For example, although the date listed for the beginning of the Ordovician period is 485 million years ago, it is actually 485.4 with an uncertainty (plus or minus) of 1.9 million years.  Polar stratospheric clouds are clouds that occur in the lower stratosphere at very low temperatures. that the Eocene hothouse world was caused by runaway global warming from released methane clathrates deep in the oceans. The Eocene spans the time from the end of the Paleocene Epoch to the beginning of the Oligocene Epoch. This continued thru the Early Eocene until aboout 49 million years ago. The remains of Titanoboa, a snake recorded as attaining up to 12.8 m (42 ft) in length, was discovered in South America along with other large reptilian megafauna.. Cooling began mid-period, and by the end of the Eocene continental interiors had begun to dry out, with forests thinning out considerably in some areas. Introduction: The Paleocene–Eocene Thermal Maximum (PETM) is one of the most intense and abrupt intervals of global warming in the geological record.It occurred around 56 million years ago, at the boundary between the Paleocene and Eocene epochs. High zircon saturation temperature (up to 800 °C) and Ti in zircon temperature (up to 980 °C) estimations suggest there is a period of thermal anomaly during ~53–49 Ma. "The early Eocene Epoch (50 million years ago) was about as warm as the Earth has been over the past 65 million years, since the extinction of the dinosaurs," Ivany says. A sharp increase in atmospheric carbon dioxide was observed with a maximum of 4000 ppm: the highest amount of atmospheric carbon dioxide detected during the Eocene.  The main hypothesis for such a radical transition was due to the continental drift and collision of the India continent with the Asia continent and the resulting formation of the Himalayas. Multiple proxies, such as oxygen isotopes and alkenones, indicate that at the Eocene–Oligocene transition, the atmospheric carbon dioxide concentration had decreased to around 750–800 ppm, approximately twice that of present levels.. Reptile fossils from this time, such as fossils of pythons and turtles, are abundant. The Eocene epoch (55.8 ± 0.2 - 33.9 ± 0.1 Ma) is a major division of the geologic timescale and the second epoch of the Paleogene period in the Cenozoic era.  It was determined that in order to maintain the lower stratospheric water vapor, methane would need to be continually released and sustained. Early results led the team to bring in Hagit Affek, assistant professor of geology and geophysics at Yale University, and Yale Ph.D. candidate Peter Douglas for collaborative study. As a result of the warmer climate and the sea level rise associated with the early Eocene, more wetlands, more forests, and more coal deposits would have been available for methane release. Drifting into the Icehouse Large ice sheets formed in Antarctica starting 34 million years ago, then, later, on Greenland —about 3 million years ago—and in North America and Northern Europe within the past million years. This warming has been linked to a similarly rapid increase in the concentration of greenhouse gases in Earths atmosphere, which acted to trap heat and drive up global temperatures by more than 5 °C in just a few thousand years. , At the end of the Middle Eocene Climatic Optimum, cooling and the carbon dioxide drawdown continued through the late Eocene and into the Eocene–Oligocene transition around 34 million years ago. Palm trees were growing as far north as Alaska and northern Europe during the early Eocene, although they became less abundant as the climate cooled.  Sources for this large influx of carbon dioxide could be attributed to volcanic out-gassing due to North Atlantic rifting or oxidation of methane stored in large reservoirs deposited from the PETM event in the sea floor or wetland environments. The model runs concluded that while the lake did reduce the seasonality of the region greater than just an increase in carbon dioxide, the addition of a large lake was unable to reduce the seasonality to the levels shown by the floral and faunal data. Marking the start of the Eocene, the planet heated up in one of the most rapid (in geologic terms) and extreme global warming events recorded in geologic history, called the Paleocene-Eocene Thermal Maximum or Initial Eocene Thermal Maximum (PETM or IETM). The time is divided into 4 stages. The research team is currently using the same analytical process to determine Eocene Epoch mean annual and seasonal temperatures in polar-regions. The specimen dates to the early Eocene period and is expected to fetch between £8000 and £12000 at auction. DOI: 10.1098/rsbl.2020.0735 "The agreement among different methods gives us confidence in the results and enables us to use these methods in other locations, such as Antarctica. Tropical rainforests grew as far north as northern North America and Europe. Any ice growth was slowed immensely and would lead to any present ice melting. Until now, temperature data for subtropical regions were limited. The SU and Yale research team found that average Eocene water temperature along the subtropical U.S. Gulf Coast hovered around 27 degrees centigrade (80 degrees Fahrenheit), slightly cooler than earlier studies predicted. The Eocene is usually broken into lower and upper subdivisions. The cooling also brought seasonal changes.  The creation of the Antarctic circumpolar current would isolate the cold water around the Antarctic, which would reduce heat transport to the Antarctic along with creating ocean gyres that result in the upwelling of colder bottom waters. Early forms of many other modern mammalian orders appeared, including bats, proboscidians (elephants), primates, rodents, and marsupials. By the end of the period, deciduous forests covered large parts of the northern continents, including North America, Eurasia and the Arctic, and rainforests held on only in equatorial South America, Africa, India and Australia. As seen by proxy evidence and model simulations, this warming was widespread across the globe. Fields were spreading across the middles of the continents and they were being filled up by large grazing mammals. Another requirement for polar stratospheric clouds is cold temperatures to ensure condensation and cloud production. An isolated cold water channel developed between the two continents. , The end of the Eocene was marked by the Eocene–Oligocene extinction event, also known as the Grande Coupure. If we compare the early Eocene production of methane to current levels of atmospheric methane, the early Eocene would have produced triple the amount of methane.  The increase in atmospheric carbon dioxide is considered to be due to increased seafloor spreading rates between Australia and Antarctica and increased amounts of volcanism in the region. The question seems simple enough: What happens to the Earth’s temperature when atmospheric carbon dioxide levels increase? The start of the Eocene is marked by a brief period in which the concentration of the carbon isotope 13C in the atmosphere was exceptionally low in comparison with the more common isotope 12C. The name “Paleocene” comes from Greek and refers to the “old(er)” (παλαιός, palaios) “new” (καινός, kainos) fauna that arose during the epoch. The breakdown of methane in an atmosphere containing oxygen produces carbon monoxide, water vapor and infrared radiation. The Paleogene is made up of three epochs: The Paleocene Epoch; The Eocene Epoch; The Oligocene Epoch; Each epoch has unique characteristics for climate, geography, plants and animals. Scottish geologist Charles Lyell (ignoring the Quaternary) had divided the Tertiary epoch into the Eocene, Miocene, Pliocene, and New Pliocene (Holocene) periods in 1833. A multitude of feedbacks also occurred in the models due to the polar stratospheric clouds' presence. Mammals became the dominant land animals during this epoch. Another method considered for producing the warm polar temperatures were polar stratospheric clouds. of a geologic epoch within the Paleogene period from about 56 to 34 million years ago. The sediments that accumulated there contain one of the richest and best-preserved fossil records in the country. Dawn redwoods were far more extensive as well. 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