Climate: Difference between revisions

[[Paleoclimatology]] is the study of ancient climates. [[Paleoclimatologists]] seek to explain climate variations for all parts of the [[Earth]] during any given [[Geology|geologic]] period, beginning with the time of the Earth's formation.<ref>{{Cite web |title=paleoclimatology {{!}} science |url=https://www.britannica.com/science/paleoclimatology |access-date=2022-09-01 |website=Britannica |language=en |archive-date=2022-09-01 |archive-url=https://web.archive.org/web/20220901163506/https://www.britannica.com/science/paleoclimatology |url-status=live }}</ref> Since very few direct observations of climate were available before the 19th century, [[paleoclimate]]s are inferred from [[Proxy (climate)|proxy variables]]. They include non-biotic evidence—such as [[Sediment|sediments]] found in [[lake beds]] and [[ice core]]s—and [[Biotic component|biotic]] evidence—such as [[Dendrochronology|tree rings]] and coral. [[Climate model]]s are mathematical models of past, present, and future climates. Climate change may occur over long and short timescales due to various factors. Recent warming is discussed in terms of [[global warming]], which results in redistributions of [[Life|biota]]. For example, as climate scientist [[Lesley Ann Hughes]] has written: "a 3&nbsp;°C [5&nbsp;°F] change in mean annual temperature corresponds to a shift in isotherms of approximately {{Convert|300|–|400|km|mi|disp=sqbr|abbr=on}} in latitude (in the temperate zone) or {{Convert|500|m|ft|disp=sqbr|abbr=on}} in elevation. Therefore, species are expected to move upwards in elevation or towards the poles in [[latitude]] in response to shifting climate zones."<ref>{{Cite book|title=Biological consequences of globalwarming: is the signal already|last=Hughes|first=Lesley|year=2000|pages=56}}</ref><ref name="TIEE-20000201">{{cite journal |last=Hughes |first=Leslie |title=Biological consequences of global warming: is the signal already apparent? |url=http://www.cell.com/trends/ecology-evolution/abstract/S0169-5347(99)01764-4 |date=1 February 2000 |journal=[[Trends in Ecology and Evolution]] |volume=15 |issue=2 |pages=56–61 |doi=10.1016/S0169-5347(99)01764-4 |pmid=10652556 |access-date=November 17, 2016 |archive-date=12 October 2013 |archive-url=https://web.archive.org/web/20131012051437/http://www.cell.com/trends/ecology-evolution/abstract/S0169-5347(99)01764-4 |url-status=live |url-access=subscription }}</ref>

The WMO originated from the [[International Meteorological Organization]] which set up a technical commission for climatology in 1929. At its 1934 [[Wiesbaden]] meeting, the technical commission designated the thirty-year period from 1901 to 1930 as the reference time frame for climatological standard normals. In 1982, the WMO agreed to update climate normals, and these were subsequently completed on the basis of climate data from 1 January 1961 to 31 December 1990.<ref name="WMO history">{{cite web | title=Commission For Climatology: Over Eighty Years of Service |year=2011 | publisher=World Meteorological Organization | url=http://www.wmo.int/pages/prog/wcp/ccl/documents/WMO1079_web.pdf |pages=6, 8, 10, 21, 26 | access-date=1 September 2015|archive-url=https://web.archive.org/web/20150913033109/http://www.wmo.int/pages/prog/wcp/ccl/documents/WMO1079_web.pdf|archive-date=13 September 2015}}</ref> The 1961–1990 climate normals serve as the baseline reference period. The next set of climate normals to be published by WMO is from 1991 to 2010.<ref>{{Cite web |title=WMO Climatological Normals |publisher=[[World Meteorological Organization]] |url=https://community.wmo.int/wmo-climatological-normals |access-date=2022-08-21 |archive-date=2022-08-21 |archive-url=https://web.archive.org/web/20220821010013/https://community.wmo.int/wmo-climatological-normals |url-status=live }}</ref> Aside from collecting from the most common atmospheric variables (air temperature, pressure, precipitation and wind), other variables such as humidity, visibility, cloud amount, solar radiation, soil temperature, pan evaporation rate, days with thunder and days with hail are also collected to measure change in climate conditions.<ref>{{Cite book |date=2017 |title=WMO Guidelines on the Calculation of Climate Normals |url=https://library.wmo.int/doc_num.php?explnum_id=4166 |access-date=2022-08-20 |publisher=World Meteorological Organization |format=PDF |isbn=978-92-63-11203-3 |archive-date=2022-08-08 |archive-url=https://web.archive.org/web/20220808132316/https://library.wmo.int/doc_num.php?explnum_id=4166 |url-status=live }}</ref>

The difference between climate and weather is usefully summarized by the popular phrase "Climate is what you expect, weather is what you get."<ref>National Weather Service Office Tucson, Arizona. [http://www.wrh.noaa.gov/twc/ Main page.] {{Webarchive|url=https://web.archive.org/web/20170312090813/http://www.wrh.noaa.gov/twc/ |date=2017-03-12 }} Retrieved on 2007-06-01.</ref> Over [[history|historical]] time spans, there are a number of nearly constant variables that determine climate, including [[latitude]], altitude, proportion of land to water, and proximity to oceans and mountains. All of these variables change only over periods of millions of years due to processes such as [[plate tectonics]]. Other climate determinants are more dynamic: the [[thermohaline circulation]] of the ocean leads to a 5&nbsp;°C (9&nbsp;°F) warming of the northern Atlantic Ocean compared to other ocean basins.<ref>{{cite web |first=Stefan |last=Rahmstorf |url=http://www.pik-potsdam.de/~stefan/thc_fact_sheet.html |title=The Thermohaline Ocean Circulation: A Brief Fact Sheet |publisher=Potsdam Institute for Climate Impact Research |archive-url=https://web.archive.org/web/20130327151821/http://www.pik-potsdam.de/~stefan/thc_fact_sheet.html |archive-date=2013-03-27 |url-status=live |access-date=2008-05-02}}</ref> Other [[ocean current]]s redistribute heat between land and water on a more regional scale. The density and type of vegetation coverage affects solar heat absorption,<ref>{{cite web |first1=Gertjan |last1=de Werk |first2=Karel |last2=Mulder |url=http://www.enhr2007rotterdam.nl/documents/W15_paper_DeWerk_Mulder.pdf |url-status=dead |title=Heat Absorption Cooling For Sustainable Air Conditioning of Households |series=Sustainable Urban Areas Rotterdam |date=2007 |archive-url=https://web.archive.org/web/20080527223539/http://www.enhr2007rotterdam.nl/documents/W15_paper_DeWerk_Mulder.pdf |archive-date=2008-05-27 |access-date=2008-05-02}}</ref> water retention, and rainfall on a regional level. Alterations in the quantity of atmospheric [[greenhouse gas]]es (particularly [[carbon dioxide]] and [[methane]]) determines the amount of solar energy retained by the planet, leading to [[global warming]] or [[global cooling]]. The variables which determine climate are numerous and the interactions complex, but there is general agreement that the broad outlines are understood, at least insofar as the determinants of historical climate change are concerned.<ref>[https://www.un.org/en/climatechange/what-is-climate-change What Is Climate Change?]</ref><ref name=Ledley1999>{{cite journal|author = Ledley, T.S.|year = 1999|title = Climate change and greenhouse gases|journal = [[Eos (journal)|EOS]]|volume = 80|issue = 39|page = 453|doi = 10.1029/99EO00325|last2 = Sundquist|first2 = E. T.|last3 = Schwartz|first3 = S. E.|last4 = Hall|first4 = D. K.|last5 = Fellows|first5 = J. D.|last6 = Killeen|first6 = T. L.|bibcode = 1999EOSTr..80Q.453L|hdl = 2060/19990109667|doi-access = free|hdl-access = free}}</ref>

Climate classifications are systems that categorize the world's climates. A climate classification may correlate closely with a [[biome]] classification, as climate is a major influence on life in a region. One of the most used is the [[Köppen climate classification]] scheme first developed in 1899.<ref>{{cite journal |last1=Beck |first1=Hylke E. |last2=Zimmermann |first2=Niklaus E. |last3=McVicar |first3=Tim R. |last4=Vergopolan |first4=Noemi |last5=Berg |first5=Alexis |last6=Wood |first6=Eric F. |author6-link=Eric Franklin Wood |date=30 October 2018 |title=Present and future Köppen-Geiger climate classification maps at 1-km resolution |journal=Scientific Data |language=en |volume=5 |pages=180214 |bibcode=2018NatSD...580214B |doi=10.1038/sdata.2018.214 |issn=2052-4463 |pmc=6207062 |pmid=30375988}}</ref>

[[File:Change in Average Temperature With Fahrenheit.svg|thumb|upright=1.35|right|Surface air temperature change over the past 50 years.<ref>{{Cite web |title=GISS Surface Temperature Analysis (v4) |url=https://data.giss.nasa.gov/gistemp/maps/index_v4.html |access-date=12 January 2024 |website=NASA}}</ref>]]

[[File:Global Temperature And Forces With Fahrenheit.svg|thumb|upright=1.35|right|Observed temperature from NASA<ref name="nasa temperatures">{{cite web |title=Global Annual Mean Surface Air Temperature Change |url=https://data.giss.nasa.gov/gistemp/graphs_v4/ |publisher=NASA |access-date=23 February 2020 |archive-date=16 April 2020 |archive-url=https://web.archive.org/web/20200416074510/https://data.giss.nasa.gov/gistemp/graphs_v4/ |url-status=live }}.</ref> vs the 1850–1900 average used by the IPCC as a pre-industrial baseline.<ref name="ipcc pre industrial baseline">{{harvnb|IPCC AR5 SYR Glossary|2014|page=124}}.</ref> The primary driver for increased global temperatures in the industrial era is human activity, with natural forces adding variability.<ref name="USGCRP Chapter 3 Figure 3-1 panel 2">{{harvnb|USGCRP Chapter 3|2017}} [https://science2017.globalchange.gov/chapter/3#fig-3-1 Figure 3.1 panel 2] {{Webarchive|url=https://web.archive.org/web/20180409042234/https://science2017.globalchange.gov/chapter/3/#fig-3-1 |date=2018-04-09 }}, [https://web.archive.org/web/20171103182210/https://science2017.globalchange.gov/chapter/3/#fig-3-3 Figure 3.3 panel 5] .</ref>]]

In recent usage, especially in the context of [[environmental policy]], the term "climate change" often refers only to changes in modern climate, including the rise in average surface [[temperature]] known as [[global warming]]. In some cases, the term is also used with a presumption of human causation, as in the [[United Nations]] [[UNFCCC|Framework Convention on Climate Change]] (UNFCCC). The UNFCCC uses "climate variability" for non-human caused variations.<ref>{{cite web|url=http://www.grida.no/climate/ipcc_tar/wg1/518.htm |title=Glossary |work=Climate Change 2001: The Scientific Basis. Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Change |access-date=2008-05-22 |date=2001-01-20 |publisher=[[Intergovernmental Panel on Climate Change]] |url-status=dead |archive-url=https://web.archive.org/web/20170126132100/http://www.grida.no/climate/ipcc_tar/wg1/518.htm |archive-date=2017-01-26 }}</ref>