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Line 1: − + − {{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 − |quote=(p1) ... 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. (pp. 21–22) Some scientific conclusions or theories have been so thoroughly examined and tested, and supported by so many independent observations and results, that their likelihood of subsequently being found to be wrong is vanishingly small. Such conclusions and theories are then regarded as settled facts. This is the case for the conclusions that the Earth system is warming and that much of this warming is very likely due to human activities. − |deadurl=yes − |archiveurl=https://web.archive.org/web/20140529161102/http://www.nap.edu/catalog.php?record_id=12782 − |archivedate=29 May 2014 − |df= − }}</ref> There is no general agreement in scientific, media or policy documents as to the precise term to be used to refer to [[Human impact on the environment|anthropogenic]] forced change; either "global warming" or "climate change" may be used.<ref name=":2" /><ref name=":3" /><ref name=":1" /> − + − Factors that can shape climate are called [[climate forcing]]s or "forcing mechanisms".<ref name="Smith2013" /> These 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 [[Anthropogenic effect|anthropogenic]]—caused by humans—(e.g. increased [[Greenhouse gas emissions|emissions of greenhouse gases]] and dust) or natural (e.g., changes in solar output, the earth's orbit, volcano eruptions).+ − Physical evidence to observe climate change includes a range of parameters. 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 name=":4" /> [[dendrochronology]], [[sea level change]], and [[glacial geology]]. Other physical evidence includes [[arctic sea ice decline]], cloud cover and precipitation, vegetation, animals and [[Historical impacts of climate change|historical and archaeological evidence]].+ + − ==Terminology==+ − The most general definition of climate change is a change in the statistical properties (principally its [[central tendency|mean]] and [[statistical variability|spread]])<ref>{{cite web+ − | title=Understanding and Attributing Climate Change − | work=Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change − | publisher=Intergovernmental Panel on Climate Change (IPCC) | year=2007 − | editor1-last=Solomon | editor1-first=S. − | editor2-first=D. | editor2-last=Qin − | editor3-first=M. | editor3-last=Manning − | editor4-first=Z. | editor4-last=Chen − | editor5-first=M. | editor5-last=Marquis − | editor6-first=K.B. | editor6-last=Averyt − | editor7-first=M. | editor7-last=Tignor − | editor8-first=H.L. | editor8-last=Miller − | url=https://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch9s9-1.html − }}</ref> 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 "climate change" is often used to refer specifically to anthropogenic climate change (also known as [[global warming]]). Anthropogenic climate change is caused by human activity, as opposed to changes in climate that may have resulted as part of Earth's natural processes.<ref name=":2">{{cite web |date=21 March 1994 |title=The United Nations Framework Convention on Climate Change |url=http://unfccc.int/resource/ccsites/zimbab/conven/text/art01.htm |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 affect.<ref name=":3">{{cite web |title=What's in a Name? Global Warming vs. Climate Change |publisher=NASA |url=http://www.nasa.gov/topics/earth/features/climate_by_any_other_name.html |accessdate=23 July 2011}}</ref> − A related term, "climatic change", was proposed by the [[World Meteorological Organization]] (WMO) in 1966 to encompass all forms of climatic variability on time-scales longer than 10 years, but regardless of cause. During the 1970s, the term climate change replaced climatic change to focus on anthropogenic causes, as it became clear that human activities had a potential to drastically alter the climate.<ref name=":1" /> Climate change was incorporated in the title of the [[Intergovernmental Panel on Climate Change]] (IPCC) and the [[UN Framework Convention on Climate Change]] (UNFCCC). Climate change is now used as both a technical description of the process, as well as a noun used to describe the problem.<ref name=":1">{{cite book |last=Hulme |first=Mike |year=2016 |title=Concept of Climate Change, in: The International Encyclopedia of Geography |publisher=Wiley-Blackwell/Association of American Geographers (AAG) |url=https://www.academia.edu/10358797/Climate_change_concept_of_ |accessdate=16 May 2016}}</ref>+ − ==Causes==+ − {{See also|Attribution of recent climate change}}+ − 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=Smith2013>{{cite book |last=Smith |first=Ralph C. |year=2013 |title=Uncertainty Quantification: Theory, Implementation, and Applications |series=Computational Science and Engineering |publisher=SIAM |isbn=1611973228 |volume=12 |page=23 |url=https://books.google.com/books?id=Tc1GAgAAQBAJ&pg=PA23}}</ref> These include processes such as variations in [[solar radiation]], variations in the Earth's orbit, variations in the [[albedo]] or reflectivity of the continents, atmosphere, and oceans, [[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 more slowly in reaction to climate forcings, while others respond more quickly. There are also key [[Ecological threshold|threshold factors]] which when exceeded can produce rapid change.+ + + + + + + + + − 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 anthropogenic (e.g. increased emissions of greenhouse gases and dust) or natural (e.g., changes in solar output, the earth's orbit, volcano eruptions).+ + + − 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 [[Abrupt climate change|abruptly]], but the full response to forcing mechanisms might not be fully developed for centuries or even longer.+ − ===Internal forcing mechanisms===+ − 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 |year=2011 |title=Glossary |publisher=NASA Earth Observatory |url=http://earthobservatory.nasa.gov/Glossary/index.php?mode=alpha&seg=b&segend=d |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> Natural changes in the climate system ("internal forcings") result in internal "climate variability".<ref>{{cite web |author=IPCC |authorlink=Intergovernmental Panel on Climate Change |year=2007 |title=What are Climate Change and Climate Variability? |publisher=[[Intergovernmental Panel on Climate Change|IPCC]] |url=https://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch9s9-1.html}}</ref> Examples include the type and distribution of species, and changes in ocean-atmosphere circulations. − + − {{Main|Thermohaline circulation}}+ − {{See also|Climate inertia}}+ − [[File:Ecinfigtwo.jpg|thumb|right|[[Pacific decadal oscillation]] 1925 to 2010]]+ − + + − The oceanic aspects of these circulations can generate variability on centennial timescales due to the ocean having hundreds of times more mass than in the [[Atmosphere of Earth|atmosphere]], and thus very high [[Volumetric heat capacity|thermal inertia.]] For example, alterations to ocean processes such as thermohaline circulation play a key role in redistributing heat in the world's oceans. Due to the long timescales of this circulation, ocean temperature at depth is still adjusting to effects of the [[Little Ice Age]]<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> which occurred between the 1600 and 1800s.+ − + + − ====Life====+ − Life affects climate through its role in the [[carbon cycle|carbon]] and [[water cycle]]s and through such mechanisms as [[albedo]], [[evapotranspiration]], [[Cloud|cloud formation]], and [[weathering]].<ref>{{cite journal |last1=Spracklen |first1=D. V. |last2=Bonn |first2=B. |last3=Carslaw |first3=K. S. |year=2008 |title=Boreal forests, aerosols and the impacts on clouds and climate |journal=Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences |doi=10.1098/rsta.2008.0201 |pmid=18826917 |bibcode=2008RSPTA.366.4613S |volume=366 |issue=1885 |pages=4613–26 |ref=harv}}</ref><ref>{{cite journal |last1=Christner |first1=B. C. |last2=Morris |first2=C. E. |last3=Foreman |first3=C. M. |last4=Cai |first4=R. |last5=Sands |first5=D. C. |year=2008 |title=Ubiquity of Biological Ice Nucleators in Snowfall |journal=Science |doi=10.1126/science.1149757 |pmid=18309078 |bibcode=2008Sci...319.1214C |volume=319 |issue=5867 |page=1214 |ref=harv}}</ref><ref>{{cite journal |last1=Schwartzman |first1=David W. |last2=Volk |first2=Tyler |year=1989 |title=Biotic enhancement of weathering and the habitability of Earth |journal=Nature |bibcode=1989Natur.340..457S |doi=10.1038/340457a0 |volume=340 |issue=6233 |pages=457–60 |ref=harv}}</ref> Examples of how life may have affected past climate include:+ − * [[glaciation]] 2.3 billion years ago triggered by the evolution of oxygenic [[photosynthesis]], which depleted the atmosphere of the greenhouse gas carbon dioxide and introduced free oxygen.<ref>{{cite journal |ref=harv |doi=10.1073/pnas.0504878102 |title=The Paleoproterozoic snowball Earth: A climate disaster triggered by the evolution of oxygenic photosynthesis |year=2005 |last1=Kopp |first1=R.E. |last2=Kirschvink |first2=J.L. |last3=Hilburn |first3=I.A. |last4=Nash |first4=C.Z. |journal=Proceedings of the National Academy of Sciences |volume=102 |issue=32 |pages=11131–36 |pmid=16061801 |pmc=1183582|bibcode = 2005PNAS..10211131K }}</ref><ref>{{cite journal |ref= harv |doi=10.1126/science.1071184 |title= Life and the Evolution of Earth's Atmosphere |year=2002 |last1= Kasting |first1=J.F. |journal= Science |volume=296 |issue=5570 |pages= 1066–68 |pmid=12004117 |last2=Siefert |first2=JL|bibcode = 2002Sci...296.1066K }}</ref> − * another glaciation 300 million years ago ushered in by long-term burial of [[lignin|decomposition-resistant]] [[detritus]] of vascular land-plants (creating a [[carbon sink]] and [[Coal#Formation|forming coal]])<ref>{{cite journal |ref=harv |doi=10.1126/science.271.5252.1105 |title= Middle to Late Paleozoic Atmospheric CO2 Levels from Soil Carbonate and Organic Matter |year=1996 |last1=Mora |first1=C.I. |last2=Driese |first2=S.G. |last3=Colarusso |first3=L. A. |journal=Science |volume=271 |issue=5252 |pages=1105–07 |bibcode= 1996Sci...271.1105M}}</ref><ref>{{cite journal |ref=harv |doi=10.1073/pnas.96.20.10955 |title=Atmospheric oxygen over Phanerozoic time |year=1999 |last1=Berner |first1=R.A. |journal=Proceedings of the National Academy of Sciences |volume=96 |issue=20 |pages= 10955–57 |pmid=10500106 |pmc=34224|bibcode = 1999PNAS...9610955B }}</ref> − * termination of the [[Paleocene–Eocene Thermal Maximum]] 55 million years ago by flourishing marine [[phytoplankton]]<ref>{{cite journal |ref=harv |doi=10.1038/35025035 |year=2000 |last1=Bains |first1=Santo |last2=Norris |first2=Richard D. |last3=Corfield |first3=Richard M. |last4=Faul |first4=Kristina L. |journal=Nature |volume=407 |issue=6801 |pages=171–74 |pmid=11001051 |title=Termination of global warmth at the Palaeocene/Eocene boundary through productivity feedback|bibcode = 2000Natur.407..171B }}</ref><ref name=Zachos1999>{{cite journal |ref=harv |doi=10.1080/11035890001221188 |title=An assessment of the biogeochemical feedback response to the climatic and chemical perturbations of the LPTM |year= 2000 |last1=Zachos |first1= J.C. |last2= Dickens |first2=G.R. |journal= GFF |volume=122 |pages=188–89}}</ref> − * reversal of global warming 49 million years ago by [[Azolla event|800,000 years of arctic azolla blooms]]<ref>{{cite journal |doi=10.1111/j.1472-4669.2009.00195.x |title=The Eocene Arctic Azolla bloom: Environmental conditions, productivity and carbon drawdown |year=2009 |last1=Speelman |first1=E.N. |last2=Van Kempen |first2=M.M.L. |last3=Barke |first3=J. |last4=Brinkhuis |first4=H. |last5=Reichart |first5=G.J. |last6=Smolders |first6=A.J.P. |last7=Roelofs |first7=J.G.M. |last8=Sangiorgi |first8=F. |last9=De Leeuw |first9=J.W. |last10=Lotter |first10=A.F. |last11=Sinninghe Damsté |first11=J.S. |journal=Geobiology |volume=7 |issue=2 |pages=155–70 |pmid=19323694}}</ref><ref>{{cite journal |ref=harv |doi=10.1038/nature04692 |title=Episodic fresh surface waters in the Eocene Arctic Ocean |year=2006 |last1=Brinkhuis |first1=Henk |last2=Schouten |first2=Stefan |last3=Collinson |first3=Margaret E. |last4=Sluijs |first4=Appy |last5=Sinninghe Damsté |first5=Jaap S. Sinninghe |last6=Dickens |first6=Gerald R. |last7=Huber |first7=Matthew |last8=Cronin |first8=Thomas M. |last9=Onodera |first9=Jonaotaro |last10=Takahashi |first10=Kozo |last11=Bujak |first11=Jonathan P. |last12=Stein |first12=Ruediger |last13=Van Der Burgh |first13=Johan |last14=Eldrett |first14=James S. |last15=Harding |first15=Ian C. |last16=Lotter |first16=André F. |last17=Sangiorgi |first17=Francesca |last18=Van Konijnenburg-Van Cittert |first18=Han van Konijnenburg-van |last19=De Leeuw |first19=Jan W. |last20=Matthiessen |first20=Jens |last21=Backman |first21=Jan |last22=Moran |first22=Kathryn |last23=Expedition 302 |journal=Nature |volume=441 |issue=7093 |pages=606–09 |pmid=16752440 |first23=Scientists|bibcode = 2006Natur.441..606B }}</ref> − * [[global cooling]] over the past 40 million years driven by the expansion of grass-grazer [[ecosystem]]s<ref>{{cite journal |ref=harv |doi=10.1086/320791 |title=Cenozoic Expansion of Grasslands and Climatic Cooling |year=2001 |last1=Retallack |first1=Gregory J. |journal=The Journal of Geology |volume=109 |issue=4 |pages=407–26 |bibcode=2001JG....109..407R}}</ref><ref>{{cite journal |doi=10.1130/0091-7613(1997)025<0039:MTPVCA>2.3.CO;2 |title= Miocene to present vegetation changes: A possible piece of the Cenozoic cooling puzzle |year=1997 |last1=Dutton |first1=Jan F. |last2=Barron |first2=Eric J. |journal=Geology |volume=25 |page=39|bibcode = 1997Geo....25...39D }}</ref> − ===External forcing mechanisms===+ − {{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|CO<sub>2</sub>]], temperature and dust from the [[Vostok, Antarctica|Vostok]] ice core over the last 450,000 years}} − + − [[File:Mauna Loa CO2 monthly mean concentration.svg|thumb|right|Increase in atmospheric {{CO2}} levels]]+ − {{Main|Global warming}}+ − 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 − |deadurl=yes − |archiveurl=https://web.archive.org/web/20140529161102/http://www.nap.edu/catalog.php?record_id=12782 − |archivedate=29 May 2014 − |df= − }} − </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 |author1=Susan Solomon |author2=Gian-Kasper Plattner |author3=[[Reto Knutti]] |author4=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 = 1704–09| pmc = 2632717| journal = Proceedings of the National Academy of Sciences of the United States of America |bibcode = 2009PNAS..106.1704S| ref = harv }}</ref> − {{quotation|"... 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 CO<sub>2</sub> levels. This is due to emissions from [[fossil fuel]] combustion, followed by [[particulate|aerosols]] (particulate matter in the atmosphere), and the CO<sub>2</sub> released by [[cement]] manufacture.<ref>{{cite web|url=https://www.science.org.au/learning/general-audience/science-booklets-0/science-climate-change/3-are-human-activities-causing|title=3. Are human activities causing climate change? {{!}} Australian Academy of Science|website=www.science.org.au|access-date=2017-08-12}}</ref> Other factors, including land use, [[ozone depletion]], animal husbandry ([[ruminant]] animals such as [[cattle]] produce [[methane]],<ref name="Steinfeld2006">{{cite book | last = Steinfeld | first = H. |author2=P. Gerber |author3=T. Wassenaar |author4=V. Castel |author5=M. Rosales |author6=C. de Haan | title = Livestock's long shadow | year = 2006 | url = http://www.fao.org/docrep/010/a0701e/a0701e00.HTM}}</ref> as do [[termite]]s), 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.<ref name="NYT-20151128">{{cite news |author=The Editorial Board |title=What the Paris Climate Meeting Must Do |url=https://www.nytimes.com/2015/11/29/opinion/sunday/what-the-paris-climate-meeting-must-do.html |date=28 November 2015 |work=[[The New York Times]] |accessdate=28 November 2015 }}</ref>+ − + − {{Main|Milankovitch cycles}}+ − + − Slight variations in Earth's motion 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 [[Kinematics|kinematic]] change 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 affect 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=https://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=2 April 2009 |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|pages=420–25|issue=5|ref=harv|bibcode=1989TeNov...1..420G}}</ref><ref>{{cite web|title=Same forces as today caused climate changes 1.4 billion years ago|url=http://www.sdu.dk/en/Om_SDU/Fakulteterne/Naturvidenskab/Nyheder/2015_03_10_climate_cycles|website=sdu.dk|publisher=University of Denmark.|deadurl=yes|archiveurl=https://web.archive.org/web/20150312163250/http://www.sdu.dk/en/Om_SDU/Fakulteterne/Naturvidenskab/Nyheder/2015_03_10_climate_cycles|archivedate=12 March 2015|df=dmy-all}}</ref>+ − + − The [[IPCC]] notes that Milankovitch cycles drove the [[ice age]] cycles, [[CO2|CO<sub>2</sub>]] 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 CO<sub>2</sub> in the oceans changed, as well as other factors affecting air-sea CO<sub>2</sub> 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}} − {{further|Cosmic ray#Postulated role in climate change}} − [[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 of [[energy]] input to the Earth. Other sources include [[geothermal]] energy from the Earth's core, tidal energy from the Moon and heat from the decay of radioactive compounds. 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 75% as much power as it does today.<ref name=ribas2010>{{Cite conference | last=Ribas | first=Ignasi | conference=Proceedings of the IAU Symposium 264 'Solar and Stellar Variability – Impact on Earth and Planets' | title=The Sun and stars as the primary energy input in planetary atmospheres | volume=264 | pages=3–18 |date=February 2010 | doi=10.1017/S1743921309992298 | bibcode=2010IAUS..264....3R |arxiv = 0911.4872 }}</ref> 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|pages=421–50|ref=harv|bibcode=2006RvMG...62..421M}}</ref><ref>{{cite journal |ref=harv |doi=10.1126/science.1110873 |title=Zircon Thermometer Reveals Minimum Melting Conditions on Earliest Earth |year=2005 |last1=Watson |first1=E.B. |journal=Science |volume=308 |issue=5723 |pages=841–44 |pmid=15879213 |last2=Harrison |first2=TM|bibcode = 2005Sci...308..841W }}</ref> and [[Archean]]<ref>{{cite journal |ref=harv |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 |last1=Hagemann |first1=Steffen G. |last2=Gebre-Mariam |first2=Musie |last3=Groves |first3=David I. |journal=Geology |volume=22 |issue=12 |page=1067|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. |author2=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 |ref=harv |doi=10.1126/science.276.5316.1217 |title=The Early Faint Sun Paradox: Organic Shielding of Ultraviolet-Labile Greenhouse Gases |year=1997 |last1=Sagan |first1=C. |journal=Science |volume=276 |issue=5316 |pages=1217–21 |pmid=11536805 |last2=Chyba |first2=C|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 from the present, 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.<ref name=mnras361>{{citation | last1=Schröder | first1=K.-P. | last2=Connon Smith | first2=Robert | title=Distant future of the Sun and Earth revisited | journal=[[Monthly Notices of the Royal Astronomical Society]] | volume=386 | issue=1 | pages=155–63 | doi=10.1111/j.1365-2966.2008.13022.x | date=2008 | bibcode=2008MNRAS.386..155S | arxiv=0801.4031 }}</ref> − − [[File:Carbon14 with activity labels.svg|thumb|upright=2|Solar activity events recorded in radiocarbon. Values since 1950 not shown.]] − Solar output [[solar variation|varies]] on shorter time scales, including the 11-year [[solar cycle]]<ref>{{cite journal |ref=harv |doi=10.1038/351042a0 |title=The Sun's luminosity over a complete solar cycle |year=1991 |last1=Willson |first1=Richard C. |last2=Hudson |first2=Hugh S. |journal=Nature |volume=351 |issue=6321 |pages=42–44 |bibcode=1991Natur.351...42W}}</ref> and longer-term [[modulation]]s.<ref>{{cite journal |ref=harv |doi=10.1029/2002GL016038 |title=Secular total solar irradiance trend during solar cycles 21–23 |year=2003 |last1=Willson |first1=Richard C. |journal=Geophysical Research Letters |volume=30 |issue=5 |pages=n/a |bibcode=2003GeoRL..30.1199W}}</ref> Solar intensity variations, possibly as a result of the Wolf, [[Spörer Minimum|Spörer]], and the [[Maunder Minimum|Maunder Minima]], 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> This event extended from 1550 to 1850 AD and 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=28 February 2011}}</ref><ref>{{cite journal |ref=harv |doi=10.1034/j.1600-0889.2000.d01-7.x |title=Solar irradiance during the last 1200 years based on cosmogenic nuclides |year=2000 |last1=Bard |first1=Edouard |last2=Raisbeck |first2=Grant |last3=Yiou |first3=Françoise |last4=Jouzel |first4=Jean |journal=Tellus B |volume=52 |issue=3 |pages=985–92|bibcode = 2000TellB..52..985B }}</ref> Solar variation may also have affected 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. − − 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 |ref=harv |doi=10.1029/2009GL038429 |title=Cosmic ray decreases affect atmospheric aerosols and clouds |year=2009 |last1=Svensmark |first1=Henrik |last2=Bondo |first2=Torsten |last3=Svensmark |first3=Jacob |journal=Geophysical Research Letters |volume=36 |issue=15 |pages=n/a |bibcode=2009GeoRL..3615101S}}</ref> − − A 2010 study suggests "that the effects of solar variability on temperature throughout the atmosphere may be contrary to current expectations".<ref> − {{Cite journal − | issn = 0028-0836 − | volume = 467 − | issue = 7316 − | pages = 696–699 − | last = Haigh − | first = Joanna D. − | author2 = Ann R. Winning − | author3 = Ralf Toumi − | author4 = 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 = harv − | url = http://spiral.imperial.ac.uk/bitstream/10044/1/18858/2/Nature_467_7316_2010.pdf − }} − </ref> − − In 2011, [[CERN]] announced the initial results from its [[CLOUD experiment]] in the ''[[Nature (journal)|Nature]]'' journal.<ref>{{cite journal|author1=Jasper Kirkby|author2=<Please add first missing authors to populate metadata.>|display-authors=1|year=2011|title=CERN’s CLOUD experiment provides unprecedented insight into cloud formation|url=http://press.cern/press-releases/2011/08/cerns-cloud-experiment-provides-unprecedented-insight-cloud-formation|journal=Nature|pages=|doi=10.1038/news.2011.504|ref=harv}}</ref> The results indicate that ionisation from cosmic rays significantly enhances aerosol formation in the presence of sulfuric 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. − − ====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 Chichón]] and [[Pinatubo]]). [[El Niño-Southern Oscillation|El Niño]] is a separate event, from ocean variability.]] − The [[Volcano|eruptions]] considered to be large enough to affect the Earth's climate on a scale of more than 1 year are the ones that inject over 100,000 [[ton]]s of [[sulfur dioxide|SO<sub>2</sub>]] into the [[stratosphere]].<ref name = "2004miles">{{cite journal − − | last1 = Miles | first1 = M.G. − | last2 = Grainger | first2 = R.G. − | last3 = Highwood | first3 = E.J. − | title = The significance of volcanic eruption strength and frequency for climate − | journal = Quarterly Journal of the Royal Meteorological Society − | date = 2004 − | volume = 130 | pages = 2361–76 − | issue = 602 − | doi = 10.1256/qj.30.60 − | url = https://dx.doi.org/10.1256/qj.30.60 − | format = PDF − − | doi-broken-date = 2017-01-16 − }}</ref> This is due to the optical properties of SO<sub>2</sub> and sulfate aerosols, which strongly absorb or scatter solar radiation, creating a global layer of [[sulfuric acid]] haze.<ref>{{cite web − − | title = Volcanic Gases and Climate Change Overview − | url = http://volcanoes.usgs.gov/hazards/gas/climate.php − | website = usgs.gov − | publisher = USGS − | accessdate = 31 July 2014 − − }}</ref> On average, such eruptions occur several times per century, and cause cooling (by partially blocking the transmission of solar radiation to the Earth's surface) for a period of several years. − − The eruption of [[Mount Pinatubo]] in 1991, the second largest terrestrial eruption of the 20th century, affected the climate substantially, subsequently global temperatures decreased by about 0.5 °C (0.9 °F) for up to three years.<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=8 October 2009 − − }}</ref><ref>{{cite web − − | last1 = Diggles | first1 = Michael − | title = The Cataclysmic 1991 Eruption of Mount Pinatubo, Philippines − | url=http://pubs.usgs.gov/fs/1997/fs113-97/ − | website = usgs.gov − | accessdate = 31 July 2014 − − }}</ref> Thus, the cooling over large parts of the Earth reduced surface temperatures in 1991–93, the equivalent to a reduction in net radiation of 4 watts per square meter.<ref name = "nasa">{{cite web − − | last1 = Newhall | first1 = Chris − | title = The Atmospheric Impact of the 1991 Mount Pinatubo Eruption − | url = http://pubs.usgs.gov/pinatubo/self/ − | website = usgs.gov − | publisher = USGS − | accessdate = 31 July 2014 − − }}</ref> The [[Mount Tambora]] eruption 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 − |pages=230–59 − |issue=2 − |ref=harv − }}</ref> Much larger eruptions, known as [[large igneous province]]s, occur only a few times every fifty – one hundred million years – through [[flood basalt]], and caused in Earth past 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 − |pages=1–33 − |bibcode=2001ESRv...53....1W − |ref=harv − − }}</ref> − − Small eruptions, with injections of less than 0.1 Mt of sulfur dioxide into the stratosphere, affect the atmosphere only subtly, as temperature changes are comparable with natural variability. However, because smaller eruptions occur at a much higher frequency, they too significantly affect Earth's atmosphere.<ref name = "2004miles" /><ref name = "1997graf">{{cite journal − − | last1 = Graf | first1 = H.-F. − | last2 = Feichter | first2 = J. − | last3 = Langmann | first3 = B. − | title = Volcanic sulphur emissions: Estimates of source strength and its contribution to the global sulphate distribution − | journal = Journal of Geophysical Research: Atmospheres − | date = 1997 − | volume = 102 | pages = 10727–38 − | doi = 10.1029/96JD03265 − | url = https://dx.doi.org/10.1029/96JD03265 − | format = PDF − | bibcode=1997JGR...10210727G − − }}</ref> − − [[Prediction of volcanic activity|Seismic monitoring]] maps current and future trends in volcanic activities, and tries to develop early warning systems. In [[climate model]]ling the aim is to study the physical mechanisms and feedbacks of volcanic forcing.<ref>{{cite web − − | title = IPCC Fourth Assessment Report: Climate Change 2007 − | url= http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch9s9-6-2-2.html − | website = ipcc.ch − | access-date = 31 July 2014 − − }}</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 |access-date=21 January 2008 |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 |access-date=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==== − {{Main|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 journal| year =1999| title = Paleoaltimetry incorporating atmospheric physics and botanical estimates of paleoclimate| journal = Geological Society of America Bulletin| volume = 111| pages = 497–511| issue = 4 | doi = 10.1130/0016-7606(1999)111<0497:PIAPAB>2.3.CO;2| first4 = K.A.| last2 = Wolfe | first1 = C.E.| last3 = Molnar | first2 = J.A.| first3 = P.| last4 = Emanuel| last1 = Forest|bibcode = 1999GSAB..111..497F }}</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=1 July 2008 |publisher=[[NASA]] Earth Observatory |deadurl=yes |archiveurl=https://web.archive.org/web/20070802015424/http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=16401 |archivedate=2 August 2007 |df=dmy }}</ref><ref>{{cite journal|url=http://www.whoi.edu/oceanus/viewArticle.do?id=2508|title=How the Isthmus of Panama Put Ice in the Arctic|first=Gerald H.|last=Haug |first2=Lloyd D. |last2=Keigwin |date=22 March 2004|journal=Oceanus |volume=42 |issue=2 |publisher=[[Woods Hole Oceanographic Institution]] |accessdate=1 October 2013}}</ref> During the [[Carboniferous]] period, about 300 to 360 million years ago, plate tectonics may have triggered large-scale storage of carbon and increased [[wikt:glaciation|glaciation]].<ref>{{cite journal|title=Isotope stratigraphy of the European Carboniferous: proxy signals for ocean chemistry, climate and tectonics|date=1999-09-30|volume=161|issue=1–3|doi=10.1016/S0009-2541(99)00084-4|pages=127–63|first=Peter |last=Bruckschen|first2=Susanne |last2=Oesmanna|first3=Ján |last3=Veizer |ref=harv |journal=Chemical Geology|bibcode=1999ChGeo.161..127B}}</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|first=Judith T. |last=Parrish|title=Climate of the Supercontinent Pangea|journal=Chemical Geology|year=1993|volume=101|pages=215–33 |doi=10.1086/648217|issue=2|publisher=The University of Chicago Press|jstor=30081148|ref=harv|bibcode = 1993JG....101..215P }}</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. − − ==== Other mechanisms ==== − The Earth receives an influx of [[ion]]ized particles known as [[cosmic rays]] from a variety of external sources, including the Sun. A hypothesis holds that an increase in the cosmic ray flux would increase the ionization in the atmosphere, leading to greater cloud cover. This, in turn, would tend to cool the surface. The non-solar cosmic ray flux may vary as a result of a [[Near-Earth supernova|nearby supernova]] event, the [[solar system]] passing through a dense [[interstellar cloud]], or the oscillatory movement of the Sun's position with respect to the [[galactic plane]]. The latter can increase the flux of high-energy cosmic rays coming from the [[Virgo cluster]].<ref name=Atri2014>{{cite journal − | title=Cosmic rays and terrestrial life: A brief review − | last1=Atri | first1=Dimitra | last2=Melott | first2=Adrian L. − | journal=Astroparticle Physics − | volume=53 | pages=186–90 | date=January 2014 − | doi=10.1016/j.astropartphys.2013.03.001 − | bibcode=2014APh....53..186A | arxiv=1211.3962 }}</ref> − − Evidence exists that the [[Chicxulub impact]] some 66 million years ago had severely affected the Earth's climate. Large quantities of sulfate aerosols were kicked up into the atmosphere, decreasing global temperatures by up to 26 °C and producing sub-freezing temperatures for a period of 3−16 years. The recovery time for this event took more than 30 years.<ref name=Brugger2017>{{citation − | contribution=Severe environmental effects of Chicxulub impact imply key role in end-Cretaceous mass extinction − | last1=Brugger | first1=Julia − | last2=Feulner | first2=Georg | last3=Petri | first3=Stefan − | title=19th EGU General Assembly, EGU2017, proceedings from the conference held 23-28 April, 2017 in Vienna, Austria., p.17167 − | date=April 2017 | bibcode=2017EGUGA..1917167B | postscript=. }}</ref> − − ==Physical evidence and effects== − [[File:16-008-NASA-2015RecordWarmGlobalYearSince1880-20160120.png|thumb|center|upright=2.25|<center>Global temperature anomalies for 2015 compared to the 1951–1980 baseline. 2015 was the [[global warming|warmest year]] in the [[NASA]]/[[NOAA]] [[temperature record]], which starts in 1880. It has since been superseded by 2016 ([[NASA]]/[[NOAA]]; 20 January 2016).<ref name="NASA-20160120">{{cite web |last1=Brown |first1=Dwayne |last2=Cabbage |first2=Michael |last3=McCarthy |first3=Leslie |last4=Norton |first4=Karen |title=NASA, NOAA Analyses Reveal Record-Shattering Global Warm Temperatures in 2015 |url=http://www.nasa.gov/press-release/nasa-noaa-analyses-reveal-record-shattering-global-warm-temperatures-in-2015 |date=20 January 2016 |work=[[NASA]] |accessdate=21 January 2016 }}</ref></center>]] − [[File:NSFmonsoonsandclimatesince200AD.jpg|thumb|upright=1.15|right|Comparisons between Asian [[Monsoon]]s from 200 [[AD]] to 2000 AD (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|upright=1.15|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 name=":4">{{cite journal | last1 = Petit | first1 = 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 = 429–46 | date = 1999-06-03 | doi = 10.1038/20859 | issue = 1 | first2 = J. |last2=Jouzel | first3 = D. |last3=Raynaud | first4 = N.I. |last4=Barkov | first5 = J.-M. |last5=Barnola | first6 = I. |last6=Basile | first7 = M. |last7=Bender | first8 = J. |last8=Chappellaz | first9 = M. |last9=Davis | first10 = G. |last10=Delaygue | first11 = M. |last11=Delmotte | first12 = V.M. |last12=Kotlyakov | first13 = M. |last13=Legrand | first14 = V.Y. |last14=Lipenkov | first15 = C. |last15=Lorius | first16 = C. |last16=Ritz | first17 = E. |last17=Saltzman | ref = harv | bibcode=1999Natur.399..429P}}</ref> [[dendrochronology]], [[sea level change]], and [[glacial geology]]. − − ===Temperature (surface and oceans)=== − 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. Taking the record as a whole, most of the 20th century had been unprecedentedly warm, while the 19th and 17th centuries were quite cool.<ref>{{cite web|url=https://www.nexis.com/docview/getDocForCuiReq?lni=3SKF-JCM0-00DS-B1WD&csi=271028&oc=00240&perma=true|title=CLIMATE WARMEST SINCE MIDDLE AGES|last=Von Radowitz|first=John|date=April 23, 1998|website=Century Newspapers LTD|access-date=}}</ref> − − 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, as are other climate metrics noted in subsequent categories. − − ===Glaciers=== − [[Glacier]]s are considered among the most sensitive indicators of climate change.<ref name="Seiz2007">{{cite report|last=Seiz |first=G. |author2=N. Foppa |title=The activities of the World Glacier Monitoring Service (WGMS) |year=2007 |url=http://www.meteoswiss.admin.ch/web/en/climate/climate_international/gcos/inventory/wgms.Par.0008.DownloadFile.tmp/gcosreportwgmse.pdf |accessdate=21 June 2009 |deadurl=yes |archiveurl=https://web.archive.org/web/20090325100331/http://www.meteoswiss.admin.ch/web/en/climate/climate_international/gcos/inventory/wgms.Par.0008.DownloadFile.tmp/gcosreportwgmse.pdf |archivedate=25 March 2009 }}</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 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 km<sup>2</sup>, and preliminary estimates indicate that the remaining ice cover is around 445,000 km<sup>2</sup>. 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 the present.<ref name="Zemp2008">{{cite report| last = Zemp | first = M. |author2=I.Roer |author3=A.Kääb |author4=M.Hoelzle |author5=F.Paul |author6=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=21 June 2009}}</ref><ref name=EPAGlacialBalance>{{cite web|url=https://www.epa.gov/climate-indicators/climate-change-indicators-glaciers|title=Climate Change Indicators: Glaciers|first=US|last=EPA,OA|website=US EPA}}</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=3 October 2011|deadurl=yes|archiveurl=https://web.archive.org/web/20111015042711/http://www.stratigraphy.org/column.php?id=Chart%2FTime%20Scale|archivedate=15 October 2011|df=dmy-all}}</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. − − Data from [[NASA]]'s Grace satellites show that the land ice sheets in both [[Antarctica]] (upper chart) and [[Greenland]] (lower) have been losing mass since 2002. Both ice sheets have seen an acceleration of ice mass loss since 2009.<ref>{{cite web|url=https://climate.nasa.gov/vital-signs/land-ice/|title=Land ice - NASA Global Climate Change}}</ref> − − ===Arctic sea ice decline=== − {{Main|Arctic sea ice decline|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>{{cite web | url=https://climate.nasa.gov/evidence/ | accessdate=2017-12-16 | publisher=Earth Science Communications Team at NASA's Jet Propulsion Laboratory | website=NASA Global Climate Change | title=Climate Change: How do we know? | editor1-first=Holly | editor1-last=Shaftel }}</ref> Sea ice is frozen seawater that floats on the ocean surface. It covers millions of square kilometers 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 13.2 percent per decade, relative to the 1981 to 2010 average.<ref>{{cite web | editor1-first=Holly | editor1-last=Shaftel |title=Arctic Sea Ice Minimum|url=https://climate.nasa.gov/vital-signs/arctic-sea-ice/|website=NASA Global Climate Change|publisher=Earth Science Communications Team at NASA's Jet Propulsion Laboratory|accessdate=21 June 2015}}</ref> The 2007 Arctic summer sea ice retreat was unprecedented. Decades of shrinking and thinning in a warm climate has put the Arctic sea ice in a precarious position, it is now vulnerable to atmospheric anomalies.<ref name=":0">{{Cite journal | last1=Zhang | first1=Jinlun | last2=Lindsay | first2=Ron | last3=Steele | first3=Mike | last4=Schweiger | first4=Axel |date=11 June 2008|title=What drove the dramatic retreat of arctic sea ice during summer 2007?|url=|journal=Geophysical Research Letters|volume=35|pages=1–5|via= | doi=10.1029/2008GL034005 | bibcode=2008GeoRL..3511505Z }}</ref> "Both extent and volume anomaly fluctuate little from January to July and then decrease steeply in August and September".<ref name=":0" /> This decrease is because of lessened ice production as a result of the unusually high SAT. During the Arctic summer, a slower rate of sea ice production is the same as a faster rate of sea ice melting. [[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.]] − − ===Sea level change=== − {{Main|Sea level|Sea level rise}} − [[File:Projected change in global sea level rise if atmospheric carbon dioxide concentrations were to either quadruple or double (NOAA GFDL).png|thumb|The estimated change in sea level caused by carbon dioxide emissions.]] − 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=21 July 2009}}</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><ref>{{Cite news|url=http://graphics.straitstimes.com/STI/STIMEDIA/Interactives/2017/rising-seas/virtual-reality/index.html|title=Singapore underwater|work=The Straits Times|access-date=2017-05-31|language=en}}</ref><ref>{{Cite news|url=http://graphics.straitstimes.com/STI/STIMEDIA/Interactives/2017/rising-seas/long-form/index.html|title=How Singapore is responding to the threat of rising sea levels|work=The Straits Times|access-date=2017-05-31|language=en}}</ref> − − According to recent studies, global-mean sea level rose by 195 mm during the period from 1870 to 2004.<ref>{{Cite journal|last=Church|first=John A.|last2=White|first2=Neil J.|date=2006-01-16|title=A 20th century acceleration in global sea-level rise|url=http://doi.wiley.com/10.1029/2005GL024826|journal=Geophysical Research Letters|language=en|volume=33|issue=1|pages=n/a–n/a|doi=10.1029/2005gl024826|issn=1944-8007|bibcode=2006GeoRL..33.1602C}}</ref> Since 2004, satellite-based records indicate that there has been a further 43 mm of global-mean sea levels rise, {{as of|2017|July|lc=y}}.<ref>{{cite web|url=https://climate.nasa.gov/vital-signs/sea-level/|title=NASA Global Climate Change, Vital Signs|last=|first=|date=|website=|archive-url=|archive-date=|dead-url=|access-date=2 April 2018}}</ref> − − ===Ice cores=== − [[File:Five Myr Climate Change.svg|thumb|The Antarctic temperature changes during the last several [[Glacial period|glacial]] and [[interglacial]] cycles of the present [[ice age]], according to [[δ18O]] ratios.]] − 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 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. − − ===Cloud cover and precipitation=== − {{see also|Cloud|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 clouds and precipitation 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=1889–922 |doi=10.1002/joc.680 |date=December 2001 |bibcode = 2001IJCli..21.1889N |ref=harv }}</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=935–45 |doi=10.1016/j.quascirev.2003.06.019 |date=April 2004 |bibcode = 2004QSRv...23..935F |ref=harv }}</ref> In July 2016 scientists published evidence of increased cloud cover over polar regions,<ref>{{cite journal|url=http://www.nature.com/nature/journal/vaop/ncurrent/full/nature18273.html|title=Evidence for climate change in the satellite cloud record|first1=Joel R.|last1=Norris|first2=Robert J.|last2=Allen|first3=Amato T.|last3=Evan|first4=Mark D.|last4=Zelinka|first5=Christopher W.|last5=O’Dell|first6=Stephen A.|last6=Klein|date=4 August 2016|publisher=|journal=Nature|volume=536|issue=7614|pages=72–75|via=www.nature.com|doi=10.1038/nature18273|bibcode=2016Natur.536...72N}}</ref> as predicted by climate models.<ref>{{cite journal|url=http://www.nature.com/news/clouds-get-high-on-climate-change-1.20230|title=Clouds get high on climate change|first=Alexandra|last=Witze|date=11 July 2016|publisher=|doi=10.1038/nature.2016.20230|journal=Nature}}</ref> − − Climatological temperatures substantially affect cloud cover and 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 cloud cover and precipitation).<ref name = ORNL_paleoclimate/> In contrast, the world's climate was cloudier and 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 cloud cover 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 |bibcode = 2006JHyd..319...83H |ref=harv }}</ref><ref>{{cite journal |author1=Smith, T. M. |author2=Yin, X. |author3=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= harv}}</ref> − Similar slight overall increase in global river runoff and in average soil moisture has been perceived.<ref name = USGS_watercycletrend/> − − ===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 CO<sub>2</sub>. 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 |date=2011-11-15 |title=UK trees' fruit ripening '18 days earlier' |publisher=Bbc.co.uk |url=https://www.bbc.co.uk/news/science-environment-15721263 |accessdate=1 November 2012}}</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 |last1=Sahney |first1=S. |last2=Benton |first2=M.J. |last3=Falcon-Lang |first3=H.J. |year=2010 |title=Rainforest collapse triggered Pennsylvanian tetrapod diversification in Euramerica |journal=Geology |doi=10.1130/G31182.1 |bibcode=2010Geo....38.1079S |volume=38 |issue=12 |pages=1079–82 |ref=harv |url=https://www.academia.edu/368820/Rainforest_collapse_triggered_Pennsylvanian_tetrapod_diversification_in_Euramerica |format=PDF |accessdate=27 November 2013}}</ref><ref>{{cite journal |last1=Bachelet |first1=D. |last2=Neilson |first2=R. |last3=Lenihan |first3=J. M. |last4=Drapek |first4=R.J. |year=2001 |title=Climate Change Effects on Vegetation Distribution and Carbon Budget in the United States |journal=[[Ecosystems]] |doi=10.1007/s10021-001-0002-7 |volume=4 |issue=3 |pages=164–85 |ref=harv}}</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"/> Such stress 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 climate science is called [[dendroclimatology]], and is one of the many ways they research [[Proxy (climate)|climate trends prior to written records]].<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=volume 11|location=New York|pages=|editor2-last=Swetnam|editor2-first=Thomas W.|editor3-last=Diaz|editor3-first=Henry F.}}</ref> − − ====Forest genetic resources==== − Even though this is a field with many uncertainties, it is expected that over the next 50 years climate changes will have an effect on the diversity of [[forest genetic resources]] and thereby on the distribution of forest tree species and the composition of forests. Diversity of [[forest genetic resources]] enables the potential for a species (or a population) to adapt to climatic changes and related future challenges such as temperature changes, drought, pests, diseases and forest fire. However, species are not naturally capable to adapt in the pace of which the climate is changing and the increasing temperatures will most likely facilitate the spread of pests and diseases, creating an additional threat to forest trees and their populations.<ref>{{cite journal|last1=Konert, M.; Fady, B.; Gömöry, D.; A'Hara, S.; Wolter, F; Ducci, F.; Koskela, J.; Bozzano,M.; Maaten, T. & Kowalczyk, J.|title=Use and Transfer of forest reproductive material in Europe in the context of climate change|journal=European Forest Genetic Resources Programme|url=http://www.euforgen.org/fileadmin/templates/euforgen.org/upload/Publications/Thematic_publications/EUFORGEN_FRM_use_transfer.pdf}}</ref> To inhibit these problems human interventions, such as transfer of [[forest reproductive material]], may be needed.<ref>{{cite journal|last1=Koskela, J.; Buck, A.; Teissier du Cros, E.|title=Climate change and forest genetic diversity – Implications for sustainable forest management in Europe|journal=European Forest Genetic Resources Programme|url=http://www.euforgen.org/fileadmin/templates/euforgen.org/upload/Publications/Thematic_publications/EUFORGEN_FGR_and_Climate_change_web.pdf}}</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 |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 |doi=10.1023/B:JOPL.0000029433.85764.a5 |volume=32 |issue=2 |pages=197–213 | ref = harv|bibcode=2004JPall..32..197L }}</ref><ref>{{cite journal | last = Birks | first = H.H. | title = The importance of plant macrofossils in the reconstruction of Lateglacial vegetation and climate: examples from Scotland, western Norway, and Minnesota, US | journal = Quaternary Science Reviews | volume = 22 | issue = 5–7 | pages = 453–73 |date=March 2003 | doi = 10.1016/S0277-3791(02)00248-2|bibcode = 2003QSRv...22..453B | ref = harv | url = https://bora.uib.no/bitstream/1956/387/4/1956-387.pdf }}</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 |pages=267–83 |year=1999 |doi=10.1016/S0034-6667(98)00058-X |issue=3–4 |last2=Fujiki |first2=Toshiyuki |last3=Morita |first3=Yoshimune |ref=harv}}</ref> and especially since the [[last glacial maximum]].<ref>{{cite journal |first=I. Colin |last=Prentice |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=2038–56 |year=1991 |doi=10.2307/1941558 |jstor=1941558 |ref=harv}}</ref> − − − − ===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 = 419–33 | date = 1999-05-04 | doi = 10.1002/(SICI)1099-1417(1998090)13:5<419::AID-JQS410>3.0.CO;2-D | author2 = Lemdahl, G.; Lowe, J.J.; Walkling, A.|bibcode = 1998JQS....13..419C | ref = harv }}</ref> − The studies of the impact in vertebrates are few mainly from [[Developing country|developing countries]], where there are the fewest studies; between 1970 and 2012, vertebrates declined by 58 percent, with freshwater, marine, and terrestrial populations declining by 81, 36, and 35 percent, respectively.<ref>Ripple, W.J., Wolf C., Newsome T. M., Galetti M., Alamgir M., Crist E., Mahmoud M.I., Laurance W.F., & other scientist signatories +15 364 (2017). World Scientists’ Warning to Humanity: A Second Notice. BioScience. bix125.</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. [http://www.fao.org/docrep/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=1194–212 |doi=10.1111/j.1365-2486.2009.02046.x |date=April 2010 |ref=harv|bibcode=2010GCBio..16.1194B }}</ref> − − ===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 journal| first1 = P.B. | title = Cultural Responses to Climate Change During the Late Holocene| url=http://www.ldeo.columbia.edu/~peter/Resources/Publications/deMenocal.2001.pdf| last1 = Demenocal | journal = [[Science (journal)|Science]]| volume = 292 | pages = 667–73 | year = 2001 | doi = 10.1126/science.1059827| pmid=11303088| issue=5517|bibcode = 2001Sci...292..667D }}</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 rise<ref name=viking01>{{Cite journal| first1 = S.M.| title = Networks and nodal points: the emergence of towns in early Viking Age Scandinavia| url=https://www.cambridge.org/core/journals/antiquity/article/networks-and-nodal-points-the-emergence-of-towns-in-early-viking-age-scandinavia/2C4533F891FADEA7695BD91A31F2628E| last1 = Sindbaek| journal = [[Antiquity (journal)|Antiquity]]| volume = 81| pages = 119–32 | year = 2007| issue=311| doi=10.1017/s0003598x00094886}}</ref> and also the collapse of various civilizations.<ref name=Demenocal01/> − [[File:Glacier Mass Balance.png|thumb|right|upright=1.15|Decline in thickness of glaciers worldwide over the past half-century]] − − ==History== − {{Main|History of climate change science}} − − [[Historical climatology]] is the study of historical changes in climate and their effect on human history and development. The primary sources include written records such as [[sagas]], [[chronicle]]s, [[map]]s and [[local history]] literature as well as pictorial representations such as [[painting]]s, [[drawing]]s and even [[rock art]]. This differs from [[paleoclimatology]] which encompasses climate change over the entire [[history of Earth]]. Notable climate events known to paleoclimatology are provided in this [[list of periods and events in climate history]]. − − Prior to the 18th century, scientists had not suspected that prehistoric climates were different from the modern period. By the late 18th century, geologists found evidence of a succession of [[Geologic time scale|geological ages]] with changes in climate. There were various competing theories about these changes, and [[James Hutton]], whose ideas of cyclic change over huge periods of time were later dubbed [[uniformitarianism]], was among those who found signs of past glacial activity in places too warm for [[glaciers]] in modern times.<ref name="Davis">{{Cite book|last=Young |first=Davis A. |title=The biblical Flood: a case study of the Church's response to extrabiblical evidence |publisher=[[Eerdmans]] |location=Grand Rapids, Mich |year=1995 |pages= |isbn=0-8028-0719-4 |url=http://www.bringyou.to/apologetics/p82.htm |accessdate=2008-09-16 |deadurl=yes |archiveurl=https://web.archive.org/web/20070331124027/http://www.bringyou.to/apologetics/p82.htm |archivedate=31 March 2007 |df=dmy-all }}</ref> In 1815 [[Jean-Pierre Perraudin]] described for the first time how glaciers might be responsible for the giant boulders seen in alpine valleys.<ref name="nasa-paleo">{{cite web |url=http://earthobservatory.nasa.gov/Features/Paleoclimatology/paleoclimatology_intro.php |title=Paleoclimatology |author=Holli Riebeek |date=28 June 2005 |publisher=NASA |accessdate=1 July 2009 }}</ref> − − By the end of the 19th century, scientific opinion had turned decisively against any belief in a human influence on climate. And whatever the regional effects, few imagined that humans could affect the climate of the planet as a whole.<ref name=aiphist2>{{cite web |url=http://history.aip.org/climate/public.htm |title=The Public and Climate Change |work=The Discovery of Global Warming | year=2011 |author=Spencer Weart}}</ref> However, in 1899 [[Thomas Chrowder Chamberlin]] developed at length the idea that changes in climate could result from changes in the concentration of atmospheric carbon dioxide.<ref name=WH1965>{{cite web|url=https://dge.carnegiescience.edu/labs/caldeiralab/Caldeira%20downloads/PSAC,%201965,%20Restoring%20the%20Quality%20of%20Our%20Environment.pdf|title=Restoring the Quality of Our Environment|year=1965|publisher=The White House}}</ref> − − In 1967, taking advantage of the ability of digital computers to integrate absorption curves numerically, [[Syukuro Manabe]] and Richard Wetherald made the first detailed calculation of the greenhouse effect incorporating convection (the "Manabe-Wetherald one-dimensional radiative-convective model").<ref>{{cite web |url=http://history.aip.org/climate/GCM.htm |title=General Circulation Models of Climate |work=The Discovery of Global Warming | year=2011 |author=Spencer Weart}}</ref><ref>{{cite journal |author1=Manabe S. |author2=Wetherald R.T. | year = 1967 | title = Thermal Equilibrium of the Atmosphere with a Given Distribution of Relative Humidity | url = | journal = Journal of the Atmospheric Sciences | volume = 24 | issue = 3| pages = 241–59 | doi=10.1175/1520-0469(1967)024<0241:teotaw>2.0.co;2| bibcode=1967JAtS...24..241M}}</ref> They found that, in the absence of unknown feedbacks such as changes in clouds, a doubling of carbon dioxide from the current level would result in approximately 2 °C increase in global temperature. − − In 1985 a joint UNEP/WMO/ICSU Conference on the "Assessment of the Role of Carbon Dioxide and Other Greenhouse Gases in Climate Variations and Associated Impacts" concluded that greenhouse gases "are expected" to cause significant warming in the next century and that some warming is inevitable.<ref>{{cite web|url = http://www.scopenvironment.org/downloadpubs/scope29/statement.html|author = World Meteorological Organisation (WMO)|year = 1986|title = Report of the International Conference on the assessment of the role of carbon dioxide and of other greenhouse gases in climate variations and associated impacts|location = Villach, Austria|accessdate = 28 June 2009|deadurl = yes|archiveurl = https://web.archive.org/web/20131121040937/http://www.scopenvironment.org/downloadpubs/scope29/statement.html|archivedate = 21 November 2013|df = dmy-all}}</ref> Since the 1990s, scientific research on climate change has included multiple disciplines and has expanded. Research during this period has been summarized in the Assessment Reports by the [[Intergovernmental Panel on Climate Change]]. − {{Portal|Environment|Global warming|Energy}}+ − {{cmn|colwidth=30em| − − * [[Climate change in popular culture]] − * [[Global change]] − * [[Homogenization (climate)|Homogenization]] − '''Climate of recent glaciations'''+ − + + − '''Climate of the past'''+ − * [[Cretaceous Thermal Maximum]] − * [[Permo-Carboniferous]] Glaciation − * [[Snowball Earth]] − − '''Recent climate''' − * [[Anthropocene]] − * [[CORA dataset]] temperature and salinity of global oceans − * [[Effects of global warming]] − * [[Extreme weather]] − * [[Global terrestrial stilling]] − * [[Hardiness zone]] − * [[Holocene climatic optimum]] − * [[Land surface effects on climate]] − * [[Medieval Warm Period]] − * [[Temperature record of the past 1000 years]] − }} − − ==Notes== − {{Reflist}} + − * {{Cite book+ − | 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. |editor2=Qin, D. |editor3=Manning, M. |editor4=Chen, Z. |editor5=Marquis, M. |editor6=Averyt, K.B. |editor7=Tignor, M. |editor8= 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 − |ref =harv − }} (pb: {{ISBNT|978-0-521-70596-7}}). − * {{Cite book − | 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 − | editor = Core Writing Team |editor2=Pachauri, R.K |editor3=Reisinger, A. − | publisher = IPCC − | url= http://www.ipcc.ch/publications_and_data/ar4/syr/en/contents.html − | isbn = 92-9169-122-4 − |ref =harv − }}. − * {{Cite book − |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. − |editor2=Ding, Y. − |editor3=Griggs, D.J. − |editor4=Noguer, M. − |editor5=van der Linden, P.J. − |editor6=Dai, X. − |editor7=Maskell, K. − |editor8=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 − |ref=harv − |deadurl=yes − |archiveurl=https://web.archive.org/web/20160330214626/http://grida.no/publications/other/ipcc_tar/?src=%2Fclimate%2Fipcc_tar%2Fwg1%2Findex.htm − |archivedate=30 March 2016 − |df= − }} (pb: {{ISBNT|0-521-01495-6}}). − − ==Further reading== − {{Refbegin|30em}} − * {{cite book − | author = Ipcc ar4 wg1 − | author-link = IPCC − | year = 2007 − | 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 − | editor1-last = Solomon |editor1-first=S. |editor2-last=Qin |editor2-first=D. |editor3-last=Manning |editor3-first=M. |editor4-last=Chen |editor4-first=Z. |editor5-last=Marquis |editor5-first=M. |editor6-last=Averyt |editor6-first=K.B. |editor7-last=Tignor |editor7-first=M. |editor8-last=Miller |editor8-first=H.L. − | publisher = Cambridge University Press − | isbn = 978-0-521-88009-1 − | url = http://www.ipcc.ch/publications_and_data/ar4/wg1/en/contents.html − }} (pb: {{ISBNT|978-0-521-70596-7}}). − * {{cite book − | author = Ipcc ar4 syr − | author-link = IPCC − | year = 2007 − | 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 − | editor1 = Core Writing Team |editor2-last=Pachauri |editor2-first=R.K |editor3-last=Reisinger |editor3-first=A. − | publisher = IPCC − | isbn = 92-9169-122-4 − | url= http://www.ipcc.ch/publications_and_data/ar4/syr/en/contents.html − }} − * {{cite journal |last=Emanuel |first=K. |date=August 2005 |title=Increasing destructiveness of tropical cyclones over the past 30 years |journal=Nature |pmid=16056221 |doi=10.1038/nature03906 |bibcode=2005Natur.436..686E |volume=436 |issue=7051 |pages=686–88 |url=ftp://texmex.mit.edu/pub/emanuel/PAPERS/NATURE03906.pdf |ref=harv}} − * {{cite book |last1=Edwards |first1=Paul Geoffrey |last2=Miller |first2=Clark A. |year=2001 |title=Changing the atmosphere: expert knowledge and environmental governance |publisher=MIT Press |location=Cambridge, Massachusetts |isbn=0-262-63219-5}} − * {{cite book |last=McKibben |first=Bill |year=2011 |title=The Global Warming Reader |publisher=[[OR Books]] |location=New York, N.Y. |isbn=978-1-935928-36-2}} − * {{cite journal |last=Ruddiman |first=W.F. |year=2003 |title=The anthropogenic greenhouse era began thousands of years ago |journal=Climate Change |doi=10.1023/B:CLIM.0000004577.17928.fa |volume=61 |issue=3 |pages=261–23 |ref=harv}} − * {{cite book |last=Ruddiman |first=William F. |year=2005 |title=Plows, plagues, and petroleum: how humans took control of climate |publisher=Princeton University Press |location=Princeton, N.J |isbn=0-691-13398-0}} − * {{cite journal |last1=Ruddiman |first1=W.F. |last2=Vavrus |first2=S.J. |last3=Kutzbach |first3=J.E. |year=2005 |title=A test of the overdue-glaciation hypothesis |journal=Quaternary Science Reviews |doi=10.1016/j.quascirev.2004.07.010 |bibcode=2005QSRv...24....1R |volume=24 |issue=11 |pages=1–10 |ref=harv}} − * {{cite encyclopedia |last1=Schelling |first1=Thomas C. |authorlink=Thomas Schelling |editor-last=Henderson |editor-first=David R. |editorlink=David R. Henderson |year=2002 |encyclopedia=[[Concise Encyclopedia of Economics]] |edition=1st |title=Greenhouse Effect |publisher=[[Library of Economics and Liberty]] |url=http://www.econlib.org/library/Enc1/GreenhouseEffect.html |ref=harv}} {{OCLC|317650570|50016270|163149563}} − * {{cite journal |last1=Schmidt |first1=G.A. |last2=Shindel |first2=D.T. |last3=Harder |first3=S. |year=2004 |title=A note of the relationship between ice core methane concentrations and insolation |journal=Geophys. Res. Lett. |doi=10.1029/2004GL021083 |bibcode=2004GeoRL..3123206S |volume=31 |issue=23 |page=L23206 |url=http://www.agu.org/pubs/crossref/2004/2004GL021083.shtml |ref=harv}} − * {{cite book |editor-last=Wagner |editor-first=Frederic H. |year=2009 |title=Climate Change in Western North America: Evidence and Environmental Effects |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}} − * [https://science2017.globalchange.gov/ Climate Science Special Report] – U.S. Global Change Research Program − * [http://www.sourcewatch.org/index.php?title=Climate_change:_Resources Climate Change Resources] from [[SourceWatch]] − * [http://www.ncdc.noaa.gov/indicators/ Global Climate Change Indicators] from [[NOAA]] − * [https://climate.nasa.gov/ Global Climate Change] from [[NASA]] (US) − * [https://web.archive.org/web/20140307034819/http://dels.nas.edu/resources/static-assets/exec-office-other/climate-change-full.pdf Climate Change: Evidence & Causes], from the [[Royal Society]] and the [[U.S. National Academy of Sciences]] − * [http://www.ipcc.ch/ Intergovernmental Panel on Climate Change (IPCC)] − * [http://www.ucsusa.org/global_warming#.WFVRJHC1yLx Confronting the Realities of Climate Change] Union of Concerned Scientists − * [https://skepticalscience.com/earths-climate-system.html A rough guide to the components of Earth's Climate System] − − {{global warming|gstate=expanded}} − {{Doomsday}} − {{Use dmy dates|date=July 2011}} − {{DEFAULTSORT:Climate Change}}+ − + − [[Category:Climate and weather statistics]] − [[Category:Climate history]] − [[Category:Carbon finance]] − [[Category:Economic problems]] − [[Category:Articles containing video clips]] −
Reverted edits by a hidden user to last revision by DavidB4-bot
'''Climate change''' is a change in the statistical distribution of [[weather]] patterns when that change lasts for an extended period of time (i.e., decades to millions of years). Climate change may refer to a change in average weather conditions, or in the time variation of weather within the context of longer-term average conditions. Climate change is caused by factors such as [[wikt:biotic|biotic]] processes, variations in [[Sunlight|solar radiation]] received by Earth, [[plate tectonics]], and [[volcanic eruptions]]. Certain human activities have been identified as primary causes of ongoing climate change, often referred to as [[global warming]].<ref>
'''Climate change''' is the new name used by [[liberal]]s for their [[global warming]] hoax, which they coined as it became obvious that there is no crisis in global warming. The modification in terminology is identical to what [[liberals]] did in redefining "evolution" to be "change over time," which of course is a meaningless expression just as "climate change" is.
[[Scientist]]s actively work to understand past and future [[climate]] by using [[Proxy (climate)|observations]] and theoretical models. A climate record—extending deep into the Earth's past—has been assembled, and continues to be built up, based on geological evidence from [[borehole]] temperature profiles, [[ice core|cores removed from deep accumulations of ice]], [[flora]]l and [[fauna]]l records, glacial and [[Periglaciation|periglacial]] processes, stable-isotope and other analyses of sediment layers, and records of past sea levels. More recent data are provided by the instrumental record. [[General circulation model]]s, based on the [[Outline of physical science|physical sciences]], are often used in theoretical approaches to match past climate data, make future projections, and link causes and effects in climate change.
Climate change does occur naturally, which scientists say has occurred in repeated cycles of cooling (see [[Ice Age]]s) and warming over millions of years. Yet many writers have been urging America to fund an ill-conceived initiative to "stop global warming", as if warmer nights or winters would make human life more difficult. The term "climate change" has largely replaced the term "global warming", in ideological discussions.
Ideologues insist that the world's top scientists have reached a "consensus" that most of the warming which land-based weather stations have recorded in the last century is due to human activity. The basis for this claim is a set of reports published by the [[IPCC]], an agency of the United Nations. The assumption is that the government-appointed representatives who run the IPCC would be completely objective and neutral, and would place finding and revealing the truth ahead of any nationalistic interests.
A lot of money is spent publicizing one side's position in the debate:
* ''Newsweek'' purports to take readers inside the world of “Global-Warming Deniers: A Well-Funded Machine” without mentioning that the global-warming alarmists are even better funded, in some cases with government support. [https://www.washingtontimes.com/news/2007/aug/15/the-hottest-year-1934/]
Journalists omit mention of key scientific points:
* Good news is no news, which is why the mainstream media largely ignores all studies showing net benefits of climate change. [http://wattsupwiththat.com/2013/10/17/the-good-side-of-climate-change/]
Ideologues use all sorts of tricks to convince the general public to support them on the climate change issue. A perennial favorite is to trumpet the current year as the "[[warmest year on record]]", as if one [[outlier]] denotes a [[trend]]. Probably the most insidious kind of trick is to accuse objective people of cherry-picking and censorship, while hypocritically doing just that themselves.
The allegedly harmful effects of climate change include warming temperatures, changing weather patterns, an increase in sea level and in general any climate event affected by global warming.<ref>http://chaser.env.nagoya-u.ac.jp/~kengo/lec/IPCC_TAR-FRONT.pdf</ref> Climate change is one of the top [[Environmental Issues|environmental issues]], with [[liberal]]s and [[conservative]]s evenly divided on whether [[global warming]] is man-made or, if it is significantly occurring, is a natural event — along with [[global cooling]].
Jack M. Hollander wrote:
*The planet has warmed since the mid-1800s, but before that it cooled for more than five centuries. Cycles of warming and cooling have been part of Earth's natural [[climate history]] for millions of years. So what is the [[global warming debate]] about? It's about the proposition that human use of [[fossil fuels]] has contributed significantly to the past century's warming, and that expected future warming may have catastrophic global consequences. But hard evidence for this human contribution simply does not exist; the evidence we have is suggestive at best. Does that mean the human effects are not occurring? Not necessarily. But [[Climategate media coverage#Climategate media coverage|media coverage]] of global warming has been so alarmist that it fails to convey how flimsy the evidence really is. Most people don't realize that many strong statements about a human contribution to global warming are based more on [[politics]] than on [[science]]. Indeed, the climate change issue has become so highly [[Politicization of science|politicized]] that its scientific and political aspects are now almost indistinguishable.<ref>http://goliath.ecnext.com/coms2/summary_0199-2875898_ITM Global Warming: Both Sides</ref>
==Questions==
#What is the most important greenhouse gas?
#*AGW proponents say it's [[carbon dioxide]]
#*A peer-reviewed scientific paper says it's [[water vapor]]<ref>[http://thejll.com/Frascati/ReichelThejllLassenSCL.pdf "Water vapor is the most important greenhouse gas ..."]</ref>
#What is the role of clouds?
#*Low-altitude clouds reflect some of the sun's radiation back into the atmosphere, cooling the earth. It's not yet known whether global warming will dissipate clouds, which would effectively speed up the process of climate change, or increase [[cloud cover]], which would slow it down. [http://www.time.com/time/health/article/0,8599,1912448,00.html#ixzz1EyuBDJo1]
#What are the uncertainties in understanding climatic change?
#*The UN's climate panel said recently there is '''a 90% chance''' that most of the last 50 to 100 years of global warming are due to human activity
#*[[Sallie Baliunas]] points out that the same climate panel also said, "Our ability to quantify the human influence on global climate is limited because the expected signal is still emerging from the noise of natural variability, and because there are uncertainties in key factors" [http://oldfraser.lexi.net/publications/books/g_warming/solar.html]
==Links==
*[[cloud cover]]
*[[ice age]]
==Hypocrisy==
Many times, AGW advocates pay lip service to general principles which they themselves violate, while broadcasting false accusations that their opponents are violating these principles. The AGW side has made every effort to censor their opponents, heaping enormous pressure on scientists and other academics to silence them. Accordingly, the US media gave great publicity to [[James Hansen]] when he accused NASA of trying to silence him.<ref>Hansen "shot to fame when he accused the administration of trying to censor his views on climate change" [http://www.dailytech.com/Blogger+finds+Y2K+bug+in+NASA+Climate+Data/article8383.htm]</ref>
====Ocean-atmosphere variability====
==Environmentalism and climate change==
The main contention of [[environmentalist]]s like [[Al Gore]] is the argument that:
#The earth's atmosphere warmed one or two degrees Fahrenheit (0.8 Centigrade) during the 20th century.
#Most of this warming is man-made.
The ocean and atmosphere can work together to spontaneously generate internal climate variability that can persist for years to decades at a time.<ref>{{cite journal |last1=Brown |first1=Patrick T. |last2=Li |first2=Wenhong |last3=Cordero |first3=Eugene C. |last4=Mauget |first4=Steven A. |date=2015-04-21 |title=Comparing the model-simulated global warming signal to observations using empirical estimates of unforced noise |journal=Scientific Reports |issn=2045-2322 |url=http://www.nature.com/articles/srep09957 |doi=10.1038/srep09957 |pmc=4404682 |pmid=25898351 |volume=5|page=9957 |bibcode=2015NatSR...5E9957B }}</ref><ref>{{cite journal |last=Hasselmann |first=K. |date=1976-12-01 |title=Stochastic climate models Part I. Theory |journal=Tellus |issn=2153-3490 |doi=10.1111/j.2153-3490.1976.tb00696.x |volume=28 |issue=6 |pages=473–85 |url=http://onlinelibrary.wiley.com/doi/10.1111/j.2153-3490.1976.tb00696.x/abstract|bibcode=1976TellA..28..473H }}</ref> Examples of this type of variability include the [[El Niño–Southern Oscillation]], the [[Pacific decadal oscillation]], and the [[Atlantic multidecadal oscillation|Atlantic Multidecadal Oscillation]]. These variations can affect global average surface temperature by redistributing heat between the deep ocean and the atmosphere<ref>{{cite journal |last1=Meehl |first1=Gerald A. |last2=Hu |first2=Aixue |last3=Arblaster |first3=Julie M. |last4=Fasullo |first4=John |last5=Trenberth |first5=Kevin E. |date=2013-04-08 |title=Externally Forced and Internally Generated Decadal Climate Variability Associated with the Interdecadal Pacific Oscillation |url=http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-12-00548.1 |journal=Journal of Climate |issn=0894-8755 |doi=10.1175/JCLI-D-12-00548.1 |volume=26 |issue=18 |pages=7298–310|bibcode=2013JCli...26.7298M }}</ref><ref>{{cite journal |last1=England |first1=Matthew H. |last2=McGregor |first2=Shayne |last3=Spence |first3=Paul |last4=Meehl |first4=Gerald A. |last5=Timmermann |first5=Axel |last6=Cai |first6=Wenju |last7=Gupta |first7=Alex Sen |last8=McPhaden |first8=Michael J. |last9=Purich |first9=Ariaan |date=2014-03-01 |title=Recent intensification of wind-driven circulation in the Pacific and the ongoing warming hiatus |journal=Nature Climate Change |issn=1758-678X |doi=10.1038/nclimate2106 |volume=4 |issue=3 |pages=222–27|url=http://www.nature.com/nclimate/journal/v4/n3/full/nclimate2106.html|bibcode=2014NatCC...4..222E }}</ref> and/or by altering the cloud/water vapor/sea ice distribution which can affect the total energy budget of the earth.<ref>{{cite journal |last1=Brown |first1=Patrick T. |last2=Li |first2=Wenhong |last3=Li |first3=Laifang |last4=Ming |first4=Yi |date=2014-07-28 |title=Top-of-atmosphere radiative contribution to unforced decadal global temperature variability in climate models |journal=Geophysical Research Letters |issn=1944-8007 |doi=10.1002/2014GL060625 |volume=41 |issue=14 |page=2014GL060625 |url=http://onlinelibrary.wiley.com/doi/10.1002/2014GL060625/abstract|bibcode=2014GeoRL..41.5175B }}</ref><ref>{{cite journal |last1=Palmer |first1=M. D. |last2=McNeall |first2=D. J. |date=2014-01-01 |title=Internal variability of Earth's energy budget simulated by CMIP5 climate models |journal=Environmental Research Letters |issn=1748-9326 |doi=10.1088/1748-9326/9/3/034016 |volume=9 |issue=3 |page=034016 |url=http://stacks.iop.org/1748-9326/9/i=3/a=034016|bibcode=2014ERL.....9c4016P }}</ref>
#The warming is likely to continue and to be harmful to human, animal and plant life.
#We must all work together to stop it by reducing emission of [[greenhouse gases]].
==Science and climate change==
[[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 the formation of the [[Antarctic Circumpolar Current|ACC]], which keeps warm waters away from Antarctica.]]
Jack M. Hollander wrote:
<blockquote>... climate change remains a fascinating and important scientific subject. Climate dynamics and climate history are extraordinarily complex, and despite intensive study for decades, scientists are not yet able to explain satisfactorily such basic phenomena as extreme weather events ([[hurricane]]s, [[tornado]]es, [[drought]]s), El Nino variations, historical [[climate cycles]], and trends of [[atmospheric temperature]]s. The scientific uncertainties about all these matters are great, and not surprisingly, competent scientists disagree in their interpretations of what is and is not known.<ref>http://goliath.ecnext.com/coms2/summary_0199-2875898_ITM</ref></blockquote>
William Happer wrote:
<blockquote>The current debates about global climate change are complicated by our not understanding the physics of the sun or of the earth’s atmosphere and oceans well enough to dismiss them as major causes of climate change on the earth. Dramatic climate changes like the [[medieval warm period]] at the time of the [[Viking]] settlements of [[Iceland]] and [[Greenland]] from about a.d. 900 to 1250, and the subsequent “[[little ice age]],” from about 1250 to 1700, which led to extinction of the Greenland settlements, were certainly not caused by manmade changes in the concentration of [[carbon dioxide]] in the atmosphere.<ref>http://media.hoover.org/documents/0817939326_27.pdf</ref></blockquote>
One of the major problems with many scientists' conclusions about climate change is a misunderstanding of [[correlation]] versus [[causation]]. Some studies show correlations between increasing concentrations of atmospheric greenhouse gases and increasing [[precipitation]], and between human activity and atmospheric greenhouse gases, and then go so far as to conclude that humans are causing increased rain, snow, and catastrophic flooding.<ref>Gillis, Justin. "Study Links Rise in Rain and Snow to Human Actions." ''The New York Times'', February 16, 2011. https://www.nytimes.com/2011/02/17/science/earth/17extreme.html?_r=2&ref=science</ref><ref>Schiermeier, Quirin. "Increased Flood Risk Linked to Global Warming." 2011. ''Nature'', Vol. 470, p. 316. http://www.nature.com/news/2011/110216/full/470316a.html</ref> Correlation does not imply causation. This is especially true considering the relatively short periods of data used (a few decades at most) compared to the Earth's age, and the fact that weather patterns have been cyclic throughout history (see [[climate cycles]]).
====Human influences====
==History of Climate Change vs. Global Warming==
The term climate change has its origins several decades ago when physicist Gilbert Plass published a study called ''The Carbon Dioxide Theory of Climatic Change'' in 1956.<ref>http://onlinelibrary.wiley.com/doi/10.1111/j.2153-3490.1956.tb01206.x/abstract</ref>
In this study, Plass postulated the release of CO2 into the atmosphere by industrial and other human activities may have caused the temperature rise noticed in the twentieth century.
The term global warming was first thought to be used by Wallace Broecker, a geochemist from [[Columbia University]]'s Lamont-Doherty Geological Observatory. His paper, ''Climatic Change: Are We on the Brink of a Pronounced Global Warming?'' <ref>http://blogs.ei.columbia.edu/files/2009/10/broeckerglobalwarming75.pdf</ref> acknowledged the scenario of global warming, though there was a common acknowledgement that airborne aerosols may cause global cooling.
A National Academy of Science study of carbon dioxide's impact on climate published in 1979 also used the term global warming to refer to surface temperature change.<ref>http://www.atmos.ucla.edu/~brianpm/download/charney_report.pdf</ref> Jule Charney of the [[Massachusetts Institute of Technology]] in Cambridge declared: "If carbon dioxide continues to increase, we find no reason to doubt that climate changes will result and no reason to believe that these changes will be negligible.” Climate change was still used to refer to the other changes thought to be caused by increased CO2.
====Orbital variations====
==Further reading==
* [http://www.worldwatch.org/files/pdf/CCRG.pdf Climate Change Reference Guide]
* [http://www.who.int/heli/risks/climate/climatedirectory/en/index1.html Climate change: directory of references/resources]
* [http://www.ncdc.noaa.gov/monitoring-references/faq/global-warming.php National Climatic Data Center]
* [http://www.realclimate.org/ Real Climate]
* [http://www.ipcc.ch/report/ar5/wg1/ IPCC Fifth Assessment Report]
* [http://www.thegwpf.com/ The Global Warming Policy Forum]
[[File:Aridity ice age vs early holocene vs modern.jpg|thumb|right|''Top:'' [[Arid]] ice age climate{{Clear}}''Middle:'' [[Atlantic period|Atlantic Period]], warm and wet{{Clear}}''Bottom:'' Potential vegetation in climate now if not for human effects like agriculture.<ref name=ORNL_paleoclimate>{{cite journal | editor1-last=Adams | editor1-first=J.M. | editor2-last=Faure | editor2-first=H. | year=1997 | url=http://www.esd.ornl.gov/projects/qen/nerc.html | title=Review and Atlas of Palaeovegetation: Preliminary land ecosystem maps of the world since the Last Glacial Maximum | publisher=Oak Ridge National Laboratory | publication-place=Tennessee | deadurl=yes | archiveurl=https://web.archive.org/web/20080116122058/http://www.esd.ornl.gov/projects/qen/nerc.html | archivedate=16 January 2008 | df=dmy-all }} QEN members.</ref>]]
==See also==
==See also==
*[[anthropogenic global warming]]
* [[Blue carbon]]
==Links==
* [[Bond event]]
*[http://goliath.ecnext.com/coms2/summary_0199-2875898_ITM Global warming: both sides]
*[http://www.no-carbon-tax.org Australian Anti-Climate Hypocrisy Site]
[[Category:Environmentalism]]
{{Climategate scandal}}
==References==
==References==
<references/>
[[Category:Climate Change]]
[[Category:Climate change| ]]
[[Category:Liberal Falsehoods]]
[[Category:Future problems]]