Epoch: Ordovician
Mean CO2 Concentration: 4200 parts per million (10.5 times that of today) Mean Surface Temperature: 16 °C (2 degrees above current) How long ago?: 480 to 420 million years ago Climate: The Ordovician saw the highest sea levels of the Paleozoic, and the low relief of the continents led to many shelf deposits being formed under hundreds of meters of water. Sea level rose more or less continuously throughout the Early Ordovician, leveling off somewhat during the middle of the period. Locally, some regressions occurred, but sea level rise continued in the beginning of the Late Ordovician. A change was soon on the cards, however, and sea levels fell steadily in accord with the cooling temperatures for the ~30 million years leading up to the Hirnantian glaciation. Within this icy stage, sea level seems to have risen and dropped somewhat, but despite much study the details remain unresolved. At the beginning of the period, around 480 million years ago, the climate was very hot due to high levels of CO2, which gave a strong greenhouse effect. The marine waters are assumed to have been around 45°C, which restricted the diversification of complex multi-cellular organisms. But over time, the climate become cooler, and around 460 million years ago, the ocean temperatures became comparable to those of present day equatorial waters. As with North America and Europe, Gondwana was largely covered with shallow seas during the Ordovician. Shallow clear waters over continental shelves encouraged the growth of organisms that deposit calcium carbonates in their shells and hard parts. The Panthalassic Ocean covered much of the northern hemisphere, and other minor oceans included Proto-Tethys, Paleo-Tethys, Khanty Ocean, which was closed off by the Late Ordovician, Iapetus Ocean, and the new Rheic Ocean. As the Ordovician progressed, we see evidence of glaciers on the land we now know as Africa and South America. At the time these land masses were sitting at the South Pole, and covered by ice caps. Comments: The climate cooled into an Ice Age despite CO2 concentration averaging 4,200 parts per million for the entire period. Epoch: Carboniferous Mean CO2 Concentration: 800 parts per million (twice that of today) Mean Surface Temperature: 14 °C (same as modern global temperature) How long ago?: 360 to 330 million years ago Climate: The early part of the Carboniferous was mostly warm; in the later part of the Carboniferous, the climate cooled. Glaciations in Gondwana, triggered by Gondwana's southward movement, continued into the Permian and because of the lack of clear markers and breaks, the deposits of this glacial period are often referred to as Permo-Carboniferous in age. The cooling and drying of the climate led to the Carboniferous Rainforest Collapse (CRC). Tropical rainforests fragmented and then were eventually devastated by climate change. Epoch: Permian Mean CO2 Concentration: 900 parts per million Mean Surface Temperature: 16 °C How long ago?: 280 to 250 million years ago Climate: The climate in the Permian was quite varied. At the start of the Permian, the Earth was still at the grip of an Ice Age from the Carboniferous. Glaciers receded around the mid-Permian period as the climate gradually warmed, drying the continent's interiors. In the late Permian period, the drying continued although the temperature cycled between warm and cool cycles. Epoch: Triassic Mean CO2 Concentration: 1750 parts per million (4.5 times that of today) Mean Surface Temperature: 17 °C How long ago?: 250 to 200 million years ago Climate: The Triassic climate was generally hot and dry, forming typical red bed sandstones and evaporites. There is no evidence of glaciation at or near either pole; in fact, the polar regions were apparently moist and temperate, a climate suitable for reptile-like creatures. Pangaea's large size limited the moderating effect of the global ocean; its continental climate was highly seasonal, with very hot summers and cold winters. It probably had strong, cross-equatorial monsoons. Epoch: Jurassic Mean CO2 Concentration: 1950 parts per million (5 times that of today) Mean Surface Temperature: 16.5°C (lower than Triassic period) How long ago?: 200 to 145 million years ago Climate: Early & Middle: “The Pangean Mega-monsoon was in full swing during the Early and Middle Jurassic. The interior of Pangea was very arid and hot. Deserts covered what is now the Amazon and Congo rainforests. China, surrounded by moisture bearing winds was lush and verdant. Late: “During the Late Jurassic the global climate began to change due to breakup of Pangea. The interior of Pangea became less dry, and seasonal snow and ice frosted the polar regions.” Epoch: Cretaceous Mean CO2 Concentration: 1700 parts per million (4.5 times that of today) Mean Surface Temperature: 18°C (higher than Jurassic period even if CO2 conc. was 250 ppm lower) How long ago?: 145 to 65 million years ago Climate: The Berriasian epoch showed a cooling trend that had been seen in the last epoch of the Jurassic. There is evidence that snowfalls were common in the higher latitudes and the tropics became wetter than during the Triassic and Jurassic. Glaciation was however restricted to alpine glaciers on some high-latitude mountains, though seasonal snow may have existed farther south. Rafting by ice of stones into marine environments occurred during much of the Cretaceous but evidence of deposition directly from glaciers is limited to the Early Cretaceous of the Eromanga Basin in southern Australia. After the end of the Berriasian, however, temperatures increased again, and these conditions were almost constant until the end of the period. This trend was due to intense volcanic activity which produced large quantities of carbon dioxide. The production of large quantities of magma, variously attributed to mantle plumes or to extensional tectonics, further pushed sea levels up, so that large areas of the continental crust were covered with shallow seas. The Tethys Sea connecting the tropical oceans east to west also helped in warming the global climate. Warm-adapted plant fossils are known from localities as far north as Alaska and Greenland, while dinosaur fossils have been found within 15 degrees of the Cretaceous south pole. A very gentle temperature gradient from the equator to the poles meant weaker global winds, contributing to less upwelling and more stagnant oceans than today. This is evidenced by widespread black shale deposition and frequent anoxic events. Sediment cores show that tropical sea surface temperatures may have briefly been as warm as 42 °C (107 °F), 17 °C (31 °F) warmer than at present, and that they averaged around 37 °C (99 °F). Meanwhile deep ocean temperatures were as much as 15 to 20 °C (27 to 36 °F) higher than today's. Epoch: Paleocene Mean CO2 Concentration: Not readily available Mean Surface Temperature: Not readily avai-lable How long ago?: 65 to 56 million years ago Climate: The early Paleocene was cooler and dryer than the preceding Cretaceous, though temperatures rose sharply during the Paleocene–Eocene Thermal Maximum. The climate became warm and humid worldwide towards the Eocene boundary, with subtropical vegetation growing in Greenland and Patagonia, crocodiles swimming off the coast of Greenland, and early primates evolving in tropical palm forests of northern Wyoming. The Earth's poles were cool and temperate; North America, Europe, Australia and southern South America were warm and temperate; equatorial areas had tropical climates; and north and south of the equatorial areas, climates were hot and arid. Epoch: Eocene Mean CO2 Concentration: Not readily available Mean Surface Temperature: Not readily available How long ago?: 56 to 34 million years ago Climate: One of the unique features of the Eocene’s climate as mentioned before was the equable and homogeneous climate that existed in the early parts of the Eocene. The Eocene Epoch contained a wide variety of different climate conditions that includes the warmest climate in the Cenozoic Era and ends in an icehouse climate. The evolution of the Eocene climate began with warming after the end of the Palaeocene-Eocene Thermal Maximum (PETM) at 56 million years ago to a maximum during the Eocene Optimum at around 49 million years ago. During this period of time, little to no ice was present on Earth with a smaller difference in temperature from the equator to the poles. Following the maximum, was a descent into an icehouse climate from the Eocene Optimum to the Eocene-Oligocene transition at 34 million years ago. During this decrease ice began to reappear at the poles, and the Eocene-Oligocene transition is the period of time where the Antarctic ice sheet began to rapidly expand. A multitude of proxies support the presence of a warmer equable climate being present during this period of time. A few of these proxies include the presence of fossils native to warm climates, such as crocodiles, located in the higher latitudes, the presence in the high-latitudes of frost-intolerant flora such as palm trees which cannot survive during sustained freezes, and fossils of snakes found in the tropics that would require much higher average temperatures to sustain them. Using isotope proxies to determine ocean temperatures indicate sea surface temperatures in the tropics as high as 35 °C (95 °F) and bottom water temperatures that are 10 °C (18 °F) higher than present day values. With these bottom water temperatures, temperatures in areas where deep-water forms near the poles are unable to be much cooler than the bottom water temperatures. An issue arises, however, when trying to model the Eocene and reproduce the results that are found with the proxy data. Using all different ranges of greenhouse gases that occurred during the early Eocene, models were unable to produce the warming that was found at the poles and the reduced seasonality that occurs with winters at the poles being substantially warmer. The models, while accurately predicting the tropics, tend to produce significantly cooler temperatures of up to 20 °C (36 °F) underneath the actual determined temperature at the poles. This error has been classified as the “equable climate problem”. To solve this problem, the solution would involve finding a process to warm the poles without warming the tropics. Epoch: Oligocene Mean CO2 Concentration: Not readily available Mean Surface Temperature: Not readily available How long ago?: 34 to 23 million years ago Climate: The Paleogene Period general temperature decline is interrupted by an Oligocene 7 million year stepwise climate change. A deeper 8.2 °C, 400,000 year temperature depression leads the 2 °C, 7 million year stepwise climate change 33.5 Ma (Million years ago). The stepwise climate change began 25.5Ma and lasted through 32.5 Ma, as depicted in the PaleoTemps chart. The Oligocene climate change was a global increase in ice volume and a 55 M (181 feet) decrease in sea level (35.7-33.5 Ma) with a closely related (25.5-32.5 Ma) temperature depression. The 7 million year depression abruptly terminated within 1-2 million years of the La Garita Caldera eruption at 28-26 Ma. A deep 400,000 year glaciated Oligocene Miocene boundary event is recorded at McMurdo Sound and King George Island. Epoch: Miocene Mean CO2 Concentration: Not readily available Mean Surface Temperature: Not readily available How long ago?: 23 to 5 million years ago Climate: The earth went from the Oligocene Epoch through the Miocene and into the Pliocene as it cooled into a series of Ice Ages. The Miocene boundaries are not marked by a single distinct global event but consist rather of regional boundaries between the warmer Oligocene and the cooler Pliocene. Epoch: Today (May 2019) Mean CO2 Concentration: 415 parts per million Mean Surface Temperature: 14 °C Sources: - www.amazon.com/Global-Warming-Pseudoscience-James-Clancy/dp/1478373482 - dinopedia.fandom.com/wiki/Main_Page - pubs.geoscienceworld.org/gsabulletin - www.scotese.com - www.palaeos.com - 540 - 65 Myr BP : Royer, Dana L. and Robert A. Berner, Isabel P. Montañez, Neil J. Tabor, David J. 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