Editing Climate variability and change (section)

=== Proxy measurements ===
[[File:Vostok Petit data.svg|thumb|right|upright=1.35|Variations in [[CO2|CO<sub>2</sub>]], temperature and dust from the [[Vostok, Antarctica|Vostok]] ice core over the last 450,000 years.]]
Various archives of past climate are present in rocks, trees and fossils. From these archives, indirect measures of climate, so-called proxies, can be derived. Quantification of climatological variation of precipitation in prior centuries and epochs is less complete but approximated using proxies such as marine sediments, ice cores, cave stalagmites, and tree rings.<ref>{{cite journal|last1=Dominic |first1=F. |last2=Burns |first2=S.J. |last3=Neff |first3=U. |last4=Mudulsee |first4=M. |last5=Mangina |first5=A |last6=Matter |first6=A. |date=April 2004 |title=Palaeoclimatic interpretation of high-resolution oxygen isotope profiles derived from annually laminated speleothems from Southern Oman|journal=Quaternary Science Reviews |volume=23 |issue=7–8 |pages=935–45 |bibcode=2004QSRv...23..935F |doi=10.1016/j.quascirev.2003.06.019}}</ref> Stress, too little precipitation or unsuitable temperatures, can alter the growth rate of trees, which allows scientists to infer climate trends by analyzing the growth rate of tree rings. This branch of science studying this called [[dendroclimatology]].<ref>{{Cite book|url=https://books.google.com/books?id=e9Ez2dRGmioC|title=Dendroclimatology: progress and prospect|publisher=Springer Science & Business Media|year=2010|isbn=978-1-4020-4010-8|editor1-last=Hughes|editor1-first=Malcolm K.|series=Developments in Paleoenvironmental Research|volume=11|location=New York|editor2-last=Swetnam|editor2-first=Thomas W.|editor3-last=Diaz|editor3-first=Henry F.}}</ref> Glaciers leave behind [[moraine]]s that contain a wealth of material—including organic matter, quartz, and potassium that may be dated—recording the periods in which a glacier advanced and retreated.

Analysis of ice in cores drilled from an [[ice sheet]] such as the [[Antarctic ice sheet]], can be used to show a link between temperature and global sea level variations. The air trapped in bubbles in the ice can also reveal the CO<sub>2</sub> variations of the atmosphere from the distant past, well before modern environmental influences. The study of these ice cores has been a significant indicator of the changes in CO<sub>2</sub> over many millennia, and continues to provide valuable information about the differences between ancient and modern atmospheric conditions. The <sup>18</sup>O/<sup>16</sup>O ratio in calcite and ice core samples [[Oxygen isotope ratio cycle|used to deduce ocean temperature in the distant past]] is an example of a temperature proxy method.

The remnants of plants, and specifically pollen, are also used to study climatic change. Plant distributions vary under different climate conditions. Different groups of plants have pollen with distinctive shapes and surface textures, and since the outer surface of pollen is composed of a very resilient material, they resist decay. Changes in the type of pollen found in different layers of sediment indicate changes in plant communities. These changes are often a sign of a changing climate.<ref>{{cite journal|last1=Langdon|first1=P.G.|last2=Barber|first2=K.E.|last3=Lomas-Clarke|first3=S.H.|last4=Lomas-Clarke|first4=S.H.|date=August 2004|title=Reconstructing climate and environmental change in northern England through chironomid and pollen analyses: evidence from Talkin Tarn, Cumbria|journal=Journal of Paleolimnology|volume=32|issue=2|pages=197–213|bibcode=2004JPall..32..197L|doi=10.1023/B:JOPL.0000029433.85764.a5|s2cid=128561705}}</ref><ref>{{cite journal|last=Birks|first=H.H.|date=March 2003|title=The importance of plant macrofossils in the reconstruction of Lateglacial vegetation and climate: examples from Scotland, western Norway, and Minnesota, US|url=https://bora.uib.no/bitstream/1956/387/4/1956-387.pdf|journal=Quaternary Science Reviews|volume=22|issue=5–7|pages=453–73|bibcode=2003QSRv...22..453B|doi=10.1016/S0277-3791(02)00248-2|hdl=1956/387|hdl-access=free|access-date=20 April 2018|archive-date=11 June 2007|archive-url=https://web.archive.org/web/20070611133600/https://bora.uib.no/bitstream/1956/387/4/1956-387.pdf|url-status=dead}}</ref> As an example, pollen studies have been used to track changing vegetation patterns throughout the [[Quaternary glaciation]]s<ref>{{cite journal|last1=Miyoshi|first1=N|last2=Fujiki|first2=Toshiyuki|last3=Morita|first3=Yoshimune|year=1999|title=Palynology of a 250-m core from Lake Biwa: a 430,000-year record of glacial–interglacial vegetation change in Japan|journal=Review of Palaeobotany and Palynology|volume=104|issue=3–4|pages=267–83|doi=10.1016/S0034-6667(98)00058-X|bibcode=1999RPaPa.104..267M}}</ref> and especially since the [[last glacial maximum]].<ref>{{cite journal|last=Prentice|first=I. Colin|author2=Bartlein, Patrick J|author3=Webb, Thompson|year=1991|title=Vegetation and Climate Change in Eastern North America Since the Last Glacial Maximum|journal=Ecology|volume=72|issue=6|pages=2038–56|doi=10.2307/1941558|jstor=1941558|bibcode=1991Ecol...72.2038P }}</ref> Remains of [[beetle]]s are common in freshwater and land sediments. Different species of beetles tend to be found under different climatic conditions. Given the extensive lineage of beetles whose genetic makeup has not altered significantly over the millennia, knowledge of the present climatic range of the different species, and the age of the sediments in which remains are found, past climatic conditions may be inferred.<ref name="Coope-1999">{{cite journal |last1=Coope |first1=G.R. |last2=Lemdahl |first2=G. |last3=Lowe  |first3=J.J. |last4=Walkling  |first4=A. |date=4 May 1999 |title=Temperature gradients in northern Europe during the last glacial – Holocene transition (14–9 14 C kyr BP) interpreted from coleopteran assemblages |journal=[[Journal of Quaternary Science]] |volume=13 |issue=5 |pages=419–33 |bibcode=1998JQS....13..419C |doi=10.1002/(SICI)1099-1417(1998090)13:5<419::AID-JQS410>3.0.CO;2-D}}</ref>