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Early Climate

Who deforested Central Africa: Humans or climate?

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Excavations in Cameroon. (Credit: © IRD / R. Oslisly)

Jan. 7, 2013 — It is a much debated question: why did Central African forests become partially fragmented between 2,500 and 2,000 years ago, leaving room for more open forest landscapes and savannah? Recently, a publication attempted to explain that it was the farming Bantu peoples who were responsible for this, through the large-scale clearing that they undertook. But several IRD experts and their partners (1) contest this argument in Science magazine. The fragmentation of the Central African forest was the result of drastic climate change. In fact, during this period a phase of general desiccation spread from the equatorial region right to the edges of the Sahel. Numerous...

Coral records suggest El Nino activity rises above background

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Georgia Tech researchers use a hydraulic drill to remove cores from a large fossil coral “rock” on a beach on Fanning Island in the central Pacific. In the laboratory, the cores provide information about the temperature and rainfall changes associated with past El Nino activity. (Credit: Georgia Tech Photo: Jordan Watson)

Jan. 3, 2013 — By examining a set of fossil corals that are as much as 7,000 years old, scientists have dramatically expanded the amount of information available...

Ups and downs of biodiversity after mass extinction

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The climate after the largest mass extinction so far 252 million years ago was cool, later very warm and then cool again. Thanks to the cooler temperatures, the diversity of marine fauna ballooned, as paleontologists from the University of Zurich have reconstructed. The warmer climate, coupled with a high CO2 level in the atmosphere, initially gave rise to new, short-lived species. In the longer term, however, this climate change had an adverse effect on biodiversity and caused species to...

New approach allows past data to be used to improve future climate projections

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Detail of an ice core from 2668 meters depth. (Credit: Dr. Sepp Kipfstuhl, Alfred Wegener Institute)

Climate scientists are still grappling with one of the main questions of modern times: how high will global temperatures rise if the atmospheric concentration of carbon dioxide doubles. Many researchers are now turning to the past because it holds clues to how nature reacted to climate change before the anthropogenic impact. The divergent results of this research, however, have made it...

Carbon buried in the soil rises again

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A research team that includes a University of California, Davis, plant scientist has identified a source of carbon emissions that could play a role in understanding past and future global change.

 

While earlier studies have found that erosion can bury carbon in the soil, acting as a carbon sink, or storage, the new study published this week in the journal Proceedings of the National Academy of Sciences found that part of that sink is only temporary.

"It's all part of...

Climate modeler identifies trigger for Earth's last big freeze

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For more than 30 years, climate scientists have debated whether flood waters from melting of the enormous Laurentide Ice Sheet, which ushered in the last major cold episode on Earth about 12,900 years ago, flowed northwest into the Arctic first, or east via the Gulf of St. Lawrence, to weaken ocean thermohaline circulation and have a frigid effect on global climate.

 

Now University of Massachusetts Amherst geoscientist Alan Condron, with Peter Winsor at the University of...

After long-ago mass extinction, global warming hindered species' recovery

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Researchers have discovered why plants and animals had a hard time recovering from the largest mass extinction in Earth's history 250 million years ago. The reason: global warming.

Because of environmental consequences of rising temperatures, those species that survived the extinction didn't fully recover for 5 million years.

The study adds a new chapter to the story of how life was forever altered by giant volcanic eruptions in the Early Triassic period -- an event now called the...

Did the changing climate shrink Europe's ancient hippos?

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Giant German hippopotamuses wallowing on the banks of the Elbe are not a common sight. Yet 1.8 million years ago hippos were a prominent part of European wildlife, when mega-fauna such as woolly mammoths and giant cave bears bestrode the continent. Now palaeontologists writing in Boreas, believe that the changing climate during the Pleistocene Era may have forced Europe's hippos to shrink to pygmy sizes before driving them to warmer climes.

"Species of hippo ranged across pre-historic...

A sharper look into the past for archaeology and climate research

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Drilling work to retreive a varve core from Lake Suigetsu, Japan. (Credit: © Achim Brauer / GFZ)

By using a new series of measurements of radiocarbon dates on seasonally laminated sediments from Lake Suigetsu in Japan, a more precise calibration of radiocarbon dating will be possible. In combination with an accurate count of the seasonal layered deposits in the lake, the study resulted in an unprecedented precision of the known 14C method with which it is now possible to date older...

Tropical collapse in Early Triassic caused by lethal heat: Extreme temperatures blamed for 'Dead Zone'

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A paleogeographic reconstruction of the Early Triassic world (Smithian substage) around 252-247 million years ago, showing a ‘dead zone’ in the tropics. Marine reptiles (ichthyosaurs), terrestrial tetrapods and fish almost exclusively occurred in higher latitudes (>30 °N and >40 °S) with rare exceptions. (Credit: Yadong Sun, University of Leeds)

Scientists have discovered why the 'broken world' following the worst extinction of all time lasted so long -- it was simply too...

Ice age polarity reversal was global event: Extremely brief reversal of geomagnetic field, climate variability, and super volcano

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Some 41,000 years ago, a complete and rapid reversal of the geomagnetic field occured. Magnetic studies of the GFZ German Research Centre for Geosciences on sediment cores from the Black Sea show that during this period, during the last ice age, a compass at the Black Sea would have pointed to the south instead of north.

 

Moreover, data obtained by the research team formed around GFZ researchers Dr. Norbert Nowaczyk and Prof. Helge Arz, together with additional data from...

Climate change: Circulation of Atlantic Ocean was faster during last Ice Age than today

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Simplified concept of the Ocean Circulation: Warm and saline surface waters (red) transport heat from the Southern Hemisphere to the North Atlantic. Due to cooling these waters gain in density, sink into the deeper Ocean and flow back southward (blue). In a slow diffusive process the deep waters upwell again in the Indian and the Pacific Ocean closing the circle of the wind, salt and heat driven "global conveyor belt". The new study concludes that during the Last Glacial the strength...

Clam shells yield clues to Atlantic’s climate history

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 Two Iowa State University graduate students are just back from the Gulf of Maine with another big catch of clam shells.

 

Shelly Griffin and Madelyn Mette recently boarded a lobster boat, dropped a scallop dredge into 30 meters of ocean water and pulled up load after load of Arctica islandica.

“These are the clams that end up in clam chowder,” said Alan Wanamaker, an assistant professor of geological and atmospheric sciences in the College of Liberal Arts and...

Prehistoric rocks contain clues for future climate

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For most of the past decade, Dr. Wan Yang has spent his summers in the Bogda Mountains in northwest China, collecting rock samples that predate dinosaurs by millions of years in an effort to better understand the history of Earth's climate and perhaps gain clues about future climate change.

"The formation of rocks has everything to do with climate," says the associate professor of geological sciences and engineering at Missouri University of Science and Technology. "Different climate...

Nunavut's mysterious ancient life could return by 2100 as Arctic warms

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View from the study site at the beginning of the fieldwork in the end of June 2010. (Credit: Alexandre Guertin-Pasquier)

Global climate change means that recently discovered ancient forests in Canada's extreme north could one day return, according to Alexandre Guertin-Pasquier of the University of Montreal's Department of Geography, who is presenting his findings at the Canadian Paleontology Conference in Toronto today.

"According to the data model, climate conditions on Bylot...

Dinosaur die out might have been second of two closely timed extinctions

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 The most-studied mass extinction in Earth history happened 65 million years ago and is widely thought to have wiped out the dinosaurs. New University of Washington research indicates that a separate extinction came shortly before that, triggered by volcanic eruptions that warmed the planet and killed life on the ocean floor.

The well-known second event is believed to have been triggered by an asteroid at least 6 miles in diameter slamming into Mexico's Yucatán Peninsula. But...

Drastic desertification: Researchers study Dead Sea climate past, finding dramatic results

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— Over the past 10,000 years, climate changes in the Dead Sea region have led to surprisingly swift desertification within mere decades. This is what researchers from the University of Bonn and their Israeli colleagues found when analyzing pollen in sediments and fluctuations in sea levels, calling the findings 'dramatic.'

The results are presented in the current issue of the international geosciences journal Quaternary Science Reviews, whose print version is published Aug. 23...

1.5 million years of climate history revealed after scientists solve mystery of the deep

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A new study has successfully reconstructed temperature from the deep sea to reveal how global ice volume has varied over the glacial-interglacial cycles of the past 1.5 million years.

Scientists have announced a major breakthrough in understanding Earth's climate machine by reconstructing highly accurate records of changes in ice volume and deep-ocean temperatures over the last 1.5 million years.

The study, which is reported in the journal Science, offers new insights into a...

Tropical climate in the Antarctic: Palm trees once thrived on today’s icy coasts 52 million years ago

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1000pa (Aug. 1, 2012) — Given the predicted rise in global temperatures in the coming decades, climate scientists are particularly interested in warm periods that occurred in the geological past. Knowledge of past episodes of global warmth can be used to better understand the relationship between climate change, variations in atmospheric carbon dioxide and the reaction of Earth’s biosphere. An international team led by scientists from the Goethe University and the Biodiversity and...

Atmospheric CO2 drove climate change during longest interglacial

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1000pa (July 31, 2012) — Known as the marine isotope stage 11 (MIS 11), the interglacial period centered around 400,000 years ago was the longest and possibly the warmest interglacial in the past 0.5 million years. Because the orbital configurations, atmospheric greenhouse gas concentrations, climate, and faunal characteristics during MIS 11 closely resemble those of the past 5,000 years, paleoclimatologists use MIS 11 as a geological analogue of the present and the near...

Cooling, not population loss, led to fewer fires after 1500 in New World

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1000pa (July 29, 2012) — In the years after Columbus' voyage, burning of New World forests and fields diminished significantly -- a phenomenon some have attributed to decimation of native populations by European diseases. But a new University of Utah-led study suggests global cooling resulted in fewer fires because both preceded Columbus in many regions worldwide.

"The drop in fire [after about A.D. 1500] has been linked previously to the population collapse. We're saying no...

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Book review

Dinosaurs Encyclopedia

Book Review

Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages ... WRITTEN BY A PROFESSIONAL paleontologist specifically for young readers, this guide to the Dinosauria is packed...