The Late Cenozoic Ice Age,National Academy of Sciences - The National Academies Press - Continental Glaciation through Geologic Times https://www.nap.edu/read/11798/chapter/8#80 or Antarctic Glaciation began 33.9 million years ago at the Eocene-Oligocene Boundary and is ongoing. It is Earth's current

ice age An ice age is a long period of reduction in the temperature of Earth's surface and atmosphere, resulting in the presence or expansion of continental and polar ice sheets and alpine glaciers. Earth's climate alternates between ice ages and gre ...

or icehouse period. Its beginning is marked by the formation of the Antarctic ice sheets. Six million years after the start of the Late Cenozoic Ice Age, the

East Antarctic Ice Sheet The East Antarctic Ice Sheet (EAIS) is one of two large ice sheets in Antarctica, and the largest on the entire planet. The EAIS lies between 45° west and 168° east longitudinally. The EAIS holds enough ice to raise global sea levels by and ...

had formed, and 14 million years ago it had reached its current extent. In the last three million years, glaciations have spread to the northern hemisphere. It commenced with

Greenland Greenland ( kl, Kalaallit Nunaat, ; da, Grønland, ) is an island country in North America that is part of the Kingdom of Denmark. It is located between the Arctic and Atlantic oceans, east of the Canadian Arctic Archipelago. Greenland is ...

becoming increasingly covered by an ice sheet in late

Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58 During the

Pleistocene Epoch The Pleistocene ( , often referred to as the ''Ice age'') is the geological epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was finally confirmed in ...

(starting 2.58 Ma ago), the

Quaternary glaciation The Quaternary glaciation, also known as the Pleistocene glaciation, is an alternating series of glacial and interglacial periods during the Quaternary period that began 2.58 Ma (million years ago) and is ongoing. Although geologists describ ...

developed with decreasing mean temperatures and increasing amplitudes between glacials and interglacials. During the

glacial period A glacial period (alternatively glacial or glaciation) is an interval of time (thousands of years) within an ice age that is marked by colder temperatures and glacier advances. Interglacials, on the other hand, are periods of warmer climate bet ...

s of the Pleistocene, large areas of northern North America and northern

Eurasia Eurasia (, ) is the largest continental area on Earth, comprising all of Europe and Asia. Primarily in the Northern and Eastern Hemispheres, it spans from the British Isles and the Iberian Peninsula in the west to the Japanese archipelag ...

have been covered by ice sheets. All_palaeotemps

History of discovery and naming

German naturalist

Karl Friedrich Schimper Karl Friedrich Schimper (15 February 1803 – 21 December 1867) was a German botanist, naturalist and poet. Life Early life and education Schimper was born in Mannheim, on February 15, 1803, to Friedrich Ludwig Heinrich Schimper and ...

coined the term , meaning ''ice age'', in 1837. For a long time, the term referred only to glacial periods. Over time, this developed into the concept that they were all part of a much longer ice age. The concept that the earth is currently in an ice age that began around 30 million years ago can be dated back to at least 1966.The Stanford Daily - Stanford, California, United States - ''Man's Relation To Nature Topic Of Eiseley's Lecture'' - 1966 October 20. As a geologic time period, the Late Cenozoic Ice Age was used at least as early as 1973.

The climate before the polar ice caps

The last greenhouse period began 260 million years ago during the late

Permian Period The Permian ( ) is a geologic period and stratigraphic system which spans 47 million years from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.9 Mya. It is the last period of the Paleoz ...

at the end of the

Karoo Ice Age The late Paleozoic icehouse, also known as the Late Paleozoic Ice Age (LPIA) and formerly known as the Karoo ice age, was an ice age that began in the Late Devonian and ended in the Late Permian, occurring from 360 to 255 million years ago (Mya), ...

. It lasted all through the time of the non-avian dinosaurs during the

Mesozoic Era The Mesozoic Era ( ), also called the Age of Reptiles, the Age of Conifers, and colloquially as the Age of the Dinosaurs is the second-to-last era of Earth's geological history, lasting from about , comprising the Triassic, Jurassic and Cretace ...

, and ended 33.9 million years ago in the middle of the

Cenozoic Era The Cenozoic ( ; ) is Earth's current geological era, representing the last 66million years of Earth's history. It is characterised by the dominance of mammals, birds and flowering plants, a cooling and drying climate, and the current configu ...

(the current Era). This greenhouse period lasted 226.1 million years. The hottest part of the last greenhouse earth was the Late Paleocene - Early Eocene. This was a hothouse period that lasted from 65 to 55 million years ago. The hottest part of this torrid age was the Paleocene-Eocene Thermal Maximum, 55.5 million years ago. Average global temperatures were around 30 °C (86 °F). This was only the second time that Earth reached this level of warmth since the

Precambrian The Precambrian (or Pre-Cambrian, sometimes abbreviated pꞒ, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of th ...

. The other time was during the

Cambrian Period The Cambrian Period ( ; sometimes symbolized Ꞓ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million years ago (m ...

, which ran from 538.8 million years ago to 485.4 million years ago. During the early

Eocene The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', " ...

, Australia and

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the souther ...

were connected to Antarctica. 53 million years ago during the

Eocene Epoch The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', "daw ...

, summer high temperatures in

Antarctica Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean, it contains the geographic South Pole. Antarctica is the fifth-largest co ...

were around 25 °C (77 °F). Temperatures during winter were around 10 °C (50 °F). It did not frost during the winter. The climate was so warm that trees grew in Antarctica. '' Arecaceae'' (palm trees) grew on the coastal lowlands, and ''

Fagus Beech (''Fagus'') is a genus of deciduous trees in the family Fagaceae, native to temperate Europe, Asia, and North America. Recent classifications recognize 10 to 13 species in two distinct subgenera, ''Engleriana'' and ''Fagus''. The ''Engle ...

'' (beech trees) and ''

Pinophyta Conifers are a group of cone-bearing seed plants, a subset of gymnosperms. Scientifically, they make up the division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a single extant class, Pinopsida. All ex ...

'' (conifers) grew on the hills just inland from the coast. As the global climate became cooler, the planet was seeing a decrease in forests, and an increase in savannas. Animals were evolving to have a larger body size.

Glaciation of the southern hemisphere

Australia drifted away from Antarctica forming the

Tasmanian Passage The Tasmanian Passage, also Tasmanian Gateway or Tasmanian Seaway, is the name of ocean waters between Australia and Antarctica. It was formed from the separation of the two continental plates of Australia and Antarctica about 30 to 40 million ...

, and

drifted away from Antarctica forming the

Drake Passage The Drake Passage (referred to as Mar de Hoces Hoces Sea"in Spanish-speaking countries) is the body of water between South America's Cape Horn, Chile and the South Shetland Islands of Antarctica. It connects the southwestern part of the Atla ...

. This caused the formation of the

Antarctic Circumpolar Current The Antarctic Circumpolar Current (ACC) is an ocean current that flows clockwise (as seen from the South Pole) from west to east around Antarctica. An alternative name for the ACC is the West Wind Drift. The ACC is the dominant circulation feat ...

, a current of cold water surrounding Antarctica. This current still exists today, and is a major reason for why Antarctica has such an exceptionally cold climate. The Eocene-Oligocene Boundary 33.9 million years ago was the transition from the last greenhouse period to the present icehouse climate. At this point, when ~25% more of Antarctica's surface was above sea level and able to support land-based ice sheets relative to today, CO₂ levels had dropped to 750 ppm. This was the beginning of the Late Cenozoic Ice Age. This was when the ice sheets reached the ocean, the defining point. 33 million years ago was the evolution of the thylacinid marsupial (''Badjcinus''). The first balanids, cats, eucalypts, and pigs came about 30 million years ago. The brontothere and embrithopod mammals went extinct at this time. At 29.2 million years ago, there were three ice caps in the high elevations of Antarctica. One ice cap formed in the

Dronning Maud Land Queen Maud Land ( no, Dronning Maud Land) is a roughly region of Antarctica claimed by Norway as a dependent territory. It borders the claimed British Antarctic Territory 20° west and the Australian Antarctic Territory 45° east. In additi ...

. Another ice cap formed in the

Gamburtsev Mountain Range The Gamburtsev Mountain Range (also known as the Gamburtsev Subglacial Mountains) is a subglacial mountain range located in East Antarctica, just underneath the lofty Dome A, near the Southern Pole of Inaccessibility. The range was discovered by ...

. Another ice cap formed in the

Transantarctic Mountains The Transantarctic Mountains (abbreviated TAM) comprise a mountain range of uplifted (primarily sedimentary) rock in Antarctica which extend, with some interruptions, across the continent from Cape Adare in northern Victoria Land to Coats Land. ...

. At this point, the ice caps weren't very big yet. Most of Antarctica wasn't covered by ice. By 28.7 million years ago, the Gamburtsev ice cap was now much larger due to the colder climate. CO₂ continued to fall and the climate continued to get colder. At 28.1 million years ago, the Gamburtsev and Transantarctic ice caps merged into a main central ice cap. At this point, ice was now covering a majority of the continent. 28 million years ago was the time period in which the largest land mammal existed, the ''

Paraceratherium ''Paraceratherium'' is an extinct genus of hornless rhinoceros. It is one of the largest terrestrial mammals that has existed and lived from the early to late Oligocene epoch (34–23 million years ago). The first fossils were discovere ...

''. The Dronning Maud ice cap merged with the main ice cap 27.9 million years ago. This was the formation of the

. 25 million years ago brought about the first deer. It also was the time period in which the largest flying bird existed, the ''

Pelagornis sandersi ''Pelagornis sandersi'' is an extinct species of pseudotooth bird, whose fossil remains date from 25 million years ago, during the Chattian age of the Oligocene. The sole specimen of ''P. sandersi'' has a wingspan estimated between , giving i ...

''. Global refrigeration set in 22 million years ago. 20 million years ago brought about the first bears, giraffes, giant anteaters, and hyenas. There was also an increase in the diversity of birds. The first bovids, kangaroos, and mastodons came about 15 million years ago. This was the warmest part of the Late Cenozoic Ice Age, with average global temperatures around 18.4 °C (65.1 °F). Atmospheric CO₂ levels were around 700 ppm. This time period was called the Mid-Miocene Climatic Optimum (MMCO). By 14 million years ago, the Antarctic ice sheets were similar in size and volume to present times. Glaciers were starting to form in the mountains of the Northern Hemisphere. The

Great American Interchange The Great American Biotic Interchange (commonly abbreviated as GABI), also known as the Great American Interchange and the Great American Faunal Interchange, was an important late Cenozoic paleozoogeographic biotic interchange event in which la ...

began 9.5 million years ago (with the highest rate of species crossing occurring around 2.7 million years ago). This was the migration of different land and freshwater animals between North and South America. During this time, armadillos, glyptodonts, ground sloths, hummingbirds, meridiungulates, opossums, and phorusrhacids migrated from South America to North America. Also, bears, deer, coatis, ferrets, horses, jaguars, otters, saber-toothed cats, skunks, and tapirs migrated from North America to South America. Around 7 million years ago, the first potential

hominin The Hominini form a taxonomic tribe of the subfamily Homininae ("hominines"). Hominini includes the extant genera ''Homo'' (humans) and '' Pan'' (chimpanzees and bonobos) and in standard usage excludes the genus ''Gorilla'' (gorillas). The t ...

Sahelanthropus ''Sahelanthropus tchadensis'' is an extinct species of the Homininae (African apes) dated to about , during the Miocene epoch. The species, and its genus ''Sahelanthropus'', was announced in 2002, based mainly on a partial cranium, nicknamed '' ...

is estimated to have lived. The australopithecines first appear in the fossil record around 4 million years ago, and diversified vastly over the next 2 million years. The

Mediterranean Sea The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western and Southern Europe and Anatolia, on the south by North Africa, and on the ...

was dry between 6 and 5 million years ago. Five million years ago brought about the first hippopotami and tree sloths. Elephants, zebras, and other grazing herbivores became more diverse. Lions, members of the genus ''

Canis ''Canis'' is a genus of the Caninae which includes multiple extant species, such as wolves, dogs, coyotes, and golden jackals. Species of this genus are distinguished by their moderate to large size, their massive, well-developed skulls an ...

'', and other large carnivores became more diverse. The burrowing rodents, birds, kangaroos, small carnivores, and vultures increase in size. There was a decrease in the number of perissodactyl mammals, and the nimravid carnivores went extinct. The first mammoths came about 4.8 million years ago. The evolution of the ''

Australopithecus ''Australopithecus'' (, ; ) is a genus of early hominins that existed in Africa during the Late Pliocene and Early Pleistocene. The genus ''Homo'' (which includes modern humans) emerged within ''Australopithecus'', as sister to e.g. ''Austral ...

'' occurred four million years ago. This was also the time of the largest freshwater turtle, ''

Stupendemys ''Stupendemys'' is an extinct genus of freshwater side-necked turtle, belonging to the family Podocnemididae. It is the largest freshwater turtle known to have existed, with a carapace over 2 meters long. Its fossils have been found in northe ...

''. The first modern elephants, gazelles, giraffes, lions, rhinoceros, and zebras came about at this time. Between 3.6 and 3.4 million years ago, there was a sudden but brief warming period.

Glaciation of the northern hemisphere

Arctic Sea Ice - September 2009 to March 2010 (4497233026)

The glaciation of the

Arctic The Arctic ( or ) is a polar region located at the northernmost part of Earth. The Arctic consists of the Arctic Ocean, adjacent seas, and parts of Canada ( Yukon, Northwest Territories, Nunavut), Danish Realm ( Greenland), Finland, Iceland ...

in the Northern Hemisphere commenced with Greenland becoming increasingly covered by an ice sheet in late

Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58 The evolution of the

Paranthropus ''Paranthropus'' is a genus of extinct hominin which contains two widely accepted species: '' P. robustus'' and '' P. boisei''. However, the validity of ''Paranthropus'' is contested, and it is sometimes considered to be synonymous with '' Au ...

occurred 2.7 million years ago. 2.58 million years ago was the official start of the

, the current phase of the Late Cenozoic Ice Age. Throughout the Pleistocene, there have been

s (cold periods with extended glaciation) and

interglacial periods An interglacial period (or alternatively interglacial, interglaciation) is a geological interval of warmer global average temperature lasting thousands of years that separates consecutive glacial periods within an ice age. The current Holocene in ...

(warm periods with less glaciation). The term

stadial Stadials and interstadials are phases dividing the Quaternary period, or the last 2.6 million years. Stadials are periods of colder climate while interstadials are periods of warmer climate. Each Quaternary climate phase is associated with a ...

is another word for glacial period, and

interstadial Stadials and interstadials are phases dividing the Quaternary period, or the last 2.6 million years. Stadials are periods of colder climate while interstadials are periods of warmer climate. Each Quaternary climate phase is associated with a M ...

is another word for interglacial period. The oscillation between glacial and interglacial periods is due to the

Milankovitch cycles Milankovitch cycles describe the collective effects of changes in the Earth's movements on its climate over thousands of years. The term was coined and named after Serbian geophysicist and astronomer Milutin Milanković. In the 1920s, he hypot ...

. These are cycles that have to do with Earth's axial tilt and orbital eccentricity. Earth is currently tilted at 23.5 degrees. Over a 41,000 year cycle, the tilt oscillates between 22.1 and 24.5 degrees. When the tilt is greater (high obliquity), the seasons are more extreme. During times when the tilt is less (low obliquity), the seasons are less extreme. Less tilt also means that the polar regions receive less light from the sun. This causes a colder global climate as ice sheets start to build up. The shape of Earth's orbit around the sun affects the Earth's climate. Over a 100,000 year cycle, Earth oscillates between having a circular orbit to having a more elliptical orbit. From 2.58 million years ago to about 1.73 million ± 50,000 years ago, the degree of axial tilt was the main cause of glacial and interglacial periods. 2.5 million years ago brought about the evolution of the earliest ''

Smilodon ''Smilodon'' is a genus of the extinct machairodont subfamily of the felids. It is one of the most famous prehistoric mammals and the best known saber-toothed cat. Although commonly known as the saber-toothed tiger, it was not closely related ...

'' species. ''

Homo habilis ''Homo habilis'' ("handy man") is an extinct species of archaic human from the Early Pleistocene of East and South Africa about 2.31 million years ago to 1.65 million years ago (mya). Upon species description in 1964, ''H. habilis'' was highly ...

'' appeared about two million years ago. This is the first named species of the genus ''

Homo ''Homo'' () is the genus that emerged in the (otherwise extinct) genus '' Australopithecus'' that encompasses the extant species ''Homo sapiens'' (modern humans), plus several extinct species classified as either ancestral to or closely relat ...

'', although this classification is increasingly controversial. Conifer trees became more diverse in the high latitudes. The ancestor of cattle evolved in India, the '' Bos primigenus'' (aurochs). Australopithecines are estimated to have become extinct around 1.7 million years ago. The evolution of ''

Homo antecessor ''Homo antecessor'' (Latin "pioneer man") is an extinct species of archaic human recorded in the Spanish Sierra de Atapuerca, a productive archaeological site, from 1.2 to 0.8 million years ago during the Early Pleistocene. Populations of th ...

'' occurred 1.2 million years ago. ''Paranthropus'' also became extinct. Around 850,000 ± 50,000 years ago, the degree of orbital eccentricity became the main driver of glacial and interglacial periods rather than the degree of tilt, and this pattern continues to present-day. 800,000 years ago, the short-faced bear ('' Arctodus simus'') became abundant in North America. The evolution of the ''

Homo heidelbergensis ''Homo heidelbergensis'' (also ''H. sapiens heidelbergensis''), sometimes called Heidelbergs, is an extinct species or subspecies of archaic human which existed during the Middle Pleistocene. It was subsumed as a subspecies of '' H. erectus'' ...

'' happened 600,000 years ago. The evolution of

Neanderthal Neanderthals (, also ''Homo neanderthalensis'' and erroneously ''Homo sapiens neanderthalensis''), also written as Neandertals, are an extinct species or subspecies of archaic humans who lived in Eurasia until about 40,000 years ago. While ...

s occurred 350,000 years ago. 300,000 years ago, ''

Gigantopithicus ''Gigantopithecus'' ( ; ) is an extinct genus of ape from roughly 2 million to 350,000 years ago during the Early to Middle Pleistocene of southern China, represented by one species, ''Gigantopithecus blacki''. Potential identifications have al ...

'' went extinct. 250,000 years ago in Africa were the first anatomically modern humans.

Last Glacial Period

The last glacial period began 115,000 years ago and ended 11,700 years ago. This time period saw the great advancement of polar ice sheets into the middle latitudes of the Northern Hemisphere. The

Toba eruption The Youngest Toba eruption was a supervolcano eruption that occurred around 74,000 years ago at the site of present-day Lake Toba in Sumatra, Indonesia. It is one of the Earth's largest known explosive eruptions. The Toba catastrophe theory ...

75,000 years ago in present day Sumatra,

Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania between the Indian and Pacific oceans. It consists of over 17,000 islands, including Sumatra, Java, Sulawesi, and parts of Borneo and New Guine ...

has been linked to a bottleneck in the human DNA. The six to ten years of cold weather during the volcanic winter destroyed many food sources and greatly reduced the human population. 50,000 years ago, Homo sapiens migrated out of Africa. They began replacing other Hominins in Asia. They also began replacing Neanderthals in Europe. However some of the Homo sapiens and Neanderthals interbred. Currently, persons of European descent are two to four percent Neanderthal. With the exception of this small amount of Neanderthal DNA that exists today, Neanderthals became extinct 30,000 years ago. The

last glacial maximum The Last Glacial Maximum (LGM), also referred to as the Late Glacial Maximum, was the most recent time during the Last Glacial Period that ice sheets were at their greatest extent. Ice sheets covered much of Northern North America, Northern Eu ...

ran from 26,500 years ago to 20,000 years ago. Although different ice sheets reached maximum extent at somewhat different times, this was the time when ice sheets overall were at maximum extent. According to ''Blue Marble 3000'' (a video by the Zurich University of Applied Sciences), the average global temperature around 19,000 BCE (about 21,000 years ago) was 9.0 °C (48.2 °F). This is about 4.8 °C (8.6 °F) colder than the 1850-1929 average, and 6.0 °C (10.8 °F) colder than the 2011-2020 average. The figures given by the Intergovernmental Panel On Climate Change (IPCC) estimate a slightly lower global temperature than the figures given by the Zurich University of Applied Sciences. However, these figures are not exact figures and are open more to interpretation. According to the IPCC, average global temperatures increased by 5.5 ± 1.5 °C (9.9 ± 2.7 °F) since the last glacial maximum, and the rate of warming was about 10 times slower than that of the 20th century. It appears that they are defining the present as the early period of instrumental records when temperatures were less affected by human activity, but they do not specify exact years, or give a temperature for the present.

Berkeley Earth Berkeley Earth is a Berkeley, California-based independent 501(c)(3) non-profit focused on land temperature data analysis for climate science. Berkeley Earth was founded in early 2010 (originally called the Berkeley Earth Surface Temperature pro ...

publishes a list of average global temperatures by year. It shows that temperatures were stable from the beginning of records in 1850 until 1929. The average temperature during these years was 13.8 °C (56.8 °F). When subtracting 5.5 ± 1.5 °C (9.9 ± 2.7 °F) from the 1850-1929 average, the average temperature for the last glacial maximum comes out to 8.3 ± 1.5 °C (46.9 ± 2.7 °F). This is about 6.7 ± 1.5 °C (12.0 ± 2.7 °F) colder than the 2011-2020 average. This figure is open to interpretation because the IPCC does not specify 1850-1829 as being the present, or give any exact set of years as being the present. It also does not state whether or not they agree with the figures given by Berkeley Earth. According to the United States Geographical Survey (USGS), permanent summer ice covered about 8% of Earth's surface and 25% of the land area during the last glacial maximum. The USGS also states that sea level was about 125 m (410 ft) lower than in present times (2012). The volume of ice on Earth was around 17,000,000 mi³ (71,000,000 km³), which is about 2.1 times Earth's current volume of ice. The extinction of the

woolly rhinoceros The woolly rhinoceros (''Coelodonta antiquitatis'') is an extinct species of rhinoceros that was common throughout Europe and Asia during the Pleistocene epoch and survived until the end of the last glacial period. The woolly rhinoceros was a me ...

(''Coelodonta antiquitus'') occurred 15,000 years ago after the last glacial maximum.

Current Interglacial Period

Anna_Ancher_-_Harvesters_-_Google_Art_Project

The Earth is currently in an interglacial period which began 11,700 years ago. This is traditionally referred to as the

Holocene The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene togeth ...

epoch and is currently (as of 2018) recognized as such by the

International Commission on Stratigraphy The International Commission on Stratigraphy (ICS), sometimes referred to unofficially as the "International Stratigraphic Commission", is a daughter or major subcommittee grade scientific daughter organization that concerns itself with stratigr ...

. However, there is debate as to whether it is actually a separate epoch or merely an interglacial period within the Pleistocene epoch. This period can also be referred to as the

Flandrian interglacial The Flandrian interglacial or stage is the name given by geologists and archaeologists in the British Isles to the first, and so far only, stage of the Holocene epoch (the present geological period), covering the period from around 12,000 years ago ...

or Flandrian stage. According to Blue Marble 3000, the average global temperature at the beginning of the current interglacial period was around 12.9 °C (55.2 °F). Agriculture began 11,500 years ago. Equidae,

giant ground sloths ''Megatherium'' ( ; from Greek () 'great' + () 'beast') is an extinct genus of ground sloths endemic to South America that lived from the Early Pliocene through the end of the Pleistocene. It is best known for the elephant-sized type species ' ...

, and short-faced bears became extinct 11,000 years ago. The Smilodon became extinct 10,000 years ago, as well as the mainland species of the woolly mammoth. Between 9,000 and 5,000 years ago was the

Holocene Climatic Optimum The Holocene Climate Optimum (HCO) was a warm period that occurred in the interval roughly 9,000 to 5,000 years ago BP, with a thermal maximum around 8000 years BP. It has also been known by many other names, such as Altithermal, Climatic Optim ...

. According to Blue Marble 3000, in 6,000 BCE, the average global temperature was 14.2 °C (57.6 °F). This was a warmer period than when instrumental records began in the 19th century, but now it's cooler than the present. The

giant lemur Subfossil lemurs are lemurs from Madagascar that are represented by recent (subfossil) remains dating from nearly 26,000 years ago to approximately 560 years ago (from the late Pleistocene until the Holocene). They include both extant ...

went extinct around this time. Around 3,200 BCE (5,200 years ago) the first writing system was invented. It was the cuneiform script used in

Mesopotamia Mesopotamia ''Mesopotamíā''; ar, بِلَاد ٱلرَّافِدَيْن or ; syc, ܐܪܡ ܢܗܪ̈ܝܢ, or , ) is a historical region of Western Asia situated within the Tigris–Euphrates river system, in the northern part of the F ...

(present day

Iraq Iraq,; ku, عێراق, translit=Êraq officially the Republic of Iraq, '; ku, کۆماری عێراق, translit=Komarî Êraq is a country in Western Asia. It is bordered by Turkey to Iraq–Turkey border, the north, Iran to Iran–Iraq ...

). The last mammoths at

Wrangel Island Wrangel Island ( rus, О́стров Вра́нгеля, r=Ostrov Vrangelya, p=ˈostrəf ˈvrangʲɪlʲə; ckt, Умӄиԓир, translit=Umqiḷir) is an island of the Chukotka Autonomous Okrug, Russia. It is the 91st largest island in the w ...

off the coast of

Siberia Siberia ( ; rus, Сибирь, r=Sibir', p=sʲɪˈbʲirʲ, a=Ru-Сибирь.ogg) is an extensive geographical region, constituting all of North Asia, from the Ural Mountains in the west to the Pacific Ocean in the east. It has been a part o ...

went extinct around 3,700 years ago. Being in an interglacial, there is less ice than there was during the last glacial period. However, the last glacial period was just one part of the ice age that still continues today. Even though Earth is in an interglacial, there is still more ice than times outside of ice ages. There are also currently ice sheets in the Northern Hemisphere, which means that there is more ice on Earth than there was during the first 31 million years of the Late Cenozoic Ice Age. During that time, only the Antarctic ice sheets existed. Currently (as of 2012), about 3.1% of Earth's surface and 10.7% of the land area is covered in year-round ice according to the USGS. The total volume of ice presently on Earth is about 33,000,000 km³ (8,000,000 mi³) (as of 2004). The current sea level (as of 2009) is 70 m (230 ft) lower than it would be without the ice sheets of Antarctica and Greenland. Based on the Milankovitch cycles, the current interglacial period is predicted to be unusually long, continuing for another 25,000 to 50,000 years beyond present times. There are also high concentrations of greenhouse gases in the atmosphere from human activity, and it is almost certain to get higher in the coming decades. This will lead to higher temperatures. In 25,000 to 50,000 years, the climate will begin to cool due to the Milankovich cycles. However, the high levels of greenhouse gases are predicted to keep it from getting cold enough to build up enough ice to meet the criteria of a glacial period. This would effectively extend the current interglacial period an additional 100,000 years placing the next glacial period 125,000 to 150,000 years in the future.

References

External links

Blue Marble 3000
an animation by Zurich University of Applied Sciences showing global ice sheets from 19,000 BCE to 3000 CE {{Greenhouse and Icehouse Earth History of Antarctica Antarctic region Aquitanian (stage) Burdigalian Calabrian (stage) Cenozoic Chattian Gelasian Holocene Ice ages Langhian Late Pleistocene Middle Pleistocene Messinian Miocene Neogene Oligocene Paleogene Phanerozoic Piacenzian Pleistocene Pliocene Quaternary Rupelian Serravallian Tortonian Zanclean