Dab solver - Climate change

Most tools require the use of JavaScript. If you are using Firefox with the NoScript addon, please mark toolserver.org as trusted. See the Help page for details.

Feedback / Report a bug

0 points on this page / 18,545 points earned collectively this month / Disambiguate pages on your watchlist

{{About||current and future climatological effects of human influences|global warming|the study of past climate change|paleoclimatology|temperatures on the longest time scales|geologic temperature record}}

{{pp-semi-indef}}
{{bots|deny=Citation bot}}
{{atmospheric sciences}}

Climate change is a significant and lasting change in the statistical distribution of [[weather]] patterns over periods ranging from decades to millions of years. It may be a change in average weather conditions, or in the distribution of weather around the average conditions (i.e., more or fewer extreme weather events). Climate change is caused by factors that include oceanic processes (such as [[Thermohaline circulation|oceanic circulation]]),  processes, variations in [[Sunlight|solar radiation]] received by Earth, [[plate tectonics]] and [[volcanic eruptions]], and human-induced alterations of the natural world; these latter effects are currently causing [[global warming]], and "climate change" is often used to describe human-specific impacts.

Scientists actively work to understand past and future climate by using [[Proxy (climate)|observations]] and theoretical models. [[Borehole]] temperature profiles, [[ice core]]s, floral and faunal records, glacial and periglacial processes, stable isotope and other sediment analyses, and sea level records serve to provide a climate record that spans the geologic past. More recent data are provided by the instrumental record. Physically based [[general circulation model]]s are often used in theoretical approaches to match past climate data, make future projections, and link causes and effects in climate change.
318 lines hidden (37637 characters)
* [http://site.videoproject.com/coralreefs/ Climate Change:  Coral Reefs on the Edge] An online video presentation by Prof. Ove Hoegh-Guldberg, University of Auckland
*[http://cdkn.org/ [[Climate & Development Knowledge Network]], run by an alliance of organisations that include [[PwC]] and ]
{{global warming|gstate=expanded}}
{{Use dmy dates|date=July 2011}}

{{DEFAULTSORT:Climate Change}}
[[Category:Climate change| ]]
[[Category:Climate and weather statistics]]
[[Category:Climate history]]
[[Category:Carbon finance]]
[[Category:Economic problems]]

Single scrollbar

Warning: This page is currently semi-protected, and can be edited only by established registered users.

{{About||current and future climatological effects of human influences|global warming|the study of past climate change|paleoclimatology|temperatures on the longest time scales|geologic temperature record}}

'''Climate change''' is a significant and lasting change in the statistical distribution of [[weather]] patterns over periods ranging from decades to millions of years. It may be a change in average weather conditions, or in the distribution of weather around the average conditions (i.e., more or fewer extreme weather events). Climate change is caused by factors that include oceanic processes (such as [[Thermohaline circulation|oceanic circulation]]), <<link:0>> processes, variations in [[Sunlight|solar radiation]] received by Earth, [[plate tectonics]] and [[volcanic eruptions]], and human-induced alterations of the natural world; these latter effects are currently causing [[global warming]], and "climate change" is often used to describe human-specific impacts.

Scientists actively work to understand past and future climate by using [[Proxy (climate)|observations]] and theoretical models. [[Borehole]] temperature profiles, [[ice core]]s, floral and faunal records, glacial and periglacial processes, stable isotope and other sediment analyses, and sea level records serve to provide a climate record that spans the geologic past. More recent data are provided by the instrumental record. Physically based [[general circulation model]]s are often used in theoretical approaches to match past climate data, make future projections, and link causes and effects in climate change.

==Terminology==
The most general definition of ''climate change'' is a change in the statistical properties of the climate system when considered over long periods of time, regardless of cause.<ref>{{cite web |title=Glossary – Climate Change |work=Education Center – Arctic Climatology and Meteorology |publisher=NSIDC National Snow and Ice Data Center |url=http://nsidc.org/arcticmet/glossary/climate_change.html}}; [http://www.ipcc.ch/ipccreports/tar/wg1/518.htm Glossary], in {{Harvnb|IPCC TAR WG1|2001}}.</ref> Accordingly, fluctuations over periods shorter than a few decades, such as [[El Niño]], do not represent climate change.

The term sometimes is used to refer specifically to climate change caused by human activity, as opposed to changes in climate that may have resulted as part of Earth's natural processes.<ref>{{cite web |title=The United Nations Framework Convention on Climate Change |date=21 March 1994 |url=http://unfccc.int/essential_background/convention/background/items/1349.php|quote=''Climate change'' means a change of climate which is attributed directly or indirectly to human activity that alters the composition of the global atmosphere and which is in addition to natural climate variability observed over comparable time periods.}}</ref>
In this sense, especially in the context of [[environmental policy]], the term ''climate change'' has become synonymous with [[human impact on the environment|anthropogenic]] [[global warming]]. Within scientific journals, ''global warming'' refers to surface temperature increases while ''climate change'' includes global warming and everything else that increasing greenhouse gas levels will affect.<ref>{{cite web|title=What's in a Name? Global Warming vs. Climate Change|url=http://www.nasa.gov/topics/earth/features/climate_by_any_other_name.html|publisher=NASA|accessdate=23 July 2011}}</ref>

==Causes==
On the broadest scale, the rate at which energy is received from the sun and the rate at which it is lost to space determine the equilibrium temperature and climate of Earth. This energy is distributed around the globe by winds, ocean currents, and other mechanisms to affect the climates of different regions.

Factors that can shape climate are called [[climate forcing]]s or "forcing mechanisms".<ref name=EPA-Glossary>{{cite book|last=US EPA|title=Glossary of climate change terms|url=http://www.epa.gov/climatechange/glossary.html#F}}</ref> These include processes such as variations in [[solar radiation]], variations in the Earth's orbit, [[orogeny|mountain-building]] and [[continental drift]] and changes in [[greenhouse gas]] concentrations. There are a variety of [[Climate feedback|climate change feedbacks]] that can either amplify or diminish the initial forcing. Some parts of the climate system, such as the oceans and ice caps, respond slowly in reaction to climate forcings, while others respond more quickly.

Forcing mechanisms can be either "internal" or "external".   Internal forcing mechanisms are natural processes within the climate system itself (e.g., the [[thermohaline circulation]]).   External forcing mechanisms can be either natural (e.g., changes in solar output) or anthropogenic (e.g., increased emissions of greenhouse gases).

Whether the initial forcing mechanism is internal or external, the response of the climate system might be fast (e.g., a sudden cooling due to airborne [[volcanic ash]] reflecting sunlight), slow (e.g. [[thermal expansion]] of warming ocean water), or a combination (e.g., sudden loss of [[albedo]] in the arctic ocean as sea ice melts, followed by more gradual thermal expansion of the water).  Therefore, the climate system can respond abruptly, but the full response to forcing mechanisms might not be fully developed for centuries or even longer.

===Internal forcing mechanisms===
Natural changes in the components of Earth's climate system and their interactions are the cause of internal climate variability, or "internal forcings."
Scientists generally define the five components of earth's climate system to include [[Earth's Atmosphere|atmosphere]], [[hydrosphere]], [[cryosphere]], [[lithosphere]] (restricted to the surface soils, rocks, and sediments), and [[biosphere]].<ref>{{cite web
|url= http://earthobservatory.nasa.gov/Glossary/index.php?mode=alpha&seg=b&segend=d
|title=Glossary
|publisher=NASA Earth Observatory
|year=2011
|accessdate=8 July 2011
|quote=Climate System: The five physical components (atmosphere, hydrosphere, cryosphere, lithosphere, and biosphere) that are responsible for the climate and its variations.}}</ref>{{failed verification|reason=The archived talk page discussion points to such a distinction, but it is still fuzzy on who to cite. The ref here does not support the distinction we are drawing. SBHB mentions a book that may be useful - see talk archive 3. ([[User talk:Awickert|talk]]) 21 July 2011 (UTC)|date=July 2011}}

====Ocean variability====
{{Main|Thermohaline circulation}}
[[File:Ecinfigtwo.jpg|thumb|right|[[Pacific Decadal Oscillation]] 1925 to 2010]]

The ocean is a fundamental part of the climate system, some changes in it occurring at longer timescales than in the [[Atmosphere of Earth|atmosphere]], massing hundreds of times more and having very high [[Volumetric heat capacity|thermal inertia]] (such as the ocean depths still lagging today in temperature adjustment from the [[Little Ice Age]]).{{clarify|reason=Had an HTML comment "THIS SENTENCE MAKES NO SENSE" that couldn't be readily dated, though it was apparently after March 2011. I can't speak for the original tagger, but I agree the statement is confusing. -BDD|date=January 2013}}<ref>Kirk Bryan, Geophysical Fluid Dynamics Laboratory. [http://www.gfdl.noaa.gov/bibliography/related_files/kb8602.pdf?PHPSESSID=3ce1d32ab89d5b593b86c95ce91614df Man's Great Geophysical Experiment]. U.S. [[National Oceanic and Atmospheric Administration]].</ref>

Short-term fluctuations (years to a few decades) such as the [[El Niño-Southern Oscillation]], the [[Pacific decadal oscillation]], the [[North Atlantic oscillation]], and the [[Arctic oscillation]], represent climate variability rather than climate change. On longer time scales, alterations to ocean processes such as thermohaline circulation play a key role in redistributing heat by carrying out a very slow and extremely deep movement of water and the long-term redistribution of heat in the world's oceans.

[[File:Ocean circulation conveyor belt.jpg|thumb|right|A schematic of modern [[thermohaline]] circulation. Tens of millions of years ago, continental plate movement formed a land-free gap around Antarctica, allowing formation of the [[Antarctic Circumpolar Current|ACC]] which keeps warm waters away from Antarctica.]]

====Life====

Life affects climate through its role in the [[carbon cycle|carbon]] and [[water cycle]]s and such mechanisms as [[albedo]], [[evapotranspiration]], [[Cloud| cloud formation]], and [[weathering]].<ref>Spracklen. D. et al., (2008). [http://rsta.royalsocietypublishing.org/content/366/1885/4613.abstract "Boreal forests, aerosols and the impacts on clouds and climate"] ''Phil. Trans. Roy. Soc. A'', 366, 4613-4626.</ref><ref>{{Cite journal|author=Christner BC, Morris CE, Foreman CM, Cai R, Sands DC |title=Ubiquity of biological ice nucleators in snowfall |journal=Science |volume=319 |issue=5867 |pages=1214 |year=2008 |pmid=18309078 | url = http://www.sciencemag.org/content/319/5867/1214.short | doi = 10.1126/science.1149757 |bibcode=2008Sci...319.1214C}}</ref><ref>David W. Schwartzman and Tyler Volk (1989). [http://www.nature.com/nature/journal/v340/n6233/abs/340457a0.html "Biotic enhancement of weathering and the habitability of Earth"] [[Nature (journal)|''Nature'']], vol 340, pp. 457-460</ref> Examples of how life may have affected past climate include: [[glaciation]] 2.3 billion years ago triggered by the evolution of oxygenic [[photosynthesis]],<ref>{{cite journal |first1=Robert E. |last1=Kopp |first2=Joseph L. |last2=Kirschvink |first3=Isaac A. |last3=Hilburn |first4=Cody Z. |last4=Nash | 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 | url=http://www.pnas.org/cgi/reprint/0504878102v1 | doi=10.1073/pnas.0504878102 | pmid=16061801 | pmc=1183582 | bibcode=2005PNAS..10211131K}}</ref><ref>Kasting JF, Seifert JL (2002). [http://www3.geosc.psu.edu/~jfk4/PersonalPage/Pdf/Science_02.pdf "Life and the evolution of Earth's atmosphere"] ''Science'' 296:1066–1068.</ref> glaciation 300 million years ago ushered in by long-term burial of [[lignin|decomposition-resistant]] [[detritus]] of vascular land plants ([[Coal#Formation|forming coal]]),<ref>{{cite journal | author = Mora, C.I. | coauthors = Driese, S.G.; Colarusso, L.A.| year = 1996 | title = Middle to Late Paleozoic Atmospheric {{co2}} Levels from Soil Carbonate and Organic Matter | journal = Science | volume = 271 | issue = 5252 | pages = 1105–1107 | url = http://www.sciencemag.org/content/271/5252/1105.abstract | doi = 10.1126/science.271.5252.1105|bibcode = 1996Sci...271.1105M }}</ref><ref>{{cite journal |url=http://www.pnas.org/cgi/content/full/96/20/10955 |title=Atmospheric oxygen over Phanerozoic time |first=Robert A. |last=Berner |issue=20 |pages=10955–57 |year=1999|journal=Proc. Natl. Acad. Sci. U.S.A. |pmid=10500106 |doi=10.1073/pnas.96.20.10955 |volume=96 |pmc=34224 |bibcode=1999PNAS...9610955B}}</ref> termination of the [[Paleocene-Eocene Thermal Maximum]] 55 million years ago by flourishing marine [[phytoplankton]],<ref>{{cite journal | author = Bains, S. | coauthors = Norris, R.D.; Corfield, R.M.; Faul, K.L. | year = 2000 | title = Termination of global warmth at the Palaeocene/Eocene boundary through productivity feedback | journal = Nature | volume = 407 | issue = 6801 | pages = 171–4 | url = http://www.imedea.uib-csic.es/master/cambioglobal/Modulo_1_02/Subject_General/Bibliography_general/P_E_global_warmth.pdf | doi = 10.1038/35025035 | pmid = 11001051}}</ref><ref name=Zachos1999>{{cite journal | doi = 10.1080/11035890001221188 | author = Zachos, J.C. | coauthors = Dickens, G.R. | year = 2000 | title = An assessment of the biogeochemical feedback response to the climatic and chemical perturbations of the LPTM | url = http://www.tandfonline.com/doi/abs/10.1080/11035890001221188#preview | volume = 122 | issue = 1 | pages = 188–189 | journal = GFF}}</ref>
reversal of global warming 49 million years ago by [[Azolla event|800,000 years of arctic azolla blooms]],<ref>Speelman, E. N., and Coauthors (2009). [http://www.ncbi.nlm.nih.gov/pubmed/19323694 "The Eocene Arctic Azolla bloom: environmental conditions, productivity, and carbon drawdown"] ''Geobiology'', 7, 155-170.</ref><ref>{{Cite journal | author = Henk Brinkhuis, Stefan Schouten; | year = 2006 | title = Episodic fresh surface waters in the Eocene Arctic Ocean | journal = Nature | volume = 441 | issue = 7093 | pages = 606–609 | url = http://igitur-archive.library.uu.nl/bio/2007-0807-200221/sinninghe_06_episodic_fresh.pdf | doi = 10.1038/nature04692 | pmid = 16752440}}</ref> and global cooling over the past 40 million years driven by the expansion of grass-grazer [[ecosystem]]s.<ref>{{cite journal | last = Retallack | first = Gregory | title = Cenozoic Expansion of Grasslands and Climatic Cooling | journal = [[The Journal of Geology]] | volume = 109 | issue = | pages = 407–426 | publisher = University of Chicago Press | location = | year = 2001 | url = http://pages.uoregon.edu/dogsci/_media/directory/faculty/greg/grasslandscooling.pdf?id=directory%3Afaculty%3Agreg%3Aabout&cache=cache |doi = | accessdate = | bibcode = }}</ref><ref>Dutton, Jan F. and Barron, Eric J. (1997). [http://geology.geoscienceworld.org/content/25/1/39.abstract “Miocene to present vegetation changes: A possible piece of the Cenozoic cooling puzzle”] ''Geology'', v. 25, p. 39-41.</ref>

===External forcing mechanisms===
[[File:Mauna Loa Carbon Dioxide-en.svg|thumb|right|Increase in atmospheric {{CO2}} levels]]
{{multiple image|direction=vertical|width=220| footer = |image1=MilankovitchCyclesOrbitandCores.png|caption1= Milankovitch cycles from 800,000 years ago in the past to 800,000 years in the future.|image2=Vostok Petit data.svg||caption2= Variations in [[CO2|CO2]], temperature and dust from the [[Vostok, Antarctica|Vostok]] ice core over the last 450,000 years}}

====Orbital variations====
{{Main|Milankovitch cycles}}

Slight variations in Earth's orbit lead to changes in the seasonal distribution of sunlight reaching the Earth's surface and how it is distributed across the globe. There is very little change to the area-averaged annually averaged sunshine; but there can be strong changes in the geographical and seasonal distribution. The three types of orbital variations are variations in Earth's [[Orbital eccentricity|eccentricity]], changes in [[axial tilt|the tilt angle of Earth's axis of rotation]], and [[precession]] of Earth's axis. Combined together, these produce [[Milankovitch cycles]] which have a large impact on climate and are notable for their correlation to [[glacial period|glacial]] and [[interglacial period]]s,<ref name="msu milankovitch">{{cite web |url=http://www.homepage.montana.edu/~geol445/hyperglac/time1/milankov.htm|archiveurl=http://web.archive.org/web/20110716144130/http://www.homepage.montana.edu/~geol445/hyperglac/time1/milankov.htm|archivedate=2011-07-16|title= Milankovitch Cycles and Glaciation|accessdate=2009-04-02|publisher= University of Montana}}</ref> their correlation with the advance and retreat of the [[Sahara]],<ref name="msu milankovitch" /> and for their [[cyclostratigraphy|appearance]] in the [[geologic record|stratigraphic record]].<ref>{{cite journal|doi=10.1111/j.1365-3121.1989.tb00403.x|title=A Milankovitch scale for Cenomanian time|year=1989|author=Gale, Andrew S.|journal=Terra Nova|volume=1|page=420|issue=5}}</ref>

The [[IPCC]] notes that Milankovitch cycles drove the ice age cycles, [[CO2|CO2]] followed temperature change "with a lag of some hundreds of years," and that as a feedback amplified temperature change.<ref>[http://www.ipcc.ch/publications_and_data/ar4/wg1/en/faq-6-1.html FAQ 6.1: What Caused the Ice Ages and Other Important Climate Changes Before the Industrial Era?] in {{Harvnb|IPCC AR4 WG1|2007}}.</ref> The depths of the ocean have a lag time in changing temperature ([[thermal inertia]] on such scale). Upon seawater temperature change, the solubility of CO2 in the oceans changed, as well as other factors impacting air-sea CO2 exchange.<ref>[http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch6s6-4.html Box 6.2: What Caused the Low Atmospheric Carbon Dioxide Concentrations During Glacial Times?] in {{Harvnb|IPCC AR4 WG1|2007}} .</ref>

====Solar output====
{{Main|Solar variation}}
[[File:Solar Activity Proxies.png|thumb|Variations in solar activity during the last several centuries based on observations of [[sunspot]]s and [[beryllium]] isotopes. The period of extraordinarily few sunspots in the late 17th century was the [[Maunder minimum]].]]

The [[Sun]] is the predominant source for [[energy]] input to the Earth. Both long- and short-term variations in solar intensity are known to affect global climate.

[[History of the Earth|Three to four billion years ago]] the sun emitted only 70% as much power as it does today. If the atmospheric composition had been the same as today, liquid water should not have existed on Earth. However, there is evidence for the presence of water on the early Earth, in the [[Hadean]]<ref name="Marty, B. 2006 421">{{cite journal|doi=10.2138/rmg.2006.62.18|title=Water in the Early Earth|year=2006|author=Marty, B.|journal=Reviews in Mineralogy and Geochemistry|volume=62|page=421}}</ref><ref>{{cite journal|doi=10.1126/science.1110873|year=2005|month=May|title=Zircon thermometer reveals minimum melting conditions on earliest Earth|volume=308|issue=5723|pages=841–4|issn=0036-8075|pmid=15879213|journal=Science|author1=Watson, Eb|author2=Harrison, Tm|bibcode = 2005Sci...308..841W }}</ref> and [[Archean]]<ref>{{cite journal|doi=10.1130/0091-7613(1994)022<1067:SWIISL>2.3.CO;2|title=Surface-water influx in shallow-level Archean lode-gold deposits in Western, Australia|year=1994|author=Hagemann, Steffen G.|journal=Geology|volume=22|page=1067|last2=Gebre-Mariam|first2=Musie|last3=Groves|first3=David I.|issue=12|bibcode = 1994Geo....22.1067H }}</ref><ref name="Marty, B. 2006 421"/> eons, leading to what is known as the [[faint young Sun paradox]].<ref name="Sagan1972">{{cite book | last = Sagan | first = C. | coauthors = G. Mullen | title = Earth and Mars: Evolution of Atmospheres and Surface Temperatures | year = 1972| url = http://www.sciencemag.org/cgi/content/abstract/177/4043/52?ck=nck}}</ref> Hypothesized solutions to this paradox include a vastly different atmosphere, with much higher concentrations of greenhouse gases than currently exist.<ref>{{cite journal|doi=10.1126/science.276.5316.1217|title=The Early Faint Sun Paradox: Organic Shielding of Ultraviolet-Labile Greenhouse Gases|year=1997|author=Sagan, C.|journal=Science|volume=276|pages=1217–21|pmid=11536805|last2=Chyba|first2=C|issue=5316|author2=Chyba|bibcode = 1997Sci...276.1217S }}</ref> Over the following approximately 4 billion years, the energy output of the sun increased and atmospheric composition changed. The [[Great Oxygenation Event]] – oxygenation of the atmosphere around 2.4 billion years ago – was the most notable alteration. Over the next five billion years the sun's ultimate death as it becomes a [[red giant]] and then a [[white dwarf]] will have large effects on climate, with the red giant phase possibly ending any life on Earth that survives until that time.

Solar output also [[solar variation|varies]] on shorter time scales, including the 11-year [[solar cycle]]<ref>{{cite journal|last=Willson|first=Richard C.|date=1991-05-02|title=The Sun's luminosity over a complete solar cycle|journal=Nature|volume=351|pages=42–44|url=http://www.nature.com/nature/journal/v351/n6321/abs/351042a0.html|doi=10.1038/351042a0 |coauthors=Hugh S. Hudson|issue=6321|bibcode=1991Natur.351...42W}}</ref> and longer-term [[modulation]]s.<ref>{{cite journal|last=Willson|first=Richard C.|title=Secular total solar irradiance trend during solar cycles 21–23|journal=Geophys. Res. Lett. |volume=30 |issue=5 |page=1199 |url=http://www.agu.org/pubs/crossref/2003/2002GL016038.shtml |doi=10.1029/2002GL016038|year=2003 |coauthors=Alexander V. Mordvinov |bibcode=2003GeoRL..30e...3W}}</ref> Solar intensity variations are considered to have been influential in triggering the Little Ice Age,<ref>{{cite book |chapter=Solar Irradiance Changes and the Relatively Recent Climate |chapterurl=http://books.nap.edu/openbook.php?record_id=4778&page=36 |title=Solar influences on global change |publisher=National Academy Press |location=Washington, D.C |year=1994 |page=36 |isbn=0-309-05148-7 |url=http://books.nap.edu/openbook.php?record_id=4778&page=R1}}</ref> and some of the warming observed from 1900 to 1950. The cyclical nature of the sun's energy output is not yet fully understood; it differs from the very slow change that is happening within the sun as it ages and evolves. Research indicates that solar variability has had effects including the [[Maunder minimum]] from 1645 to 1715 [[Anno Domini|A.D.]], part of the Little Ice Age from 1550 to 1850 A.D. that was marked by relative cooling and greater glacier extent than the centuries before and afterward.<ref name="Little Ice Age definition">{{cite web| publisher=[[NASA]] Earth Observatory | title= Glossary I-M|url=http://earthobservatory.nasa.gov/Glossary/?mode=alpha&seg=l&segend=n| accessdate=2011-02-28}}</ref><ref>{{cite journal |author=Bard E, Raisbeck G, Yiou Francoise, Jouzel Jean|title=Solar irradiance during the last 1200 years based on cosmogenic nuclides |journal=Tellus B |volume=52 |issue=3 |pages=985–992 |doi=10.1034/j.1600-0889.2000.d01-7.x |date=June 2000 |bibcode=2000TellB..52..985B}}</ref> Some studies point toward solar radiation increases from cyclical sunspot activity affecting global warming, and climate may be influenced by the sum of all effects (solar variation, anthropogenic [[radiative forcing]]s, etc.).<ref name="Goddard Space Flight Center">{{cite news| title = NASA Study Finds Increasing Solar Trend That Can Change Climate | year = 2003| url = http://www.nasa.gov/centers/goddard/news/topstory/2003/0313irradiance.html}}</ref><ref>{{cite journal |author=Svensmark H, Bondo T, Svensmark J |title=Cosmic ray decreases affect atmospheric aerosols and clouds |journal=Geophys. Res. Lett. |volume=36 |pages=L15101 |year=2009 |doi=10.1029/2009GL038429 |url=http://www.agu.org/pubs/crossref/2009/2009GL038429.shtml |bibcode=2009GeoRL..3615101S |issue=15}}</ref>

Interestingly, a 2010 study<ref>
{{Cite journal
| issn = 0028-0836
| volume = 467
| issue = 7316
| pages = 696–9
| last = Haigh
| first = Joanna D.
| coauthors = Ann R. Winning, Ralf Toumi, Jerald W. Harder
| title = An influence of solar spectral variations on radiative forcing of climate
| journal = Nature
| date = 2010-10-07
| doi = 10.1038/nature09426
| quote = Currently there is insufficient observational evidence to validate the spectral variations observed by SIM, or to fully characterize other solar cycles, but our findings raise the possibility that the effects of solar variability on temperature throughout the atmosphere may be contrary to current expectations.
| pmid = 20930841
| bibcode=2010Natur.467..696H
}}
</ref> ''suggests'', “that the effects of solar variability on temperature throughout the atmosphere may be contrary to current expectations.”

In an Aug 2011 Press Release,<ref>{{cite journal |author=Jasper Kirkby,|title=Role of sulphuric acid,ammonia and galactic cosmic rays in atmospheric aerosol nucleation |journal=Nature |doi=10.1038/news.2011.504 |pages= |year=2011 |url=http://press.web.cern.ch/press/PressReleases/Releases2011/PR15.11E.html |display-authors=1 |author2=<Please add first missing authors to populate metadata.>}}{{dead link|date=November 2012}}</ref> [[CERN]] announced the publication in the [[Nature (journal)|Nature]] journal the initial results from its [[CLOUD]] experiment. The results indicate that ionisation from cosmic rays significantly enhances aerosol formation in the presence of sulphuric acid and water, but in the lower atmosphere where ammonia is also required, this is insufficient to account for aerosol formation and additional trace vapours must be involved. The next step is to find more about these trace vapours, including whether they are of natural or human origin.

====Magnetic field strength====
Some recent (2006+) analysis suggests that global climate is correlated with the strength of [[Earth's magnetic field]].<ref>{{cite journal|url=http://www.sciencedirect.com/science/article/pii/S0012821X06007667|title=Are there connections between the Earth's magnetic field and climate?|year=2006|last1=Courtillot|first1=Vincent|last2=Gallet|first2=Yves|last3=Le Mouël|first3=Jean-Louis|last4=Fluteau|first4=Frédéric |last5=Genevey|first5=Agnès|journal=Earth and Planetary Science Letters|volume=253|page=620|issue=328–339}}</ref><ref>{{cite web|url=http://www.spacedaily.com/2006/090112183735.ojdq7esu.html|title=The earth's magnetic field impacts climate: Danish study |date=Jan 12, 2009|publisher=SpaceDaily.com|accessdate=2013-01-05}}</ref>

====Volcanism====
[[File:Msu 1978-2010.jpg|thumb|right|In atmospheric temperature from 1979 to 2010, determined by [[Microwave sounding unit|MSU]] [[NASA]] satellites, effects appear from [[aerosols]] released by major volcanic eruptions ([[El&nbsp;Chichón]] and [[Pinatubo]]). [[El Niño-Southern Oscillation|El&nbsp;Niño]] is a separate event, from ocean variability.]]
Volcanic eruptions release gases and [[Atmospheric particulate matter|particulates]] into the atmosphere. [[Volcano|Eruption]]s large enough to affect climate occur on average several times per century, and cause cooling (by partially blocking the transmission of solar radiation to the Earth's surface) for a period of a few years. The eruption of [[Mount Pinatubo]] in 1991, the second largest terrestrial eruption of the 20th century<ref>{{cite web|url=http://pubs.usgs.gov/fs/1997/fs113-97/|title=The Cataclysmic 1991 Eruption of Mount Pinatubo, Philippines |last=Diggles|first=Michael|date=28 February 2005|work=U.S. Geological Survey Fact Sheet 113-97|publisher=[[United States Geological Survey]]|accessdate=2009-10-08}}</ref> (after the 1912 eruption of [[Novarupta]]<ref>{{cite journal|doi=10.1130/B25768.1|title=The transition from explosive to effusive eruptive regime: The example of the 1912 Novarupta eruption, Alaska|year=2006|last1=Adams|first1=Nancy K.|last2=Houghton|first2=Bruce F.|last3=Fagents|first3=Sarah A.|last4=Hildreth|first4=Wes|journal=Geological Society of America Bulletin|volume=118|page=620|issue=5–6}}</ref>) affected the climate substantially. Global temperatures decreased by about 0.5 °C (0.9 °F). The eruption of [[Mount Tambora]] in 1815 caused the [[Year Without a Summer]].<ref>{{cite journal|doi=10.1191/0309133303pp379ra|title=Climatic, environmental and human consequences of the largest known historic eruption: Tambora volcano (Indonesia) 1815|year=2003|last1=Oppenheimer|first1=Clive|journal=Progress in Physical Geography|volume=27|page=230|issue=2}}</ref> Much larger eruptions, known as [[large igneous province]]s, occur only a few times every hundred million years, but may cause global warming and [[mass extinction]]s.<ref>{{cite journal|doi=10.1016/S0012-8252(00)00037-4|title=Large igneous provinces and mass extinctions|year=2001|last1=Wignall|first1=P|journal=Earth-Science Reviews|volume=53|page=1|bibcode=2001ESRv...53....1W}}</ref>

Volcanoes are also part of the extended [[carbon cycle]]. Over very long (geological) time periods, they release carbon dioxide from the Earth's crust and mantle, counteracting the uptake by sedimentary rocks and other geological [[carbon dioxide sink]]s. The [[US Geological Survey]] estimates are that volcanic emissions are at a much lower level than the effects of current human activities, which generate 100-300 times the amount of carbon dioxide emitted by volcanoes.<ref>{{cite web|url=http://volcanoes.usgs.gov/Hazards/What/VolGas/volgas.html|title= Volcanic Gases and Their Effects|accessdate=2008-01-21|date=2006-01-10|publisher= U.S. Department of the Interior}}</ref> A review of published studies indicates that annual volcanic emissions of carbon dioxide, including amounts released from mid-ocean ridges, volcanic arcs, and hot spot volcanoes, are only the equivalent of 3 to 5 days of human caused output. The annual amount put out by human activities may be greater than the amount released by [[Supervolcano|supererruptions]], the most recent of which was the [[Toba catastrophe theory|Toba eruption]] in Indonesia 74,000 years ago.<ref name="www.agu.org">{{cite web | title = Human Activities Emit Way More Carbon Dioxide Than Do Volcanoes | url = http://www.agu.org/news/press/pr_archives/2011/2011-22.shtml | publisher =[[American Geophysical Union]] | date = 14 June 2011 | accessdate = 20 June 2011 }}</ref>

Although volcanoes are technically part of the lithosphere, which itself is part of the climate system, the IPCC explicitly defines volcanism as an external forcing agent.<ref>[http://www.ipcc.ch/publications_and_data/ar4/syr/en/annexes.html Annexes],{{page needed|date=October 2011}} in {{Harvnb|IPCC AR4 SYR|2007}}.</ref>

====Plate tectonics====
Over the course of millions of years, the motion of tectonic plates reconfigures global land and ocean areas and generates topography. This can affect both global and local patterns of climate and atmosphere-ocean circulation.<ref>{{cite doi|10.1130.2F0016-7606.281999.29111.3C0497:PIAPAB.3E2.3.CO.3B2}}</ref>

The position of the continents determines the geometry of the oceans and therefore influences patterns of ocean circulation. The locations of the seas are important in controlling the transfer of heat and moisture across the globe, and therefore, in determining global climate. A recent example of tectonic control on ocean circulation is the formation of the [[Isthmus of Panama]] about 5 million years ago, which shut off direct mixing between the [[Atlantic]] and [[Pacific]] Oceans. This strongly affected the [[western boundary current|ocean dynamics]] of what is now the [[Gulf Stream]] and may have led to Northern Hemisphere ice cover.<ref>{{cite web | url=http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=16401 | title=Panama: Isthmus that Changed the World | accessdate=2008-07-01 | publisher=[[NASA]] Earth Observatory }}</ref><ref>{{cite web|url=http://www.whoi.edu/oceanus/viewArticle.do?id=2508|title=How the Isthmus of Panama Put Ice in the Arctic|last=Gerald H.|first=Haug|date=2004-03-22|publisher=WHOI: Oceanus|accessdate=2009-07-21}}</ref> During the [[Carboniferous]] period, about 300 to 360 million years ago, plate tectonics may have triggered large-scale storage of carbon and increased [[wiktionary:glaciation|glaciation]].<ref>{{cite journal|title=Isotope stratigraphy of the European Carboniferous: proxy signals for ocean chemistry, climate and tectonics| url=http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V5Y-3XNK494-8&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=7db7616e9dc94e6ed49a817195926851|journal=Chemical Geology|date=1999-09-30|volume=161|issue=1–3|doi=10.1016/S0009-2541(99)00084-4|page=127|author1=Peter Bruckschen|author2=Susanne Oesmanna|author3=Ján Veizer|author-separator=,}}</ref> Geologic evidence points to a "megamonsoonal" circulation pattern during the time of the [[supercontinent]] [[Pangaea]], and climate modeling suggests that the existence of the supercontinent was conducive to the establishment of monsoons.<ref>{{cite journal|author=Judith T. Parrish|title=Climate of the Supercontinent Pangea|journal=Chemical Geology|year=1993|volume=101|pages=215–233 |doi=|issue=2|doi_brokendate=2009-09-18|publisher=The University of Chicago Press|jstor=30081148}}</ref>

The size of continents is also important. Because of the stabilizing effect of the oceans on temperature, yearly temperature variations are generally lower in coastal areas than they are inland. A larger supercontinent will therefore have more area in which climate is strongly seasonal than will several smaller continents or [[island]]s.

====Human influences====
{{Main|Global warming}}
{{Main|Climate change mitigation}}

In the context of climate variation, anthropogenic factors are human activities which affect the climate. The [[Scientific opinion on climate change|scientific consensus on climate change]] is "that climate is changing and that these changes are in large part caused by human activities,"<ref>
{{Cite book
| publisher = The National Academies Press
| isbn = 0-309-14588-0
| last = America's Climate Choices: Panel on Advancing the Science of Climate Change; National Research Council
| title = Advancing the Science of Climate Change
| location = Washington, D.C.
| year = 2010
| url = http://www.nap.edu/catalog.php?record_id=12782
}}
</ref>
and it "is largely irreversible."<ref>{{cite journal| publisher = Proceedings of the National Academy of Sciences of the United States of America | title = Irreversible climate change due to carbon dioxide emissions | author= Susan Solomon, Gian-Kasper Plattner, Reto Knutti, and Pierre Friedlingstein | year = 2009 | url = http://www.pnas.org/content/early/2009/01/28/0812721106.full.pdf+html| pmid = 19179281| doi = 10.1073/pnas.0812721106| volume = 106| issue = 6| pages = 1704–9| pmc = 2632717| journal = Proceedings of the National Academy of Sciences of the United States of America |bibcode = 2009PNAS..106.1704S }}</ref>
{{quotation|“Science has made enormous inroads in understanding climate change and its causes, and is beginning to help develop a strong understanding of current and potential impacts that will affect people today and in coming decades. This understanding is crucial because it allows decision makers to place climate change in the context of other large challenges facing the nation and the world. There are still some uncertainties, and there always will be in understanding a complex system like Earth’s climate. Nevertheless, there is a strong, credible body of evidence, based on multiple lines of research, documenting that climate is changing and that these changes are in large part caused by human activities. While much remains to be learned, the core phenomenon, scientific questions, and hypotheses have been examined thoroughly and have stood firm in the face of serious scientific debate and careful evaluation of alternative explanations.”|[[United States National Research Council]], ''Advancing the Science of Climate Change''}}

Of most concern in these anthropogenic factors is the increase in CO2 levels due to emissions from [[fossil fuel]] combustion, followed by [[particulate|aerosols]] (particulate matter in the atmosphere) and [[cement]] manufacture. Other factors, including land use, [[ozone depletion]], animal agriculture<ref name="Steinfeld2006">{{cite book | last = Steinfeld | first = H. | coauthors = P. Gerber, T. Wassenaar, V. Castel, M. Rosales, C. de Haan | title = Livestock's long shadow | year = 2006 | url = http://www.fao.org/docrep/010/a0701e/a0701e00.HTM}}</ref> and [[deforestation]], are also of concern in the roles they play - both separately and in conjunction with other factors - in affecting climate, [[microclimate]], and measures of climate variables.

==Physical evidence for and examples of climatic change==
[[File:NSFmonsoonsandclimatesince200AD.jpg|thumb|325px|left|Comparisons between Asian [[Monsoon]]s from 200 [[A.D.]] to 2000 [[A.D.]] (staying in the background on other plots), Northern Hemisphere temperature, Alpine glacier extent (vertically inverted as marked), and human history as noted by the U.S. [[National Science Foundation|NSF]].]]
[[File:NASAarctic temp trends rt.jpg|thumb|right|Arctic temperature anomalies over a 100 year period as estimated by [[NASA]]. Typical high monthly variance can be seen, while longer-term averages highlight trends.]]
Evidence for climatic change is taken from a variety of sources that can be used to reconstruct past climates. Reasonably complete global records of surface temperature are available beginning from the mid-late 19th century. For earlier periods, most of the evidence is indirect—climatic changes are inferred from changes in [[Proxy (climate)|proxies]], indicators that reflect climate, such as [[vegetation]], [[ice core]]s,<ref>{{cite journal | last = Petit | first = J. R. | title = Climate and atmospheric history of the past 420,000 years from the Vostok ice core, Antarctica | journal = [[Nature (journal)|Nature]] | volume = 399 | pages = 429–436 | date = 1999-06-03 | url = http://www.nature.com/nature/journal/v399/n6735/full/399429a0.html | doi = 10.1038/20859 | last1 = Gómez-Brenes | first1 = RA | last2 = Humberto Ruiloba | first2 = M | last3 = Bressani | first3 = R | issue = 1 | author1 = J. Jouzel | author2 = D. Raynaud | author3 = N. I. Barkov | author4 = J.-M. Barnola | author5 = I. Basile | author6 = M. Bender | author7 = J. Chappellaz | author8 = M. Davis | author9 = G. Delaygue | author-separator = , | author-name-separator = | author = , E. Saltzman and M. Stievenard |bibcode = 1999Natur.399..429P }}</ref> [[dendrochronology]], [[sea level change]], and [[glacial geology]].

===Temperature measurements and proxies===
The [[instrumental temperature record]] from surface stations was supplemented by [[radiosonde|radiosonde balloons]], extensive atmospheric monitoring by the mid-20th century, and, from the 1970s on, with [[Satellite temperature measurements|global satellite data]] as well. The 18O/16O 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, as are other climate metrics noted in subsequent categories.

===Historical and archaeological evidence===
{{Main|Historical impacts of climate change}}
Climate change in the recent past may be detected by corresponding changes in settlement and agricultural patterns.<ref name=Demenocal01>{{cite doi|10.1126/science.1059827}}</ref> [[Archaeological]] evidence, [[oral history]] and [[historical documents]] can offer insights into past changes in the climate. Climate change effects have been linked to the collapse of various civilizations.<ref name=Demenocal01/>

[[File:Glacier Mass Balance.png|thumb|right|Decline in thickness of glaciers worldwide over the past half-century]]

===Glaciers===
[[Glacier]]s are considered among the most sensitive indicators of climate change.<ref name="Seiz2007">{{cite report| last = Seiz | first = G. | coauthors = N. Foppa | title = The activities of the World Glacier Monitoring Service (WGMS) | format= PDF | year = 2007| url = http://www.meteoswiss.admin.ch/web/en/climate/climate_international/gcos/inventory/wgms.Par.0008.DownloadFile.tmp/gcosreportwgmse.pdf| accessdate = 2009-06-21}}{{dead link|date=November 2012}}</ref> Their size is determined by a [[mass balance]] between snow input and melt output. As temperatures warm, glaciers retreat unless snow precipitation increases to make up for the additional melt; the converse is also true.

Glaciers grow and shrink due both to natural variability and external forcings. Variability in temperature, precipitation, and englacial and subglacial hydrology can strongly determine the evolution of a glacier in a particular season. Therefore, one must average over a decadal or longer time-scale and/or over a many individual glaciers to smooth out the local short-term variability and obtain a glacier history that is related to climate.

A world glacier inventory has been compiled since the 1970s, initially based mainly on aerial photographs and maps but now relying more on satellites. This compilation tracks more than 100,000 glaciers covering a total area of approximately 240,000&nbsp;km2, and preliminary estimates indicate that the remaining ice cover is around 445,000&nbsp;km2. The World Glacier Monitoring Service collects data annually on [[retreat of glaciers since 1850|glacier retreat]] and [[glacier mass balance]] From this data, glaciers worldwide have been found to be shrinking significantly, with strong glacier retreats in the 1940s, stable or growing conditions during the 1920s and 1970s, and again retreating from the mid-1980s to present.<ref name="Zemp2008">{{cite report| last = Zemp | first = M. | coauthors = I.Roer, A.Kääb, M.Hoelzle, F.Paul, W. Haeberli | title = United Nations Environment Programme - Global Glacier Changes: facts and figures| format= PDF| year = 2008| url = http://www.grid.unep.ch/glaciers/pdfs/summary.pdf| accessdate = 2009-06-21}}</ref>

The most significant climate processes since the middle to late [[Pliocene]] (approximately 3 million years ago) are the glacial and [[interglacial]] cycles. The present interglacial period (the [[Holocene]]) has lasted about 11,700 years.<ref name="ICS2008">{{cite web |url= http://www.stratigraphy.org/column.php?id=Chart/Time%20Scale |title=International Stratigraphic Chart|year=2008|publisher=International Commission on Stratigraphy|accessdate=2011-10-03}}</ref> Shaped by [[Milankovitch cycles|orbital variations]], responses such as the rise and fall of [[Continental climate|continental]] ice sheets and significant sea-level changes helped create the climate. Other changes, including [[Heinrich event]]s, [[Dansgaard–Oeschger event]]s and the [[Younger Dryas]], however, illustrate how glacial variations may also influence climate without the [[orbital forcing]].

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. Similarly, by [[tephrochronology|tephrochronological]] techniques, the lack of glacier cover can be identified by the presence of soil or volcanic [[tephra]] horizons whose date of deposit may also be ascertained.

[[Image:Arctic sea ice loss animation.gif|thumb|right|300px|This time series, based on satellite data, shows the annual Arctic sea ice minimum since 1979. The September 2010 extent was the third lowest in the satellite record.]]

===Arctic sea ice loss===
{{Main|Polar ice packs|Climate change in the Arctic}}
The decline in Arctic sea ice, both in extent and thickness, over the last several decades is further evidence for rapid climate change.<ref>[http://climate.nasa.gov/evidence/ NASA Global Climate Change "Climate Change: How do we know?"],</ref> Sea ice is frozen seawater that floats on the ocean surface. It covers millions of square miles in the polar regions, varying with the seasons. In the [[Arctic]], some sea ice remains year after year, whereas almost all [[Southern Ocean]] or Antarctic sea ice melts away and reforms annually. Satellite observations show that Arctic sea ice is now declining at a rate of 11.5 percent per decade, relative to the 1979 to 2000 average.<ref>{{cite web|url=http://nsidc.org/sotc/sea_ice.html |title=National Snow and Ice Data Center "State of the Cryosphere" |publisher=Nsidc.org |date= |accessdate=2011-09-10}}</ref>

[[File:Plant Productivity in a Warming World.ogv|thumb|This video summarizes how climate change, associated with increased carbon dioxide levels, has affected plant growth.]]

===Vegetation===

A change in the type, distribution and coverage of vegetation may occur given a change in the climate. Some changes in climate may result in increased precipitation and warmth, resulting in improved plant growth and the subsequent sequestration of airborne CO2. A gradual increase in warmth in a region will lead to earlier flowering and fruiting times, driving a change in the timing of life cycles of dependent organisms. Conversely, cold will cause plant bio-cycles to lag.<ref>{{cite web|last=Kinver |first=Mark |url=http://www.bbc.co.uk/news/science-environment-15721263 |title=UK trees' fruit ripening '18 days earlier' |publisher=Bbc.co.uk |date=2011-11-15 |accessdate=2012-11-01}}</ref> Larger, faster or more radical changes, however, may result in vegetation stress, rapid plant loss and desertification in certain circumstances.<ref name="SahneyBentonFalconLang 2010RainforestCollapse">{{cite journal | url=http://geology.geoscienceworld.org/cgi/content/abstract/38/12/1079 | author= Sahney, S., Benton, M.J. & Falcon-Lang, H.J. | year=2010 | title= Rainforest collapse triggered Pennsylvanian tetrapod diversification in Euramerica | journal=Geology | doi=10.1130/G31182.1 | volume = 38 | pages = 1079–1082 | format=PDF | issue=12 }}</ref><ref>{{cite journal | last = Bachelet | first = D| title = Climate Change Effects on Vegetation Distribution and Carbon Budget in the United States | journal = [[Ecosystems]] | volume = 4| pages = 164–185 | year = 2001 | url = http://www.usgcrp.gov/usgcrp/Library/nationalassessment/forests/Ecosystems2%20Bachelet.pdf |format=PDF| doi = 10.1007/s10021-001-0002-7 | coauthors = R.Neilson,J.M.Lenihan,R.J.Drapek | issue = 3}}</ref> An example of this occurred during the [[Carboniferous Rainforest Collapse]] (CRC), an extinction event 300 million years ago. At this time vast rainforests covered the equatorial region of Europe and America. Climate change devastated these tropical rainforests, abruptly fragmenting the habitat into isolated 'islands' and causing the extinction of many plant and animal species.<ref name="SahneyBentonFalconLang 2010RainforestCollapse"/>

Satellite data available in recent decades indicates that global terrestrial net primary production increased by 6% from 1982 to 1999, with the largest portion of that increase in tropical ecosystems, then decreased by 1% from 2000 to 2009.<ref>{{cite journal | last = Nemani | first = Ramakrishna| title = Climate-Driven Increases in Global Terrestrial Net Primary Production from 1982 to 1999 | journal = Science | volume = 300| pages = 1560–3 | year = 2003 | url = http://www.sciencemag.org/content/300/5625/1560.abstract | doi = 10.1126/science.1082750 | coauthors = C.D. Keeling, H. Hashimoto, W.M. Jolly, S.C. Piper, C.J. Tucker, R.B. Myneni, and S.W. Running. | issue = 5625 | pmid = 12791990|bibcode = 2003Sci...300.1560N }}</ref><ref>{{cite journal | last = Zhao| first = Maosheng| title = Drought-induced reduction in global terrestrial net primary production from 2000 through 2009 | journal = Science | volume = 329| pages = 940–3 | year = 2010 | url = http://www.sciencemag.org/content/329/5994/940.abstract | doi = 10.1126/science.1192666 | coauthors = S.W. Running. | issue = 5994 | pmid = 20724633|bibcode = 2010Sci...329..940Z }}</ref>

===Pollen analysis===
[[Palynology]] is the study of contemporary and fossil [[palynomorph]]s, including [[pollen]]. Palynology is used to infer the geographical distribution of plant species, which 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 in lakes, bogs, or river deltas indicate changes in plant communities. These changes are often a sign of a changing climate.<ref>{{cite journal | last = Langdon | first = PG | 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 | month = August | year = 2004 | url = http://www.springerlink.com/content/t7m324u675701133/ | doi = 10.1023/B:JOPL.0000029433.85764.a5 | author1 = Barber KE | author2 = , Lomas-Clarke SH | author-separator = , | last3 = Lomas-Clarke (Previously Morriss) | first3 = S.H.}}</ref><ref>{{cite journal | last = Birks | first = HH | title = The importance of plant macrofossils in the reconstruction of Lateglacial vegetation and climate: examples from Scotland, western Norway, and Minnesota, USA | journal = Quaternary Science Reviews | volume = 22 | issue = 5–7 | pages = 453–473 | month = March | year = 2003 | url = http://www.sciencedirect.com/science/article/B6VBC-47YH3W8-2/2/fde5760538b5b3adb92d8564ea968b9a | doi = 10.1016/S0277-3791(02)00248-2|bibcode = 2003QSRv...22..453B }}</ref> As an example, palynological studies have been used to track changing vegetation patterns throughout the [[Quaternary glaciation]]s<ref>{{cite journal|last1=Miyoshi|first1=N|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|page=267|year=1999|doi=10.1016/S0034-6667(98)00058-X|issue=3–4}}</ref> and especially since the [[last glacial maximum]].<ref>{{cite journal|author1=Colin Prentice, I|author2=Bartlein, Patrick J|author3=Webb, Thompson|title=Vegetation and Climate Change in Eastern North America Since the Last Glacial Maximum|journal=Ecology|volume=72|issue=6|pages=2038–2056|year=1991|doi=10.2307/1941558|jstor=1941558}}</ref>

[[File:Aridity ice age vs early holocene vs modern.jpg|thumb|right|''Top:'' [[Arid]] ice age climate{{-}}''Middle:'' [[Atlantic period|Atlantic Period]], warm and wet{{-}}''Bottom:'' Potential vegetation in climate now if not for human effects like agriculture.<ref name = ORNL_paleoclimate>Adams J.M. & Faure H. (1997) (eds.), QEN members. [http://www.esd.ornl.gov/projects/qen/nerc.html Review and Atlas of Palaeovegetation: Preliminary land ecosystem maps of the world since the Last Glacial Maximum]. Oak Ridge National Laboratory, TN, USA.</ref>]]

===Precipitation===

Past precipitation can be estimated in the modern era with the global network of precipitation gauges. Surface coverage over oceans and remote areas is relatively sparse, but, reducing reliance on [[interpolation]], satellite data has been available since the 1970s.<ref name = IJC_precip>{{cite journal |author=New, M., Todd, M., Hulme, M. and Jones, P. |title=Review: Precipitation measurements and trends in the twentieth century |journal=International Journal of Climatology |volume=21 |issue=15 |pages=1889–1922 |doi=10.1002/joc.680 |date=December 2001 |url=http://espace.library.uq.edu.au/view/UQ:195263|bibcode = 2001IJCli..21.1889N }}</ref> 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 |author=Dominic, F., Burns, S.J., Neff, U., Mudulsee, M., Mangina, A. and Matter, A. |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=935–945 |doi=10.1016/j.quascirev.2003.06.019 |date=April 2004 |url=http://www.sciencedirect.com/science/article/pii/S0277379104000174|bibcode = 2004QSRv...23..935F }}</ref>

Climatological temperatures substantially affect precipitation. For instance, during the [[Last Glacial Maximum]] of 18,000 years ago, thermal-driven [[evaporation]] from the oceans onto continental landmasses was low, causing large areas of extreme desert, including [[polar desert]]s (cold but with low rates of precipitation).<ref name = ORNL_paleoclimate/> In contrast, the world's climate was wetter than today near the start of the warm [[Atlantic period|Atlantic Period]] of 8000 years ago.<ref name = ORNL_paleoclimate/>

Estimated global land precipitation increased by approximately 2% over the course of the 20th century, though the calculated trend varies if different time endpoints are chosen, complicated by [[El Niño-Southern Oscillation|ENSO]] and other oscillations, including greater global land precipitation in the 1950s and 1970s than the later 1980s and 1990s despite the positive trend over the century overall.<ref name = IJC_precip/><ref name = USGS_watercycletrend>{{cite journal |author=Huntington, T.G. (U.S. Geological Survey) |title=Evidence for intensification of the global water cycle: Review and synthesis |journal=Journal of Hydrology |volume=319 |issue=1–4 |pages=83–95 |doi=10.1016/j.jhydrol.2005.07.003 |date=March 2006 |url=http://www.sciencedirect.com/science/article/pii/S0022169405003215|bibcode = 2006JHyd..319...83H }}</ref><ref>{{cite journal |author= Smith, T. M.; Yin, X.; Gruber, A. |title=Variations in annual global precipitation (1979-2004), based on the Global Precipitation Climatology Project 2.5° analysis |journal=Geophysical Research Letters |volume=33 |issue=6 |doi=10.1029/2005GL025393 |year= 2006 |bibcode=2006GeoRL..3306705S}}</ref>
Similar slight overall increase in global river runoff and in average soil moisture has been perceived.<ref name = USGS_watercycletrend/>

===Dendroclimatology===
[[Dendroclimatology]] is the analysis of tree ring growth patterns to determine past climate variations.<ref>{{Cite book | title = Dendroclimatology : progress and prospect | year = 2010 | publisher = Springer | location = New York | isbn = 978-1-4020-4010-8 | pages = }}
</ref> Wide and thick rings indicate a fertile, well-watered growing period, whilst thin, narrow rings indicate a time of lower rainfall and less-than-ideal growing conditions.

===Ice cores===
Analysis of ice in a core 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 CO2 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 CO2 over many millennia, and continues to provide valuable information about the differences between ancient and modern atmospheric conditions.

===Animals===
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=Coope1999>{{cite journal | last = Coope | first = G.R. | 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 = 419–433 | date = 1999-05-04 | url = http://www3.interscience.wiley.com/cgi-bin/abstract/61001707/ABSTRACT | doi = 10.1002/(SICI)1099-1417(1998090)13:5<419::AID-JQS410>3.0.CO;2-D | coauthors = Lemdahl, G.; Lowe, J.J.; Walkling, A.|bibcode = 1998JQS....13..419C }}</ref>

Similarly, the historical abundance of various [[fish]] species has been found to have a substantial relationship with observed climatic conditions.<ref>
FAO Fisheries Technical Paper. No. 410. Rome, FAO. 2001. [ftp://ftp.fao.org/docrep/fao/005/y2787e/y2787e02.pdf Climate Change and Long-Term Fluctuations of Commercial Catches]. United Nations Food and Agriculture Organization.</ref> Changes in the [[primary productivity]] of [[autotrophs]] in the oceans can affect marine food webs.<ref>{{cite journal |author=Brown, C. J., Fulton, E. A., Hobday, A. J., Matear, R. J., Possingham, H. P., Bulman, C., Christensen, V., Forrest, R. E., Gehrke, P. C., Gribble, N. A., Griffiths, S. P., Lozano-Montes, H., Martin, J. M., Metcalf, S., Okey, T. A., Watson, R. and Richardson, A. J.|title=Effects of climate-driven primary production change on marine food webs: Implications for fisheries and conservation |journal=Global Change Biology |volume=16 |issue=4 |pages=1194–1212 |doi=10.1111/j.1365-2486.2009.02046.x |date=April 2010 |url=http://espace.library.uq.edu.au/view/UQ:195263}}</ref>

===Sea level change===
{{Main|Sea level|Current sea level rise}}
Global sea level change for much of the last century has generally been estimated using [[tide gauge]] measurements collated over long periods of time to give a long-term average. More recently, [[altimeter]] measurements — in combination with accurately determined [[satellite]] orbits — have provided an improved measurement of global sea level change.<ref>{{cite web|url=http://sealevel.colorado.edu/documents.php|title=Sea Level Change|publisher=University of Colorado at Boulder|accessdate=2009-07-21}}</ref> To measure sea levels prior to instrumental measurements, scientists have dated [[coral reef]]s that grow near the surface of the ocean, coastal sediments, [[marine terrace]]s, [[ooids]] in [[limestone]]s, and nearshore archaeological remains. The predominant dating methods used are [[Uranium-thorium dating|uranium series]] and [[radiocarbon dating|radiocarbon]], with [[cosmogenic radionuclide dating|cosmogenic radionuclides]] being sometimes used to date terraces that have experienced relative sea level fall. In the early [[Pliocene]], global temperatures were 1-2˚C warmer than the present temperature, yet sea level was 15–25 meters higher than today.<ref>{{cite web|last=Hansen|first=James|title=Science Briefs: Earth's Climate History|url=http://www.giss.nasa.gov/research/briefs/hansen_15/|publisher=NASA GISS|accessdate=25 April 2013}}</ref>
{{-}}

==See also==
{{Col-begin}}
{{Col-break}}
* [[4 Degrees and Beyond International Climate Conference]]
* [[Abrupt climate change]] and links therein
* [[Attribution of recent climate change]]
* [[Blue carbon]]
* [[Climate change in literature]]
* [[Geologic time scale]]
* [[Temperature record]]
* [[Solar variation]]
* [[Homogenization (climate)|Homogenization]]

'''Climate of recent glaciations'''
* [[Bond event]]
{{Col-break}}
{{Portal|Environment|Global warming|Energy}}
'''Climate of the past'''
* [[Snowball Earth]]
* [[Ice age]]s
* [[Paleocene–Eocene Thermal Maximum]]
* [[Permo-Carboniferous]] Glaciation
'''Recent climate'''
* [[Anthropocene]]
* [[Effects of global warming on oceans]]
* [[Hardiness zone]]
* [[Holocene climatic optimum]]
* [[Medieval Warm Period]]
* [[Temperature record of the past 1000 years]]
* [[CORA dataset]] temperature and salinity of global oceans
{{Col-end}}

==Notes==
{{Reflist|30em}}

==References==
* {{Citation
 |postscript =
| year   = 2007
| author = IPCC AR4 WG1
| author-link = IPCC
| title  = Climate Change 2007: The Physical Science Basis
| series = Contribution of Working Group I to the [[IPCC Fourth Assessment Report|Fourth Assessment Report]] of the Intergovernmental Panel on Climate Change
| editor = Solomon, S.; Qin, D.; Manning, M.; Chen, Z.; Marquis, M.; Averyt, K.B.; Tignor, M.; and Miller, H.L.
| publisher = Cambridge University Press
| url  = http://www.ipcc.ch/publications_and_data/ar4/wg1/en/contents.html
| isbn = 978-0-521-88009-1
}} (pb: {{ISBNT|978-0-521-70596-7}}).

* {{Citation
 |postscript =
| year   = 2007
| author = IPCC AR4 SYR
| author-link = IPCC
| title  = Climate Change 2007: Synthesis Report
| series = Contribution of Working Groups I, II and III to the [[IPCC Fourth Assessment Report|Fourth Assessment Report]] of the Intergovernmental Panel on Climate Change
| editors = Core Writing Team; Pachauri, R.K; and Reisinger, A.
| publisher = IPCC
| url= http://www.ipcc.ch/publications_and_data/ar4/syr/en/contents.html
| isbn = 92-9169-122-4
}}.

* {{Citation
 |postscript =
| year   = 2001
| author = IPCC TAR WG1
| author-link = IPCC
| title  = Climate Change 2001: The Scientific Basis
| series = Contribution of Working Group I to the [[IPCC Third Assessment Report|Third Assessment Report]] of the Intergovernmental Panel on Climate Change
| editor =  Houghton, J.T.; Ding, Y.; Griggs, D.J.; Noguer, M.; van der Linden, P.J.; Dai, X.; Maskell, K.; and Johnson, C.A.
| publisher = Cambridge University Press
| url = http://www.grida.no/publications/other/ipcc%5Ftar/?src=/climate/ipcc_tar/wg1/index.htm
| isbn = 0-521-80767-0
}} (pb: {{ISBNT|0-521-01495-6}}).

==Further reading==
{{Refbegin|30em}}
* {{Cite book
 |postscript =
| year   = 2007
| author = IPCC AR4 WG1
| author-link = IPCC
| chapter = Summary for Policymakers
| chapterurl = http://www.ipcc.ch/publications_and_data/ar4/wg1/en/spm.html
| title  = Climate Change 2007: The Physical Science Basis
| series = Contribution of Working Group I to the [[IPCC Fourth Assessment Report|Fourth Assessment Report]] of the Intergovernmental Panel on Climate Change
| editor = Solomon, S.; Qin, D.; Manning, M.; Chen, Z.; Marquis, M.; Averyt, K.B.; Tignor, M.; and Miller, H.L.
| publisher = Cambridge University Press
| url  = http://www.ipcc.ch/publications_and_data/ar4/wg1/en/contents.html
| isbn = 978-0-521-88009-1
}} (pb: {{ISBNT|978-0-521-70596-7}}).
*{{Cite book
 |postscript =
| year   = 2007
| author = IPCC AR4 SYR
| author-link = IPCC
| chapter = Summary for Policymakers
| chapterurl = http://www.ipcc.ch/publications_and_data/ar4/syr/en/spm.html
| title  = Climate Change 2007: Synthesis Report
| series = Contribution of Working Groups I, II and III to the [[IPCC Fourth Assessment Report|Fourth Assessment Report]] of the Intergovernmental Panel on Climate Change
| editors = Core Writing Team; Pachauri, R.K; and Reisinger, A.
| publisher = IPCC
| url= http://www.ipcc.ch/publications_and_data/ar4/syr/en/contents.html
| isbn = 92-9169-122-4
}}.
*{{Cite journal |author=Emanuel K |title=Increasing destructiveness of tropical cyclones over the past 30 years |journal=Nature |volume=436 |issue=7051 |pages=686–8 |year=2005 |month=August |pmid=16056221 |doi=10.1038/nature03906 |url=ftp://texmex.mit.edu/pub/emanuel/PAPERS/NATURE03906.pdf |format=PDF |bibcode=2005Natur.436..686E}}
*{{Cite book |author=Edwards, Paul Geoffrey; Miller, Clark A. |title=Changing the atmosphere: expert knowledge and environmental governance |publisher=MIT Press |location=Cambridge, Mass |year=2001 |pages= |isbn=0-262-63219-5 }}
*{{Cite book |author=McKibben, Bill |title=''The Global Warming Reader''|publisher=[[OR Books]] |location=New York, N.Y. |year=2011 |pages= |isbn=978-1-935928-36-2 }}
*{{Cite journal |author=Ruddiman, W. F. |title=The anthropogenic greenhouse era began thousands of years ago |journal=Climate Change |volume=61 |issue=3 |pages=261–293 |year=2003 |doi=10.1023/B:CLIM.0000004577.17928.fa}}
*{{Cite book |author=William F. Ruddiman |title=Plows, plagues, and petroleum: how humans took control of climate |publisher=Princeton University Press |location=Princeton, N.J |year=2005 |pages= |isbn=0-691-13398-0 }}
*{{Cite journal |author=Ruddiman, W. F., Vavrus, S. J. and Kutzbach, J. E. |title=A test of the overdue-glaciation hypothesis |journal=Quaternary Science Review |volume=24 |issue=11 |pages= |year=2005}}
*{{Cite journal |author=Schmidt, G. A., Shindel, D. T. and Harder, S. |title=A note of the relationship between ice core methane concentrations and insolation |journal=Geophys. Res. Lett. |volume=31 |pages=L23206 |year=2004 |doi=10.1029/2004GL021083 |url=http://www.agu.org/pubs/crossref/2004/2004GL021083.shtml |bibcode=2004GeoRL..3123206S |issue=23}}
* Wagner, Frederic H., (ed.) ''Climate Change in Western North America: Evidence and Environmental Effects'' (2009). ISBN 978-0-87480-906-0
{{Refend}}

==External links==
{{wikiquote}}
{{Spoken Wikipedia|En-Climate_change.ogg|2010-03-19}}
{{Wikinews category|Climate change}}
{{Commons category|Climate change}}
*[http://www.b4esummit.com/ Climate Summit 2011 - London] from the [[B4E Business for the Environment]]
*{{dmoz|Science/Environment/Climate_Change|Climate Change}}
* [http://www.sourcewatch.org/index.php?title=Climate_change:_Resources Climate Change Resources] from [[SourceWatch]]
* [http://ucblibraries.colorado.edu/govpubs/us/climatechange.htm Climate Change] from the ''UCB Libraries GovPubs''
* [http://www.metoffice.gov.uk/climatechange/ Climate Change] from the [[Met Office]] (UK)
* [http://climate.nasa.gov/ Global Climate Change] from [[NASA]] (US)
* [http://www.oceanmotion.org/html/impact/climate-variability.htm Ocean Motion: Satellites Record Weakening North Atlantic Current]
* [http://www.ipcc.ch/ Intergovernmental Panel on Climate Change (IPCC)]
* [http://ourworld.unu.edu/en/series/climate/ United Nations University's 'Our World 2' Climate Change Video Briefs]
* [http://ourworld.unu.edu/en/cop15-filmfestival/ United Nations University's 'Our World 2' Indigenous voices on climate change films]
{{In Our Time|Climate Change|p00546l7|Climate_Change}}
* [http://www.germanwatch.org/klima/ccpi.htm Climate Change Performance Index 2010]
* [http://www.centerforoceansolutions.org/research-libraries Climate Library] at Center for Ocean Solutions, Stanford University
* [http://site.videoproject.com/coralreefs/ Climate Change: Coral Reefs on the Edge] An online video presentation by Prof. Ove Hoegh-Guldberg, University of Auckland
*[http://cdkn.org/ [[Climate & Development Knowledge Network]], run by an alliance of organisations that include [[PwC]] and <<link:1>>]
{{global warming|gstate=expanded}}
{{Use dmy dates|date=July 2011}}

{{DEFAULTSORT:Climate Change}}
[[Category:Climate change| ]]
[[Category:Climate and weather statistics]]
[[Category:Climate history]]
[[Category:Carbon finance]]
[[Category:Economic problems]]

Edit summary:
This is a minor edit Watch this page

Cancel

Dab solver - Climate change

Tools

Interaction