Archives par mot-clé : Geology

Plate tectonics may have driven ‘Cambrian Explosion’

by University of Exeter, June 19, 2019 in ScienceDaily/from Nature


A team of scientists have given a fresh insight into what may have driven the “Cambrian Explosion” — a period of rapid expansion of different forms of animal life that occurred over 500 million years ago.

While a number of theories have been put forward to explain this landmark period, the most credible is that it was fuelled by a significant rise in oxygen levels which allowed a wide variety of animals to thrive.

The new study suggests that such a rise in oxygen levels was the result of extraordinary changes in global plate tectonics.

During the formation of the supercontinent ‘Gondwana’, there was a major increase in continental arc volcanism — chains of volcanoes often thousands of miles long formed where continental and oceanic tectonic plates collided. This in turn led to increased ‘degassing’ of CO2 from ancient, subducted sedimentary rocks.

This, the team calculated, led to an increase in atmospheric CO2and warming of the planet, which in turn amplified the weathering of continental rocks, which supplied the nutrient phosphorus to the ocean to drive photosynthesis and oxygen production.

In hot pursuit of dinosaurs: Tracking extinct species on ancient Earth via biogeograph

by Charles the moderator, May 31, 2019 in WUWT


University of Tokyo

One researcher at the University of Tokyo is in hot pursuit of dinosaurs, tracking extinct species around ancient Earth. Identifying the movements of extinct species from millions of years ago can provide insights into ancient migration routes, interaction between species, and the movement of continents.

“If we find fossils on different continents from closely related species, then we can guess that at some point there must have been a connection between those continents,” said Tai Kubo, Ph.D., a postdoctoral researcher affiliated with the University Museum at the University of Tokyo.

A map of life – biogeography

Previous studies in biogeography — the geographic distribution of plants and animals — had not considered the evolutionary relationships between ancient species. The new method that Kubo designed, called biogeographical network analysis, converts evolutionary relationships into geographical relationships.

By combining data from fossils and models of the ancient Earth, researchers can map where ancient species may have migrated. This method, called biogeographical network analysis, converts evolutionary relationships between species into geographical relationships. This method was used in research by Tai Kubo, Ph.D., a postdoctoral researcher affiliated with the University Museum at the University of Tokyo. Credit Caitlin Devor, The University of Tokyo, CC-BY Usage Restrictions Image by Caitlin Devor, The University of Tokyo, CC-BY

Tertiary hyperthermal events: precursors of the current situation?

by A. Jacobs & A. Préat, May 20, 2019 in SSRN.Elsevier


The focus of this study is based on a detailed analysis of the hyperthermal events of the

Paleocene / Eocene limit of 56 Ma and the lower Eocene (for the 54-52 Ma interval, Figure 1).

This example will show that the Earth has experienced many times much higher temperatures

than today, with warmer, sometimes more acidic oceans and an atmosphere much richer in CO2

(or CH4) than the current one. Are these past events precursors of the current situation?

Keywords: global warming, climate change, Paleocene, Eocene, hyperthermal events

The Relationship between Atmospheric Carbon Dioxide Concentration and Global Temperature for the Last 425 Million Years

by William J. Davis, September 2017, in ResearchGate


Assessing human impacts on climate and biodiversity requires an understanding of the relationship between the concentration of carbon dioxide (CO2) in the Earth’s atmosphere and global temperature (T). Here I explore this relationship empirically using comprehensive, recently-compiled databases of stable-isotope proxies from the Phanerozoic Eon (~540 to 0 years before the present) and through complementary modeling using the atmospheric absorption/transmittance code MODTRAN. Atmospheric CO2 concentration is correlated weakly but negatively with linearly-detrended T proxies over the last 425 million years.

New evidence suggests volcanoes caused biggest mass extinction ever

by University of Cincinnati, April 15, 2019 in ScienceDaily from Nature


Mercury found in ancient rock around the world supports theory that eruptions caused ‘Great Dying’ 252 million years ago.

Researchers say mercury buried in ancient rock provides the strongest evidence yet that volcanoes caused the biggest mass extinction in the history of the Earth.

The extinction 252 million years ago was so dramatic and widespread that scientists call it “the Great Dying.” The catastrophe killed off more than 95 percent of life on Earth over the course of hundreds of thousands of years.

Paleontologists with the University of Cincinnati and the China University of Geosciences said they found a spike in mercury in the geologic record at nearly a dozen sites around the world, which provides persuasive evidence that volcanic eruptions were to blame for this global cataclysm.

The study was published this month in the journal Nature Communications.

The eruptions ignited vast deposits of coal, releasing mercury vapor high into the atmosphere. Eventually, it rained down into the marine sediment around the planet, creating an elemental signature of a catastrophe that would herald the age of dinosaurs.

“Volcanic activities, including emissions of volcanic gases and combustion of organic matter, released abundant mercury to the surface of the Earth,” said lead author Jun Shen, an associate professor at the China University of Geosciences.

If CO2 Caused Mid-Pliocene Warming, What Caused late-Pliocene Cooling? You Guessed!

by P. Homewood, April 7, 2019 in NotaLotofPeopleKnowThat


ABSTRACT

It is thought that the Northern Hemisphere experienced only ephemeral glaciations from the Late Eocene to the Early Pliocene epochs (about 38 to 4 million years ago), and that the onset of extensive glaciations did not occur until about 3 million years ago. Several hypotheses have been proposed to explain this increase in Northern Hemisphere glaciation during the Late Pliocene. Here we use a fully coupled atmosphere-ocean general circulation model and an ice-sheet model to assess the impact of the proposed driving mechanisms for glaciation and the influence of orbital variations on the development of the Greenland ice sheet in particular. We find that Greenland glaciation is mainly controlled by a decrease in atmospheric carbon dioxide during the Late Pliocene. By contrast, our model results suggest that climatic shifts associated with the tectonically driven closure of the Panama seaway, with the termination of a permanent El Niño state or with tectonic uplift are not large enough to contribute significantly to the growth of the Greenland ice sheet; moreover, we find that none of these processes acted as a priming mechanism for glacial inception triggered by variations in the Earth’s orbit.

https://www.researchgate.net/publication/23222627_Late_Pliocene_Greenland_glaciation_controlled_by_a_decline_in_atmospheric_CO2_levels

 

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Weird science: Tectonics in the tropics trigger Earth’s ice ages, study finds

by Anthony Watts, March 15, 2019 in WUWT


Over the last 540 million years, the Earth has weathered three major ice ages — periods during which global temperatures plummeted, producing extensive ice sheets and glaciers that have stretched beyond the polar caps.

Now scientists at MIT, the University of California at Santa Barbara, and the University of California at Berkeley have identified the likely trigger for these ice ages.

In a study published in Science, the team reports that each of the last three major ice ages were preceded by tropical “arc-continent collisions” — tectonic pileups that occurred near the Earth’s equator, in which oceanic plates rode up over continental plates, exposing tens of thousands of kilometers of oceanic rock to a tropical environment.

The scientists say that the heat and humidity of the tropics likely triggered a chemical reaction between the rocks and the atmosphere. Specifically, the rocks’ calcium and magnesium reacted with atmospheric carbon dioxide, pulling the gas out of the atmosphere and permanently sequestering it in the form of carbonates such as limestone.

Over time, the researchers say, this weathering process, occurring over millions of square kilometers, could pull enough carbon dioxide out of the atmosphere to cool temperatures globally and ultimately set off an ice age.

Major cosmic impact 12,800 years ago

by James Kennett et al., March 13, 2019 in CO2Coalition


When UC Santa Barbara geology professor emeritus James Kennett and colleagues set out years ago to examine signs of a major cosmic impact that occurred toward the end of the Pleistocene epoch, little did they know just how far-reaching the projected climatic effect would be.

“It’s much more extreme than I ever thought when I started this work,” Kennett noted. “The more work that has been done, the more extreme it seems.”

He’s talking about the Younger Dryas Impact Hypothesis, which postulates that a fragmented comet slammed into the Earth close to 12,800 years ago, causing rapid climatic changes, megafaunal extinctions, sudden human population decrease and cultural shifts and widespread wildfires (biomass burning). The hypothesis suggests a possible triggering mechanism for the abrupt changes in climate at that time, in particular a rapid cooling in the Northern Hemisphere, called the Younger Dryas, amid a general global trend of natural warming and ice sheet melting evidenced by changes in the fossil and sediment record.

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

by K. Richard, March 11, 2019 in NoTricksZone


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

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

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

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

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

New Paper: PETM Was Caused by Climate Change… Ancient Climate Change Caused Climate Change… AEUHHH????

by David Middleton, January 23, 2019 in WUWT


Note how the PETM (55 Ma) is about as far from a CO2 analog to modern times as it possibly could be… unless the PETM stomata data are correct, in which case AGW is even more insignificant than previously thought.

Regarding temperatures, the PETM is also about as far from being an analog to modern times as it possibly could be.

 

Figure 2.  High latitude SST (°C) From benthic foram δ18O.  Funny how the PETM is often cited as a nightmarish version of a real-world RCP8.5… While the warmer EECO is a climatic optimum. (Zachos et al., 2001). Note: Older is to the right.

 

 

 

Fake Science: “The Anthropocene Is Coming to Mars”… From Where?

by David Middleton, January 18, 2019 in WUWT


“The Anthropocene as a geological epoch is not formally recognized”… So… “The term Anthropocene has” NOT “been widely used for the current period in Earth’s geological history“.  It may be frequently used by activists and scientists who are ignorant of basic geology, but geologically speaking the term “Anthropocene” does not exist in any relationship to any period, epoch, age, era or eon in Earth’s geological history.

..

Yes, we have no Anthropocene, we have no Anthropocene today… Sung to the tune of Yes, We Have No Bananas.

Bacterial origin of the red pigmentation of Phanerozoic carbonate rocks: an integrated study of geology-biology-chemistry

by A. Préat et  al., December 2018 in GeologicaBelgica (with .pdf)


Abstract

Explaining the color of rocks is still a complex problem. This question was raised long ago in the community of geologists, particularly for the pigmentation of the ‘red marbles’ of the Frasnian of Belgium at the beginning of the last century, with many unsatisfactory hypotheses. Our recent analysis of different red carbonate rocks in Europe and North Africa (Morocco) may provide an alternative explanation for the color of these rocks. For this it was necessary to bring together diverse and complementary skills involving geologists, microbiologists and chemists. We present here a synthesis of these works. It is suggested that the red pigmentation of our studied Phanerozoic carbonate rocks, encompassing a time range from Pragian to Oxfordian, may be related to the activity of iron bacteria living in microaerophilic environments. A major conclusion is that this red color is only related to particular microenvironments and has no paleogeographic or climatic significance. All red carbonates have not necessarily acquired their pigmentation through the process established in this review. Each geological series must be analyzed in the light of a possible contribution of iron bacteria and Fungi.

Une question des plus simples en géologie : la couleur des roches ?

by Alain Préat, 21 décembre 2018 in ScienceClimatEnergie


pdf in ENGLISH

 

 Introduction

Cet article est le résultat d’une recherche multi-disciplinaire entre géologues et biologistes. Une synthèse de cette recherche vient d’être publiée en décembre 2018 sur le site de Geologica BelgicaUn article déjà publié dans SCE peut également être consulté.

Contrairement à ce que l’on peut penser, une question simple nécessite parfois des années de recherches avec des équipes diverses et des moyens sophistiqués. La question simple concerne ici la géologie et plus particulièrement la couleur des roches sédimentaires.

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Molecular fossils from phytoplankton reveal secular Pco2 trend over the Phanerozoic

by C.R. Witkowski et al., November28,  2018 in SciAdvances


Here, we reconstructed Phanerozoic PCO2 from a single proxy: the stable carbon isotopic fractionation associated with photosynthesis (Ɛp) that increases as PCO2 increases. This concept has been widely applied to alkenones, but here, we expand this concept both spatially and temporally by applying it to all marine phytoplankton via a diagenetic product of chlorophyll, phytane. We obtained data from 306 marine sediments and oils, which showed that Ɛp ranges from 11 to 24‰, agreeing with the observed range of maximum fractionation of Rubisco (i.e., 25 to 28‰). The observed secular PCO2 trend derived from phytane-based Ɛp mirrors the available compilations of PCO2over the past 420 Ma, except for two periods in which our higher estimates agree with the warm climate during those time periods. Our record currently provides the longest secular trend in PCO2 based on a single marine proxy, covering the past 500 Ma of Earth history

Fig. 2Ɛp calculated from phytane in Witkowski et al., 2018

See also here

Climate, life and the movement of continents: New connections

by University of Texas at Austin, November 15, 2018 in ScienceDaily


A new study by The University of Texas at Austin has demonstrated a possible link between life on Earth and the movement of continents. The findings show that sediment, which is often composed of pieces of dead organisms, could play a key role in determining the speed of continental drift. In addition to challenging existing ideas about how plates interact, the findings are important because they describe potential feedback mechanisms between tectonic movement, climate and life on Earth.

The study, published Nov. 15 in Earth and Planetary Science Letters, describes how sediment moving under or subducting beneath tectonic plates could regulate the movement of the plates and may even play a role in the rapid rise of mountain ranges and growth of continental crust


 

Paleoclimatological Context and Reference Level of the 2°C and 1.5°C Paris Agreement Long-Term Temperature Limits

by S. Lüning & F. Vahrenholt, December12, 2017 in FrontEarthSci


The Paris Agreement adopted in December 2015 during the COP21 conference stipulates that the increase in the global average temperature is to be kept well below 2°C above “pre-industrial levels” and that efforts are pursued to limit the temperature increase to 1.5°C above “pre-industrial levels.” In order to further increase public acceptance of these limits it is important to transparently place the target levels and their baselines in a paleoclimatic context of the past 150,000 years (Last Interglacial, LIG) and in particular of the last 10,000 years (Holocene; Present Interglacial, PIG). Intense paleoclimatological research of the past decade has firmed up that pre-industrial temperatures have been highly variable which needs to be reflected in the pre-industrial climate baseline definitions …

See also here

500 Million Years of Unrelatedness between Atmospheric CO2 and Temperature

by Davis W.J., 2017 in CO2Science


Davis, W.J. 2017. The relationship between atmospheric carbon dioxide concentration and global temperature for the last 425 million years. Climate 5: 76; doi: 10.3390/cli5040076.

Writing by way of introduction to his work, Davis (2017) notes that “a central question for contemporary climate policy is how much of the observed global warming is attributable to the accumulation of atmospheric CO2 and other trace greenhouse gases emitted by human activities.” If you talk to a climate alarmist, the answer you receive from such an inquiry will likely be “almost all.” A climate skeptic, on the other hand, will likely respond that the answer is “likely none.”

Hoping to provide some crucial information on this topic, Davis analyzed the relationship between historic temperature and atmospheric CO2 using the most comprehensive assemblage of empirical databases of these two variables available for the Phanerozoic period (522 to 0 million years before present; Mybp). In all, 6680 proxy temperature and 831 proxy CO2 measurements were utilized, enabling what Davis described as “the most accurate quantitative empirical evaluation to date of the relationship between atmospheric CO2concentration and temperature.” Multiple statistical procedures and analyses were applied to the proxy records and the resultant relationship is depicted in the figure below.

Egalement voir ici

Geologists: No Link Between Climate Warming And Rock Slides in European Alps!

by P. Gosselin, September 23, 2018 in NoTricksZone


Last year, August, 2017, a massive rockslide occurred on the north flank of the Piz Cengalo (3369 m) in the Swiss Alps, above the village of Bondo, located near the border to Italy.

No data suggesting warming is behind rock slides

In total some 4 million tonnes of rock and mud came tumbling down. The dramatic incident highlighted the hazards posed by rock slides for villages located near the picturesque mountains of the European Alps.

Though rockslides are not unusual, there has been growing scrutiny behind their causes lately. Unsurprisingly climate alarmists are opportunistically pointing the finger at climate warming.

 

 

A Geological Feud Over the Meghalayan? Or Just More Rubbish Published by the American Association for the Advancement of Science of America?

by David Middleton, September 24, 2018 in WUWT


Alternate Title: Yes, We Have No Anthropocene, We Have No Anthropocene Today! (Sung to the tune of Yes, We Have No Bananas)

 

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

500 Million Years of Unrelatedness between Atmospheric CO2 and Temperature

by Davis W.J., 2017 in Climate/CO2Science


One final gem from Davis’ work is a pronouncement that follows a discussion on the lack of correlation between CO2 and temperature across the historical record, where he aptly reminds us that “correlation does not imply causality, but the absence of correlation proves conclusively the absence of causality.” Consequently, there should be no more doubt regarding the ineffectiveness of atmospheric CO2 to control or drive climate change. It is simply nothing more than a bit player, whose influence has been continually overestimated by climate alarmists. The big question now is whether or not 500 million years of these data will convince them otherwise!

from Davis 2017

Egalement: Le changement climatique : la règle en géologie

Highlights From the 2018 BP Statistical Review of World Energy

by David Middleton, September 12, 2018 in WUWT


Statistical Review of World Energy

Global primary energy consumption grew strongly in 2017, led by natural gas and renewables, with coal’s share of the energy mix continuing to decline

Energy developments

  • Primary energy consumption growth averaged 2.2% in 2017, up from 1.2 % last year and the fastest since 2013. This compares with the 10-year average of 1.7% per year.
  • By fuel, natural gas accounted for the largest increment in energy consumption, followed by renewables and then oil.
  • Energy consumption rose by 3.1% in China. China was the largest growth market for energy for the 17th consecutive year.

Carbon emissions

  • Carbon emissions increased by 1.6%, after little or no growth for the three years from 2014 to 2016.

[…]

BP

Despite the Never-Ending Death of Coal: It’s Still a Fossil Fueled World

Out with the Anthropocene – in with the Meghalayan

by Anthony Watts, September 11, 2018 in WUWT


WUWT readers may recall that climate activists wanted the current epoch we live in to be named the “Anthropocene”, because they believe humans are the dominate force on the planet. The official organization that decides such things, The International Commission on Stratigraphy, would have none of it, and nixed the naming recently. Now, here’s a summary of the the Meghalayan.


Welcome to the new Meghalayan age – here’s how it fits with the rest of Earth’s geologic history

Steve Petsch

Associate Professor of Geosciences, University of Massachusetts Amherst

Jurassic, Pleistocene, Precambrian. The named times in Earth’s history might inspire mental images of dinosaurs, trilobites or other enigmatic animals unlike anything in our modern world.

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10 New Reconstructions Show Today’s Temperatures Still Among The Coldest Of The Last 10,000 Years

by K. Richard, September 10, 2018 in NoTricksZone


Even though CO2 concentrations hovered well below 300 ppm throughout most of the Holocene, newly published paleoclimate reconstructions affirm that today’s surface temperatures are only slightly warmer (if at all) than the coldest periods of the last 10,000 years.  This contradicts the perspective that temperatures rise in concert with CO2 concentrations.

 

Bottom Graph Source: Rosenthal et al. (2013)

Climatariat News Network: Interior Secretary Ryan Zinke isn’t a geologist because climate change.

by D. Middelton, September 8, 2018 in WUWT


Guest CNN-bashing by David Middleton (a geologist)

ran across this April 2018 article while looking for something else.  I totally missed this episode of Trump Derangement Syndrome.

Secretary Zinke’s stance on climate change is one of several reasons the Climatariat News Network decided that he was being dishonest in describing himself as a geologist…

A Second Letter to the Geological Society

by Andy May, August 29, 2018 in WUWT


In June of this year, Howard Dewhirst, a fellow of The Geological Society (London), wrote a letter to the President of the Society voicing the concern of 33 current and former fellows of the society, as well as other concerned geoscientists, that the Society’s position on climate change is outdated and one-sided. As of this writing, receipt of the letter has been acknowledged, but no reply has been received. Given the long period of time, Howard has sent a second letter to the Society, it is reproduced below.

Dear President

We understand that the council is reviewing the The Geological Society’s 2010 and 2013 position papers on climate change which was the subject of the letter we wrote to the society in early June. We also understand that despite the clear interest amongst Fellows – and other scientists, that the society will not be publishing further letters until the new position paper has been agreed. If true, we (the contributors to the first letter) think this is unfortunate, as now would be the very time to solicit informed opinion from Fellows and others as there clearly is not a consensus. …