jan 27, 2022 in WUWT

Radiocarbon dating from a prehistoric cemetery in Northern Russia reveals human stress caused by a global cooling event 8,200 years ago Early hunter gatherers developed more complex social systems and, unusually, a large cemetery when faced by climate

Peer-Reviewed Publication

 

16:00 (GMT), Thursday 27 January 2022

Climate change in the Early Holocene

  • Radiocarbon dating from a prehistoric cemetery in Northern Russia reveals human stress caused by a global cooling event 8,200 years ago
  • Early hunter gatherers developed more complex social systems and, unusually, a large cemetery when faced by climate change

New insight into how our early ancestors dealt with major shifts in climate is revealed in research,  published today [27 Jan] in Nature Ecology & Evolution, by an international team, led by Professor Rick Schulting from Oxford University’s School of Archaeology.

It reveals, new radiocarbon dates show the large Early Holocene cemetery of Yuzhniy Oleniy Ostrov, at Lake Onega, some 500 miles north of Moscow, previously thought to have been in use for many centuries, was, in fact, used for only one to two centuries. Moreover, this seems to be in response to a period of climate stress.

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climate-debate

Sea Levels Near B.C. Canada Were 90 Meters Higher Than Today 14,500 Years Ago

by K. Richard, Aug 23, 2021 in NoTricksZone

A new study suggests British Columbia (Canada) relative sea levels remained 10 meters higher than they are today until they fell to their present levels in the last ~1800 years. Two other new studies suggest sea levels were still 0.8 to 1 meter higher than today during the Medieval Warm Period.

After the peak of the last glacial about 20,000 years ago, relative sea levels subsequently rose from 120 meters below modern sea levels to heights of 90 meters above today’s by ~14,500 years ago in the Douglas Channel near British Columbia, Canada (Letham et al., 2021).

Sea levels proceeded to fall 75 to 80 meters over the next 3000 years, or about -2.5 meters per century (-25 mm/yr), and then they remained 10-15 m above present for the next ~9000 years.

“We determine that central Douglas Channel was ice-free following the Last Glacial Maximum by ∼14,500 BP and RSL was at least 90 m higher than today. Isostatic rebound caused RSL to fall to 21 m asl by 11,500 BP, though there may have been a glacial re-advance that would have paused RSL fall around the beginning of the Younger Dryas. RSL fell to 10–15 m asl by 10,000 BP, and continued to drop at a slower rate towards its current position, which it reached by ∼1800 years ago.”

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