Glacial period

{{main|Quaternary glaciation|timeline of glaciation}}

File:Co2 glacial cycles 800k.png cycles as represented by atmospheric CO₂, measured from ice core samples going back 800,000 years. The stage names are part of the North American and the European Alpine subdivisions. The correlation between both subdivisions is tentative.]]

Within the Quaternary, which started about 2.6 million years before present, there have been a number of glacials and interglacials.{{cite book |author1=Gibbard, P. |author2=van Kolfschoten, T. |chapter=Chapter 22: The Pleistocene and Holocene Epochs |chapter-url=http://www-qpg.geog.cam.ac.uk/people/gibbard/GTS2004Quat.pdf |editor1=Gradstein, F. M. |editor2=Ogg, James G. |editor3=Smith, A. Gilbert |title=A Geologic Time Scale 2004 |publisher=Cambridge University Press |location=Cambridge |year=2004 |isbn=978-0-521-78142-8}} At least eight glacial cycles have occurred in the last 740,000 years alone.{{Cite journal

| last = Augustin | first = Laurent | title = Eight glacial cycles from an Antarctic ice core

| journal = Nature | volume = 429 | issue = 6992 | pages = 623–8

| year = 2004 | doi = 10.1038/nature02599

| pmid = 15190344|display-authors=etal| bibcode = 2004Natur.429..623A| doi-access = free}} Changes in atmospheric {{CO2}} and associated radiative forcing were among the primary drivers of globally cold glacial and warm interglacial climates{{Citation | vauthors=((Hain, M. P.)), ((Chalk, T. B.)) | year=2025 | title=Greenhouse gas effects on Quaternary climates | publisher=Elsevier | url=https://earth-system-biogeochemistry.net/wp-content/uploads/2025/01/Hain-and-Chalk-2024-EQS-Milankovitch-vs-CO2.pdf | doi=10.1016/b978-0-323-99931-1.00271-3}}, with changes in ocean physical circulation, biological productivity and seawater acid-base chemistry likely causing most of the recorded {{CO2}} changes{{Citation | vauthors=((Hain, M. P.)), ((Sigman, D. M.)) | year=2024 | title=CO2 in Earth’s Ice Age Cycles | publisher=Oxford University Press | url=https://earth-system-biogeochemistry.net/wp-content/uploads/2025/01/Hain-and-Sigman-2024-ORE-PDFxx.pdf | doi=10.1093/acrefore/9780190228620.013.879}}

{{main|Penultimate Glacial Period}}

The Penultimate Glacial Period (PGP) is the glacial period that occurred before the Last Glacial Period. It began about 194,000 years ago and ended 135,000 years ago, with the beginning of the Eemian interglacial.{{cite journal |last1=Nehme |first1=Carole |last2=Verheyden |first2=Sophie |last3=Breitenbach |first3=Sebastian F.M. |last4=Gillikin |first4=David P. |last5=Verheyden |first5=Anouk |last6=Cheng |first6=Hai |last7=Edwards |first7=R. Lawrence |last8=Hellstrom |first8=John |last9=Noble |first9=Stephen R. |last10=Farrant |first10=Andrew R. |last11=Sahy |first11=Diana |last12=Goovaerts |first12=Thomas |last13=Salem |first13=Ghada |last14=Claeys |first14=Philippe |display-authors=4|title=Climate Dynamics During the Penultimate Glacial Period Recorded in a Speleothem from Kanaan Cave, Lebanon (central Levant) |journal=Quaternary Research |date=July 2018 |volume=90 |issue=1 |pages=10–25 |doi=10.1017/qua.2018.18|bibcode=2018QuRes..90...10N |s2cid=134924228 |url=http://minerva.union.edu/gillikid/pdfs/Nehme_etal_2018_QR.pdf}}

{{main|Last Glacial Period}}

The last glacial period was the most recent glacial period within the Quaternary glaciation at the end of the Pleistocene, and began about 110,000 years ago and ended about 11,700 years ago. The glaciations that occurred during the glacial period covered many areas of the Northern Hemisphere and have different names, depending on their geographic distributions: Wisconsin (in North America), Devensian (in Great Britain), Midlandian (in Ireland), Würm (in the Alps), Weichsel (in northern Central Europe), Dali (in East China), Beiye (in North China), Taibai (in Shaanxi) Luoji Shan (in southwest Sichuan), Zagunao (in northwest Sichuan), Tianchi (in the Tian Shan) Jomolungma (in the Himalayas), and Llanquihue (in Chile). The glacial advance reached the Last Glacial Maximum about 26,500 BP. In Europe, the ice sheet reached Northern Germany. Over the last 650,000 years, there have been on average seven cycles of glacial advance and retreat.

{{See also|Milankovitch cycles}}

Since orbital variations are predictable,{{cite journal|author1=F. Varadi |author2=B. Runnegar |author3=M. Ghil |author-link3=Michael Ghil |title=Successive Refinements in Long-Term Integrations of Planetary Orbits |journal=The Astrophysical Journal |volume=592 |issue=1 |year=2003 |pages=620–630 |doi=10.1086/375560 |bibcode=2003ApJ...592..620V |doi-access=free }} computer models that relate orbital variations to climate can predict future climate possibilities.

Work by Berger and Loutre suggests that the current warm climate may last another 50,000 years.{{cite journal |vauthors=Berger A, Loutre MF | title=Climate: An exceptionally long interglacial ahead? | journal=Science | volume=297 | issue=5585 | year=2002 | pages=1287–8 | doi=10.1126/science.1076120 | pmid=12193773| s2cid=128923481 }} The amount of heat trapping (greenhouse) gases being emitted into the Earth's oceans and its atmosphere may delay the next glacial period by an additional 50,000 years.{{cite journal |last1=Tyrrell|first1=Toby |title=Calcium Carbonate Cycling in Future Oceans and its Influence on Future Climates |journal=Journal of Plankton Research |date=16 November 2007 |volume=30 |issue=2 |pages=141–156 |doi=10.1093/plankt/fbm105|doi-access=free }}{{cite journal |last1=Ganopolski |first1=A. |last2=Winkelmann |first2=R. |author2-link=Ricarda Winkelmann |last3=Schellnhuber |first3=H. J. |title=Critical Insolation–CO2 Relation for Diagnosing Past and Future Glacial Inception |journal=Nature |date=14 January 2016 |volume=529 |issue=7585 |pages=200–203 |doi=10.1038/nature16494|pmid=26762457 |bibcode=2016Natur.529..200G |s2cid=4466220 }}

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{{Wiktionary|glaciation}}

{{Ice Ages}}

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{{DEFAULTSORT:Glacial Period}}

Period