Changes

When people talk about climate change they are usually talking about the problem of human-caused  [[global warming]], which is happening now (see [[global warming]] for more details). But the climate of the Earth has changed over not just thousands of years, but tens or hundreds of millions of years.<ref name="Alley" />  

When people talk about climate change they are usually talking about the problem of human-caused  [[global warming]], which is happening now (see [[global warming]] for more details). But the climate of the Earth has changed over not just thousands of years, but tens or hundreds of millions of years.<ref name="Alley" />  

The earth's climate changes over time, so it could be hotter or colder at a certain time. For example about 60 million years ago there were a lot of volcanoes, which burnt a lot of underground ''organic matter'' (squashed and [[Fossil|fossilized]] dead plants and animals became coal, gas and oil). A lot of carbon dioxide and [[methane]] went up in the air.<ref name=":1">{{Cite web|last=Lee|first=Howard|date=2020-03-19|title=Sudden Ancient Global Warming Event Traced to Magma Flood|url=https://www.quantamagazine.org/sudden-ancient-global-warming-event-traced-to-magma-flood-20200319/|access-date=2022-08-01|website=Quanta Magazine|language=en}}</ref>  

The earth's climate changes over time, so it could be hotter or colder at a certain time. For example about 60 million years ago there were a lot of volcanoes, which burnt a lot of underground ''organic matter'' (squashed and [[Fossil|fossilized]] dead plants and animals became coal, gas and oil). A large amount of carbon dioxide and [[methane]] went up in the air.<ref name=":1">{{Cite web|last=Lee|first=Howard|date=2020-03-19|title=Sudden Ancient Global Warming Event Traced to Magma Flood|url=https://www.quantamagazine.org/sudden-ancient-global-warming-event-traced-to-magma-flood-20200319/|access-date=2022-08-01|website=Quanta Magazine|language=en}}</ref>  

At times in the past, the temperature was much cooler, with the last [[glaciation]] ending about ten thousand years ago.<ref name=":3">Imbrie J. & Imbrie, K.P. 1979. Ice ages: solving the mystery. Short Hills NJ: Enslow. ISBN 978-0-89490-015-0</ref><ref name=Alley>Alley R.B. 2000. ''The two-mile time machine: ice cores, abrupt climate change, and our future''. Princeton University Press. ISBN 0-691-10296-1</ref> [[Ice age|Ice Ages]] are times when the Earth got colder, and more ice froze at the [[North Pole|North]] and [[South Pole|South Poles]].<ref name=":2">{{Cite web|title=Problem Solving Activity: What Causes Ice Ages?|url=https://gml.noaa.gov/outreach/info_activities/pdfs/PSA_ice_ages.pdf|access-date=2022-08-01|archive-date=2021-12-27|archive-url=https://web.archive.org/web/20211227233840/https://gml.noaa.gov/outreach/info_activities/pdfs/PSA_ice_ages.pdf|url-status=dead}}</ref> Sometimes even the whole Earth has been covered in ice, and was much colder than today.<ref name=":4">{{cite journal | author=Williams G.E. & Schmidt P.W. | title=Paleomagnetism of the Paleoproterozoic Gowganda and Lorrain formations, Ontario: low palaeolatitude for Huronian glaciation | journal=EPSL | year=1997 | volume=153 | issue=3 | pages=157–169 | url=http://www.cosis.net/abstracts/EAE03/08262/EAE03-J-08262.pdf | doi=10.1016/S0012-821X(97)00181-7 | bibcode=1997E&PSL.153..157W | issn=0012-821X | access-date=2022-08-05 | archive-date=2016-06-09 | archive-url=https://web.archive.org/web/20160609195723/http://www.cosis.net/abstracts/EAE03/08262/EAE03-J-08262.pdf | url-status=dead }}</ref><ref name=":5">{{cite journal |author=Evans D.A; Beukes N.J. & Kirschvink J.L. |title=Low-latitude glaciation in the Palaeoproterozoic era |journal=Nature |volume=386 |issue=6622 |pages=262–6 |date=1997 |doi=10.1038/386262a0 |url=http://www.nature.com/nature/journal/v386/n6622/abs/386262a0.html|bibcode = 1997Natur.386..262E |s2cid=4364730 }}</ref>  

At times in the past, the temperature was much cooler, with the last [[glaciation]] ending about ten thousand years ago.<ref name=":3">Imbrie J. & Imbrie, K.P. 1979. Ice ages: solving the mystery. Short Hills NJ: Enslow. ISBN 978-0-89490-015-0</ref><ref name=Alley>Alley R.B. 2000. ''The two-mile time machine: ice cores, abrupt climate change, and our future''. Princeton University Press. ISBN 0-691-10296-1</ref> [[Ice age|Ice Ages]] are times when the Earth got colder, and more ice froze at the [[North Pole|North]] and [[South Pole|South Poles]].<ref name=":2">{{Cite web|title=Problem Solving Activity: What Causes Ice Ages?|url=https://gml.noaa.gov/outreach/info_activities/pdfs/PSA_ice_ages.pdf|access-date=2022-08-01|archive-date=2021-12-27|archive-url=https://web.archive.org/web/20211227233840/https://gml.noaa.gov/outreach/info_activities/pdfs/PSA_ice_ages.pdf|url-status=dead}}</ref> There have been times when Earth has been covered in ice, and was much colder than today.<ref name=":4">{{cite journal | author=Williams G.E. & Schmidt P.W. | title=Paleomagnetism of the Paleoproterozoic Gowganda and Lorrain formations, Ontario: low palaeolatitude for Huronian glaciation | journal=EPSL | year=1997 | volume=153 | issue=3 | pages=157–169 | url=http://www.cosis.net/abstracts/EAE03/08262/EAE03-J-08262.pdf | doi=10.1016/S0012-821X(97)00181-7 | bibcode=1997E&PSL.153..157W | issn=0012-821X | access-date=2022-08-05 | archive-date=2016-06-09 | archive-url=https://web.archive.org/web/20160609195723/http://www.cosis.net/abstracts/EAE03/08262/EAE03-J-08262.pdf | url-status=dead }}</ref><ref name=":5">{{cite journal |author=Evans D.A; Beukes N.J. & Kirschvink J.L. |title=Low-latitude glaciation in the Palaeoproterozoic era |journal=Nature |volume=386 |issue=6622 |pages=262–6 |date=1997 |doi=10.1038/386262a0 |url=http://www.nature.com/nature/journal/v386/n6622/abs/386262a0.html|bibcode = 1997Natur.386..262E |s2cid=4364730 }}</ref>  

There is no one reason why there are Ice Ages. Changes in the [[Earth's orbit]] around the Sun, and the Sun getting brighter or dimmer are events which do happen.<ref name=":2" /> Also how much the Earth is tilted compared to the Sun might make a difference.<ref name=":6">{{Cite web|title=When and how did the ice age end? Could another one start?|url=https://www.amnh.org/explore/ology/earth/ask-a-scientist-about-our-environment/how-did-the-ice-age-end}}</ref> Another source of change is the activities of living things (see [[Great Oxygenation Event]] and [[Huronian glaciation]]).<ref name=":7">{{cite journal | author=Robert E. Kopp | display-authors=etal | title=The Paleoproterozoic snowball Earth: a climate disaster triggered by the evolution of oxygenic photosynthesis | journal=Proc. Natl. Acad. Sci. U.S.A. | year=2005 | volume=102 | issue=32 | pages=11131–6 | doi=10.1073/pnas.0504878102 | pmid=16061801 | pmc=1183582 | bibcode=2005PNAS..10211131K | doi-access=free }}</ref><ref name=":8">{{cite journal|last=Lane|first=Nick|date=2010|title=First breath: Earth's billion-year struggle for oxygen|url=https://www.newscientist.com/article/mg20527461.100-first-breath-earths-billionyear-struggle-for-oxygen.html|journal=New Scientist|issue=2746|doi=}}  A snowball period, c2.4–c2.0 billion years ago, was triggered by the Great Oxygenation Event [http://ptc-cam.blogspot.com/2010/02/first-breath-earths-billion-year.html] {{Webarchive|url=https://web.archive.org/web/20110106141826/http://ptc-cam.blogspot.com/2010/02/first-breath-earths-billion-year.html|date=2011-01-06}}</ref>

There is no one reason why there are Ice Ages. Changes in the [[Earth's orbit]] around the Sun, and the Sun getting brighter or dimmer are events which do happen.<ref name=":2" /> Also how much the Earth is tilted compared to the Sun might make a difference.<ref name=":6">{{Cite web|title=When and how did the ice age end? Could another one start?|url=https://www.amnh.org/explore/ology/earth/ask-a-scientist-about-our-environment/how-did-the-ice-age-end}}</ref> Another source of change is the activities of living things (see [[Great Oxygenation Event]] and [[Huronian glaciation]]).<ref name=":7">{{cite journal | author=Robert E. Kopp | display-authors=etal | title=The Paleoproterozoic snowball Earth: a climate disaster triggered by the evolution of oxygenic photosynthesis | journal=Proc. Natl. Acad. Sci. U.S.A. | year=2005 | volume=102 | issue=32 | pages=11131–6 | doi=10.1073/pnas.0504878102 | pmid=16061801 | pmc=1183582 | bibcode=2005PNAS..10211131K | doi-access=free }}</ref><ref name=":8">{{cite journal|last=Lane|first=Nick|date=2010|title=First breath: Earth's billion-year struggle for oxygen|url=https://www.newscientist.com/article/mg20527461.100-first-breath-earths-billionyear-struggle-for-oxygen.html|journal=New Scientist|issue=2746|doi=}}  A snowball period, c2.4–c2.0 billion years ago, was triggered by the Great Oxygenation Event [http://ptc-cam.blogspot.com/2010/02/first-breath-earths-billion-year.html] {{Webarchive|url=https://web.archive.org/web/20110106141826/http://ptc-cam.blogspot.com/2010/02/first-breath-earths-billion-year.html|date=2011-01-06}}</ref>