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Line 1: − + + + − '''Global warming''' is an increase in average air temperature in the [[Earth]]'s atmosphere. + − As far back as temperature records can be reconstructed, periods of global warming and global cooling have alternated; see [[ice age]]s and [[interglacial warming]]. − In the modern period of global warming, a slight increase of {{temperature|0.8|1.4}} has been measured at weather stations throughout the world, since around 1850, when organized records began to be kept. Since this happens to correlate with increases in [[carbon dioxide]], many have speculated about their possible relationship. Despite this, there is no completely proven model explaining the rise in global temperatures.+ − ==Controversy==+ − {{main|Global Warming Controversy}} − Since 1989, advocates have clashed on the issue of whether human beings are more responsible than nature for modern periods of global warming; see "[[greenhouse warming]]" and [[global warming theory]].<ref>Some people predicted "global warming," which has come to mean extreme [[greenhouse warming]] of the atmosphere leading to catastrophic environmental consequences. [http://www.junkscience.com/news/robinson.htm]</ref>+ + + + − Most non-scientific support for the global warming theory rests on popular accounts such as Al Gore's ''[[An Inconvenient Truth]]'' or on reports issued by the UN's [[IPCC]]. However, Keston Green of Monash University and Scott Armstrong of the Wharton School wrote that:+ − *Because the forecasting processes examined in Chapter 8 overlook scientific evidence on forecasting, the [[IPCC]] forecasts of climate change are not scientific. <ref>http://www.forecastingprinciples.com/Public_Policy/WarmAudit31.pdf</ref>+ − Former vice-president [[Al Gore]] calls it a [[moral issue]], while climate scientist [[Richard Lindzen]] says, "It is probably the most immoral thing you could do to restrain energy so that the billions in the earth who don’t have access to electricity won't conveniently get it." <ref>http://www.americaabroadmedia.org/media/On line extra materials/Climate change - lindzen interview.doc</ref>+ − However, it is to be noted that many proponents of the theory propose energy conservation only until 'green' energy generation becomes predominant.{{Fact}} − In the general, the term ''global warming'' can be used for any upward trend in the [[global mean temperature]], but it is mostly used to refer to the 1° F warming since 1850. − The two sides are divided on whether this warming is a natural recovery from the [[Little Ice Age]] or a man-made environmental phenomenon. There are also debates regarding the potential positive or negative effects of a warming. − Republicans and Democrats in the U.S. are evenly split on the issue. ''Boston Globe'' writer [[Ellen Goodman]] wrote:+ − * Only 23 percent of college-educated Republicans believe the warming is due to humans, while 75 percent of college-educated Democrats believe it. <ref> [http://www.boston.com/news/globe/editorial_opinion/oped/articles/2007/02/09/no_change_in_political_climate/] </ref>+ − Controversy and scientific inaccuracies may have contributed to addressing 'Climate Change' in place of using Global Warming. As the northern pole region melts, the southern pole region ice is growing <ref>[http://www.csmonitor.com/2008/0110/p14s01-sten.html], http://www.csmonitor.com/2008/0110/p14s01-sten.html, As arctic ice melts, South Pole ice grows, january 10, 2008</ref>+ + + + − + − Average [[Earth]] surface air temperature has risen about 1° F since 1970. + − − Nonetheless, controversy has persisted over the influence of urban warming on reported large-scale surface-air temperature trends. <ref name="col" /> − According to temperature reconstruction made within an [[Old Earth]] paradigm, there have been many cycles of naturally-caused global warming and cooling over many millions of years (see [[climate cycles]]). Some scientists, including [[Richard Lindzen]] of [[MIT]], [[Sallie Baliunas]] of [[Harvard]] and [[Fred Singer]] (independent), say that the recent warming could be part of another natural cycle or random fluctuations in the atmosphere. However, many scientists also think that human activities were most likely the cause of the the planet's recent warming.+ + + + + + + + + + + + + − + + + + + + − + + + + + + + + + − :Indeed, a recent Gallup poll of climate scientists in the American Meteorological Society and in the American Geophysical Union shows that a vast majority doubts that there has been any identifiable man-caused warming to date (49 percent asserted no, 33 percent did not know, 18 percent thought some has occurred; however, among those actively involved in research and publishing frequently in peer-reviewed research journals, none believes that any man-caused global warming has been identified so far). <ref name="cato">http://www.cato.org/pubs/regulation/regv15n2/reg15n2g.html</ref>+ − Oddly enough, even though 82% of US climate scientists refused to support the global warming theory{{fact}} then, [[liberal]] activists were already claiming a scientific consensus for [[anthropogenic global warming]]. (It's hard to understand how 18 percent credence in ''any'' global warming translates into "consensus" support for ''human-caused'' global warming.)+ + + + − The campaign to convince the public (and their elected representatives) that the "science is settled" began in 1988 or 1989.+ − + + − By the 2008 elections both candidates for the Presidency of the United States were proposing plans to mitigate climate change.+ + + + + − ==Natural Variability of the Climate System==+ − Evolutionary scientists who believe in global warming think that the Earth has experienced numerous [[Ice Age|ice age]]s over two million years, during which global temperatures dropped approximately {{temperature|6|11}} and then returned to normal. The frigid temperatures allowed ice sheets to expand southward, covering much of [[Asia]], [[Europe]], and [[North America]]. The cooling associated with ice ages is gradual, while the terminations are relatively rapid. However, even the rapid terminations of ice ages take centuries to millennia.+ − + + + − Since the [[Viking spacecraft]] reached [[Mars]] in the 1970s until recent readings were taken, the average temperature on Mars has risen {{temperature|0.6|1.1}} just as the average temperature on the earth has risen. Since human industrialization is clearly not to blame for the change on Mars, other causes are being considered. One possibility is that dust storms are changing the albedo of the planet, allowing it to warm, while another possibility is that solar variations from the sun are causing the warming.<ref>http://www.space.com/scienceastronomy/070404_gw_mars.html</ref><ref>http://www.heartland.org/Article.cfm?artId=17977</ref>+ + − Recently, it has also been found that similar to the Earth and Mars, [[Neptune]] is also undergoing global warming. Measurements taken at the Lowell observatory in [[Arizona]] have shown an increase in Neptune's brightness and temperature since 1980 following the same pattern seen on Earth and Mars. The researchers who discovered this warming suggest there may be a correlation between the warming and solar variations.<ref>http://www.agu.org/pubs/crossref/2007.../2006GL028764.shtml</ref>+ + + + + − + + + + + − On the other hand [[Uranus]] has had no net change in temperature since 1977. A rapid increase in temperature reversed itself. The reasons for this are not understood.<ref>http://www.boulder.swri.edu/~layoung/eprint/ur149/Young2001Uranus.pdf</ref>+ + − Global temperatures change on other plants even when there is no life, something which strongly supports the idea that humans are not necessarily the cause of earth's global warming. Moreover, the temperature on Uranus has fluctuated back and forth. There is no reason that fluctuations cannot occur on earth, too.+ + + − + − 'Global Warming Now World's Most Boring Topic’ <ref>http://newsbusters.org/node/14167</ref>+ − The need to fight "global warming" has become part of the dogma of the liberal conscience. <ref name="cato" />+ − Clearly, "global warming" is a tempting issue for many very important groups to exploit. + − − + − Assessments of climate science by the [[United Nations]] (see [[IPCC]] - ''Intergovernmental Panel on Climate Change'')+ − have claimed that scientists are 90% sure that over 50% of the observed global warming in recent decades is human-caused, and that continued global warming should be expected over at least the next century. ''Science'' published a literature search by Naomi Oreskes concluding that "scientific consensus" supports the IPCC reports. <ref>http://www.sciencemag.org/cgi/content/full/306/5702/1686</ref> − Several prominent scientists have pointed out the [[politicized science]] of the UN's assessment methods. The scientific reports are submitted to a panel of representatives appointed by each country in the IPCC. Several scientists whose research demonstrates that climate change is taking place have complained about their work being misrepresented by the U.N.+ − *In addition, a number of the participants have testified to the pressures placed on them to emphasize results supportive of the current scenario and to suppress other results. That pressure has frequently been effective, and a survey of participants reveals substantial disagreement with the final report. <ref name="cato" />+ + + + + + − Richard Lindzen wrote:+ − :Perhaps more important are the pressures being brought to bear on scientists to get the "right" results. Such pressures are inevitable, given how far out on a limb much of the scientific community has gone. The situation is compounded by the fact that some of the strongest proponents of "global warming" in Congress are also among the major supporters of science (Sen. Gore is notable among those). <ref name="cato" />+ − Christopher Monckton wrote an article titled Climate Sensitivity Reconsidered. + − :States that Intergovernmental Panel on Climate Change studies are flawed. The present analysis suggests the models failure to predict other climatic phenomena arises from defects in its evaluation of radioactive forcing, no-feedbacks climate sensitivity parameter and feedback multiplier. In conclusion, that there may be no "Climate Crisis" and for governments to reduce emissions may be pointless or even harmful. <ref>http://www.aps.org/units/fps/newsletters/200807/monckton.cfm , Climate Sensativity Reconsidered, July 2008</ref> This was published on a forum of the American Physical Society with the following disclaimer "The article has not undergone any scientific peer review" and "the APS disagrees with the articles conclusions" In fact, the APS disagrees with the article without ever reviewing it. − After the successful completion of a lawsuit against his movie '[[The Great Global Warming Swindle]]', filmmaker Martin Durkin statements read <ref>[http://www.cnsnews.com/public/content/article.aspx?RsrcID=32796 UK Broadcaster Scolded for Film on Global Warming[ CNSNEWS July 22, 2008</ref> + − *“Everywhere you are told that man-made [[climate change]] is proved beyond doubt,” “But you are being told lies.”+ − *“This is a story of how a theory about climate turned into a political [[ideology]] ... it is the story of the distortion of a whole area of [[science]].”+ − *“as the frenzy over man-made [[global warming]] grows shriller, many senior scientists say the actual scientific basis for the [[theory]] is crumbling.”+ + + − + − *[[Al Gore]] claims that Himalayan glaciers are shrinking and global warming is to blame. Yet the September 2006 issue of the American Meteorological Society's Journal of Climate reported, "Glaciers are growing in the Himalayan Mountains, confounding global warming alarmists who recently claimed the glaciers were shrinking and that global warming was to blame." <ref name="sun">http://www.suntimes.com/news/otherviews/450392,CST-EDT-REF30b.article</ref>+ − <!-- This is wrong. Read the paper and you will see that it never claimed anything which contradicted global warming theory; indeed, the anomalous growing of these particular glaciers was expected. --> − *Gore claims the snow cap atop Africa's Mt. Kilimanjaro is shrinking and that global warming is to blame. Yet according to the November 23, 2003, issue of Nature magazine, "Although it's tempting to blame the ice loss on global warming, researchers think that deforestation of the mountain's foothills is the more likely culprit. Without the forests' humidity, previously moisture-laden winds blew dry. No longer replenished with water, the ice is evaporating in the strong equatorial sunshine." <ref name="sun" />\+ + + − *Al Gore is therefore an example of how in such an important debate [[deceitful|deceit]] tactics have been used by liberals to make a position seem more solid than it is.+ − + − + − According to his website,<ref>[http://www.johnmccain.com/Informing/News/PressReleases/BA6709C3-B27D-4EF9-81E6-2BA9D6F8AB20.htm John McCain on Global warming.]</ref> [[Republican]] Presidential candidate [[John McCain]] will take a more "aggressive approach" to global warming which he has declared as "undeniable and urgent." He was supported in this in June 2008 by Republican governor [[Arnold Schwarzenegger]] who said McCain was the "real deal on the environment".<ref>[http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2008/06/30/MNDB11H66C.DTL&type=politics Schwarzenegger backs McCain on climate Change]</ref>.+ − + − [[Barack Obama]] believes "that global warming is not just the greatest [[environmental]] [[challenge]] facing our planet—it is one of our greatest challenges of any kind." During his first 100 days in office, he would enact a giant and far-reaching [[tax]] "an economy-wide cap on U.S. carbon emissions that will reduce U.S. emissions by the amount scientists agree is necessary (80%) or '''$45 Trillion dollars'''". <ref>[http://business.timesonline.co.uk/tol/business/industry_sectors/natural_resources/article4079036.ece World needs $45 trillion energy revolution] Timesonline.uk, June 6, 2008</ref> He comments "Putting a price on carbon is the most important step we can to take to reduce emissions."<ref>[http://presidentialprofiles2008.org/Obama/tab1.html Leguea of Conservation Voters] presidentialprofiles2008.org</ref>+ − + − A [[British]] court has determined that Al Gore's movie "An Inconvenient Truth" contains at least eleven material falsehoods <ref>[http://newsbusters.org/blogs/noel-sheppard/2007/10/09/court-identifies-eleven-inaccuracies-al-gore-s-inconvenient-truth], http://newsbusters.org/blogs/noel-sheppard/2007/10/09/court-identifies-eleven-inaccuracies-al-gore-s-inconvenient-truth, October 9, 2007</ref>+ + + + + − Those inaccuracies include the following+ − * The film claims that melting snows on Mount Kilimanjaro evidence global warming. The Government's expert was forced to concede that this is not correct.+ − * The film suggests that evidence from ice cores proves that rising CO2 causes temperature increases over 650,000 years. The Court found the film misleading: over that period the rises in CO2 lagged behind the temperature rises by 800-2000 years. − * The film uses emotive images of [[Hurricane Katrina]] and suggests that this has been caused by global warming. The Government's expert had to accept that it was "not possible" to attribute one-off events to global warming. − * The film shows the drying up of Lake Chad and claims that this was caused by global warming. The Government's expert had to accept that this was not the case. − * The film claims that a study showed that polar bears had drowned due to disappearing arctic ice. It turned out that Mr Gore had misread the study: in fact four polar bears drowned and this was because of a particularly violent storm. − * The film threatens that global warming could stop the Gulf Stream throwing Europe into an ice age: the Claimant's evidence was that this was a [[scientific]] impossibility. − * The film blames global warming for species losses including coral reef bleaching. The Government could not find any evidence to support this claim. − * The film suggests that the [[Greenland]] ice covering could melt causing sea levels to rise dangerously. The evidence is that Greenland will not melt for millennia. − * The film suggests that the Antarctic [[ice]] covering is melting, the evidence was that it is in fact increasing. − * The film suggests that sea levels could rise by 7m causing the displacement of millions of people. The evidence is that sea levels are expected to rise by about 40cm over the next hundred years and that there is no such threat of massive migration. − * The film claims that rising sea levels has caused the evacuation of certain Pacific islands to [[New Zealand]]. The Government are unable to substantiate this and the Court observed that this appears to be a false claim. − + − + + − + − | valign="top" width="35%"|+ − * [[Roger Revelle]]+ − * [[Achim Steiner]]+ − * [[Fred Singer]] − * [[Richard Lindzen]] − * [[Sallie Baliunas]] − * [[Lonnie Thompson]] − | valign="top" width="33%"| − * [[James E. Hansen]] − * [[Michael Mann]] − * [[Charles Keeling]] − * [[Edwin A. Hernández-Delgado]] − |} − ==See Also==+ − *[[Anthropogenic global warming theory]] − *[[Global Warming Controversy]] − *[[Politics of global warming]] − *[[Liberal_hysteria#Global_Warming_Derangement_Syndrome|Global Warming Derangement Syndrome]] − *[[Socialist Environmental Disasters]] − *[[An Inconvenient Truth]] − *[[Previous Breaking News/Global Warming|Articles about '''Global Warming''' from previous "Breaking News"]] − *[[More News/Global Warming|Articles about '''Global Warming''' from "More News"]] − ==External Links==+ − <small> − *[http://www.aim.org/wls/category/global-warming/ What Liberals Say - Category: Global Warming], [[Accuracy In Media]] − *[http://global-warming.accuweather.com/2007/12/attempting_to_stop_global_warm_1.html Attempting to Stop Global Warming is Futile and a Mistake, says letter to the UN] − *[http://www.nationalpost.com/news/story.html?id=164004 Signatories of an open letter on the UN climate-conference] − *[http://schwinger.harvard.edu/~motl/global-temperature-not-exist.pdf Does a global temperature exist?], ''Journal of Non-Equilibrium Thermodynamics'', June 2007. − *[http://environment.guardian.co.uk/climatechange/story/0,,2032821,00.html The appliance of science] by Mike Hulme. − *[http://www.climatecrisis.net/ ''An Inconvenient Truth''], Film by [[Al Gore]] − *[http://video.google.com/videoplay?docid=2332531355859226455&q=great+global+warming+swindle ''The Great Global Warming Swindle'' - Documentary Film] − *[http://www.physics.harvard.edu/~motl/iris-effect.pdf Climate Sensitivity and Observed Negative Feedbacks], lecture by Richard Lindzen and Roberto Rondanelli. − *[http://www.physics.harvard.edu/~motl/lindzen-nature-of-arguments.pdf Nature of Arguments for Anthropogenic Global Warming], by Richard Lindzen − *[http://www.independent.org/store/book_detail.asp?bookID=42 ''Hot Talk, Cold Science: Global Warmings's Unfinished Debate'', by S. Fred Singer] − *[http://www.cato.org/pubs/regulation/regv15n2/reg15n2g.html Global Warming: The Origin and Nature of the Alleged Scientific Consensus] - [[Richard S. Lindzen]], Alfred P. Sloan Professor of Meteorology at the [[Massachusetts Institute of Technology]] − *[http://www.independent.org/publications/tir/article.asp?issueID=47&articleID=604 "Should We Have Acted Thirty Years Ago to Prevent Climate Change?", by Randall G. Holcombe]. − *[http://www.independent.org/publications/tir/article.asp?issueID=25&articleID=296 "After Kyoto: A Global Scramble for Advantage," by Bruce Yandle]. − *[http://www.ncpa.org/sub/dpd/index.php?Article_ID=2319 The physical evidence of earth's unstoppable 1,500-year climate cycle] − *[http://www.independent.org/publications/article.asp?id=1714 "Is There a Basis for Global Warming Alarm?", by Richard Lindzen] − *[http://www.independent.org/publications/policy_reports/detail.asp?type=full&id=5 "New Perspectives in Climate Change: What the EPA Isn’t Telling Us"] − *[http://www.heartland.org/Article.cfm?artId=17181 Survey Shows Climatologists Are Split on Global Warming] − *[http://www.magma.ca/~hurleyp/FightingTheHoax.htm Fighting the Hoax] − *[http://www.climateaudit.org Climate Audit], Steve McIntyre's blog − *[http://www.realclimate.org Real Climate], blog by a group of climatologists including Michael Mann</small> − ===Critique of the Hockey Stick Reconstruction===+ − <small> − *[http://www.climateaudit.org/pdf/mcintyre.mckitrick.2003.pdf Corrections To The Mann et. al. (1998) Proxy Data Base And Northern Hemispheric Average Temperature Series] by Stephen McIntyre and Ross McKitrick, ''Energy & Enviornment'' volume 14, 2003. − *[http://blogs.nature.com/climatefeedback/2007/05/the_decay_of_the_hockey_stick.html The Decay of the Hockey Stick by Von Storch] published on the journal ''Nature'''s blog, May 3, 2007. − *[http://www.technologyreview.com/Energy/13830/ A Global Warming Bombshell] by Richard A. Muller, ''Technology Review'' , Oct. 2004; calls into question famous graph by Michael Mann. − *[http://www.sciencemag.org/cgi/content/abstract/306/5696/679 Reconstructing Past Climate from Noisy Data] by Hans von Storch, Eduardo Zorita, Julie M. Jones, Yegor Dimitriev, Fidel González-Rouco, Simon F. B. Tett, ''Science'' magazine, 22 October 2004. − − + − + + − {{liberalism}}+ − + − + − + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +
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[[Image:RobinsonWhatWarmsTheEarth.gif|right|frame]]
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{{dablink|This article is about the current period of increasing global temperature. For other periods of warming in Earth's history, see [[Paleoclimatology]] and [[Geologic temperature record]].}}
<!-- Please keep the intro as a simple declarative sentence. Details should be placed later. -->
{{Double image stack|right|Instrumental Temperature Record.png|Global Warming Map.jpg|280|Global mean surface temperature anomaly relative to 1961–1990|Mean surface temperature anomalies during the period 1995 to 2004 with respect to the average temperatures from 1940 to 1980}}
'''Global warming''' is the increase in the [[Instrumental temperature record|average measured temperature]] of the [[Earth]]'s near-surface air and [[ocean]]s since the mid-20th century, and its projected continuation.
Global surface temperature increased 0.74 [[Plus-minus sign|±]] 0.18 °[[Celsius|C]] (1.33 ± 0.32 °[[Fahrenheit|F]]) during the 100 years ending in 2005.<ref name="grida7a">{{cite web | url= http://ipcc-wg1.ucar.edu/wg1/Report/AR4WG1_Print_SPM.pdf | format=[[Portable Document Format|PDF]] | title=Summary for Policymakers | work=Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change | accessdate=2007-02-02 | date=[[2007-02-05]] | publisher=[[Intergovernmental Panel on Climate Change]]|quote=The updated hundred-year linear trend (1906 to 2005) of 0.74 °C [0.56 °C to 0.92 °C] is therefore larger than the corresponding trend for 1901 to 2000 given in the TAR of 0.6 °C [0.4 °C to 0.8 °C].}}</ref><ref>Global surface temperature is defined in the [[AR4|IPCC Fourth Assessment Report]] as the average of near-surface air temperature over land and sea surface temperature.</ref> The [[Intergovernmental Panel on Climate Change]] (IPCC) concludes "most of the observed increase in globally averaged temperatures since the mid-twentieth century is very likely [[Attribution of recent climate change|due to]] the observed increase in [[anthropogenic]] [[greenhouse gas]] concentrations"<ref name="grida7">{{cite web | url= http://ipcc-wg1.ucar.edu/wg1/Report/AR4WG1_Print_SPM.pdf | format=[[Portable Document Format|PDF]] | title=Summary for Policymakers | work=Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change | accessdate=2007-02-02 | date=[[2007-02-05]] | publisher=[[Intergovernmental Panel on Climate Change]]|quote=}}</ref><ref>Global surface temperature is defined in the [[AR4|IPCC Fourth Assessment Report]] as the average of near-surface air temperature over land and sea surface temperature.</ref> via an enhanced [[greenhouse effect]]. Natural phenomena such as [[solar variation]] combined with [[volcano]]es probably had a small warming effect from pre-industrial times to 1950 and a small cooling effect from 1950 onward.<ref>
{{cite web | url= http://ipcc-wg1.ucar.edu/wg1/Report/AR4WG1_Print_Ch09.pdf | format=[[Portable Document Format|PDF]] | title=Understanding and Attributing Climate Change | work=Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change | accessdate=2007-05-20 | date=[[2007-05-07]] | publisher=[[Intergovernmental Panel on Climate Change]] | last=Hegerl | first=Gabriele C. | coauthors=''et al.'' | pages=690 | quote=Recent estimates (Figure 9.9) indicate a relatively small combined effect of natural forcings on the global mean temperature evolution of the seconds half of the twentieth century, with a small net cooling from the combined effects of solar and volcanic forcings}}</ref><ref>{{cite journal | last=Ammann | first = Caspar | coauthors =''et al.'' | date=[[2007-04-06]] | title=Solar influence on climate during the past millennium: Results from ransient simulations with the NCAR Climate Simulation Model | journal=Proceedings of the National Academy of Sciences of the United States of America | volume=104 | issue=10 | pages=3713–3718 | url=http://www.pnas.org/cgi/reprint/104/10/3713.pdf | format=[[Portable Document Format|PDF]] | quote=However, because of a lack of interactive [[ozone]], the model cannot fully simulate features discussed in (44)." "While the NH temperatures of the high-scaled experiment are often colder than the lower bound from proxy data, the modeled decadal-scale NH surface temperature for the medium-scaled case falls within the uncertainty range of the available temperature reconstructions. The medium-scaled simulation also broadly reproduces the main features seen in the proxy records." "Without anthropogenic forcing, the 20th century warming is small. The simulations with only natural forcing components included yield an early 20th century peak warming of ≈0.2 °C (≈1950 AD), which is reduced to about half by the end of the century because of increased volcanism. | doi=10.1073/pnas.0605064103 | pmid=17360418}}</ref> These basic conclusions have been endorsed by at least 30 [[Scientific opinion on climate change|scientific societies and academies of science]],<ref>The 2001 joint statement was signed by the scientific academies of [[Australia]], [[Belgium]], [[Brazil]], [[Canada]], [[the Caribbean]], [[China]], [[France]], [[Germany]], [[India]], [[Indonesia]], [[Ireland]], [[Italy]], [[Malaysia]], [[New Zealand]], [[Sweden]], and the [[UK]]. The 2005 statement added [[Japan]], [[Russia]], and the [[U.S.]] The 2007 statement added [[Mexico]] and [[South Africa]]. Professional societies include American Meteorological Society, American Geophysical Union, American Institute of Physics, American Astronomical Society, American Association for the Advancement of Science, Stratigraphy Commission of the Geological Society of London, Geological Society of America, American Chemical Society, and Engineers Australia.</ref> including all of the national academies of science of the [[G8|major industrialized countries]].<ref>{{cite web | title = The Science Of Climate Change | publisher = [[Royal Society]] | url = http://royalsociety.org/displaypagedoc.asp?id=13619 | accessdate = 2008-01-04 |month=May | year=2001}}</ref><ref>{{cite web | title = Joint science academies' statement: Global response to climate change | publisher = [[Royal Society]] | url = http://royalsociety.org/displaypagedoc.asp?id=20742 | accessdate = 2008-01-04 |month=June | year=2005}}</ref><ref>{{cite web | title = Joint science academies' statement on growth and responsibility: sustainability, energy efficiency and climate protection | publisher = [http://www.pik-potsdam.de/index_html Potsdam Institute for Climate Impact Research] | url = http://www.pik-potsdam.de/aktuelles/archiv/aktuelle/dateien/G8_Academies%20Declaration.pdf | accessdate = 2008-01-04 |month=May | year=2007|format=PDF}}</ref> While [[List of scientists opposing the mainstream scientific assessment of global warming|individual scientists]] have voiced disagreement with these findings,<ref>
{{cite web | title = Don't fight, adapt | publisher = [[National Post]] | url = http://www.nationalpost.com/news/story.html?id=164002 | accessdate = 2007-11-18 |month=December | year=2007}}
</ref> the overwhelming majority of scientists working on climate change agree with the IPCC's main conclusions.<ref>{{cite web | title = A guide to facts and fictions about climate change | publisher = [[Royal Society]] | url = http://www.royalsoc.ac.uk/downloaddoc.asp?id=1630 | accessdate = 2007-11-18 | month = March | year = 2005 | quote = "However, the overwhelming majority of scientists who work on climate change agree on the main points"}}</ref><ref>{{cite web | title = Beyond the Ivory Tower: The Scientific Consensus on Climate Change | publisher = [[Science Magazine]] | url = http://www.sciencemag.org/cgi/content/full/306/5702/1686 | accessdate = 2008-01-04 |month=December | year=2004}}</ref>
[[Climate model]] projections summarized by the IPCC indicate that average global surface temperature will likely rise a further {{nowrap|1.1 to 6.4 °C}} {{nowrap|(2.0 to 11.5 °F)}} during the twenty-first century.<ref name="grida7" /> This range of values results from the use of differing [[Special Report on Emissions Scenarios|scenarios]] of future [[greenhouse gas]] emissions as well as models with differing [[climate sensitivity]]. Although most studies focus on the period up to 2100, warming and sea level rise are expected to continue for more than a thousand years even if greenhouse gas levels are stabilized. The delay in reaching equilibrium is a result of the large heat capacity of the oceans.<ref name="grida7" />
Increasing global temperature is expected to cause [[sea level rise|sea levels to rise]], an increase in the intensity of [[extreme weather]] events, and significant changes to the amount and pattern of [[precipitation (meteorology)|precipitation]], likely leading to an expanse of tropical areas and increased pace of [[desertification]]. Other expected [[effects of global warming]] include changes in [[agricultural yield]]s, modifications of trade routes, [[retreat of glaciers since 1850|glacier retreat]], mass species [[extinction risk from climate change|extinctions]] and increases in the ranges of [[Vector (biology)|disease vectors]].
Remaining scientific [[uncertainty|uncertainties]] include the amount of warming expected in the future, and how warming and related changes will vary from region to region around the globe. [[List of Kyoto Protocol signatories|Most national governments]] have signed and ratified the [[Kyoto Protocol]] aimed at reducing greenhouse gas emissions, but there is ongoing [[Politics of global warming|political]] and [[global warming controversy|public debate]] worldwide regarding what, if any, action should be taken to [[Mitigation of global warming|reduce or reverse]] future warming or to [[Adaptation to global warming|adapt]] to its expected consequences.
==Greenhouse effect==
{{main|Greenhouse gas|Greenhouse effect}}
The detailed [[attribution of recent climate change|causes of the recent warming]] remain an active field of research, but the [[scientific opinion on climate change|scientific consensus]]<ref>
{{cite web |title=Joint science academies' statement: The science of climate change | url=http://www.royalsoc.ac.uk/displaypagedoc.asp?id=13619 | format=[[Active Server Pages|ASP]] | quote=The work of the Intergovernmental Panel on Climate Change (IPCC) represents the consensus of the international scientific community on climate change science| publisher = [[Royal Society]] | date =[[2001-05-17]] |accessdate=2007-04-01}}
</ref><ref>{{cite journal | date=[[2007-10-18]] | title=Rising to the climate challenge | journal=[[Nature (journal)|Nature]] | volume=449 | issue=7164 | url=http://www.nature.com/nature/journal/v449/n7164/full/449755a.html | accessdate=2007-11-06 | pages=755 | doi=10.1038/449755a}}</ref>
is that the increase in atmospheric greenhouse gases due to human activity caused most of the warming observed since the start of the [[Industrial Revolution|industrial era]]. This attribution is clearest for the most recent 50 years, for which the most detailed data are available.
==The Modern Warm Period==
The greenhouse effect was theorized by [[Joseph Fourier]] in 1824<ref>Cowie, J. (2007). ''Climate Change: Biological and Human Aspects''. Cambridge University Press. ISBN 978-0521696197. p. 3</ref><ref>{{cite web | title=The Discovery of Global Warming | url=http://www.aip.org/history/climate/co2.htm | format=[[HTML]] | accessdate=2008-10-14 | year=2008 | publisher=[[AIP]]}}</ref><ref>{{cite journal | first=Jean-Baptiste Joseph | last=Fourier | year=1827 | title=M´emoire sur les Temp´eratures du Globe Terrestre et des Espaces Plan´etaires | journal=M´emoires d l’Acad´emie Royale des Sciences de l’Institute de France | volume=VII | url=http://geosci.uchicago.edu/~rtp1/papers/Fourier1827Trans.pdf | accessdate=2008-10-16 | pages=570-604 }} Translated by R. T. Pierrehumbert</ref> and was first investigated quantitatively by [[Svante Arrhenius]] in 1896. It is the process by which [[Absorption (electromagnetic radiation)|absorption]] and emission of [[infrared]] radiation by [[Atmosphere|atmospheric gases]] warm a [[planet]]'s lower atmosphere and surface.
[[Image:Mauna Loa Carbon Dioxide-en.svg|thumb|280px|right|Recent increases in atmospheric carbon dioxide (CO<sub>2</sub>). The monthly CO<sub>2</sub> measurements display small seasonal oscillations in an overall yearly uptrend; each year's maximum is reached during the [[Northern Hemisphere]]'s late spring, and declines during the Northern Hemisphere growing season as plants remove some CO<sub>2</sub> from the atmosphere.]]
<ref>Hansen's group at the Goddard Institute wrote, "Global warming is now 0.6 °C [1.0 °F] in the past three decades and 0.8 °C [1.4 °F] in the past century." http://data.giss.nasa.gov/gistemp/2005/</ref> How much of this is due to contamination of the temperature record from the [[urban heat island]] effect is hard to assess. Efforts are currently underway to detect and remove this bias. Spurious warming trends that might be considered as global warming can occur almost anywhere. <ref name="col">http://climatesci.colorado.edu/2006/01/29/do-urban-areas-have-larger-long-term-temperature-trends-than-other-locations/feed/</ref>
Existence of the greenhouse effect as such is not disputed. Naturally occurring greenhouse gases have a mean warming effect of about 33 °C (59 °F), without which Earth would be uninhabitable.<ref name="IPCC_WG1_AR4_Ch1">{{cite web | title=IPCC WG1 AR4 Report — Chapter 1: Historical Overview of Climate Change Science | url=http://ipcc-wg1.ucar.edu/wg1/Report/AR4WG1_Print_Ch01.pdf | format=[[Portable Document Format|PDF]] | accessdate=2007-10-07 | year=2007 | publisher=[[IPCC]]| quote=To emit 240 W m–2, a surface would have to have a temperature
of around –19 °C. This is much colder than the conditions
that actually exist at the Earth’s surface (the global mean surface
temperature is about 14 °C). Instead, the necessary –19 °C is found
at an altitude about 5 km above the surface.
| pages = p97 (pdf page 5 of 36)
| work=IPCC WG1 AR4 Report
}}</ref><ref>Note that the Greenhouse Effect produces a temperature increase of about
33 °C (59 °F) with respect to black body predictions and not a surface temperature of 33 °C (91 °F) which is {{convert|32|°F|°C|abbr=on}} higher. The average surface temperature is about 14 °C (57 °F).
Also note that both the
Celsius and Fahrenheit temperatures are expressed to 2 significant figures even though the conversion formula produces 3.
</ref> On Earth, the major greenhouse gases are [[water vapor]], which causes about 36–70 percent of the greenhouse effect ([[Cloud forcing|not including clouds]]); [[carbon dioxide]] (CO<sub>2</sub>), which causes 9–26 percent; [[methane]] (CH<sub>4</sub>), which causes 4–9 percent; and [[ozone]], which causes 3–7 percent.<ref>{{cite journal| url=http://www.atmo.arizona.edu/students/courselinks/spring04/atmo451b/pdf/RadiationBudget.pdf| title=Earth’s Annual Global Mean Energy Budget| first=J. T.| last=Kiehl| coauthors= Kevin E. Trenberth| format=PDF | journal=Bulletin of the American Meteorological Society| pages=197–208| volume=78| issue=2| month=February| year=1997| accessdate=2006-05-01| doi=10.1175/1520-0477(1997)078<0197:EAGMEB>2.0.CO;2}}</ref><ref>{{cite web| url=http://www.realclimate.org/index.php?p=142| year=6 Apr 2005| title=Water vapour: feedback or forcing?| publisher=[[RealClimate]]| accessdate=2006-05-01}}</ref>
The issue is how the strength of the greenhouse effect changes when human activity increases the atmospheric concentrations of some greenhouse gases.
==False Claims of "Consensus"==
Human activity since the industrial revolution has increased the concentration of various greenhouse gases, leading to increased [[radiative forcing]] from CO<sub>2</sub>, [[methane]], tropospheric [[ozone]], [[CFC]]s and [[nitrous oxide]]. [[Molecule]] for molecule, methane is a more effective greenhouse gas than [[carbon dioxide]], but its concentration is much smaller so that its total [[radiative forcing]] is only about a fourth of that from carbon dioxide. Some other naturally occurring gases contribute small fractions of the greenhouse effect; one of these, [[nitrous oxide]] (N<sub>2</sub>O), is increasing in concentration owing to human activity such as agriculture. The [[Greenhouse gas#Increase of greenhouse gases|atmospheric concentrations]] of CO<sub>2</sub> and CH<sub>4</sub> have increased by 31% and 149% respectively since the beginning of the [[industrial revolution]] in the mid-1700s. These levels are considerably higher than at any time during the last 650,000 years, the period for which reliable data has been extracted from [[ice core]]s.<ref>Neftel, A., E. Moor, H. Oeschger, and B. Stauffer. (1985). [http://www.nature.com/nature/journal/v315/n6014/abs/315045a0.html "Evidence from polar ice cores for the increase in atmospheric CO<sub>2</sub> in the past two centuries"]. ''Nature'' 315:45-47.</ref> From less direct geological evidence it is believed that CO<sub>2</sub> values this high were last attained 20 million years ago.<ref>
{{cite journal| first=Paul N.| last=Pearson| coauthors=Palmer, Martin R.| journal=[[Nature (journal)|Nature]]| title= Atmospheric carbon dioxide concentrations over the past 60 million years| date=[[2000-08-17]]| volume=406| issue=6797| pages=695–699| url=http://www.nature.com/nature/journal/v406/n6797/abs/406695a0.html| doi=10.1038/35021000| format= abstract}}
</ref>
[[Fossil fuel]] burning has produced approximately three-quarters of the increase in CO<sub>2</sub> from human activity over the past 20 years. Most of the rest is due to land-use change, in particular [[deforestation]].<ref>
{{cite web |url=http://www.grida.no/climate/ipcc_tar/wg1/006.htm |title=Summary for Policymakers |work=Climate Change 2001: The Scientific Basis. Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Change |accessdate=2007-01-18 |date=[[2001-01-20]] |publisher=[[Intergovernmental Panel on Climate Change]]}}
</ref>
[[Richard Lindzen]] wrote in 1992,
The present atmospheric concentration of CO<sub>2</sub> is about 385 parts per million ([[parts-per notation|ppm]]) by volume.<ref>
{{cite web | title = Trends in Atmospheric Carbon Dioxide – Mauna Loa | last = Tans | first = Pieter | url = http://www.esrl.noaa.gov/gmd/ccgg/trends/ | publisher = [[National Oceanic and Atmospheric Administration]] | accessdate = 2008-02-15}}
</ref> Human activities have caused the atmospheric concentrations of carbon dioxide and methane to be higher today than at any point during the last 650,000 years<ref name="CCinfo">{{cite web | title = Climate Change: Basic Information | publisher = [[United States Environmental Protection Agency]] | url = http://epa.gov/climatechange/basicinfo.html | accessdate = 2007-02-09 | date = [[2006-12-14]] | quote = In common usage, 'global warming' often refers to the warming that can occur as a result of increased emissions of greenhouse gases from human activities.}}</ref> .
Future CO<sub>2</sub> levels are expected to rise due to ongoing burning of fossil fuels and land-use change. The rate of rise will depend on uncertain economic, [[sociology|sociological]], [[technology|technological]], and natural developments, but may be ultimately limited by the availability of fossil fuels. The IPCC [[Special Report on Emissions Scenarios]] gives a wide range of future CO<sub>2</sub> scenarios, ranging from 541 to 970 ppm by the year 2100.<ref>
{{cite web |url=http://www.grida.no/climate/ipcc_tar/wg1/123.htm |last = Prentice |first = I. Colin |coauthors = ''et al.'' |title = 3.7.3.3 SRES scenarios and their implications for future CO2 concentration |work = Climate Change 2001: The Scientific Basis. Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Change |accessdate=2007-04-28 |date=[[2001-01-20]] |publisher=[[Intergovernmental Panel on Climate Change]]}}
</ref>
Fossil fuel reserves are sufficient to reach this level and continue emissions past 2100, if [[coal]], [[tar sands]] or [[methane clathrate]]s are extensively used.<ref>
{{cite web |url=http://www.grida.no/climate/ipcc/emission/104.htm |title=4.4.6. Resource Availability |work=IPCC Special Report on Emissions Scenarios |accessdate=2007-04-28 |publisher=[[Intergovernmental Panel on Climate Change]]}}
</ref>
Inasmuch as the greenhouse effect is due to human activity, it is a [[forcing]] effect that is separate from forcing due to climate variability.
===Stored methane releases===
====Thawing permafrost====
{{main|Arctic methane release}}
Recent research carried out in 2008 in the Siberian Arctic has shown millions of tons of the greenhouse gas methane being released, apparently through perforations in the [[Arctic Ocean]]'s seabed permafrost,<ref>Compare: [http://www.mbari.org/news/news_releases/2007/paull-plfs.html Methane bubbling through seafloor creates undersea hills], [[Monterey Bay Aquarium Research Institute]], 5 February 2007</ref> with concentrations in some regions reaching up to 100 times above normal.<ref>{{cite web|url=http://www.independent.co.uk/environment/climate-change/exclusive-the-methane-time-bomb-938932.html|title=Exclusive: The methane time bomb|last=Connor|first=Steve|date=September 23, 2008|publisher=[[The Independant]]|accessdate=2008-10-03}}</ref><ref>{{cite web|url=http://www.independent.co.uk/news/science/hundreds-of-methane-plumes-discovered-941456.html|title=Hundreds of methane 'plumes' discovered|last=Connor|first=Steve|date=September 25, 2008|publisher=[[The Independant]]|accessdate=2008-10-03}}</ref> Current methane release has previously been estimated at 0.5 [[megatonne]]s (Mt) per year.<ref>N. Shakhova, I. Semiletov, A. Salyuk, D. Kosmach, and N. Bel’cheva (2007), [http://www.cosis.net/abstracts/EGU2007/01071/EGU2007-J-01071.pdf?PHPSESSID=e Methane release on the Arctic East Siberian shelf], ''Geophysical Research Abstracts'', '''9''', 01071</ref> Shakhova et al (2008) estimate that not less than 1,400 [[gigatonne]]s (Gt) of Carbon is presently locked up as methane and methane hydrates under the Arctic submarine permafrost, and 5-10% of that area is subject to puncturing by open [[talik]]s. They conclude that "release of up to 50 [[gigatonne]]s (Gt) of predicted amount of hydrate storage [is] highly possible for abrupt release at any time". That would increase the methane content of the planet's atmosphere by a factor of twelve,<ref>N. Shakhova, I. Semiletov, A. Salyuk, D. Kosmach (2008), [http://www.cosis.net/abstracts/EGU2008/01526/EGU2008-A-01526.pdf Anomalies of methane in the atmosphere over the East Siberian shelf: Is there any sign of methane leakage from shallow shelf hydrates?], [[European Geophysical Union|EGU]] General Assembly 2008, ''Geophysical Research Abstracts'', '''10''', EGU2008-A-01526</ref><ref>Volker Mrasek, [http://www.spiegel.de/international/world/0,1518,547976,00.html A Storehouse of Greenhouse Gases Is Opening in Siberia], ''[[Der Spiegel|Spiegel International Online]]'', 17 April 2008</ref> equivalent in greenhouse effect to a doubling in the current level of CO<sub>2</sub>. Land-based [[permafrost]] in the Siberian Arctic was also recently observed to be releasing large amounts of methane, estimated at over 4 million tons.<ref>{{cite web|url=http://www.mywire.com/a/EnvironmentNewsService/Melting-Russian-Permafrost-Could-Accelerate/1800717?ba=a&bi=17&bp=13|title=Melting Russian Permafrost Could Accelerate Global Warming|date=2006-9-7|publisher=MyWire: Environmental News Service|accessdate=2008-10-18}}</ref>
====Clathrate gun hypothesis====
<!-- Irrelevant. Also lacking backing evidence. -->
{{main|Clathrate gun hypothesis}}
[[Methane clathrate]], also known as [[methane hydrate]], was once believed to only exist in space, as extremes of cold are required for its formation. Around 6.4 trillion tonnes (6.4 [[teratonne]]s/Tt) of methane<ref>Jaschek, C. & Jaschek, M. (1992) Astron. Astrophys., 95, p. 535</ref> is trapped in deposits of methane clathrate on the deep ocean floor<ref>Buffett, B.. "Global inventory of methane clathrate: sensitivity to changes in the deep ocean.". 185-199 Earth Planet. Sci. Lett. 227 (2004)</ref>. The [[Clathrate gun hypothesis]] states that warmer deep ocean temperatures can release the methane (CH<sub>4</sub>) from the deep ocean deposits of methane clathrate<ref name="CH4GX">James P. Kennett, Kevin G. Cannariato, Ingrid L. Hendy, and Richard J. Behl, (2003) ''Methane Hydrates in Quaternary Climate Change: The Clathrate Gun Hypothesis'', Washington, DC: [[American Geophysical Union]]. ISBN 0875902960</ref>. It is theorized that this was responsible for two extinction events in earth's history; the Permian-Triassic extinction event<ref name="CH4GX" /><ref>[http://www.bbc.co.uk/science/horizon/2002/dayearthdied.shtml The Day The Earth Nearly Died], ''BBC [[Horizon (TV series)|Horizon]]'', 2002</ref> and the [[Paleocene-Eocene Thermal Maximum]]. A concentration of 5-15% methane in the atmosphere, which would occur at and around the area of a CH<sub>4</sub> release, is explosive<ref>[http://pangea.stanford.edu/Oceans/GES205/methaneGeology.pdf Methane Geology] Stanford.edu</ref>; the products of such an explosion would be 2 parts H<sub>2</sub>O to one of CO<sub>2</sub>. CH<sub>4</sub> dissipates faster than carbon dioxide (CO<sub>2</sub>), but even after 20 years has a 62 times greater [[Global warming potential]] index.
==Solar variation==
{{main|Solar variation}}
[[Image:Solar-cycle-data.png|thumb|280px|right|Solar variation over the last thirty years.]]
Some other [[hypotheses]] departing from the consensus view have been suggested to explain most of the temperature increase. One such hypothesis proposes that warming may be the result of variations in solar activity.<ref name="Svensmark2007">{{cite journal | first=Henrik | last=Svensmark | authorlink=Henrik Svensmark | year = 2007 | month = February | title = Cosmoclimatology: a new theory emerges | journal = Astronomy & Geophysics | volume = 48 | issue = 1 | pages = 18–24 | doi = 10.1111/j.1468-4004.2007.48118.x | url=http://www.spacecenter.dk/research/sun-climate/Scientific%20work%20and%20publications/svensmark_2007cosmoClimatology.pdf}}</ref><ref>{{cite web | url=http://ipcc-wg1.ucar.edu/wg1/Report/AR4WG1_Print_Ch02.pdf | last=Forster | first=Piers | coauthors=''et al.'' | format=[[Portable Document Format|PDF]] | title=Changes in Atmospheric Constituents and in Radiative Forcing | work=Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change | pages=188-193 | accessdate=2007-09-17 | date=[[2007-02-05]] | publisher=[[Intergovernmental Panel on Climate Change]]}}</ref><ref>
{{cite journal |last=Bard |first=Edouard |coauthors=Frank, Martin |date=[[2006-06-09]] |title=Climate change and solar variability: What's new under the sun? |journal=Earth and Planetary Science Letters |volume=248 |issue=1-2 |pages=1–14 |url=http://www.ifm-geomar.de/fileadmin/personal/fb1/p-oz/mfrank/Bard_and_Frank_2006.pdf |accessdate= 2007-09-17 |doi=10.1016/j.epsl.2006.06.016) |doi_brokendate=2008-06-25|format=PDF}}</ref>
A paper by Peter Stott and other researchers suggests that climate models overestimate the relative effect of greenhouse gases compared to solar forcing; they also suggest that the cooling effects of volcanic dust and sulfate aerosols have been underestimated.<ref>{{Cite journal | first=Peter A. | last=Stott | coauthors=''et al.'' | title=Do Models Underestimate the Solar Contribution to Recent Climate Change? | date=[[2003-12-03]] | journal=[[Journal of Climate]] | volume=16 | issue=24 | pages=4079–4093 | doi=10.1175/1520-0442(2003)016<4079:DMUTSC>2.0.CO;2 | accessdate=2007-04-16 | url=http://climate.envsci.rutgers.edu/pdf/StottEtAl.pdf | year=2003}}</ref>
They nevertheless conclude that even with an enhanced climate sensitivity to solar forcing, most of the warming since the mid-20th century is likely attributable to the increases in greenhouse gases.
==Natural Climate Change on Other Planets==
Two researchers at [[Duke University]], Bruce West and Nicola Scafetta, have estimated that the Sun may have contributed about 45–50 percent of the increase in the average global surface temperature over the period 1900–2000, and about 25–35 percent between 1980 and 2000.<ref>
{{cite journal | first=Nicola | last=Scafetta | coauthors=West, Bruce J. | title=Phenomenological solar contribution to the 1900–2000 global surface warming | url = http://www.fel.duke.edu/~scafetta/pdf/2005GL025539.pdf | format = [[Portable Document Format|PDF]] | date=[[2006-03-09]] | journal=[[Geophysical Research Letters]] | volume=33 | issue=5 | id=L05708 | doi=10.1029/2005GL025539 | accessdate=2007-05-08 | pages=L05708}}
</ref>
A different hypothesis is that variations in [[solar variation|solar output]], possibly amplified by cloud seeding via [[galactic cosmic ray]]s, may have contributed to recent warming.<ref>{{cite journal | first=Nigel | last=Marsh | coauthors=Henrik, Svensmark | title=Cosmic Rays, Clouds, and Climate | journal=Space Science Reviews | volume=94 | number=1–2 | pages=215–230 | year=2000 | month=November | url=http://www.dsri.dk/~hsv/SSR_Paper.pdf | format=[[Portable Document Format|PDF]] | doi=10.1023/A:1026723423896 | accessdate=2007-04-17}}
</ref> It suggests magnetic activity of the sun is a crucial factor which deflects cosmic rays that may influence the generation of cloud condensation nuclei and thereby affect the climate.<ref>{{cite journal |last=Svensmark |first=Henrik |authorlink=Henrik Svensmark |year=2000 | month=July |format=[[Portable Document Format|PDF]] |title=Cosmic Rays and Earth's Climate |journal=Space Science Reviews |volume=93 |issue=1-2 |pages=175–185 |url=http://winnetou.lcd.lu/physique/OSCIE2003/global_warming/Cosmic_rays_and_Earth_Climate_new_sven0606.pdf |accessdate= 2007-09-17 |doi=10.1023/A:1026592411634}}</ref>
One predicted effect of an increase in solar activity would be a warming of most of the [[stratosphere]], whereas an increase in greenhouse gases should produce cooling there.<ref>{{cite web | url= http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-chapter9.pdf | format=[[Portable Document Format|PDF]] | title=Understanding and Attributing Climate Change | work=Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change | accessdate=2008-02-01 | publisher=[[Intergovernmental Panel on Climate Change]] | last=Hegerl | first=Gabriele C. | coauthors=''et al.'' | pages=675}}
</ref> The observed trend since at least 1960 has been a cooling of the lower stratosphere.<ref>{{cite web|title=Climate Change 2001:Working Group I: The Scientific Basis (Fig. 2.12)|url=http://www.grida.no/climate/ipcc_tar/wg1/fig2-12.htm|year=2001|accessdate=2007-05-08}}
</ref> [[Ozone depletion|Reduction of stratospheric ozone]] also has a cooling influence, but substantial ozone depletion did not occur until the late 1970s.<ref>[http://www.nas.nasa.gov/About/Education/Ozone/history.html Ozone History<!-- Bot generated title -->]</ref> Solar variation combined with changes in [[volcano|volcanic activity]] probably did have a warming effect from pre-industrial times to 1950, but a cooling effect since.<ref name="grida7" /> In 2006, Peter Foukal and other researchers from the United States, [[Germany]], and [[Switzerland]] found no net increase of solar brightness over the last 1,000 years. [[Solar cycle]]s led to a small increase of 0.07 percent in brightness over the last 30 years. This effect is too small to contribute significantly to global warming.<ref>
{{cite journal | first=Peter | last=Foukal | coauthors=''et al.'' | title=Variations in solar luminosity and their effect on the Earth's climate. | date=[[2006-09-14]] | journal=[[Nature]] | accessdate=2007-04-16 | url=http://www.nature.com/nature/journal/v443/n7108/abs/nature05072.html | doi=10.1038/nature05072 | format=abstract | volume=443 | pages=161}}</ref><ref>{{cite pressrelease | title=Changes in Solar Brightness Too Weak to Explain Global Warming | url=http://www.ucar.edu/news/releases/2006/brightness.shtml#| publisher=[[National Center for Atmospheric Research]] | date=[[2006-09-14]] | accessdate=2007-07-13 }}</ref> One paper by Mike Lockwood and Claus Fröhlich found no relation between global warming and solar radiation since 1985, whether through variations in solar output or variations in [[cosmic ray]]s.<ref>{{cite journal | last = Lockwood | first = Mike
| authorlink = | coauthors = Claus Fröhlich | title = Recent oppositely directed trends in solar climate forcings and the global mean surface air temperature | journal = Proceedings of the Royal Society A | volume =463 | issue = | pages =2447 | date = | quote = Our results show that the observed rapid rise in global mean temperatures seen after 1985 cannot be ascribed to solar variability, whichever of the mechanisms is invoked and no matter how much the solar variation is amplified. | url = http://www.pubs.royalsoc.ac.uk/media/proceedings_a/rspa20071880.pdf | doi = 10.1098/rspa.2007.1880 | id = | accessdate = 2007-07-21 |format=PDF}}</ref> [[Henrik Svensmark]] and [[Eigil Friis-Christensen]], the main proponents of [[cloud seeding]] by galactic cosmic rays, disputed this criticism of their hypothesis.<ref>[http://www.spacecenter.dk/publications/scientific-report-series/Scient_No._3.pdf/view Reply to Lockwood and Fröhlich - The persistent role of the Sun in climate forcing — Spacecenter<!-- Bot generated title -->]</ref> A 2007 paper found that in the last 20 years there has been no significant link between changes in cosmic rays coming to Earth and cloudiness and temperature.<ref>{{cite news | publisher=[[BBC News Online]] | title='No Sun link' to climate change | url=http://news.bbc.co.uk/2/hi/science/nature/7327393.stm | author=Richard Black | date=April 3, 2008}}</ref><ref>{{cite journal | doi=10.1088/1748-9326/3/2/024001 | title=Testing the proposed causal link between cosmic rays and cloud cover | author=T Sloan and A W Wolfendale | journal=Environ. Res. Lett. | volume=3 | page=024001 | year=2008 | pages=024001}}</ref><ref>[http://arxiv.org/abs/0803.2298 preprint of this paper can be found here]</ref>
[[Pluto]] has also been found to be undergoing global warming. The overall temperature increase on Pluto has been greater than that on the earth.<ref>http://www.space.com/scienceastronomy/pluto_warming_021009.html</ref>
==Forcing and feedback==
[[Image:Radiative-forcings.svg|thumb|280px|right| Components of the current [[radiative forcing]] as estimated by the [[IPCC Fourth Assessment Report]].]]
The forces that drive climate change are said to be operating in a system called forcing. None of the effects of forcing are instantaneous. The [[Volumetric heat capacity|thermal inertia]] of the Earth's oceans and slow responses of other indirect effects mean that the Earth's current climate is not in equilibrium with the forcing imposed. [[Climate commitment]] studies indicate that even if greenhouse gases were stabilized at 2000 levels, a further warming of about {{nowrap|0.5 °C}} {{nowrap|(0.9 °F)}} would still occur.<ref>
{{cite journal |last=Meehl |first=Gerald A. |coauthors=''et al.'' |date=[[2005-03-18]] |title=How Much More Global Warming and Sea Level Rise |journal=[[Science (journal)|Science]] |volume=307 |issue=5716 |pages=1769–1772 |doi=10.1126/science.1106663 |url=http://www.sciencemag.org/cgi/reprint/307/5716/1769.pdf | format=[[Portable Document Format|PDF]] | accessdate=2007-02-11 |pmid=15774757}}
</ref>
===Climate variability===
The Earth's climate changes in response to external forcing, including [[greenhouse gases]], variations in its orbit around the [[Sun]] ([[orbital forcing]]),<ref>{{cite journal |last=Berger |first=A. |coauthors=''et al.'' |date=[[2005-12-10]] |title=On the origin of the 100-kyr cycles in the astronomical forcing |journal=Paleoceanography |volume=20 |issue=4 |pages= |id=PA4019 |url=http://www.agu.org/pubs/crossref/2005/2005PA001173.shtml |accessdate= 2007-11-05 |doi=10.1029/2005PA001173, |doi_brokendate=2008-06-25}}</ref><ref>{{cite journal |last=Genthon |first=C. |coauthors=''et al.'' |date=[[1987-10-01]] |title=Vostok Ice Core - Climatic response to CO<sub>2</sup> and orbital forcing changes over the last climatic cycle |journal=[[Nature (journal)|Nature]] |volume=329 |issue=6138 |pages=414–418 |url=http://www.nature.com/nature/journal/v329/n6138/abs/329414a0.html |accessdate= 2007-11-05 |doi=10.1038/329414a0 |format=abstract}}</ref><ref>{{cite journal |last=Alley |first=Richard B. |coauthors=''et al.'' |year=2002 |month=January |title=A northern lead in the orbital band: north-south phasing of Ice-Age events |journal=Quaternary Science Reviews |volume=21 |issue=1-3 |pages=431–441 |url=http://www.ingentaconnect.com/content/els/02773791/2002/00000021/00000001/art00072 |accessdate= 2007-11-05 |doi=10.1016/S0277-3791(01)00072-5}}</ref> changes in [[solar luminosity]], and [[volcano|volcanic]] eruptions;<ref>Robock, Alan, and Clive Oppenheimer, Eds., 2003: Volcanism and the Earth’s Atmosphere, Geophysical Monograph 139, American Geophysical Union, Washington, DC, 360 pp.</ref> all examples of the earth's own variation in temperatures, for which the [[UNFCCC]] uses the term climate variability.
===Feedback===
{{main|Effects of global warming}}
When a warming trend results in effects that induce further warming, it is known as a positive feedback; when the effects induce cooling, the process is referred to as a negative feedback. The primary positive feedback involves water vapor. The primary negative feedback is temperature-radiation: as the temperature of a body increases, the emitted radiation increases with the fourth power of its [[absolute temperature]].<ref>[http://www.britannica.com/EBchecked/topic/564843/Stefan-Boltzmann-law "Stefan-Boltzmann Law", Britannica Online]</ref> This provides a powerful negative feedback which stabilizes the climate system over time.
==Politics of Global Warming==
One of the most pronounced positive feedback effects relates to the evaporation of water. If the atmosphere is warmed, the [[saturation vapour pressure]] increases, and the quantity of water vapor in the atmosphere will tend to increase. Since water vapor is a greenhouse gas, the increase in water vapor content makes the atmosphere warm further; this warming causes the atmosphere to hold still more water vapor (a [[positive feedback]]), and so on until other processes stop the feedback loop. The result is a much larger greenhouse effect than that due to CO<sub>2</sub> alone. Although this feedback process causes an increase in the absolute moisture content of the air, the [[relative humidity]] stays nearly constant or even decreases slightly because the air is warmer.<ref name="soden1">{{cite journal| first= Brian J. | last= Soden | coauthors= Held, Isacc M. | journal= [[Journal of Climate]] | title= An Assessment of Climate Feedbacks in Coupled Ocean–Atmosphere Models | date= [[2005-11-01]] | volume= 19 | issue= 14 | url= http://www.gfdl.noaa.gov/reference/bibliography/2006/bjs0601.pdf | format= [[Portable Document Format|PDF]] | accessdate= 2007-04-21 | quote=Interestingly, the true feedback is consistently weaker than the constant relative humidity value, implying a small but robust reduction in relative humidity in all models on average" "clouds appear to provide a positive feedback in all models | pages= 3354–3360 | doi= 10.1175/JCLI3799.1}}</ref> This feedback effect can only be reversed slowly as CO<sub>2</sub> has a long average [[Greenhouse gas#Removal from the atmosphere and global warming potential|atmospheric lifetime]].
Feedback effects due to clouds are an area of ongoing research. Seen from below, clouds emit infrared radiation back to the surface, and so exert a warming effect; seen from above, clouds reflect sunlight and emit infrared radiation to space, and so exert a cooling effect. Whether the net effect is warming or cooling depends on details such as the [[list of cloud types|type]] and altitude of the cloud. These details are difficult to represent in climate models, in part because clouds are much smaller than the spacing between points on the computational grids of climate models.<ref name="soden1" />
{{Double image stack|right|Northern Hemisphere Sea Ice Extent Anomalies.png|Southern Hemisphere Sea Ice Extent Anomalies.png|280|Northern Hemisphere ice trends|Southern Hemisphere ice trends.}}
A subtler feedback process relates to changes in the [[lapse rate]] as the atmosphere warms. The atmosphere's temperature decreases with height in the [[troposphere]]. Since emission of infrared radiation varies with the fourth power of temperature, [[longwave radiation]] emitted from the upper atmosphere is less than that emitted from the lower atmosphere. Most of the radiation emitted from the upper atmosphere escapes to space, while most of the radiation emitted from the lower atmosphere is re-absorbed by the surface or the atmosphere. Thus, the strength of the greenhouse effect depends on the atmosphere's rate of temperature decrease with height: if the rate of temperature decrease is greater the greenhouse effect will be stronger, and if the rate of temperature decrease is smaller then the greenhouse effect will be weaker. Both theory and climate models indicate that with increased greenhouse gas content the rate of temperature decrease with height will be reduced, producing a negative ''lapse rate feedback'' that weakens the greenhouse effect. Measurements of the rate of temperature change with height are very sensitive to small errors in observations, making it difficult to establish whether the models agree with observations.<ref>[http://www.nap.edu/catalog.php?record_id=10850 Panel on Climate Change Feedbacks, Climate Research Committee, National Research Council, 2004: Understanding Climate Change Feedbacks.]</ref>
... dealing with the threat of warming fits in with a great variety of preexisting agendas [like] dissatisfaction with industrial society (neopastoralism), ... governmental desires for enhanced revenues (carbon taxes), and bureaucratic desires for enhanced power. <ref name="cato" />
The global average surface temperature warmed about 0.9 °F over the second half of the 20th Century.
Another important feedback process is ice-[[albedo]] feedback.<ref>{{cite web |url=http://www.grida.no/climate/ipcc_tar/wg1/295.htm |last = Stocker |first = Thomas F. |coauthors = ''et al.'' |title = 7.5.2 Sea Ice |work = Climate Change 2001: The Scientific Basis. Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Change |accessdate=2007-02-11 |date=[[2001-01-20]] |publisher=[[Intergovernmental Panel on Climate Change]]}}</ref> When global temperatures increase, ice near the poles melts at an increasing rate. As the ice melts, land or open water takes its place. Both land and open water are on average less reflective than ice, and thus absorb more solar radiation. This causes more warming, which in turn causes more melting, and this cycle continues.
Warming is also the triggering variable for the release of methane from sources both on land and on the deep ocean floor, making both of these possible feedback effects. Thawing [[permafrost]], such as the frozen [[peat]] [[bog]]s in [[Siberia]], creates a [[positive feedback]] due to release of CO<sub>2</sub> and CH<sub>4</sub>.<ref>{{cite news | first=Ian | last=Sample | title=Warming Hits 'Tipping Point' | date=[[2005-08-11]] | url=http://www.guardian.co.uk/climatechange/story/0,12374,1546824,00.html | publisher=[[The Guardian]] | accessdate=2007-01-18}}</ref> Methane discharge from permafrost is presently under intensive study. Warmer deep ocean temperatures, likewise, could release the greenhouse gas [[methane]] from the 'frozen' state of the vast deep ocean deposits of [[methane clathrate]]/[[methane hydrate]], according to the [[Clathrate Gun Hypothesis]],
Ocean ecosystems' ability to sequester carbon are expected to decline as it warms. This is because the resulting low nutrient levels of the [[mesopelagic zone]] (about 200 to 1000 m depth) limits the growth of [[diatom]]s in favor of smaller [[phytoplankton]] that are poorer [[biological pump]]s of carbon.<ref>{{cite journal |last=Buesseler |first=Ken O. |coauthors=''et al.'' |date=[[2007-04-27]] |title=Revisiting Carbon Flux Through the Ocean's Twilight Zone |journal=[[Science (journal)|Science]] |volume=316 |issue=5824 |pages=567–570 |url=http://www.sciencemag.org/cgi/content/abstract/316/5824/567 |accessdate= 2007-11-16 |format=abstract |doi=10.1126/science.1137959 |pmid=17463282}}</ref>
==Temperature changes==
{{main|Temperature record}}
===Recent===
[[Image:2000 Year Temperature Comparison.png|thumb|280px|right|Two millennia of mean surface temperatures according to different reconstructions, each smoothed on a decadal scale. The unsmoothed, annual value for 2004 is also plotted for reference.]]
Global temperatures have increased by {{nowrap|0.75 °C (1.35 °F)}} relative to the period 1860–1900, according to the [[instrumental temperature record]]. This measured temperature increase is not significantly affected by the [[urban heat island]] effect.<ref>[http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-chapter3.pdf Working group I, section 3.2.2.2 of the 2007 IPPC page 243]</ref> Since 1979, land temperatures have increased about twice as fast as ocean temperatures (0.25 °C per decade against 0.13 °C per decade).<ref>{{cite journal| last = Smith | first = Thomas M. | coauthors= Reynolds, Richard W. | title = A Global Merged Land–Air–Sea Surface Temperature Reconstruction Based on Historical Observations (1880–1997) | journal = [[Journal of Climate]] |volume = 18 |issue = 12 | issn = 0894-8755 | pages = 2021–2036 | url = http://www.ncdc.noaa.gov/oa/climate/research/Smith-Reynolds-dataset-2005.pdf | format = [[Portable Document Format|PDF]] | date = [[2005-05-15]] | accessdate = 2007-03-14 | doi = 10.1175/JCLI3362.1}}</ref> Temperatures in the lower [[troposphere]] have increased between 0.12 and 0.22 °C (0.22 and 0.4 °F) per decade since 1979, according to [[satellite temperature measurements]]. Temperature is believed to have been relatively stable over the [[Temperature record of the past 1000 years|one or two thousand years]] before 1850, with possibly regional fluctuations such as the [[Medieval Warm Period]] or the [[Little Ice Age]].{{Fact|date=June 2008}}
Sea temperatures increase more slowly than those on land both because of the larger effective heat capacity of the oceans and because the ocean can lose heat by evaporation more readily than the land.<ref>{{cite journal|title=Land/sea warming ratio in response to climate change: IPCC AR4 model results and comparison with observations|author = Rowan T. Sutton, Buwen Dong, Jonathan M. Gregory|journal=[[Geophysical Research Letters]]|volume=34|url=http://www.agu.org/pubs/crossref/2007/2006GL028164.shtml|doi=10.1029/2006GL028164|year=2007|accessdate=2007-09-19|pages=L02701}}</ref> The [[Northern Hemisphere]] has more land than the [[Southern Hemisphere]], so it warms faster. The Northern Hemisphere also has extensive areas of seasonal snow and sea-ice cover subject to the ice-albedo feedback. More greenhouse gases are emitted in the Northern than Southern Hemisphere, but this does not contribute to the difference in warming because the major greenhouse gases persist long enough to mix between hemispheres.<ref>[http://www.grida.no/CLIMATE/IPCC_TAR/WG1/pdf/TAR-04.PDF]</ref>
Based on estimates by [[NASA]]'s [[Goddard Institute for Space Studies]], 2005 was the warmest year since reliable, widespread instrumental measurements became available in the late 1800s, exceeding the previous record set in 1998 by a few hundredths of a degree.<ref>{{cite web |url= http://data.giss.nasa.gov/gistemp/2005/ |last= Hansen | first = James E. |authorlink= James Hansen |coauthors= ''et al.'' |title= Goddard Institute for Space Studies, GISS Surface Temperature Analysis |accessdate=2007-01-17 |date= [[2006-01-12]] |publisher= NASA [[Goddard Institute for Space Studies]]}}</ref> Estimates prepared by the [[World Meteorological Organization]] and the [[Climatic Research Unit]] concluded that 2005 was the second warmest year, behind 1998.<ref>
{{cite web |url= http://www.cru.uea.ac.uk/cru/press/2005-12-WMO.pdf |title= Global Temperature for 2005: second warmest year on record |accessdate=2007-04-13 |date= [[2005-12-15]] |publisher= [[Climatic Research Unit]], School of Environmental Sciences, University of East Anglia |format = [[Portable Document Format|PDF]]}}</ref><ref>{{cite web |url=http://grdc.bafg.de/servlet/is/4226/Pressemitteilung-WMO-23-Dez-05-743_E1.pdf |format=[[Portable Document Format|PDF]] |title=WMO STATEMENT ON THE STATUS OF THE GLOBAL CLIMATE IN 2005 |accessdate=2007-04-13 |date=[[2005-12-15]] |publisher=[[World Meteorological Organization]]}}</ref> Temperatures in 1998 were unusually warm because the strongest [[El Niño-Southern Oscillation]] in the past century occurred during that year.<ref name="Changnon2000">{{cite book |title=El Niño, 1997-1998: The Climate Event of the Century |last=Changnon |first=Stanley A. |authorlink= |coauthors=Bell, Gerald D. |year=2000 |publisher=Oxford University Press |location=London |isbn=0195135520 |pages= }}</ref>
Anthropogenic emissions of other [[pollutant]]s—notably sulfate [[aerosol]]s—can exert a cooling effect by increasing the reflection of incoming sunlight. This partially accounts for the cooling seen in the temperature record in the middle of the twentieth century,<ref>{{cite web |url=http://www.grida.no/climate/ipcc_tar/wg1/462.htm |last = Mitchell |first = J. F. B. |coauthors = ''et al.'' |title = 12.4.3.3 Space-time studies |work = Climate Change 2001: The Scientific Basis. Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Change |accessdate=2007-01-04 |date=[[2001-01-20]] |publisher=[[Intergovernmental Panel on Climate Change]]}}</ref> though the cooling may also be due in part to natural variability. [[James Hansen]] and colleagues have proposed that the effects of the products of fossil fuel combustion—CO<sub>2</sub> and aerosols—have largely offset one another, so that warming in recent decades has been driven mainly by non-CO<sub>2</sub> greenhouse gases.<ref name="pmid10944197">{{cite journal |author=Hansen J, Sato M, Ruedy R, Lacis A, Oinas V |title=Global warming in the twenty-first century: an alternative scenario |journal=Proc. Natl. Acad. Sci. U.S.A. |volume=97 |issue=18 |pages=9875–80 |year=2000 |month=August |pmid=10944197 |doi=10.1073/pnas.170278997}}</ref>
Paleoclimatologist [[William Ruddiman]] has argued that human influence on the global climate began around 8,000 years ago with the start of forest clearing to provide land for agriculture and 5,000 years ago with the start of Asian rice irrigation.<ref>{{cite journal |last=Ruddiman |first=William F. |authorlink=William Ruddiman |title=How Did Humans First Alter Global Climate? |volume=292 |issue=3 |journal=[[Scientific American]] |month=March | year=2005 |pages=46–53 |url=http://ccr.aos.wisc.edu/news/0305046.pdf |format=[[Portable Document Format|PDF]] |accessdate=2007-03-05}}</ref>Ruddiman's interpretation of the historical record, with respect to the methane data, has been disputed.<ref>{{cite journal |last=Schmidt |first=Gavin |authorlink=Gavin Schmidt |coauthors=''et al.'' |date=[[2004-12-10]] |title=A note on the relationship between ice core methane concentrations and insolation |journal=[[Geophysical Research Letters]] |volume=31 |issue=23 |id=L23206 |doi=10.1029/2004GL021083 |url=http://pubs.giss.nasa.gov/abstracts/2004/Schmidt_etal_2.html |accessdate=2007-03-05 |pages=L23206 |format=abstract}}</ref>
===Pre-human climate variations===
{{See|Paleoclimatology}}
{{See also|Snowball Earth}}
[[Image:Ice Age Temperature.png|thumb|250px|right|Curves of reconstructed temperature at two locations in Antarctica and a global record of variations in glacial ice volume. Today's date is on the left side of the graph.]]
Earth has experienced warming and cooling many times in the past. The recent Antarctic [[European Project for Ice Coring in Antarctica|EPICA]] ice core spans 800,000 years, including eight glacial cycles timed by [[Milankovitch cycles|orbital variations]] with [[interglacial]] warm periods comparable to present temperatures.<ref>{{cite journal | first=James | last=Hansen | coauthors=''et al.'' | url=http://www.pnas.org/cgi/reprint/103/39/14288.pdf | title=Global temperature change | journal=[[Proceedings of the National Academy of Sciences|PNAS]] | volume=103 | number=39 | pages=14288–14293 | date=[[2006-09-26]] | format=[[Portable Document Format|PDF]] | accessdate=2007-04-20 | doi=10.1073/pnas.0606291103 | pmid=17001018}}</ref>
==Al Gore's Claims==
A rapid buildup of greenhouse gases amplified warming in the early [[Jurassic]] period (about 180 million years ago), with average temperatures rising by 5 °C (9 °F). Research by the [[Open University]] indicates that the warming caused the rate of rock [[weathering]] to increase by 400%. As such weathering locks away carbon in [[calcite]] and [[dolomite]], CO<sub>2</sub> levels dropped back to normal over roughly the next 150,000 years.<ref>{{cite journal | last = Cohen | first = Anthony S. | coauthors = ''et al.'' | year = 2004 | month = February | title = Osmium isotope evidence for the regulation of atmospheric CO<sub>2</sub> by continental weathering | journal = [[Geology (journal)|Geology]] | volume = 32 | issue = 2 | pages = 157–160 | doi = 10.1130/G20158.1 | url = http://sheba.geo.vu.nl/~vonh/imagesanddata/data/Cohenetal2004.pdf | format = [[Portable Document Format|PDF]] | accessdate = 2007-03-04}}</ref>
Sudden releases of methane from [[clathrate compound]]s (the [[clathrate gun hypothesis]]) have been hypothesized as both a cause for and an effect of other warming events in the distant past, including the [[Permian–Triassic extinction event]] (about 251 million years ago) and the [[Paleocene–Eocene Thermal Maximum]] (about 55 million years ago).
==Climate models==
{{main|Global climate model}}
{{Double image stack|right|Global Warming Predictions.png|Global Warming Predictions Map.jpg|250|Calculations of global warming prepared in or before 2001 from a range of [[climate model]]s under the [[Special Report on Emissions Scenarios|SRES]] A2 emissions scenario, which assumes no action is taken to reduce emissions.|The geographic distribution of surface warming during the 21<sup>st</sup> century calculated by the [[HadCM3]] climate model if a business as usual scenario is assumed for economic growth and greenhouse gas emissions. In this figure, the globally averaged warming corresponds to 3.0 °C (5.4 °F).}}
Scientists have studied global warming with [[computer models]] of the climate. These models are based on physical principles of fluid dynamics, [[radiative transfer]], and other processes, with simplifications being necessary because of limitations in computer power and the [[complex system|complexity]] of the climate system. All modern climate models include an atmospheric model that is coupled to an ocean model and models for ice cover on land and sea. Some models also include treatments of chemical and biological processes.<ref>{{cite web | url= http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-chapter7.pdf | format=[[Portable Document Format|PDF]] | title=Chapter 7, "Couplings Between Changes in the Climate System and Biogeochemistry" | work=Fourth Assessment Report of the Intergovernmental Panel on Climate Change | accessdate=2008-02-21 | date=[[2007-02-05]] | publisher=[[Intergovernmental Panel on Climate Change]]}}</ref> These models predict that the effect of adding greenhouse gases is to produce a warmer climate.<ref>{{cite web |url=http://books.google.com/books?id=sx6DFr8rbpIC&dq=robert+lanza&printsec=frontcover&source=web&ots=S7MXYzoDqR&sig=jfUo33FtVZ3PSUS2fcc_EtawEnQ |last = Hansen |first = James |title = Climatic Change: Understanding Global Warming |work = One World: The Health & Survival of the Human Species in the 21st century |accessdate=2007-08-18 | year = 2000 |publisher= Health Press}}</ref> However, even when the same assumptions of future greenhouse gas levels are used, there still remains a considerable range of [[climate sensitivity]].
==2008 Presidential candidates on climate Change==
Including uncertainties in future greenhouse gas concentrations and climate modeling, the IPCC anticipates a warming of {{nowrap|1.1 °C to 6.4 °C}} {{nowrap|(2.0 °F to 11.5 °F)}} by the end of the 21st century, relative to 1980–1999.<ref name="grida7" /> Models have also been used to help investigate the [[Attribution of recent climate change|causes of recent climate change]] by comparing the observed changes to those that the models project from various natural and human-derived causes.
[[Bob Barr]] is the only major 2008 Presidential Candidate who has not adopted wholesale the theory of human-caused global warming.
Current climate models produce a good match to observations of global temperature changes over the last century, but do not simulate all aspects of climate.<ref>{{cite web |url=http://www.grida.no/climate/ipcc_tar/wg1/007.htm |title=Summary for Policymakers |work=Climate Change 2001: The Scientific Basis. Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Change |accessdate=2007-04-28 |date=[[2001-01-20]] |publisher=[[Intergovernmental Panel on Climate Change]]}}</ref> These models do not unambiguously attribute the warming that occurred from approximately 1910 to 1945 to either natural variation or human effects; however, they suggest that the warming since 1975 is dominated by man-made [[greenhouse gas]] emissions.
Global climate model projections of future climate are forced by imposed greenhouse gas emission scenarios, most often from the IPCC [[Special Report on Emissions Scenarios]] (SRES). Less commonly, models may also include a simulation of the [[carbon cycle]]; this generally shows a positive feedback, though this response is uncertain (under the A2 SRES scenario, responses vary between an extra 20 and 200 ppm of CO<sub>2</sub>). Some observational studies also show a positive feedback.<ref>{{cite journal |last=Torn |first=Margaret |coauthors=Harte, John |date=[[2006-05-26]] |title=Missing feedbacks, asymmetric uncertainties, and the underestimation of future warming |journal=[[Geophysical Research Letters]] |volume=33 |issue=10 |id=L10703 |url=http://www.agu.org/pubs/crossref/2006/2005GL025540.shtml |accessdate=2007-03-04 |doi=10.1029/2005GL025540, |doi_brokendate=2008-06-25}}</ref><ref>{{cite journal |last=Harte |first=John |coauthors=''et al.'' |date=[[2006-10-30]] |title=Shifts in plant dominance control carbon-cycle responses to experimental warming and widespread drought |journal=Environmental Research Letters |volume=1 |issue=1 |id=014001 |url=http://www.iop.org/EJ/article/1748-9326/1/1/014001/erl6_1_014001.html |accessdate=2007-05-02 |doi=10.1088/1748-9326/1/1/014001 |pages=014001}}</ref><ref>{{cite journal |last = Scheffer |first = Marten |coauthors = ''et al.'' |title = Positive feedback between global warming and atmospheric CO2 concentration inferred from past climate change. |journal = [[Geophysical Research Letters]] |volume = 33 |url = http://www.pik-potsdam.de/~victor/recent/scheffer_etal_T_CO2_GRL_in_press.pdf |doi = 10.1029/2005gl025044 |date = [[2006-05-26]] |accessdate = 2007-05-04 |pages = L10702|format=PDF}}</ref>
In his own words, McCain says "the overwhelming majority of scientific opinion in America today, and in the world, is that climate change is real. The fact is that it ''is'' real. The fact is that the solution to it is the development of technologies.... and a [[cap and trade]] proposal.... the debate is over."[http://www.youtube.com/watch?v=gQMxIwpK_es] Unless McCain believes that Global Warming is entirely or largely man-made, there would be no sense in supporting a cap and trade solution.
In May 2008, it was predicted that "global surface temperature may not increase over the next decade, as natural climate variations in the North Atlantic and tropical Pacific temporarily offset the projected anthropogenic warming", based on the inclusion of ocean temperature observations.<ref>{{cite journal|url=http://www.nature.com/nature/journal/v453/n7191/abs/nature06921.html|title=Advancing decadal-scale climate prediction in the North Atlantic sector|author=N. S. Keenlyside, M. Latif, J. Jungclaus, L. Kornblueh2, E. Roeckner|date=May 1, 2008|pages=84-88|journal=[[Nature (journal)|Nature]]|issue=453|accessdate=2008-07-06|doi=10.1038/nature06921}}</ref>
The representation of clouds is one of the main sources of uncertainty in present-generation models, though progress is being made on this problem.<ref>{{cite web |url=http://www.grida.no/climate/ipcc_tar/wg1/271.htm |last = Stocker |first = Thomas F. |coauthors = ''et al.'' |title = 7.2.2 Cloud Processes and Feedbacks |work = Climate Change 2001: The Scientific Basis. Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Change |accessdate=2007-03-04 |date=[[2001-01-20]] |publisher=[[Intergovernmental Panel on Climate Change]]}}</ref>
==Al Gore's "Inconvenient Truth" Movie Claims==
A minor issue in climate modeling is the perceived mismatch between actual conditions and those predicted by the models. A 2007 study by [[David Douglass]], [[John Christy]], Benjamin Pearson and [[Fred Singer]] comparing the composite output of 22 leading global climate models with actual climate data found that the models do not accurately predict observed changes to the temperature profile in the tropical troposphere. The authors note that their conclusions contrast strongly with those of recent publications based on essentially the same data.<ref>{{cite journal| last=Douglass | first=David H. | authorlink = David Douglass | coauthors=''et al.'' | date=[[2007-12-05]] | title=A comparison of tropical temperature trends with model predictions | journal=International Journal of Climatology | volume=9999 | issue=9999 | doi=10.1002/joc.1651 | url=http://icecap.us/images/uploads/DOUGLASPAPER.pdf | format=[[Portable Document Format|PDF]] | accessdate=2008-05-12}}</ref> However, a 2008 paper, published by a 17-member team led by [[Ben Santer]] of [[Lawrence Livermore National Laboratory]], found serious flaws in the previous study, instead finding that any deviations were statistically insignificant.<ref>{{cite journal|last=Santer|first=B.D.|authorlink=Benjamin D. Santer|coauthors=''et al.''|date=2008-10-10|title=Consistency of modelled and observed temperature trends in the tropical troposphere|journal=International Journal of Climatology|volume=28|issue=13|doi=10.1002/joc.1756|url=https://publicaffairs.llnl.gov/news/news_releases/2008/NR-08-10-05-article.pdf|format=[[Portable Document Format|PDF]]|accessdate=2008-10-22}}</ref>
==Attributed and expected effects==
===Environmental===
{{main|Effects of global warming}}
[[Image:Glacier Mass Balance.png|right|thumb|280px|Sparse records indicate that glaciers have been retreating since the early 1800s. In the 1950s measurements began that allow the monitoring of glacial mass balance, reported to the [[World Glacier Monitoring Service|WGMS]] and the [[National Snow and Ice Data Center|NSIDC]].]]
Although it is difficult to connect specific weather events to global warming, an increase in global temperatures may in turn cause broader [[effects of global warming|changes]], including [[Glacier mass balance|glacial retreat]], [[Arctic shrinkage]], and worldwide [[sea level rise]]. Changes in the amount and pattern of [[precipitation (meteorology)|precipitation]] may result in [[flood]]ing and [[drought]]. There may also be changes in the frequency and intensity of [[extreme weather]] events. Other effects may include changes in agricultural yields, addition of new trade routes,<ref>{{cite news |first=Jennifer |last=Macey |title=Global warming opens up Northwest Passage |url=http://www.abc.net.au/news/stories/2007/09/19/2037198.htm?section=business |publisher=ABC News |date=September 19, 2007 |accessdate=2007-12-11}}</ref> reduced summer [[streamflow]]s, species [[extinction risk from climate change|extinctions]], and increases in the range of [[Vector (biology)|disease vectors]].
Some effects on both the [[natural environment]] and [[civilization|human life]] are, at least in part, already being attributed to global warming. A 2001 report by the IPCC suggests that [[Retreat of glaciers since 1850|glacier retreat]], [[Ice shelf#Ice shelf disruption|ice shelf disruption]] such as that of the [[Larsen Ice Shelf]], [[sea level rise]], changes in rainfall patterns, and increased intensity and frequency of [[Effects of global warming#More extreme weather|extreme weather events]], are being attributed in part to global warming.<ref name="tar_wg2">{{cite web |title = Climate Change 2001: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Third Assessment Report of the Intergovernmental Panel on Climate Change |url = http://www.grida.no/climate/ipcc_tar/wg2/index.htm |publisher = [[Intergovernmental Panel on Climate Change]] |date = [[2001-02-16]] |accessdate = 2007-03-14}}</ref> While changes are expected for overall patterns, intensity, and frequencies, it is difficult to attribute specific events to global warming. Other expected effects include water scarcity in some regions and increased precipitation in others, changes in mountain snowpack, and adverse health effects from warmer temperatures.<ref>{{cite journal |author=McMichael AJ, Woodruff RE, Hales S |title=Climate change and human health: present and future risks |journal=Lancet |volume=367 |issue=9513 |pages=859–69 |year=2006 |pmid=16530580 |doi=10.1016/S0140-6736(06)68079-3}}</ref>
Increasing deaths, displacements, and economic losses projected due to [[extreme weather]] attributed to global warming may be exacerbated by [[Population growth|growing population]] densities in affected areas, although temperate regions are projected to experience some benefits, such as fewer deaths due to cold exposure.<ref name="WGII SPM AR4">{{cite web |title = Summary for Policymakers |work = Climate Change 2007: Impacts, Adaptation and Vulnerability. Working Group II Contribution to the Intergovernmental Panel on Climate Change Fourth Assessment Report |url =http://www.ipcc.ch/pdf/assessment-report/ar4/wg2/ar4-wg2-spm.pdf |format = [[Portable Document Format|PDF]] |publisher = [[Intergovernmental Panel on Climate Change]] |date = [[2007-04-13]] |accessdate = 2007-04-28}}</ref> A summary of probable effects and recent understanding can be found in the report made for the [[IPCC Third Assessment Report]] by Working Group II.<ref name="tar_wg2" /> The newer [[IPCC Fourth Assessment Report]] summary reports that there is observational evidence for an increase in intense [[tropical cyclone]] activity in the North [[Atlantic Ocean]] since about 1970, in correlation with the increase in sea surface temperature (see [[Atlantic Multidecadal Oscillation]]), but that the detection of long-term trends is complicated by the quality of records prior to routine [[satellite]] observations. The summary also states that there is no clear trend in the annual worldwide number of tropical cyclones.<ref name="grida7" />
== Scientists ==
Additional anticipated effects include sea level rise of {{nowrap|180 to 590 millimeters}} {{nowrap|(0.59 to 1.9 ft)}} in 2090-2100 relative to 1980-1999, <ref name="grida7" /> [[Climate change and agriculture|repercussions to agriculture]], [[Shutdown of thermohaline circulation|possible slowing of the thermohaline circulation]], reductions in the [[ozone layer]], increased intensity (but less frequent)<ref>{{cite journal|doi = 10.1038/ngeo202|title = Simulated reduction in Atlantic hurricane frequency under twenty-first-century warming conditions|year = 2008|author = Knutson, Thomas R.|journal = Nature Geoscience|volume = 1|pages = 359}}</ref> of [[Effects of global warming#More extreme weather|hurricanes and extreme weather events]], [[Ocean acidification|lowering]] of ocean [[pH]], and the spread of diseases such as [[malaria]] and [[dengue fever]]. One study predicts 18% to 35% of a sample of 1,103 animal and plant species would be [[extinction risk from climate change|extinct]] by 2050, based on future climate projections.<ref>{{cite journal |last= Thomas |first= Chris D. |coauthors= ''et al.'' |date= [[2004-01-08]] |title= Extinction risk from climate change |journal= [[Nature (journal)|''Nature'']] |volume= 427 |issue= 6970 |pages= 145–138 |doi= 10.1038/nature02121 |url= http://www.geog.umd.edu/resac/outgoing/GEOG442%20Fall%202005/Lecture%20materials/extinctions%20and%20climate%20change.pdf |format= [[Portable Document Format|PDF]] |accessdate= 2007-03-18}}</ref> However, few mechanistic studies have documented extinctions due to recent climate change<ref>{{cite journal |last= McLaughlin |first= John F. |coauthors= ''et al.'' |date= [[2002-04-30]] |title= Climate change hastens population extinctions |journal= [[Proceedings of the National Academy of Sciences|PNAS]] |volume= 99 |issue= 9 |pages= 6070–6074 |doi= 10.1073/pnas.052131199 |url= http://www.nd.edu/~hellmann/pnas.pdf |format= [[Portable Document Format|PDF]] |accessdate= 2007-03-29 |pmid= 11972020}}</ref> and one study suggests that projected rates of extinction are uncertain.<ref>{{cite journal |last=Botkin |first=Daniel B. |authorlink= |coauthors=''et al.'' |year=2007 |month=March |title=Forecasting the Effects of Global Warming on Biodiversity |journal=[[BioScience]] |volume=57 |issue=3 |pages=227–236 |doi=10.1641/B570306 |url=http://www.imv.dk/Admin/Public/DWSDownload.aspx?File=%2FFiles%2FFiler%2FIMV%2FPublikationer%2FFagartikler%2F2007%2F050307_Botkin_et_al.pdf |accessdate= 2007-11-30|format=PDF}}</ref>
[[Image:Rogerrevelle.jpg|thumb|right|200px|Roger Revelle]]
Global warming is expected to increase the potential geographic range and virulence
of [[tropical disease]]s.<ref>[http://www.cbsnews.com/stories/2002/06/20/tech/main512920.shtml Global Warming May Spread Diseases, Study: Pathogens Invade New Areas As Temperatures Rise], CBS News</ref> Climate change could cause a major increase in insect-borne [[Infectious diseases|diseases]] such as [[malaria]] throughout [[Europe]], [[North America]] and North [[Asia]].<ref>[http://world.merinews.com/catFull.jsp;jsessionid=EAA582BA3E049534BABAA98C515DEF1F?articleID=137538 Global warming breeds malaria]</ref>
{|
===Economic===
{{main|Economics of global warming|Low-carbon economy}}
[[Image:IPCC AR4 WGIII GHG concentration stabilization levels.png|thumb|right|280px|The projected temperature increase for a range of stabilization scenarios (the colored bands). The black line in middle of the shaded area indicates 'best estimates'; the red and the blue lines the likely limits. From the work of [[IPCC Fourth Assessment Report|IPCC AR4]].]]
Some economists have tried to estimate the aggregate net economic costs of damages from climate change across the globe. Such estimates have so far yielded no conclusive findings; in a survey of 100 estimates, the values ran from [[United States dollar|US$]]-10 per tonne of carbon (tC) (US$-3 per tonne of carbon dioxide) up to [[US$]]350/tC (US$95 per tonne of carbon dioxide), with a mean of US$43 per tonne of carbon (US$12 per tonne of carbon dioxide).<ref name="WGII SPM AR4" />
One widely publicized report on potential economic impact is the [[Stern Review]]; it suggests that extreme weather might reduce global [[gross domestic product]] by up to one percent, and that in a worst-case scenario global [[per capita]] consumption could fall 20 percent.<ref>{{cite web | url= http://news.bbc.co.uk/2/hi/business/6098362.stm | title = At-a-glance: The Stern Review | publisher = [[BBC]] |accessdate=2007-04-29 |date = [[2006-10-30]]}}</ref> The report's methodology, advocacy and conclusions have been criticized by many economists, primarily around the Review's assumptions of [[discounting]] and its choices of scenarios,<ref>Tol and Yohe (2006) "A Review of the Stern Review" ''World Economics'' '''7'''(4): 233-50. See also other critiques in ''World Economics'' '''7'''(4).</ref> while others have supported the general attempt to quantify economic risk, even if not the specific numbers.<ref>{{web cite|url=http://delong.typepad.com/sdj/2006/12/do_unto_others.html|title= Do unto others...|author=[[J. Bradford DeLong]]}}</ref><ref>{{web cite|url=http://johnquiggin.com/wp-content/uploads/2006/12/sternreviewed06121.pdf|title=Stern and the critics on discounting|author=[[John Quiggin]]}}</ref>
Preliminary studies suggest that costs and benefits of mitigating global warming are broadly comparable in magnitude.<ref>{{web cite | url=http://www.ft.com/cms/s/0/38c1bfa0-09bd-11dd-81bf-0000779fd2ac.html | title= Full quote from IPCC on costs of climate change| author=Terry Barker|date=April 14, 2008|accessdate=2008-04-14|publisher=FT.com}}</ref>
According to [[United Nations Environment Programme]] (UNEP), economic sectors likely to face difficulties related to climate change include [[bank]]s, [[Climate change and agriculture|agriculture]], transport and others.<ref>{{cite web | url=http://www.unepfi.org/fileadmin/documents/CEO_briefing_climate_change_2002_en.pdf | format= [[Portable Document Format|PDF]] | title = Climate Risk to Global Economy |last = Dlugolecki |first= Andrew |coauthors= ''et al.'' |work = CEO Briefing: UNEP FI Climate Change Working Group | publisher = [[United Nations Environment Programme]] |accessdate=2007-04-29 |year=2002}}</ref> Developing countries dependent upon agriculture will be particularly harmed by global warming.<ref>{{cite web | url= http://www.rff.org/Publications/Resources/Documents/164/RFF-Resources-164_Thomas%20Schelling.pdf | title = Thomas Schelling: Developing Countries Will Suffer Most from Global Warming| accessdate=2008-03-01 | work = Resources 164 |format=PDF}} </ref>
</small>
==References==
==Adaptation and mitigation==
{{reflist}}
{{main|Adaptation to global warming|Mitigation of global warming|Kyoto Protocol}}
The [[Scientific opinion on climate change|broad agreement]] among climate scientists that global temperatures will continue to increase has led some [[nation]]s, [[state]]s, [[corporation]]s and individuals to implement actions to try to curtail global warming or adjust to it. Many environmental groups encourage [[Individual and political action on climate change|individual action]] against global warming, often by the consumer, but also by community and regional organizations. Others have suggested a [[quota]] on worldwide fossil fuel production, citing a direct link between fossil fuel production and CO<sub>2</sub> emissions.<ref>{{cite web| title = Climate Control: a proposal for controlling global greenhouse gas emissions | publisher = Sustento Institute | url = http://sustento.org.nz/wp-content/uploads/2007/06/climate-control.pdf | format = [[Portable Document Format|PDF]] | accessdate = 2007-12-10}}</ref><ref>{{cite web | title = Rigged - The climate talks are a stitch-up, as no one is talking about supply. | first = George | last = Monbiot | url = http://www.monbiot.com/archives/2007/12/11/rigged/ | format = HTML | accessdate = 2007-12-22}}</ref>
There has also been [[business action on climate change]], including efforts at increased energy efficiency and limited moves towards use of [[alternative fuels]]. One recently developed concept is that of greenhouse gas [[emissions trading]] through which companies, in conjunction with government, agree to cap their emissions or to purchase credits from those below their allowances.
[[Category:Earth Sciences]]
The world's primary international agreement on combating global warming is the [[Kyoto Protocol]], an amendment to the [[United Nations Framework Convention on Climate Change|UNFCCC]] negotiated in 1997. The Protocol now covers more than 160 countries globally and over 55 percent of global greenhouse gas emissions.<ref>{{cite web | url=http://unfccc.int/files/essential_background/kyoto_protocol/application/pdf/kpstats.pdf | format=[[Portable Document Format|PDF]] |title=Kyoto Protocol Status of Ratification | publisher=[[United Nations Framework Convention on Climate Change]] | date=[[2006-07-10]] | accessdate=2007-04-27}}</ref> Only the [[United States]] and [[Kazakhstan]] have not ratified the treaty, with the United States historically being the world's [[greenhouse gas emissions by the United States|largest emitter]] of greenhouse gas. This treaty expires in 2012, and international talks began in May 2007 on a future treaty to succeed the current one.<ref>[http://www.boston.com/news/science/articles/2007/05/14/climate_talks_face_international_hurdles/ Climate talks face international hurdles], by Arthur Max, Associated press, 5/14/07.</ref> China and India, though exempt from its provisions as [[developing countries]], have ratified the Kyoto Protocol. China may have passed the U.S. in total annual greenhouse gas emissions according to some recent studies.<ref>{{cite web |url= http://www.berkeley.edu/news/media/releases/2008/03/10_chinaco2.shtml |title= New analysis finds alarming increase in expected growth of China CO2 emissions |accessdate=2008-03-10 |author=Sarah Yang, Media Relations |date=March 13, 2001|publisher= UC Berkeley }}</ref> Chinese Premier [[Wen Jiabao]] has called on the nation to redouble its efforts to tackle [[pollution]] and global warming.<ref>{{cite web|url=http://www.planetark.com/dailynewsstory.cfm/newsid/43027/story.htm|title=Wen Urges Greater China Effort to Fight Pollution, July 10, 2007, Reuters, via planetark.com|accessdate=2007-07-27}}</ref>
[[Category:Environmentalism]]
[[Category:Liberal Bias]]
[[U.S. President]] [[George W. Bush]] contends that the Kyoto Protocol is an unfair and ineffective means of addressing global climate change concerns, claiming it that it "exempts 80 percent of the world, including major population centers such as [[China]] and [[India]], from compliance, and would cause serious harm to the U.S. economy."<ref>{{cite web |url=http://www.whitehouse.gov/news/releases/2001/03/20010314.html|title=Text of a Letter from the President to Senators Hagel, Helms, Craig, and Roberts |accessdate=2007-11-21 |author=[[George W. Bush]] |date=March 13, 2001|publisher=Office of the Press Secretary}}</ref> Bush has instead promoted improved energy technology as a means to combat climate change,<ref>[http://www.whitehouse.gov/stateoftheunion/2008/index.html State of the Union Address], retrieved 2008-01-28. "The United States is committed to strengthening our energy security and confronting global climate change. And the best way to meet these goals is for America to continue leading the way toward the development of cleaner and more energy-efficient technology."</ref> while various state and city governments within the United States have begun their own initiatives to indicate support and compliance with the Kyoto Protocol on a local basis, such as the [[Regional Greenhouse Gas Initiative]].<ref>{{cite web| url=http://www.rggi.org/ |title=Regional Greenhouse Gas Initiative| accessdate=2006-11-07}}</ref> The [[U.S. Climate Change Science Program]] is a joint program of over 20 U.S. federal agencies working together to investigate climate change.
The IPCC's Working Group III is responsible for crafting reports that deal with the mitigation of global warming and analyzing the costs and benefits of different approaches. In the 2007 [[IPCC Fourth Assessment Report]], they conclude that no one technology or sector can be completely responsible for mitigating future warming. They find there are key practices and technologies in various sectors, such as [[energy supply]], [[transport]]ation, [[industry]], and [[agriculture]], that should be implemented to reduced global emissions. They estimate that stabilization of [[carbon dioxide equivalent]] between 445 and 710 ppm by 2030 will result in between a 0.6 percent increase and three percent decrease in global [[gross domestic product]].<ref>{{cite web | url= http://arch.rivm.nl/env/int/ipcc/pages_media/FAR4docs/final_pdfs_ar4/SPM.pdf | format=[[Portable Document Format|PDF]] | title=Summary for Policymakers | work=Climate Change 2007: The Physical Science Basis. Contribution of Working Group III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change | accessdate=2007-12-09 | date=[[2007-05-04]] | publisher=[[Intergovernmental Panel on Climate Change]]}}</ref>
According to Working Group III, to limit temperature rise to 2 degrees Celsius, "developed countries as a group would need to reduce their emissions to below 1990 levels in 2020 (on the order of –10 percent to 40 percent below 1990 levels for most of the considered regimes) and to still lower levels by 2050 (40 percent (Sic. 80 percent in Box 13.7, p776) to 95 percent below 1990 levels), even if developing countries make substantial reductions."<ref> {{cite web | url= http://www.ipcc.ch/pdf/assessment-report/ar4/wg3/ar4-wg3-chapter13.pdf | format=[[Portable Document Format|PDF]] | title= Policies, Instruments and Co-operative Arrangements | work=Policies, Instruments and Co-operative Arrangements. In Climate Change 2007: Mitigation. Contribution of Working Group III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change | accessdate=2008-04-26 | date=[[2007-05-04]] | publisher=[[Intergovernmental Panel on Climate Change]] | last=Guptal | first=Sujata | coauthors=''et al.'' | pages=21 | quote=..developed countries as a group would need to reduce their emissions to below 1990 levels in 2020 (on the order of –10% to 40% below 1990 levels for most of the considered regimes) and to still lower levels by 2050 (40% to 95% below 1990 levels), even if developing countries make substantial reductions.}} </ref>
==Economic and political debate==
{{main|Global warming controversy|Politics of global warming|Economics of global warming}}
{{see also|Climate change denial|List of countries by greenhouse gas emissions per capita|List of countries by carbon dioxide emissions per capita|List of countries by carbon dioxide emissions|List of countries by ratio of GDP to carbon dioxide emissions}}
{{Double image stack|right|GHG per capita 2000.svg|GHG by country 2000.svg|250|Per capita greenhouse gas emissions in 2000, including [[Land use, land-use change and forestry|land-use change]].|Per country greenhouse gas emissions in 2000, including land-use change.}}
Increased publicity of the scientific findings surrounding global warming has resulted in political and economic debate.<ref>{{Citation | first=Spencer | last=Weart | author-link=Spencer R. Weart | contribution=The Public and Climate Change | contribution-url=http://www.aip.org/history/climate/Public.htm | title=The Discovery of Global Warming | editor-first=Spencer | editor-last=Weart | editor-link=Spencer R. Weart | url=http://www.aip.org/history/climate/index.html | publisher=[[American Institute of Physics]] | year=2006 | access-date=2007-04-14 }}</ref> Poor regions, particularly [[Africa]], appear at greatest risk from the projected effects of global warming, while their emissions have been small compared to the developed world.<ref>{{cite news | title= Poor Nations to Bear Brunt as World Warms | first=Andrew | last=Revkin | date=[[2007-04-01]] | publisher=[[The New York Times]] | url= http://www.nytimes.com/2007/04/01/science/earth/01climate.html?ex=1333080000&en=6c687d64add0b7ba&ei=5088&partner=rssnyt&emc=rss| accessdate = 2007-05-02}}</ref> At the same time, [[developing country]] exemptions from provisions of the [[Kyoto Protocol]] have been criticized by the [[United States]] and [[Australia]], and used as part of a rationale for continued non-ratification by the U.S.<ref>{{cite web | title= China's emissions may surpass the US in 2007 | first=Catherine | last=Brahic | date=[[2006-04-25]] | publisher=[[New Scientist]] | url=http://environment.newscientist.com/article/dn11707-chinas-emissions-to-surpass-the-us-within-months.html | accessdate = 2007-05-02}}</ref>In the [[Western world]], the idea of human influence on climate has gained wider public acceptance in [[Europe]] than in the United States.<ref>{{cite news | title=More in Europe worry about climate than in U.S., poll shows | first=Thomas | last=Crampton | date=[[2007-01-04]] | publisher=[[International Herald Tribune]] | url=http://www.iht.com/articles/2007/01/04/news/poll.php | accessdate = 2007-04-14}}</ref><ref>{{cite web | title = Summary of Findings | work = Little Consensus on Global Warming. Partisanship Drives Opinion | publisher = [[Pew Research Center]] | date = [[2006-07-12]] | accessdate = 2007-04-14 | url = http://people-press.org/reports/display.php3?ReportID=280}}</ref>
The issue of climate change has sparked debate weighing the benefits of limiting [[industrial process|industrial]] [[Air pollution|emissions]] of [[greenhouse gas]]es against the [[Economics of global warming|costs]] that such changes would entail. There has been discussion in several countries about the cost and benefits of adopting [[Alternative energy|alternative energy sources]] in order to reduce carbon emissions.<ref>{{cite news |url= http://news.bbc.co.uk/2/hi/europe/6432829.stm |title= EU agrees on carbon dioxide cuts |date= [[2007-03-09]] |publisher= [[BBC]] |accessdate=2007-05-04}}</ref> Organizations and companies such as the [[Competitive Enterprise Institute]] and [[ExxonMobil]] have emphasized more conservative climate change scenarios while highlighting the potential economic cost of stricter controls.<ref>{{cite news |last=Begley |first=Sharon |title=The Truth About Denial|publisher=Newsweek |date=2007-08-13 |url=http://www.newsweek.com/id/32482 |accessdate=2007-08-13}}</ref><ref>{{cite web | title=Royal Society tells Exxon: stop funding climate change denial | url=http://www.guardian.co.uk/environment/2006/sep/20/oilandpetrol.business | first=David | last=Adams | publisher=[[The Guardian]] | date=[[2006-09-20]] | accessdate=2007-08-09}}</ref><ref name="MSNBC 01-12">{{cite news |title= Exxon cuts ties to global warming skeptics |url= http://www.msnbc.msn.com/id/16593606 |publisher= [[MSNBC]] |date= [[2007-01-12]] |accessdate= 2007-05-02}}</ref><ref>{{cite news |title= Report: Big Money Confusing Public on Global Warming |url= http://abcnews.go.com/Technology/Business/story?id=2767979&page=1 |last= Sandell |first= Clayton |publisher= [[American Broadcasting Company|ABC]] |date= [[2007-01-03]] |accessdate= 2007-04-27}}</ref> Likewise, various environmental lobbies and a number of public figures have launched campaigns to emphasize the potential [[Effects of global warming|risks of climate change]] and promote the implementation of stricter controls. Some fossil fuel companies have scaled back their efforts in recent years,<ref> {{cite news | url=http://www.usatoday.com/weather/climate/globalwarming/2007-05-18-greenpeace-exxon_N.htm |title= Greenpeace: Exxon still funding climate skeptics |date=[[2007-05-18]] |publisher= [[USA Today]] |accessdate=2007-07-09}}</ref> or called for policies to reduce global warming.<ref>{{cite press release|url=http://www.ceres.org/news/news_item.php?nid=56|title=Global Warming Resolutions at U.S. Oil Companies Bring Policy Commitments from Leaders, and Record High Votes at Laggards|date=April 28, 2004| publisher=Ceres|accessdate=2007-07-27}}</ref>
Another point of contention is the degree to which [[Newly industrialized country|emerging economies]] such as [[India]] and [[China]] should be expected to constrain their emissions. According to recent reports, China's [[List of countries by carbon dioxide emissions|gross national CO<sub>2</sub> emissions]] may now exceed those of the U.S.<ref>{{cite news| url=http://news.bbc.co.uk/2/hi/asia-pacific/7347638.stm|title= China now top carbon polluter| publisher= [[BBC News]] | date= [[2008-04-14]] | accessdate=2008-04-22}}</ref><ref>{{cite news| url=http://news.theage.com.au/china-is-biggest-co2-emitter-research/20080415-26an.html|title= China is biggest CO2 emitter : research| publisher= [[The Age]] | date= [[2008-04-15]] | accessdate=2008-04-22}}</ref><ref>{{cite news| url=http://www.usatoday.com/tech/science/2007-06-20-124188869_x.htm| title= Group: China tops world in CO2 emissions| publisher=[[Associated Press]] | date=[[2007-06-20]] | accessdate=2007-10-16}}</ref><ref>{{cite news| url=http://www.livemint.com/2007/06/20235536/China-surpassed-US-in-carbon-e.html| title= Group: China surpassed US in carbon emissions in 2006: Dutch report| publisher=[[Reuters]] | date=[[2007-06-20]] | accessdate=2007-10-16}}</ref> China has contended that it has less of an obligation to reduce emissions since its [[List of countries by carbon dioxide emissions per capita|per capita emissions]] are roughly one-fifth that of the United States.<ref>[http://www.newsvine.com/_news/2007/12/07/1147788-china-says-west-should-deal-with-warming China: US should take lead on climate], by Michael Casey, Associated Press, via newsvine.com 12/7/07. </ref> India, also exempt from Kyoto restrictions and another of the biggest sources of industrial emissions, has made similar assertions.<ref>[http://www.oregonlive.com/science/oregonian/index.ssf?/base/science/1184718333231440.xml&coll=7 India's glaciers give grim message on warming], by Somni Sengupta, 7/17/07, New York Times via oregonlive.com.</ref> The U.S. contends that if they must bear the cost of reducing emissions, then China should do the same.<ref> [http://news.bbc.co.uk/2/hi/science/nature/6610653.stm Chinese object to climate draft], BBC, 5/1/07; [http://www.washingtonpost.com/wp-dyn/content/article/2007/06/05/AR2007060502546_2.html?hpid=topnews In Battle for U.S. Carbon Caps, Eyes and Efforts Focus on China],by Steven Mufson, Washington Post, 6/6/07.</ref>
==Related climatic issues==
{{main|Ocean acidification|global dimming|ozone depletion}}
A variety of issues are often raised in relation to global warming. One is [[ocean acidification]]. Increased atmospheric CO<sub>2</sub> increases the amount of CO<sub>2</sub> dissolved in the oceans.<ref>{{cite web |url=http://science.hq.nasa.gov/oceans/system/carbon.html |title=The Ocean and the Carbon Cycle |accessdate=2007-03-04 |date=[[2005-06-21]] |work=[[NASA]]}}</ref>CO<sub>2</sub> dissolved in the ocean reacts with water to form [[carbonic acid]], resulting in acidification. Ocean surface [[pH]] is estimated to have decreased from 8.25 near the beginning of the industrial era to 8.14 by 2004,<ref>{{cite journal |last= Jacobson |first= Mark Z. |date= [[2005-04-02]] |title= Studying ocean acidification with conservative, stable numerical schemes for nonequilibrium air-ocean exchange and ocean equilibrium chemistry |journal= [[Journal of Geophysical Research]] |volume= 110 |issue= D7 |id= D07302 |url= http://www.stanford.edu/group/efmh/jacobson/2004JD005220.pdf |format=[[Portable Document Format|PDF]] |doi = 10.1029/2004JD005220 |accessdate=2007-04-28 |pages= D07302}}</ref>and is projected to decrease by a further 0.14 to 0.5 units by 2100 as the ocean absorbs more CO<sub>2</sub>.<ref name="grida7" /><ref>{{cite journal| last = Caldeira | first = Ken | coauthors= Wickett, Michael E. | title = Ocean model predictions of chemistry changes from carbon dioxide emissions to the atmosphere and ocean | journal = [[Journal of Geophysical Research]] |volume = 110 |issue = C09S04 | doi=10.1029/2004JC002671 | pages = 1–12 | url = http://www.agu.org/pubs/crossref/2005/2004JC002671.shtml | date = [[2005-09-21]] | accessdate = 2006-02-14}}</ref> Since organisms and ecosystems are adapted to a narrow range of pH, this raises [[extinction]] concerns, directly driven by increased atmospheric CO<sub>2</sub>, that could disrupt [[food chain#Food web|food webs]] and impact human societies that depend on marine ecosystem services.<ref>{{cite paper |author=Raven, John A.; ''et al.'' |title= Ocean acidification due to increasing atmospheric carbon dioxide |publisher= [[Royal Society]] |date= [[2005-06-30]] |url= http://www.royalsoc.ac.uk/displaypagedoc.asp?id=13314 |format= [[Active Server Pages|ASP]] |accessdate= 2007-05-04}}</ref>
[[Global dimming]], the gradual reduction in the amount of global direct [[irradiance]] at the Earth's surface, may have partially mitigated global warming in the late 20th century. From 1960 to 1990 human-caused aerosols likely precipitated this effect. Scientists have stated with 66–90% confidence that the effects of human-caused aerosols, along with volcanic activity, have offset some of the global warming, and that greenhouse gases would have resulted in more warming than observed if not for these dimming agents.<ref name="grida7" />
[[Ozone depletion]], the steady decline in the total amount of [[ozone]] in Earth's [[stratosphere]], is frequently cited in relation to global warming. Although there are [[Ozone depletion#Ozone depletion and global warming|areas of linkage]], the relationship between the two is not strong.
==See also==
<!-- Add new links to the glossary above, if they are not already there. -->
* [[Glossary of climate change]]
* [[List of climate change topics]]
==Notes and references==
{{reflist|colwidth=25em}}
==Further reading==
{{Wikinewscat|Climate change}}
{{Wikibooks|Climate Change}}
{{wikiversity|Topic:Climate change}}
{{Portal|Environment}}
{{EnergyPortal}}
{{refbegin}}
* {{cite book
| title = Financial Risks of Climate Change
| author = Association of British Insurers
| year= 2005-06
| url=http://www.abi.org.uk/Display/File/Child/552/Financial_Risks_of_Climate_Change.pdf
| format = [[Portable Document Format|PDF]]
}}
* {{cite journal
| last = Barnett | first = Tim P.
| coauthors = J. C. Adam, D. P. Lettenmaier
| date = [[2005-11-17]]
| title = Potential impacts of a warming climate on water availability in snow-dominated regions
| journal = [[Nature (journal)|Nature]]
| volume = 438 | issue = 7066 | pages = 303–309
| url = http://www.nature.com/nature/journal/v438/n7066/abs/nature04141.html
| doi = 10.1038/nature04141
| format = abstract
}}
* {{cite journal
| last= Behrenfeld | first= Michael J.
| coauthors = Robert T. O'Malley, David A. Siegel, Charles R. McClain, Jorge L. Sarmiento, Gene C. Feldman, Allen G. Milligan, Paul G. Falkowski, Ricardo M. Letelier, Emanuel S. Boss
| date = [[2006-12-07]]
| title = Climate-driven trends in contemporary ocean productivity
| journal = [[Nature (journal)|Nature]]
| volume = 444 | issue = 7120 | pages = 752–755
| url=http://www.icess.ucsb.edu/~davey/MyPapers/Behrenfeld_etal_2006_Nature.pdf
| format = [[Portable Document Format|PDF]]
| doi=10.1038/nature05317
}}
* {{cite journal
| first = Onelack | last= Choi
| coauthors = Ann Fisher
| month = May | year = 2005
| title = The Impacts of Socioeconomic Development and Climate Change on Severe Weather Catastrophe Losses: Mid-Atlantic Region (MAR) and the U.S.
| journal = Climate Change
| volume = 58 | issue = 1–2 | pages = 149–170
| doi = 10.1023/A:1023459216609
| url = http://www.springerlink.com/content/m6308777613702q0/
}}
* {{cite book
| last = Dyurgerov | first = Mark B.
| coauthors = Mark F. Meier
| year = 2005
| title = Glaciers and the Changing Earth System: a 2004 Snapshot
| publisher = Institute of Arctic and Alpine Research Occasional Paper #58
| url = http://instaar.colorado.edu/other/download/OP58_dyurgerov_meier.pdf
| format = [[Portable Document Format|PDF]]
| id = {{ISSN|0069-6145}}
}}
* {{cite journal
| last=Emanuel | first=Kerry A.
| authorlink=Kerry Emanuel
| date= [[2005-08-04]]
| title=Increasing destructiveness of tropical cyclones over the past 30 years.
| journal= [[Nature (journal)|Nature]]
| volume=436 | issue=7051 | pages=686–688
| url=ftp://texmex.mit.edu/pub/emanuel/PAPERS/NATURE03906.pdf
| format = [[Portable Document Format|PDF]]
| doi=10.1038/nature03906
}}
* {{cite journal
| last=Hansen | first=James
| authorlink=James Hansen
| coauthors=Larissa Nazarenko, Reto Ruedy, Makiko Sato, Josh Willis, Anthony Del Genio, Dorothy Koch, Andrew Lacis, Ken Lo, Surabi Menon, Tica Novakov, Judith Perlwitz, Gary Russell, [[Gavin A. Schmidt]], Nicholas Tausnev
| date= [[2005-06-03]]
| title=Earth's Energy Imbalance: Confirmation and Implications
| journal=[[Science (journal)|Science]]
| volume=308 | issue=5727 | pages=1431–1435
| url=http://pangea.stanford.edu/research/Oceans/GES205/Hansen_Science_Earth's%20Energy%20Balance.pdf
| format = [[Portable Document Format|PDF]]
| doi=10.1126/science.1110252
| pmid=15860591
}}
* {{cite journal
| last= Hinrichs | first= Kai-Uwe
| coauthors=Laura R. Hmelo, Sean P. Sylva
| date=[[2003-02-21]]
| title = Molecular Fossil Record of Elevated Methane Levels in Late Pleistocene Coastal Waters
| journal = [[Science (journal)|Science]]
| volume = 299
| issue = 5610
| pages = 1214–1217
| doi= 10.1126/science.1079601
| pmid = 12595688
}}
* {{cite news
| last=Hirsch | first=Tim
| publisher=[[BBC]]
| url=http://news.bbc.co.uk/2/hi/science/nature/4604332.stm
| title=Plants revealed as methane source
| date=[[2006-01-11]]
}}
* {{cite journal
| last = Hoyt | first = Douglas V.
| coauthors = Kenneth H. Schatten
| year = 1993–11
| title = A discussion of plausible solar irradiance variations, 1700–1992
| journal = [[Journal of Geophysical Research]]
| volume = 98 | issue = A11 | pages = 18,895–18,906
| url = http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1993JGR....9818895H&db_key=AST&data_type=HTML&format=&high=448f267ff303582
}}
* {{cite journal
| author = A. V. Karnaukhov
| year = 2001
| title = Role of the Biosphere in the Formation of the Earth’s Climate: The Greenhouse Catastrophe
| journal = Biophysics
| volume = 46 | issue = 6
| url = http://avturchin.narod.ru/Green.pdf
| format = [[Portable Document Format|PDF]]
}}
* {{cite book
| last = Kenneth | first = James P.
| coauthors = Kevin G. Cannariato, Ingrid L. Hendy, Richard J. Behl
| year = [[2003-02-14]]
| title = Methane Hydrates in Quaternary Climate Change: The Clathrate Gun Hypothesis
| publisher = [[American Geophysical Union]]
| url = https://www.agu.org/cgi-bin/agubooks?book=ASSP0542960
}}
* {{cite news
| last = Keppler | first = Frank
| coauthors = Marc Brass, Jack Hamilton, Thomas Röckmann
| title = Global Warming - The Blame Is not with the Plants
| url = http://www.mpg.de/english/illustrationsDocumentation/documentation/pressReleases/2006/pressRelease200601131/index.html
| publisher = [[Max Planck Society]]
| date = [[2006-01-18]]
}}
* {{cite journal
| title = The effect of increasing solar activity on the Sun's total and open magnetic flux during multiple cycles: Implications for solar forcing of climate
| last = Lean | first = Judith L.
| coauthors = Y.M. Wang, N.R. Sheeley
| year = 2002–12
| journal = [[Geophysical Research Letters]]
| volume = 29 | issue = 24
| url = http://adsabs.harvard.edu/abs/2002GeoRL..29x..77L
| doi = 10.1029/2002GL015880
| pages = 2224
| format = abstract
}}
* {{cite book
| last = Lerner | first = K. Lee
| coauthors = Brenda Wilmoth Lerner
| title = Environmental issues : essential primary sources.
| publisher = [[Thomson Gale]]
| date = [[2006-07-26]]
| isbn = 1414406258
}}
* {{cite journal
| last = McLaughlin | first = Joseph B.
| coauthors = Angelo DePaola, Cheryl A. Bopp, Karen A. Martinek, Nancy P. Napolilli, Christine G. Allison, Shelley L. Murray, Eric C. Thompson, Michele M. Bird, John P. Middaugh
| title = Outbreak of Vibrio parahaemolyticus gastroenteritis associated with Alaskan oysters
| journal = [[New England Journal of Medicine]]
| volume = 353 | issue = 14 | pages = 1463–1470
| publisher = New England Medical Society
| date = [[2005-10-06]]
| url = http://content.nejm.org/cgi/content/abstract/353/14/1463
| doi = 10.1056/NEJMoa051594
| format = abstract
| pmid = 16207848
}}''(online version requires registration)''
* {{cite journal
| last = Muscheler, Raimund
| coauthors = Fortunat Joos, Simon A. Müller, Ian Snowball
| date = [[2005-07-28]]
| title = Climate: How unusual is today's solar activity?
| journal = [[Nature (journal)|Nature]]
| volume = 436 | issue = 7012 | pages = 1084–1087
| url = http://www.cgd.ucar.edu/ccr/raimund/publications/Muscheler_et_al_Nature2005.pdf
| format = [[Portable Document Format|PDF]]
| doi = 10.1038/nature04045
}}
* {{cite journal
| last = Oerlemans | first = J.
| date = [[2005-04-29]]
| title = Extracting a Climate Signal from 169 Glacier Records
| journal = [[Science (journal)|Science]]
| volume = 308 | issue = 5722 | pages = 675–677
| url=http://www.cosis.net/abstracts/EGU05/04572/EGU05-J-04572.pdf
| format = [[Portable Document Format|PDF]]
| doi = 10.1126/science.1107046
| pmid = 15746388
}}
* {{cite journal
| last = Oreskes | first = Naomi
| authorlink=Naomi Oreskes
| date = [[2004-12-03]]
| title = Beyond the Ivory Tower: The Scientific Consensus on Climate Change
| journal = [[Science (journal)|Science]]
| volume = 306 | issue = 5702 | pages = 1686
| url = http://www.sciencemag.org/cgi/reprint/306/5702/1686.pdf
| format = [[Portable Document Format|PDF]]
| doi = 10.1126/science.1103618
}}
* {{cite journal
| last = Purse | first = Bethan V.
| coauthors = Philip S. Mellor, David J. Rogers, Alan R. Samuel, Peter P. C. Mertens, Matthew Baylis
| title = Climate change and the recent emergence of bluetongue in Europe
| journal = [[Nature Reviews Microbiology]]
| volume = 3 | issue = 2 | pages = 171–181
| month = February | year = 2005
| doi = 10.1038/nrmicro1090
| url=http://www.nature.com/nrmicro/journal/v3/n2/abs/nrmicro1090_fs.html
| format = abstract
}}
* {{cite news
| last = Revkin | first = Andrew C
| date = [[2005-11-05]]
| title = Rise in Gases Unmatched by a History in Ancient Ice
| publisher = [[The New York Times]]
| url = http://www.nytimes.com/2005/11/25/science/earth/25core.html?ei=5090&en=d5078e33050b2b0c&ex=1290574800&adxnnl=1&partner=rssuserland&emc=rss
}}
* {{cite book
| last = Ruddiman | first = William F.
| authorlink=William Ruddiman
| date = [[2005-12-15]]
| title = Earth's Climate Past and Future
| location = New York
| publisher = [[Princeton University Press]]
| isbn = 0-7167-3741-8
| url = http://www.whfreeman.com/ruddiman/
}}
* {{cite book
| last = Ruddiman | first = William F.
| authorlink=William Ruddiman
| date = [[2005-08-01]]
| title = Plows, Plagues, and Petroleum: How Humans Took Control of Climate
| location = New Jersey
| publisher = [[Princeton University Press]]
| isbn = 0-691-12164-8
}}
* {{cite journal
| last = Solanki | first = Sami K.
| authorlink=Sami Solanki
| coauthors = I.G. Usoskin, B. Kromer, M. Schussler, J. Beer
| date = [[2004-10-23]]
| title = Unusual activity of the Sun during recent decades compared to the previous 11,000 years.
| journal = [[Nature (journal)|Nature]]
| volume = 431 | pages = 1084–1087
| url = http://cc.oulu.fi/%7Eusoskin/personal/nature02995.pdf
| format = [[Portable Document Format|PDF]]
| doi = 10.1038/nature02995
}}
* {{cite journal
| last = Solanki | first = Sami K.
| authorlink=Sami Solanki
| coauthors = I. G. Usoskin, B. Kromer, M. Schüssler, J. Beer
| date = [[2005-07-28]]
| title = Climate: How unusual is today's solar activity? (Reply)
| journal = [[Nature (journal)|Nature]]
| volume = 436
| pages = E4–E5
| url = http://cc.oulu.fi/%7Eusoskin/personal/sola_nature05.pdf
| format = [[Portable Document Format|PDF]]
| doi = 10.1038/nature04046
}}
* {{cite journal
| last = Sowers | first = Todd
| date = [[2006-02-10]]
| journal = Science
| volume = 311 | issue = 5762 | pages = 838–840
| title = Late Quaternary Atmospheric CH<sub>4</sub> Isotope Record Suggests Marine Clathrates Are Stable
| doi = 10.1126/science.1121235
| pmid = 16469923
}}
* {{cite journal
| last = Svensmark | first = Henrik
| authorlink=Henrik Svensmark
| coauthors = Jens Olaf P. Pedersen, Nigel D. Marsh, Martin B. Enghoff, Ulrik I. Uuggerhøj
| year = [[2007-02-08]]
| title = Experimental evidence for the role of ions in particle nucleation under atmospheric conditions
| journal = [[Proceedings of the Royal Society]] A
| volume = 463 | issue = 2078 | pages = 385–396
| publisher = FirstCite Early Online Publishing
| doi = 10.1098/rspa.2006.1773
}}''(online version requires registration)''
* {{cite journal
| last = Walter | first = K. M.
| coauthors = S. A. Zimov, Jeff P. Chanton, D. Verbyla, [[F. Stuart Chapin III|F. S. Chapin]]
| date = [[2006-09-07]]
| title = Methane bubbling from Siberian thaw lakes as a positive feedback to climate warming
| journal = [[Nature (journal)|Nature]]
| volume = 443 | issue = 7107 | pages = 71–75
| doi = 10.1038/nature05040
}}
* {{cite journal
| last = Wang | first = Y.-M.
| coauthors = J.L. Lean, N.R. Sheeley
| date = [[2005-05-20]]
| title = Modeling the sun's magnetic field and irradiance since 1713
| journal = [[Astrophysical Journal]]
| volume = 625 | pages = 522–538
| url = http://climatesci.colorado.edu/publications/pdf/Wang_2005.pdf
| format = [[Portable Document Format|PDF]]
| doi = 10.1086/429689
}}
{{refend}}
==External links==
{{refbegin}}
; Scientific
* [http://www.ipcc.ch Intergovernmental Panel on Climate Change] and [http://www.planetark.com/dailynewsstory.cfm/newsid/44456/story.htm UN Climate Panel Report's Key Findings].
* [http://www.nature.com/climate/index.html Nature Reports Climate Change]
* [http://www.metoffice.gov.uk/research/hadleycentre/index.html The UK Met Office Hadley Centre site]
* [http://www.ncdc.noaa.gov/oa/climate/globalwarming.html#INTRO NOAA's Global Warming FAQ]
* [http://www.aip.org/history/climate Discovery of Global Warming] – An extensive introduction to the topic and the history of its discovery, written by [[Spencer R. Weart]]
* [http://news.bbc.co.uk/1/hi/world/6460635.stm Caution urged on climate 'risks']
* [http://www.virtualcentre.org/en/library/key_pub/longshad/A0701E00.htm Impact of Livestock on Global Warming (UN Report)]
; Educational
* [http://climate.jpl.nasa.gov/ Global Climate Change: NASA's Eyes on the Earth] - Climate change overviews, key indicators, multimedia and current news.
* [http://green.nationalgeographic.com/environment/global-warming/gw-overview.html What Is Global Warming?] – Shockwave presentation from [[National Geographic]]
* [http://edgcm.columbia.edu/ The EdGCM (Educational Global Climate Modelling) Project] – A free research-quality simulation for students, educators, and scientists alike, with a user-friendly interface that runs on desktop computers
* [http://discover.itsc.uah.edu/ DISCOVER] Satellite-based ocean and climate data since 1979 from [[NASA]]
* [http://www.pewclimate.org/ The Pew Center on global climate change]
* [http://www.globalwarmingart.com/ Global Warming Art]
* [http://osulibrary.oregonstate.edu/specialcollections/events/2007paulingconference/video-s3-4-washington.html Video] of a talk by [[Warren Washington]] titled "The Evolution of Global Warming Science: From Ideas to Scientific Facts"
* [http://demonstrations.wolfram.com/BestEffortGlobalWarmingTrajectories/ Best Effort Global Warming Trajectories] by Harvey Lam (Princeton University), [[The Wolfram Demonstrations Project]].
; Other
* [http://www.istl.org/01-fall/internet.html Science and Technology Sources on the Internet] – Extensive commented list of Internet resources
* [http://www.ucsusa.org/global_warming/ Union of Concerned Scientists Global Warming page]
* [http://www.abc.net.au/catalyst/stories/s1647466.htm Watch and read 'Tipping Point'], Australian science documentary about effects of global warming on rare, common, and endangered wildlife
* [http://www.un.org/climatechange Gateway to the UN System's Work on Climate Change]
{{refend}}
{{Global warming|state=expanded}}
[[Category:Global warming| ]]
[[Category:Carbon finance]]
[[Category:Climate change feedbacks and causes]]
[[Category:Economic problems]]
[[Category:History of climate]]
[[Category:Climate change]]
[[Category:Anthropocene]]
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[[bs:Globalno zatopljenje]]
[[bg:Глобално затопляне]]
[[ca:Escalfament global]]
[[ceb:Kalibotanong pagpanginit]]
[[cs:Globální oteplování]]
[[cy:Newid hinsawdd]]
[[da:Global opvarmning]]
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[[et:Globaalne soojenemine]]
[[el:Παγκόσμια θέρμανση]]
[[es:Calentamiento global]]
[[eo:Tutmonda varmiĝo]]
[[eu:Berotze globala]]
[[fa:گرمایش زمین]]
[[fr:Réchauffement climatique]]
[[fur:Riscjaldament globâl]]
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[[gl:Quentamento global]]
[[zh-classical:全球暖化]]
[[ko:지구 온난화]]
[[hy:Գլոբալ տաքացում]]
[[hi:भूमंडलीय ऊष्मीकरण]]
[[hr:Globalno zatopljenje]]
[[id:Pemanasan global]]
[[is:Heimshlýnun]]
[[it:Riscaldamento globale]]
[[he:התחממות עולמית]]
[[jv:Pamanasan global]]
[[ka:გლობალური დათბობა]]
[[lv:Globālā sasilšana]]
[[lt:Visuotinis atšilimas]]
[[hu:Globális felmelegedés]]
[[mk:Глобално затоплување]]
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[[mr:जागतिक तापमानवाढ]]
[[mn:Дэлхийн дулаарал]]
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[[ja:地球温暖化]]
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[[ru:Глобальное потепление]]
[[si:පෘථිවිය උණුසුම් වීම]]
[[simple:Global warming]]
[[sk:Globálne otepľovanie]]
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[[sv:Global uppvärmning]]
[[ta:புவி சூடாதல்]]
[[th:ปรากฏการณ์โลกร้อน]]
[[vi:Sự nóng lên của khí hậu toàn cầu]]
[[tr:Küresel ısınma]]
[[uk:Глобальне потепління]]
[[wuu:全球暖化]]
[[yi:גלאבאלע אנווארימונג]]
[[zh-yue:全球變暖]]
[[bat-smg:Gluobalėnis atšėlėms]]
[[zh:全球变暖]]