ayshfm1 wrote:We are currently in an ice age which we were slowly emerging from. The earth is normally much warmer than it is now.
Humans have lived through several ice ages.
Small correction. We are currently in the latest interglacial period (the Holocene which began about 11,700 years ago) of the most recent ice age (the Quarternary) which started 2.58 million years ago. Even before the Quarternary though the Earth was in an ice house state with ice at the southpole (but not at the north pole until the Quarternary). This ice house state is known as the Late Cenozoic Ice Age and began about 34 million years ago. You have to go back to before that to get to what is known as a Greenhouse period where both poles were ice free. Hence although Homo Sapiens which appeared about 300,000 years ago has lived through multiple interglacial and glacial periods they have all been within the same ice age (the Quarternary) which is just the latest part of a longer ice age/house state beginning 34 million years ago. Our earliest ancestor in the genus Homo, Homo Habilis, only appeared around 2.5 million years ago roughly coinciding with the start of the Quarternary.
https://en.wikipedia.org/wiki/Ice_ageThe Quaternary Glaciation / Quaternary Ice Age started about 2.58 million years ago at the beginning of the Quaternary Period when the spread of ice sheets in the Northern Hemisphere began. Since then, the world has seen cycles of glaciation with ice sheets advancing and retreating on 40,000- and 100,000-year time scales called glacial periods, glacials or glacial advances, and interglacial periods, interglacials or glacial retreats. Earth is currently in an interglacial, and the last glacial period ended about 11,700 years ago. All that remains of the continental ice sheets are the Greenland and Antarctic ice sheets and smaller glaciers such as on Baffin Island.
The definition of the Quaternary as beginning 2.58 Ma is based on the formation of the Arctic ice cap. The Antarctic ice sheet began to form earlier, at about 34 Ma, in the mid-Cenozoic (Eocene-Oligocene Boundary). The term Late Cenozoic Ice Age is used to include this early phase.[49]
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Earth has been in an interglacial period known as the Holocene for around 11,700 years,[52] and an article in Nature in 2004 argues that it might be most analogous to a previous interglacial that lasted 28,000 years.[53] Predicted changes in orbital forcing suggest that the next glacial period would begin at least 50,000 years from now. Moreover, anthropogenic forcing from increased greenhouse gases is estimated to potentially outweigh the orbital forcing of the Milankovitch cycles for hundreds of thousands of years.[54][5][4]
Hee is a list of the last six interglacial periods with approximate dates
https://en.wikipedia.org/wiki/InterglacialThe last six interglacials are:
Marine Isotope Stage 13 (524–474 thousand years ago).
Hoxnian / Holstein / Mindel-Riss / Marine Isotope Stage 11 (424–374 thousand years ago).
Purfleet Interglacial / Holstein / Mindel-Riss / Marine Isotope Stage 9 (337–300 thousand years ago).
La Bouchet Interglacial / Arousa Interglacial / Aveley Interglacial / Marine Isotope Stage 7e (242–230 thousand years ago). MIS 7a, MIS 7b and MIS 7c may or may not be included. MIS 7d was a cold period dividing the MIS 7 interglacial into two distinct periods. MIS 7e contained the climatic optimum.
Eemian / Marine Isotope Stage 5e (130–115 thousand years ago). The preceding interglacial optimum occurred during the Late Pleistocene Eemian Stage, 131–114 ka. During the Eemian the climatic optimum took place during pollen zone E4 in the type area (city of Amersfoort, Netherlands). Here this zone is characterized by the expansion of Quercus (oak), Corylus (hazel), Taxus (yew), Ulmus (elm), Fraxinus (ash), Carpinus (hornbeam), and Picea (spruce). During the Eemian Stage (from about 128,000 BCE until 113,000 BCE), sea level was between 5 and 9.4 meters higher than today[4] and the water temperature of the North Sea was about 2 °C higher than at present.
Holocene (12,000 years ago to the present). During the present interglacial, the Holocene, the climatic optimum occurred during the Subboreal (5 to 2.5 ka BP, which corresponds to 3000 BC–500 BC) and Atlanticum (9 to 5 ka, which corresponds to roughly 7000 BC–3000 BC). The current climatic phase following this climatic optimum is still within the same interglacial (the Holocene). That warm period was followed by a gradual decline until about 2000 years ago, with another warm period until the Little Ice Age (1250–1850).
https://en.wikipedia.org/wiki/Late_Cenozoic_Ice_AgeThe last greenhouse period began 260 million years ago during the late Permian Period at the end of the Karoo Ice Age. It lasted all through the time of the non-avian dinosaurs during the Mesozoic Era, and ended 33.9 million years ago in the middle of the Cenozoic Era (the current Era). This greenhouse period lasted 226.1 million years.
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Glaciation of the southern hemisphere
Australia drifted away from Antarctica forming the Tasmanian Passage, and South America drifted away from Antarctica forming the Drake Passage. This caused the formation of the Antarctic Circumpolar Current, a current of cold water surrounding Antarctica.[10] This current still exists today, and is a major reason for why Antarctica has such an exceptionally cold climate.[15]
The Eocene-Oligocene Boundary 33.9 million years ago was the transition from the last greenhouse period to the present icehouse climate.[17][18][10] 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,[19] CO2 levels had dropped to 750 ppm.[20] This was the beginning of the Late Cenozoic Ice Age. This was when the ice sheets reached the ocean,[21] the defining point.[22]
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Glaciation of the northern hemisphere
The glaciation of the Arctic in the Northern Hemisphere commenced with Greenland becoming increasingly covered by an ice sheet in late Pliocene (2.9-2.58 Ma ago).[11]
The current period is the Quaternary, which started 2.58 million years ago. It is divided into the Pleistocene, which ended 11,700 years ago, and the current Holocene. The Quaternary is also divided into alternating stadials (colder periods) and interstadials (warmer periods) The last stadial reached its peak in the Last Glacial Maximum, between 26,000 and 20,000 years ago, and the Earth is now in an interstadial.