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#REDIRECT ]
This article is about the '''physical impacts of ]'''. For some of these physical impacts, their effect on social and economic systems are also described.


{{Rcat shell|
==Definition of climate change==
{{R to section}}

}}
This article refers to reports produced by the IPCC. In their usage, "climate change" refers to a change in the state of the climate that can be identified by changes in the mean and/or variability of its properties, and that persists for extended periods, typically decades or longer (IPCC, 2007d:30).<ref name=ar4syn/> The climate change referred to may be due to natural causes or the result of human activity.

==Effects on weather==

Increasing temperature is likely to lead to increasing precipitation<ref name="ar4wg1a">{{cite web |publisher=] |author=Houghton, J.T.,Y. Ding, D.J. Griggs, M. Noguer, P.J. van der Linden, X. Dai, K.Maskell, and C.A. Johnson |title=Climate Change 2001: The Scientific Basis. Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Change. Human influences will continue to change atmospheric composition throughout the 21st century. |url=http://www.grida.no/climate/ipcc_tar/wg1/008.htm |accessdate=2007-12-03 |year=2001}}</ref><ref>{{cite web |publisher=] |editor=Houghton, J.T.,Y. Ding, D.J. Griggs, M. Noguer, P.J. van der Linden, X. Dai, K.Maskell, and C.A. Johnson |title=Climate Change 2001: The Scientific Basis. Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Change. Precipitation and Convection. |author=U. Cubasch, G.A. Meehl, et al. |url=http://www.grida.no/climate/ipcc_tar/wg1/365.htm |accessdate=2007-12-03 |year=2001}}</ref> but the effects on storms are less clear. Extratropical storms partly depend on the ], which is predicted to weaken in the northern hemisphere as the polar region warms more than the rest of the hemisphere.<ref>{{cite web |publisher=] |editor=Houghton, J.T.,Y. Ding, D.J. Griggs, M. Noguer, P.J. van der Linden, X. Dai, K.Maskell, and C.A. Johnson |title=Climate Change 2001: The Scientific Basis. Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Change. Extra-tropical storms. |author=U. Cubasch, G.A. Meehl, et al. |url=http://www.grida.no/climate/ipcc_tar/wg1/366.htm |accessdate=2007-12-03 |year=2001}}</ref>

==Extreme events==
===Fire===

Fire is a major agent for conversion of biomass and soil organic matter to CO<sub>2</sub> (Denman ''et al''., 2007:527).<ref>{{cite web
|year=2007
|title= Couplings Between Changes in the Climate System and Biogeochemistry. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change
|publisher=Cambridge University Press, Cambridge, U.K., and New York, N.Y., U.S.A.
|author=Denman, K.L. ''et al''.
|url=http://www.ipcc.ch/publications_and_data/publications_and_data_reports.htm
|accessdate=2010-01-10}}</ref> There is a large potential for future alteration in the terrestrial carbon balance through altered fire regimes. With high confidence, Schneider ''et al''. (2007:789) predicted that:<ref name=schneider>{{cite web
|year=2007
|title=Assessing key vulnerabilities and the risk from climate change. In: Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change
|publisher=Cambridge University Press, Cambridge, U.K., and New York, N.Y., U.S.A.
|author=Schneider, S.H., ''et al''.
|pages=779–810
|url= http://www.ipcc.ch/publications_and_data/publications_and_data_reports.htm
|accessdate=2009-05-20}}</ref>
*An increase in global mean temperature of about 0 to 2 °C by 2100 relative to the 1990-2000 period would result in increased fire frequency and intensity in many areas.
*An increase in the region of 2 °C or above would lead to increased frequency and intensity of fires.

===Weather===

{{See also|Extreme weather|Tropical cyclone#Global warming|List of Atlantic hurricane records}}

IPCC (2007a:8) predicted that in the future, over most land areas, the frequency of warm spells or ]s would very likely increase.<ref name=ar4wg1>{{cite web
|date=2007a
|title=Summary for Policymakers. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change
|publisher=Cambridge University Press, Cambridge, U.K., and New York, N.Y., U.S.A.
|author=IPCC
|url=http://www.ipcc.ch/publications_and_data/publications_and_data_reports.htm
|accessdate=2009-05-20}}</ref> Other likely changes are listed below:

*Increased areas will be affected by ]{{cn|date=November 2011}}
*There will be increased intense ] activity{{cn|date=November 2011}}
*There will be increased incidences of extreme high sea level (excluding ]s){{cn|date=November 2011}}

Storm strength leading to extreme weather is increasing, such as the power dissipation index of hurricane intensity.<ref>{{cite web |url=http://www.realclimate.org/index.php?p=181 |title=Hurricanes and Global Warming - Is There a Connection? |publisher=Real Climate |accessdate=2007-12-03 |author=Stefan Rahmstorf, Michael Mann, Rasmus Benestad, Gavin Schmidt, and William Connolley}}</ref> ] writes that hurricane power dissipation is highly correlated with temperature, reflecting ].<ref>{{cite journal |url=ftp://texmex.mit.edu/pub/emanuel/PAPERS/NATURE03906.pdf |title=Increasing destructiveness of tropical cyclones over the past 30 years |last=Emanuel |first=Kerry |journal=] |year=2005 |volume=436 |pmid=16056221 |issue=7051 |pages=686–8 |doi=10.1038/nature03906 |format=PDF |bibcode=2005Natur.436..686E}}</ref> However, a further study by Emanuel using current model output concluded that the increase in power dissipation in recent decades cannot be completely attributed to global warming.<ref>{{cite journal |url=ftp://texmex.mit.edu/pub/emanuel/PAPERS/Emanuel_etal_2008.pdf |title=Hurricanes and global warming: Results from downscaling IPCC AR4 simulations |last=Emanuel |first=Kerry |journal=] |year=2008 |volume=89 |pages=347–367 |doi=10.1175/BAMS-89-3-347 |format=PDF |first2=Ragoth |first3=John |last2=Sundararajan |last3=Williams|bibcode = 2008BAMS...89..347E |issue=3 }}</ref> Hurricane modeling has produced similar results, finding that hurricanes, simulated under warmer, high-CO<sub>2</sub> conditions, are more intense, however, hurricane frequency will be reduced.<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=359–64 |first2=Joseph J. |first3=Stephen T. |first4=Gabriel A. |first5=Isaac M. |last2=Sirutis |last3=Garner |last4=Vecchi |last5=Held |issue=6 |bibcode=2008NatGe...1..359K}}</ref> Worldwide, the proportion of ]s reaching ] – with wind speeds above 56 metres per second – has risen from 20% in the 1970s to 35% in the 1990s.<ref>{{cite news |url=http://www.newscientist.com/article.ns?id=dn8002 |title=Warming world blamed for more strong hurricanes |first=Fred |last=Pearce |publisher=] |date=2005-09-15 |accessdate=2007-12-03}}</ref> Precipitation hitting the US from hurricanes has increased by 7% over the 20th century.<ref>{{cite news |url=http://www.newscientist.com/channel/earth/climate-change/mg18625054.800 |title=Global warming will bring fiercer hurricanes |publisher=New Scientist Environment |date=2005-06-25 |accessdate=2007-12-03}}</ref><ref>{{cite news |url=http://www.noaanews.noaa.gov/stories2006/s2622.htm |title=Area Where Hurricanes Develop is Warmer, Say NOAA Scientists |publisher=] News Online |date=2006-05-01 |accessdate=2007-12-03}}</ref><ref>{{cite news |url=http://www.time.com/time/magazine/article/0,9171,1109337,00.html |title=Global Warming: The Culprit? |last=Kluger |first=Jeffrey |publisher=] |date=2005-09-26 |accessdate=2007-12-03}}</ref> The extent to which this is due to global warming as opposed to the ] is unclear. Some studies have found that the increase in ] may be offset by an increase in ], leading to little or no change in hurricane activity.<ref>{{cite web |url=http://www.livescience.com/environment/070417_wind_shear.html |title=Study: Global Warming Could Hinder Hurricanes |author=Thompson, Andrea |publisher=LiveScience |date=2007-04-17 |accessdate=2007-12-06}}</ref> Hoyos ''et al.'' (2006) have linked the increasing trend in number of category 4 and 5 hurricanes for the period 1970–2004 directly to the trend in sea surface temperatures.<ref name="Hoyos2006">{{cite journal |last=Hoyos |first=Carlos D. |year=2006 |title=Deconvolution of the Factors Contributing to the Increase in Global Hurricane Intensity |journal=Science |volume=312 |issue=5770 |pages=94–7 |doi=10.1126/science.1123560 |pmid=16543416 |first2=PA |first3=PJ |first4=JA |last2=Agudelo |last3=Webster |last4=Curry |bibcode = 2006Sci...312...94H }}</ref>

Increases in catastrophes resulting from extreme weather are mainly caused by increasing population densities, and anticipated future increases are similarly dominated by societal change rather than climate change.<ref name="Pielke2008">{{ cite journal |last=Pielke |first=Roger A., Jr. |coauthors=''et al.'' |year=2008 |title=Normalized Hurricane Damage in the United States: 1900–2005 |journal=Natural Hazards Review |volume=9 |issue=1 |pages=29–42 |doi=10.1061/(ASCE)1527-6988(2008)9:1(29) |url=http://forecast.mssl.ucl.ac.uk/shadow/docs/Pielkeetal2006a.pdf |format=PDF}}</ref> The ] explains that “though there is evidence both for and against the existence of a detectable anthropogenic signal in the tropical cyclone climate record to date, no firm conclusion can be made on this point.”<ref name="WMO-IWTC">{{cite press release |title=Summary Statement on Tropical Cyclones and Climate Change |publisher=World Meteorological Organization |date=2006-12-04 |url=http://www.wmo.int/pages/prog/arep/press_releases/2006/pdf/iwtc_summary.pdf |format=PDF }}</ref> They also clarified that “no individual tropical cyclone can be directly attributed to climate change.”<ref name="WMO-IWTC" />

] and Robert E. Tuleya of ] stated in 2004 that warming induced by ] may lead to increasing occurrence of highly destructive category-5 storms.<ref>{{cite journal |author=Knutson, Thomas R. and Robert E. Tuleya |title=Impact of CO<sub>2</sub>-Induced Warming on Simulated Hurricane Intensity and Precipitation:Sensitivity to the Choice of Climate Model and Convective Parameterization |journal=Journal of Climate |volume=17 |issue=18 |year=2004 |pages=3477–94 |url=http://www.gfdl.noaa.gov/reference/bibliography/2004/tk0401.pdf |doi=10.1175/1520-0442(2004)017<3477:IOCWOS>2.0.CO;2 |format=PDF |bibcode=2004JCli...17.3477K}}</ref> In 2008, Knutson ''et al.'' found that Atlantic hurricane and tropical storm frequencies could reduce under future greenhouse-gas-induced warming.<ref name="Knutson2008">{{cite journal |last=Knutson |first=Thomas |coauthors=''et al.'' |year=2008 |title=Simulated reduction in Atlantic hurricane frequency under twenty-first-century warming conditions |journal=] |volume=1 |issue=6 |pages=359–364 |doi=10.1038/ngeo202 |bibcode=2008NatGe...1..359K}}</ref> Vecchi and Soden find that ], the increase of which acts to inhibit ]s, also changes in model-projections of global warming. There are projected increases of ] in the tropical Atlantic and East Pacific associated with the deceleration of the ], as well as decreases of wind shear in the western and central Pacific.<ref>{{cite web |url=http://www.gfdl.noaa.gov/~gav/ipcc_shears.html |title=IPCC Projections and Hurricanes |publisher=Geophysical Fluids Dynamic Laboratory |accessdate=2007-12-06 |author=Brian Soden and Gabriel Vecchi}}</ref> The study does not make claims about the net effect on Atlantic and East Pacific hurricanes of the warming and moistening atmospheres, and the model-projected increases in Atlantic wind shear.<ref>{{cite journal |last=Vecchi |first=Gabriel A. |coauthors=Brian J. Soden |date=2007-04-18 |title=Increased tropical Atlantic wind shear in model projections of global warming |journal=] |volume=34 |issue=L08702 |pages=1–5 |doi=10.1029/2006GL028905 |url=http://www.gfdl.noaa.gov/reference/bibliography/2007/gav0701.pdf |format=PDF |accessdate=2007-04-21 |bibcode=2007GeoRL..3408702V}}</ref>

A substantially higher risk of extreme weather does not necessarily mean a noticeably greater risk of slightly-above-average weather.<ref>{{cite web |url=http://www.climateprediction.net/science/pubs/ccs_allen.pdf |author=Myles Allen |authorlink=Myles Allen |publisher=climateprediction.net |accessdate=2007-11-30 |title=The Spectre of Liability |format=PDF}}</ref> However, the evidence is clear that severe weather and moderate rainfall are also increasing. Increases in temperature are expected to produce more intense convection over land and a higher frequency of the most severe storms.<ref>{{cite journal |last=Del Genio |first=Tony |coauthors=''et al.'' |title=Will moist convection be stronger in a warmer climate? |journal=Geophysical Research Letters |volume=34 |doi=10.1029/2007GL030525 |year=2007 |pages=L16703 |bibcode=2007GeoRL..3416703D |issue=16}}</ref>

====Increased evaporation====

]

Over the course of the 20th century, evaporation rates have reduced worldwide;<ref>{{cite journal |url=http://www.nature.com/nature/journal/v377/n6551/abs/377687b0.html |title=Evaporation losing its strength |first=T. C. |last=Peterson |coauthors=V. S. Golubev, P. Ya. Groisman |journal=Nature |date=October 26, 2002 |volume=377 |pages=687–8 |doi=10.1038/377687b0 |format=abstract |issue=6551|bibcode = 1995Natur.377..687P }}</ref> this is thought by many to be explained by ]. As the climate grows warmer and the causes of global dimming are reduced, ] will increase due to warmer oceans. Because the world is a closed system this will cause heavier ], with more ]. This erosion, in turn, can in vulnerable tropical areas (especially in Africa) lead to ]. On the other hand, in other areas, increased rainfall lead to growth of forests in dry desert areas.

Scientists have found evidence that increased evaporation could result in more extreme ] as global warming progresses. The IPCC Third Annual Report says: "...global average water vapor concentration and precipitation are projected to increase during the 21st century. By the second half of the 21st century, it is likely that precipitation will have increased over northern mid- to high latitudes and ] in winter. At low latitudes there are both regional increases and decreases over land areas. Larger year to year variations in precipitation are very likely over most areas where an increase in mean precipitation is projected."<ref name="ar4wg1a" /><ref>{{cite web |publisher=] |editor=Houghton, J.T.,Y. Ding, D.J. Griggs, M. Noguer, P.J. van der Linden, X. Dai, K.Maskell, and C.A. Johnson |title=Climate Change 2001: The Scientific Basis. Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Change. Precipitation and Convection. |author=U. Cubasch, G.A. Meehl, et al. |url=http://www.grida.no/climate/ipcc_tar/wg1/364.htm |accessdate=2007-12-03 |year=2001}}</ref>

====Increased freshwater flow====
Research based on satellite observations, published in October, 2010, shows an increase in the flow of freshwater into the world's oceans, partly from melting ice and partly from increased precipitation driven by an increase in global ocean evaporation. The increase in global freshwater flow, based on data from 1994 to 2006, was about 18%. Much of the increase is in areas which already experience high rainfall. One effect, as perhaps experienced in the ], is to overwhelm flood control infrastructure.<ref> blog by Sandra L. Postel,
National Geographic Freshwater Fellow, based on research report by Tajdarul H. Syeda, et al, Published online before print October 4, 2010, doi: 10.1073/pnas.1003292107 ''Proceedings of the National Academy of Sciences'', posted on NatGeo NewsWatch October 8, 2010, "There is nearly 20 percent more freshwater flowing into the world's oceans than there was 10 years ago--a sign of climate change and a harbinger of more flooding.", accessed October 9, 2010</ref>

====Cost of more extreme weather====

{{See also|List of costliest Atlantic hurricanes}}

As the ] explains, “recent increase in societal impact from tropical cyclones has largely been caused by rising concentrations of population and infrastructure in coastal regions.”<ref name="WMO-IWTC" /> Pielke ''et al.'' (2008) normalized mainland U.S. hurricane damage from 1900–2005 to 2005 values and found no remaining trend of increasing absolute damage. The 1970s and 1980s were notable because of the extremely low amounts of damage compared to other decades. The decade 1996–2005 has the second most damage among the past 11 decades, with only the decade 1926–1935 surpassing its costs. The most damaging single storm is the ], with $157 billion of normalized damage.<ref name="Pielke2008" />

The American ''Insurance Journal'' predicted that “catastrophe losses should be expected to double roughly every 10 years because of increases in construction costs, increases in the number of structures and changes in their characteristics.”<ref>Insurance Journal: , April 18, 2006.</ref> The Association of British Insurers has stated that limiting carbon emissions would avoid 80% of the projected additional annual cost of tropical cyclones by the 2080s. The cost is also increasing partly because of building in exposed areas such as coasts and floodplains. The ABI claims that reduction of the vulnerability to some inevitable effects of climate change, for example through more resilient buildings and improved flood defences, could also result in considerable cost-savings in the longterm.<ref>{{cite web |url=http://www.abi.org.uk/Display/File/Child/552/Financial_Risks_of_Climate_Change.pdf |title=Financial risks of climate change |publisher=Association of British Insurers |month=June |year=2005 |format=PDF}}</ref>

==Regional climate change==

{{Main|Regional effects of global warming}}

===General effects===

In a literature assessment, Hegerl ''et al.'' (2007) assessed evidence for ] observed climate change. They concluded that since the middle of the 20th century, it was likely that human influences had significantly contributed to surface temperature increases in every continent except Antarctica.<ref>{{cite book
|year=2007
|author=Hegerl, G.C. ''et al.''
|title=Executive Summary. In (book chapter): Chapter 9: Understanding and Attributing Climate Change. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (Solomon, S. ''et al.'' (eds.))
|url=http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch9s9-es.html
|publisher=Print version: Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. This version: IPCC website
|isbn=9780521705967
|accessdate=2010-05-20}}</ref> The magazine '']'' reported on December 23, 2008, that the 10 places most affected by climate change were ], the ], ], ], the ], ]s, ], the ], the ], and ].{{dubious|date=May 2010|Most affected by climate change}}

===Northern hemisphere===
{{see also|Arctic dipole}}

In the northern hemisphere, the southern part of the ] region (home to 4,000,000 people) has experienced a temperature rise of 1&nbsp;°C to 3&nbsp;°C (1.8&nbsp;°F to 5.4&nbsp;°F) over the last 50 years.{{Citation needed|date=December 2009}} Canada, ] and Russia are experiencing initial melting of ]. This may disrupt ecosystems and by increasing bacterial activity in the soil lead to these areas becoming carbon sources instead of ]s.<ref>{{cite web |url=http://www.arctic.noaa.gov/essay_romanovsky.html |title=How rapidly is permafrost changing and what are the impacts of these changes? |author=Vladimir Romanovsky |publisher=NOAA |accessdate=2007-12-06}}</ref> A study (published in ''Science'') of changes to eastern ]'s permafrost suggests that it is gradually disappearing in the southern regions, leading to the loss of nearly 11% of Siberia's nearly 11,000 lakes since 1971.<ref>{{cite news |url=http://www.guardian.co.uk/international/story/0,,1503170,00.html |title=Shrinking lakes of Siberia blamed on global warming |author=Nick Paton Walsh |publisher=The Guardian |date=2005-06-10}}</ref> At the same time, western Siberia is at the initial stage where melting permafrost is creating new lakes, which will eventually start disappearing as in the east. Furthermore, permafrost melting will eventually cause ].

===Polar regions===
{{see also|Arctic shrinkage}}

Anisimov ''et al''. (2007) assessed the literature on impacts of climate change in Polar regions.<ref>{{cite web
|year=2007
|title=Polar regions (Arctic and Antarctic). In: Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change
|publisher=Cambridge University Press, Cambridge, U.K., and New York, N.Y., U.S.A.
|author=Anisimov, O.A. ''et al''.
|pages=653–685
|url= http://www.ipcc.ch/publications_and_data/publications_and_data_reports.htm
|accessdate=2009-05-20}}</ref> Model projections showed that Arctic terrestrial ecosystems and the active layer (the top layer of soil or rock in permafrost that is subjected to seasonal freezing and thawing) would be a small sink for carbon (i.e., net uptake of carbon) over this century (p.&nbsp;662). These projections were viewed as being uncertain. It was judged that increased emissions of carbon from thawing of permafrost could occur. This would lead to an amplification of warming.

===Upper atmosphere===
{{see also|Noctilucent cloud}}
Increased CO<sub>2</sub> levels cause warming in the ] but cooling in the ] and ]. In addition, a collapse of the ] has been observed as a possible result in part due to increased carbon dioxide concentrations, the strongest cooling and contraction occurring in that layer during ]. The most recent contraction in 2008-2009 was the largest such collapse since at least 1967.<ref>{{cite news|last=Science News|first=NASA|title=A Puzzling Collapse of Earth's Upper Atmosphere|url=http://science.nasa.gov/science-news/science-at-nasa/2010/15jul_thermosphere/|accessdate=16 July 2010|newspaper=National Aeronautics and Space Administration - Science News|date=July 15, 2010}}</ref><ref>{{cite news|last=Ho|first=Derrick|title=Scientists baffled by unusual upper atmosphere shrinkage|url=http://www.cnn.com/2010/US/07/16/nasa.upper.atmosphere.shrinking/?hpt=T2|accessdate=18 July 2010|newspaper=Cable News Network|date=July 17, 2010}}</ref><ref>{{cite journal|last=Saunders|first=Arrun|coauthors=Graham G. Swinerd, Hugh G. Lewis|title=Preliminary Results to Support Evidence of Thermospheric Contraction|journal=Advanced Maui Optical and Space Surveillance Technologies Conference|year=2009|pages=8|url=http://www.amostech.com/TechnicalPapers/2009/AtmosphericsSpace_Weather/Saunders.pdf|format=PDF}}</ref>

Recent evidence suggests that warming of the tropical oceans since a "]" in 2000 may have acted as a ], reducing the observed warming during the ]. As warming and evaporation above the Pacific Ocean, temperatures in the lower stratosphere near the ] declined due to both greenhouse gases and ]s, reducing ] levels and removing its warming effect, with vapor concentrations below 2.2 ] as measured by the HALOE instrument on the ], in the lower stratosphere of the tropics between 5°N - 5°S first being observed since 2001, although a reversal in this pattern is also likely. The water vapor in the stratosphere arrives through tall ]s, while 15% of this vapor is delivered by ]s, and through chemical breakdown of ] into water vapor and carbon dioxide, both of which are greenhouse gases. The vapor is frozen out of the stratosphere as more of the water is subjected to temperatures that freeze it out of the stratosphere. Water vapor concentrations in the lower stratosphere have declined by 10% (0.4 ppmv) since 2000, reducing warming during the decade by 25%. A rapid cooling of 4 °C to 6 °C also occurred in the lower stratosphere in the mid-1990s, while the rate of ocean warming increased. During the ], increased stratospheric water vapor led to a 30% increase in warming. After 2000, the ]s of the tropical Western Pacific, where a warm pool of water exists and where temperatures are heavily influenced by ], between 10°N - 10°S and 139° - 171° longitude became anti-correlated with temperatures at the ] in the same latitudes between 171° - 200° longitude, both measured since the early ]; although the correlation had been previously positive, since 2000 the SST anomalies increased while tropopause temperatures decreased. A sharp increase in average SSTs within the Western Pacific warm pool by more than 0.25 °C in 2000, which has since stabilized, occurred as the "cold point" temperature of the study area at the tropopause experienced a significant reduction. This resulted in less water vapor from tropical thunderstorms entering the stratosphere. However, prior to 2000, increases in average Western Pacific SSTs had resulted in increases in tropopause cold point temperatures.<ref>{{cite journal|last=Rosenlof|first=Karen H.|coauthors=George C. Reid|title=Trends in the temperature and water vapor content of the tropical lower stratosphere: Sea surface connection|journal=Journal of Geophysical Research Atmospheres|date=27 March 2008|volume=113|series=D06107|pages=15 PP.|doi=10.1029/2007JD009109|url=http://www.agu.org/pubs/crossref/2008/2007JD009109.shtml|bibcode=2008JGRD..11306107R}}</ref><ref>{{cite journal|last=Solomon|first=Susan|coauthors=Karen H. Rosenlof, Robert W. Portmann, John S. Daniel, Sean M. Davis, Todd J. Sanford, Gian-Kasper Plattner|title=Contributions of Stratospheric Water Vapor to Decadal Changes in the Rate of Global Warming|journal=Science - American Association for the Advancement of Science|date=5 March 2010|volume=327|pmid=20110466|issue=5970|pages=pp. 1219–1223|doi=10.1126/science.1182488|url=http://www.sciencemag.org/cgi/content/abstract/science.1182488|bibcode = 2010Sci...327.1219S }}</ref><ref>{{cite news|last=Harris|first=Richard|title=Atmospheric Dry Spell Eases Global Warming|url=http://www.npr.org/templates/story/story.php?storyId=123075836|accessdate=3 August 2010|newspaper=NPR|date=January 28, 2010}}</ref><ref>{{cite journal|last=Romps|first=D.M.|coauthors=Z. Kuang|title=Overshooting convection in tropical cyclones|journal=Geophysical Research Letters|year=2009|volume=36|series=L09804|issue=9|doi=10.1029/2009GL037396|bibcode=2009GeoRL..3609804R}}</ref><ref>{{cite journal|last=Ingram|first=William|title=A very simple model for the water vapour feedback on climate change|journal=Quarterly Journal of the ]|date=19 January 2010|volume=136|issue=646|pages=30–40|doi=10.1002/qj.546|url=http://www3.interscience.wiley.com/journal/123243714/abstract?CRETRY=1&SRETRY=0|bibcode = 2010QJRMS.136...30I }}</ref><ref>{{cite journal|last=Stolarski|first=Richard S.|coauthors=Anne R. Douglass, Paul A. Newman, Steven Pawson, Mark R. Schoeberl|title=Relative Contribution of Greenhouse Gases and Ozone-Depleting Substances to Temperature Trends in the Stratosphere: A Chemistry–Climate Model Study|journal=American Meteorological Society|year=2010|month=January|volume=23|issue=1|pages=28–42|doi=10.1175/2009JCLI2955.1|url=http://journals.ametsoc.org/doi/abs/10.1175/2009JCLI2955.1|bibcode = 2010JCli...23...28S }}</ref> These findings potentially support the negative feedback "]".<ref>{{cite journal |url=http://www.agu.org/pubs/crossref/2007/2007GL029698.shtml |author=Spencer, R.W., Braswell, W.D., Christy, J.R., Hnilo, J. |year=2007 |title=Cloud and radiation budget changes associated with tropical intraseasonal oscillations |journal=Geophys. Res. Lett. |volume=34 |pages=L15707 |doi=10.1029/2007GL029698 |bibcode=2007GeoRL..3415707S |issue=15}}</ref><ref>{{cite journal |url=http://www.agu.org/pubs/crossref/2009/2009GL039628.shtml |author=Lindzen, R. S., and Y.-S. Choi |year=2009 |title=On the determination of climate feedbacks from ERBE data |journal=Geophys. Res. Lett. |volume=36 |pages=L16705 |doi=10.1029/2009GL039628 |bibcode=2009GeoRL..3616705L |issue=16}}</ref>

==Geophysical systems==
===Biogeochemical cycles===

{{See also|climate change feedback}}

Climate change can have an effect on the carbon cycle in an interactive "feedback" process . A feedback exists where an initial process triggers changes in a second process that in turn influences the initial process. A positive feedback intensifies the original process, and a negative feedback reduces it (IPCC, 2007d:78).<ref name=ar4syn/> Models suggest that the interaction of the climate system and the carbon cycle is one where the feedback effect is positive (Schneider ''et al''., 2007:792).<ref name=schneider/>

Using the A2 SRES emissions scenario, Schneider ''et al''. (2007:789) found that this effect led to additional warming by 2100, relative to the 1990-2000 period, of 0.1 to 1.5 °C. This estimate was made with high confidence. The climate projections made in the IPCC Forth Assessment Report of 1.1 to 6.4 °C account for this feedback effect. On the other hand, with medium confidence, Schneider ''et al''. (2007) commented that additional releases of GHGs were possible from permafrost, peat lands, wetlands, and large stores of marine hydrates at high latitudes.

====Gas hydrates====
{{see also|Clathrate gun hypothesis|Arctic methane release}}

] are ice-like deposits containing a mixture of water and gas, the most common gas of which is methane (Maslin, 2004:1).<ref>{{cite journal
|year=2004
|title=Gas Hydrates: A Hazard for the 21st century
|publisher=Benfield Hazard Research Centre, UCL
|journal=Issues in Risk Science
|author=Maslin, M.
|pages=24
|url=http://www.abuhrc.org/Publications/Issues%20in%20Risk%20Science%20-%203.pdf
|accessdate=2009-05-20
|volume=3}}</ref> Gas hydrates are stable under high pressures and at relatively low temperatures and are found underneath the oceans and permafrost regions. Future warming at intermediate depths in the world's oceans, as predicted by climate models, will tend to destabilize gas hydrates resulting in the release of large quantities of methane. On the other hand, projected rapid ] in the coming centuries associated with global warming will tend to stabilize marine gas hydrate deposits.

====Carbon cycle====

Models have been used to assess the effect that climate change will have on the carbon cycle (Meehl ''et al''., 2007:789-790).<ref name=meehl>{{cite web
|year=2007
|title=Global Climate Projections. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change
|publisher=Cambridge University Press, Cambridge, U.K., and New York, N.Y., U.S.A.
|author=Meehl, G.A. ''et al''.
|url=http://www.ipcc.ch/publications_and_data/publications_and_data_reports.htm
|accessdate=2010-01-10}}</ref> In the Coupled Climate-Carbon Cycle Model Intercomparison Project, eleven climate models were used. Observed emissions were used in the models and future emission projections were based on the IPCC SRES A2 emissions scenario.

Unanimous agreement was found among the models that future climate change will reduce the efficiency of the land and ocean carbon cycle to absorb human-induced CO<sub>2</sub>. As a result, a larger fraction of human-induced CO<sub>2</sub> will stay airborne if climate change controls the carbon cycle. By the end of the 21st century, this additional CO<sub>2</sub> in the atmosphere varied between 20 and 220 ppm for the two extreme models, with most models lying between 50 and 100 ppm. This additional CO<sub>2</sub> led to a projected increase in warming of between 0.1 and 1.5 °C.

===Glacier retreat and disappearance===

{{Main|Retreat of glaciers since 1850}}

]

IPCC (2007a:5) found that, on average, mountain glaciers and snow cover had decreased in both the northern and southern hemispheres.<ref name= ar4wg1 /> This widespread decrease in glaciers and ice caps has contributed to observed sea level rise. With very high or high confidence, IPCC (2007d:11) made a number of predictions relating to future changes in glaciers:<ref name=ar4syn>{{cite web
|date=2007d
|title=Climate Change 2007: Synthesis Report. Contribution of Working Groups I, II and III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change
|publisher=IPCC, Geneva, Switzerland
|pages=104
|author=IPCC
|url=http://www.ipcc.ch/publications_and_data/publications_ipcc_fourth_assessment_report_synthesis_report.htm
|accessdate=2009-05-20}}</ref>
*Mountainous areas in Europe will face glacier retreat
*In Latin America, changes in precipitation patterns and the disappearance of glaciers will significantly affect water availability for human consumption, agriculture, and energy production
*In Polar regions, there will be reductions in glacier extent and the thickness of glaciers.

In historic times, glaciers grew during a cool period from about 1550 to 1850 known as the ]. Subsequently, until about 1940, glaciers around the world retreated as the climate warmed. ] declined and reversed in many cases from 1950 to 1980 as a slight global cooling occurred. Since 1980, glacier retreat has become increasingly rapid and ubiquitous, and has threatened the existence of many of the glaciers of the world. This process has increased markedly since 1995.<ref>{{cite web
|author=World Glacier Monitoring Service
|title=Home page
|url=http://www.geo.unizh.ch/wgms/fog.html
|accessdate=December 20, 2005 }}</ref>

Excluding the ]s and ]s of the Arctic and Antarctic, the total surface area of ]s worldwide has decreased by 50% since the end of the 19th century.<ref name="munichre">{{cite web |url=http://www.munichre.com/en/ts/geo_risks/climate_change_and_insurance/retreat_of_the_glaciers/default.aspx |title=Retreat of the glaciers |publisher=Munich Re Group |accessdate=2007-12-12}}</ref> Currently glacier retreat rates and mass balance losses have been increasing in the ], ], ], ], ] and ].

The loss of glaciers not only directly causes landslides, flash floods and ] overflow,<ref>{{cite web |url=http://www.rrcap.unep.org/issues/glof/ |title=Glacial Lake Outburst Flood Monitoring and Early Warning System |publisher=] |accessdate=2007-12-12}}</ref> but also increases annual variation in water flows in rivers. Glacier runoff declines in the summer as glaciers decrease in size, this decline is already observable in several regions.<ref>{{cite web |url=http://www.nichols.edu/departments/glacier/glacier.htm |title=Recent retreat of North Cascade Glaciers and changes in North Cascade Streamflow |publisher=North Cascade Glacier Climate Project |author=Mauri S. Pelto |accessdate=2007-12-28}}</ref> Glaciers retain water on mountains in high precipitation years, since the snow cover accumulating on glaciers protects the ice from melting. In warmer and drier years, glaciers offset the lower precipitation amounts with a higher meltwater input.<ref name="munichre" />

Of particular importance are the ] and ]n glacial melts that comprise the principal dry-season water source of many of the major rivers of the ], ], ] and ]n mainland. Increased melting would cause greater flow for several decades, after which "some areas of the most populated regions on Earth are likely to 'run out of water'" as source glaciers are depleted.<ref>{{cite journal
|journal=Nature
|last=Barnett
|first=T. P.
|coauthors=J. C. Adam, D. P. Lettenmaier
|title=Potential impacts of a warming climate on water availability in snow-dominated regions
|url=http://www.nature.com/nature/journal/v438/n7066/full/nature04141.html
|date=November 17, 2005
|volume=438
|pages=303–9
|accessdate=2008-02-18
|doi=10.1038/nature04141
|pmid=16292301
|issue=7066
|bibcode=2005Natur.438..303B
}}</ref> The ] contains the world's third-largest store of ice. Temperatures there are rising four times faster than in the rest of China, and glacial retreat is at a high speed compared to elsewhere in the world.<ref></ref>

According to a Reuters report, the ] glaciers that are the sources of Asia's biggest rivers—], ], ], ], ], ] and ]—could diminish as temperatures rise.<ref>{{cite web
|title=Vanishing Himalayan Glaciers Threaten a Billion
|publisher=]
|url=http://www.planetark.com/dailynewsstory.cfm/newsid/42387/story.htm
|date=2007-06-05
|accessdate=December 21, 2007 }}</ref> Approximately 2.4 billion people live in the ] of the Himalayan rivers.<ref>{{cite web |url=http://www.peopleandplanet.net/pdoc.php?id=3024 |title=Big melt threatens millions, says UN |publisher=People and the Planet |date=2007-06-24 |accessdate=2007-12-28 |archiveurl = http://web.archive.org/web/20071218132829/http://www.peopleandplanet.net/pdoc.php?id=3024 <!-- Bot retrieved archive --> |archivedate = 2007-12-18}}</ref> India, China, ], ], ] and ] could experience floods followed by ]s in coming decades. In India alone, the Ganges provides water for drinking and farming for more than 500 million people.<ref>{{cite web
|title=Ganges, Indus may not survive: climatologists
|publisher=Rediff India Abroad
|url=http://www.rediff.com/news/2007/jul/24indus.htm
|date=2007-07-25
|accessdate=December 21, 2007 }}</ref><ref>{{cite web
|author=China Daily
|title=Glaciers melting at alarming speed
|publisher=People's Daily Online
|url=http://english.peopledaily.com.cn/90001/90781/90879/6222327.html
|date=2007-07-24
|accessdate=December 21, 2007 }}</ref><ref>{{cite web
|author=Navin Singh Khadka
|title=Himalaya glaciers melt unnoticed
|publisher=]
|url=http://news.bbc.co.uk/2/hi/science/nature/3998967.stm
|date=2004-11-10
|accessdate=December 21, 2007 }}</ref> It has to be acknowledged, however, that increased seasonal runoff of Himalayan glaciers led to increased agricultural production in northern India throughout the 20th century.<ref>{{cite journal |last=Rühland |first=Kathleen |coauthors=''et al.'' |year=2006 |title=Accelerated melting of Himalayan snow and ice triggers pronounced changes in a valley peatland from northern India |journal=Geophysical Research Letters |volume=33 |pages=L15709 |doi=10.1029/2006GL026704 |bibcode=2006GeoRL..3315709R |issue=15}}</ref>

The recession of mountain glaciers, notably in Western North America, Franz-Josef Land, Asia, the Alps, the Pyrenees, Indonesia and Africa, and tropical and sub-tropical regions of South America, has been used to provide qualitative support to the rise in global temperatures since the late 19th century. Many glaciers are being lost to melting further raising concerns about future local water resources in these glaciated areas. In Western North America the 47 North Cascade glaciers observed all are retreating.<ref>{{cite web |url=http://www.nichols.edu/departments/glacier/glacier.htm |title=North Cascade Glacier Climate Project |publisher=North Cascade Glacier Climate Project |author=Mauri S. Pelto |accessdate=2007-12-28}}</ref>

]

Despite their proximity and importance to ], the mountain and valley glaciers of temperate latitudes amount to a small fraction of glacial ice on the earth. About 99% is in the great ice sheets of polar and subpolar Antarctica and Greenland. These continuous continental-scale ice sheets, {{convert|3|km|mi}} or more in thickness, cap the polar and subpolar land masses. Like rivers flowing from an enormous lake, numerous outlet glaciers transport ice from the margins of the ice sheet to the ocean.

Glacier retreat has been observed in these outlet glaciers, resulting in an increase of the ice flow rate. In ] the period since the year 2000 has brought retreat to several very large glaciers that had long been stable. Three glaciers that have been researched, Helheim, ] and Kangerdlugssuaq Glaciers, jointly drain more than 16% of the ]. Satellite images and aerial photographs from the 1950s and 1970s show that the front of the glacier had remained in the same place for decades. But in 2001 it began retreating rapidly, retreating {{convert|7.2|km|mi|abbr=on}} between 2001 and 2005. It has also accelerated from {{convert|20|m|ft|abbr=on}}/day to {{convert|32|m|ft|abbr=on}}/day.<ref>{{cite web |url=http://currents.ucsc.edu/05-06/11-14/glacier.asp |title=Rapidly accelerating glaciers may increase how fast the sea level rises|author=Emily Saarman |publisher=UC Santa Cruz Currents |date=2005-11-14 |accessdate=2007-12-28}}</ref> Jakobshavn Isbræ in western Greenland had been moving at speeds of over {{convert|24|m|ft|abbr=on}}/day with a stable terminus since at least 1950. The glacier's ice tongue began to break apart in 2000, leading to almost complete disintegration in 2003, while the retreat rate increased to over {{convert|30|m|ft|abbr=on}}/day.<ref>{{cite web |url=http://www.nasa.gov/vision/earth/lookingatearth/jakobshavn.html |title=Fastest Glacier in Greenland Doubles Speed |publisher=] |date=2004-12-01 |author=Krishna Ramanujan |accessdate=2007-12-28}}</ref>

===Oceans===

The role of the oceans in global warming is a complex one. The oceans serve as a sink for carbon dioxide, taking up much that would otherwise remain in the atmosphere, but increased levels of CO<sub>2</sub> have led to ]. Furthermore, as the temperature of the oceans increases, they become less able to absorb excess CO<sub>2</sub>. Global warming is projected to have a number of effects on the oceans. Ongoing effects include rising sea levels due to thermal expansion and melting of glaciers and ice sheets, and warming of the ocean surface, leading to increased temperature stratification. Other possible effects include large-scale changes in ocean circulation.

====Sea ice====

As the climate warms, snow cover and sea ice extent decrease. In a literature assessment, Meehl ''et al''. (2007:750) found that model projections for the 21st century showed a reduction of sea ice in both the Arctic and Antarctic.<ref name=meehl/> The range of model responses was large. Projected reductions were accelerated in the Arctic. Using the high-emission A2 SRES scenario, some models projected that summer sea ice cover in the Arctic would disappear entirely by the latter part of the 21st century.

====Sea level rise====
{{Main|Current sea level rise}}
{{further|]}}

{{Multiple image|direction=vertical|align=left|image1=Holocene Sea Level.png|image2=Recent Sea Level Rise.png|width=200|caption1=Sea level rise during the Holocene.|caption2=Sea level has been rising {{#expr: 20/120 round 1}} cm/year, based on measurements of ] from 23 long ] records in geologically stable environments.}}

IPCC (2007a:5) reported that since 1961, global average sea level had risen at an average rate of 1.8 mm/yr.<ref name=ar4wg1/> Between 1993 and 2003, the rate increased above the previous period to 3.1 mm/yr. IPCC (2007a) were uncertain whether the increase in rate from 1993 to 2003 was due to natural variations in sea level over the time period, or whether it reflected an increase in the underlying long-term trend.

IPCC (2007a:13, 14) projected sea level rise to the end of the 21st century using the ] emission ]. Across the six SRES marker scenarios, sea level was projected to rise by 18 to 59&nbsp;cm (7.1 to 23.2&nbsp;inches). This projection was for the time period 2090-2099, with the increase in level relative to average sea levels over the 1980-1999 period. Due to a lack of scientific understanding, this sea level rise estimate does not include all of the possible contributions of ice sheets.

With increasing average global temperature, the ] in the oceans expands in volume, and additional water enters them which had previously been locked up on land in ] and ]. The ] and the ]s are major ice masses, and at least the former of which may suffer irreversible decline.<ref>{{cite doi|10.1007/s00382-009-0646-0}}</ref> For most glaciers worldwide, an average volume loss of 60% until 2050 is predicted.<ref name="Schneeberger2993">{{cite journal |last=Schneeberger |first=Christian |coauthors=''et al.'' |year=2003 |title=Modelling changes in the mass balance of glaciers of the northern hemisphere for a transient 2×CO<sub>2</sub> scenario |journal=Journal of Hydrology |volume=282 |issue=1–4 |pages=145–163 |doi=10.1016/S0022-1694(03)00260-9 |bibcode=2003JHyd..282..145S}}</ref> Meanwhile, the estimated total ice melting rate over Greenland is {{convert|239|+/-|23|km3}} per year, mostly from East Greenland.<ref name="Chen2006">{{cite journal |last=Chen |first=J. L. |coauthors=Wilson, C. R.; Tapley, B. D. |year=2006 |title=Satellite Gravity Measurements Confirm Accelerated Melting of Greenland Ice Sheet |journal=Science |volume=313 |issue=5795 |pages=1958–60 |doi=10.1126/science.1129007 |pmid=16902089 |bibcode = 2006Sci...313.1958C }}</ref> The Antarctic ice sheet, however, is expected to grow during the 21st century because of increased precipitation.<ref name="ar4wg1ch5" /> Under the IPCC Special Report on Emission Scenario (SRES) A1B, by the mid-2090s global sea level will reach {{convert|0.22|to|0.44|m|in|abbr=on}} above 1990 levels, and is currently rising at about {{convert|4|mm|abbr=on}} per year.<ref name="ar4wg1ch5">{{cite web |publisher=Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. |author=Bindoff, N.L., J. Willebrand, V. Artale, A, Cazenave, J. Gregory, S. Gulev, K. Hanawa, C. Le Quéré, S. Levitus, Y. Nojiri, C.K. Shum, L.D. Talley and A. Unnikrishnan |editor=Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor and H.L. Miller |title=Observations: Oceanic Climate Change and Sea Level. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change |url=http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-chapter5.pdf |format=PDF |accessdate=2007-12-29 |year=2007}}</ref> Since 1900, the sea level has risen at an average of {{convert|1.7|mm|abbr=on}} per year;<ref name="ar4wg1ch5" /> since 1993, ] altimetry from ] indicates a rate of about {{convert|3|mm|abbr=on}} per year.<ref name="ar4wg1ch5" />

The sea level has risen more than {{convert|120|m}} since the ] about 20,000 years ago. The bulk of that occurred before 7000 years ago.<ref name="Fleming1998">{{cite journal |last=Fleming |first=Kevin |coauthors=''et al.'' |year=1998 |title=Refining the ] ] since the Last Glacial Maximum using far- and intermediate-field sites |journal=Earth and Planetary Science Letters |volume=163 |issue=1–4 |pages=327–342 |doi=10.1016/S0012-821X(98)00198-8 |bibcode=1998E&PSL.163..327F}}</ref> Global temperature declined after the ], causing a sea level lowering of {{convert|0.7|+/-|0.1|m|in|abbr=on}} between 4000 and 2500 years before present.<ref name="Goodwin1998">{{cite journal |last=Goodwin |first=Ian D. |year=1998 |title=Did changes in Antarctic ice volume influence late Holocene sea-level lowering? |journal=Quaternary Science Reviews |volume=17 |issue=4–5 |pages=319–332 |doi=10.1016/S0277-3791(97)00051-6 |bibcode = 1998QSRv...17..319G }}</ref> From 3000 years ago to the start of the 19th century, sea level was almost constant, with only minor fluctuations. However, the ] may have caused some sea level rise; evidence has been found in the Pacific Ocean for a rise to perhaps {{convert|0.9|m|abbr=on}} above present level in 700 BP.<ref>{{cite journal |last=Nunn |first=Patrick D. |year=1998 |title=Sea-Level Changes over the Past 1,000 Years in the Pacific |journal=Journal of Coastal Research |volume=14 |issue=1 |pages=23–30 |doi=10.2112/0749-0208(1998)0142.3.CO;2 }}</ref>

In a paper published in 2007, the climatologist ] ''et al.'' claimed that ice at the poles does not melt in a gradual and linear fashion, but that another according to the geological record, the ]s can suddenly destabilize when a certain threshold is exceeded. In this paper Hansen ''et al.'' state:

<blockquote>Our concern that BAU GHG scenarios would cause large sealevel rise this century (Hansen 2005) differs from estimates of IPCC (2001, 2007), which foresees little or no contribution to twentyfirst century sealevel rise from Greenland and Antarctica. However, the IPCC analyses and projections do not well account for the nonlinear physics of wet ice sheet disintegration, ice streams and eroding ice shelves, nor are they consistent with the palaeoclimate evidence we have presented for the absence of discernible lag between ice sheet forcing and sealevel rise.<ref>{{cite journal |last=Hansen |first=James |coauthors=''et al.'' |year=2007 |url=http://pubs.giss.nasa.gov/docs/2007/2007_Hansen_etal_2.pdf |title=Climate change and trace gases |journal=Phil. Trans. Roy. Soc. A |pmid=17513270 |volume=365 |issue=1856 |pages=1925–54 |format=PDF |doi=10.1098/rsta.2007.2052 |bibcode=2007RSPTA.365.1925H}}</ref></blockquote>

Sea level rise due to the collapse of an ice sheet would be distributed nonuniformly across the globe. The loss of mass in the region around the ice sheet would decrease the ] there, reducing the amount of local sea level rise or even causing local sea level fall. The loss of the localized mass would also change the ] of the Earth, as flow in the ] will require 10–15 thousand years to make up the mass deficit. This change in the moment of inertia results in ], in which the Earth's rotational axis remains fixed with respect to the sun, but the rigid sphere of the Earth rotates with respect to it. This changes the location of the ] of the Earth and further affects the ], or global potential field. A 2009 study of the effects of collapse of the ] shows the result of both of these effects. Instead of a global 5-meter sea level rise, western Antarctica would experience approximately 25 centimeters of sea level fall, while the United States, parts of Canada, and the Indian Ocean, would experience up to 6.5 meters of sea level rise.<ref>{{cite journal |doi=10.1126/science.1166510 |title=The Sea-Level Fingerprint of West Antarctic Collapse |year=2009 |last1=Mitrovica |first1=J. X. |first2=N. |first3=P. U. |journal=Science |volume=323 |pages=753 |pmid=19197056 |last2=Gomez |last3=Clark |issue=5915|bibcode = 2009Sci...323..753M }}</ref>

A paper published in 2008 by a group of researchers at the University of Wisconsin led by Anders Carlson used the deglaciation of North America at 9000 years before present as an analogue to predict sea level rise of 1.3 meters in the next century,<ref>{{cite web |url=http://www.newscientist.com/article/dn14634-sea-level-rises-could-far-exceed-ipcc-estimates.html |title=Sea level rises could far exceed IPCC estimates |accessdate=2009-01-24 |publisher=New Scientist}}</ref><ref>{{cite journal |doi=10.1038/ngeo285 |title=Rapid early Holocene deglaciation of the Laurentide ice sheet |year=2008 |author=Carlson, Anders E. |journal=Nature Geoscience |volume=1 |pages=620 |first2=Allegra N. |first3=Delia W. |first4=Rosemarie E. |first5=Gavin A. |first6=Faron S. |first7=Joseph M. |first8=Elizabeth A. |last2=Legrande |last3=Oppo |last4=Came |last5=Schmidt |last6=Anslow |last7=Licciardi |last8=Obbink |issue=9|bibcode = 2008NatGe...1..620C }}</ref> which is also much higher than the IPCC predictions. However, models of glacial flow in the smaller present-day ice sheets show that a probable maximum value for sea level rise in the next century is 80 centimeters, based on limitations on how quickly ice can flow below the ] and to the sea.<ref>{{cite journal |doi=10.1126/science.1159099 |year=2008 |month=September |author=Pfeffer, Wt; Harper, Jt; O'Neel, S |title=Kinematic constraints on glacier contributions to 21st-century sea-level rise |volume=321 |issue=5894 |pages=1340–3 |issn=0036-8075 |pmid=18772435 |journal=Science|bibcode = 2008Sci...321.1340P }}</ref>

====Temperature rise====

From 1961 to 2003, the global ocean temperature has risen by 0.10 °C from the surface to a depth of 700 m. There is variability both year-to-year and over longer time scales, with global ocean heat content observations showing high rates of warming for 1991 to 2003, but some cooling from 2003 to 2007.<ref name="ar4wg1ch5" /> The temperature of the Antarctic ] rose by 0.17 °C (0.31 °F) between the 1950s and the 1980s, nearly twice the rate for the world's oceans as a whole.<ref>{{cite journal |url=http://www.sciencemag.org/cgi/content/full/295/5558/1275?ijkey=nFvdOLNYlMNZU&keytype=ref&siteid=sci |title=Warming of the Southern Ocean Since the 1950s |first=Sarah T. |last=Gille |journal=] |date=February 15, 2002 |volume=295 |pages=1275–7 |doi=10.1126/science.1065863 |pmid=11847337 |issue=5558|bibcode = 2002Sci...295.1275G }}</ref> As well as having effects on ecosystems (e.g. by melting sea ice, affecting algae that grow on its underside), warming reduces the ocean's ability to absorb CO<sub>2</sub>. {{Citation needed|date=June 2008}}

====Acidification====

{{Main|Ocean acidification}}

Ocean acidification is an effect of rising concentrations of ] in the atmosphere, and is not a direct consequence of ]. The oceans soak up much of the CO<sub>2</sub> produced by living organisms, either as dissolved gas, or in the skeletons of tiny marine creatures that fall to the bottom to become chalk or limestone. Oceans currently absorb about one tonne of CO<sub>2</sub> per person per year. It is estimated that the oceans have absorbed around half of all CO<sub>2</sub> generated by human activities since 1800 (118 ± 19 petagrams of carbon from 1800 to 1994).<ref name="Sabine2004">{{cite journal |last=Sabine |first=Christopher L. |coauthors=''et al.'' |year=2004 |title=The Oceanic Sink for Anthropogenic CO<sub>2</sub> |journal=Science |volume=305 |issue=5682 |pages=367–371 |doi=10.1126/science.1097403 |pmid=15256665 |bibcode = 2004Sci...305..367S }}</ref>

In water, CO<sub>2</sub> becomes a weak ], and the increase in the greenhouse gas since the ] has already lowered the average ] (the laboratory measure of acidity) of seawater by 0.1 units, to 8.2. Predicted emissions could lower the pH by a further 0.5 by 2100, to a level probably not seen for hundreds of millennia and, critically, at a rate of change probably 100 times greater than at any time over this period.<ref>{{cite web |url=http://news.bbc.co.uk/1/hi/sci/tech/4633681.stm |title=Emission cuts 'vital' for oceans |date=2005-06-30 |publisher=] |accessdate=2007-12-29}}</ref><ref>{{cite web |url=http://royalsociety.org/document.asp?tip=0&id=3249 |title=Ocean acidification due to increasing atmospheric carbon dioxide |publisher=] |date=2005-06-30 |accessdate=2008-06-22}}</ref>

There are concerns that increasing acidification could have a particularly detrimental effect on ]s<ref>{{cite web |url=http://www.opendemocracy.net/globalization-climate_change_debate/2558.jsp |title=Global warming and coral reefs |author=Thomas J Goreau |publisher=Open Democracy |date=2005-05-30 |accessdate=2007-12-29}}</ref> (16% of the world's coral reefs have died from bleaching caused by warm water in 1998,<ref name="Walther2002">{{cite journal |last=Walther |first=Gian-Reto |coauthors=''et al.'' |year=2002 |title=Ecological responses to recent climate change |journal=Nature |volume=416 |issue=6879 |pages=389–395 |doi=10.1038/416389a |pmid=11919621 }}</ref> which coincidentally was the warmest year ever recorded) and other marine organisms with ] shells.<ref>{{cite web |url=http://dsc.discovery.com/news/2006/07/05/acidocean_pla.html |title=Rising Ocean Acidity Threatens Reefs |author=Larry O'Hanlon |publisher=Discovery News |date=2006-07-05 |accessdate=2007-12-29}}</ref>

In November 2009 an article in '']'' by scientists at ]'s ] reported they had found very low levels of the building blocks for the calcium chloride that forms ] shells in the ].<ref name=Canwest2009-11-20>
{{cite news
|url=http://www.canada.com/technology/Climate+change+causing+corrosive+water+affect+Arctic+marine+life+study/2242554/story.html
|title=Climate change causing 'corrosive' water to affect Arctic marine life: study
|publisher=Canadawest
|date=2009-11-19
|author=Margaret Munro
|archiveurl=http://www.webcitation.org/query?url=http%3A%2F%2Fwww.canada.com%2Ftechnology%2FClimate%2Bchange%2Bcausing%2Bcorrosive%2Bwater%2Baffect%2BArctic%2Bmarine%2Blife%2Bstudy%2F2242554%2Fstory.html&date=2009-11-21
|archivedate=2009-11-21
}}</ref>
], one of the DFO authors, asserted that the increasing acidification of the Arctic Ocean was close to the point it would start dissolving the walls of existing plankton: ''" Arctic ecosystem may be risk. In actual fact, they'll dissolve the shells."''
Because cold water absorbs CO2 more readily than warmer water the acidification is more severe in the polar regions. McLaughlin predicted the acidified water would travel to the North Atlantic within the next ten years.

====Shutdown of thermohaline circulation====

{{Main|Shutdown of thermohaline circulation}}

There is some speculation that global warming could, via a shutdown or slowdown of the thermohaline circulation, trigger localized cooling in the North Atlantic and lead to cooling, or lesser warming, in that region.<ref name="Lenton2008"/> This would affect in particular areas like ] and ] that are warmed by the ].

The chances of this near-term collapse of the circulation are unclear; there is some evidence for the short-term stability of the Gulf Stream and possible weakening of the North Atlantic drift.{{Citation needed|date=January 2009}} However, the degree of weakening, and whether it will be sufficient to shut down the circulation, is under debate. As yet, no cooling has been found in northern Europe or nearby seas.{{Citation needed|date=January 2009}} Lenton et al. found that "simulations clearly pass a THC tipping point this century".<ref name="Lenton2008">{{cite doi |10.1073/pnas.0705414105}}</ref>

IPCC (2007b:17) concluded that a slowing of the ] would very likely occur this century.<ref name=ar4wg2>{{cite book
|url=http://www.ipcc.ch/pdf/assessment-report/ar4/wg2/ar4-wg2-spm.pdf |format=PDF
|title=Summary for Policymakers. In: Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change
|accessdate=2007-11-30
|year=2007
|author=IPCC
|editors=M.L. Parry ''et al''.
|publisher=Cambridge University Press, Cambridge, U.K., and New York, N.Y., U.S.A.
|pages=7–22}}</ref> Due to global warming, temperatures across the Atlantic and Europe were still projected to increase.

====Oxygen depletion====

The amount of oxygen dissolved in the oceans may decline, with adverse consequences for ocean life.<ref>{{cite doi |10.1126/science.240.4855.996}}</ref><ref>{{cite doi |10.1038/ngeo420}}</ref>

====Sulfur aerosols====

{{Unreferenced section|date=March 2010}}
{{Main|sulfur cycle|stratospheric sulfur aerosols|plankton}}

Sulfur aerosols, especially ] have a significant effect on climate. One source of such ]s is the ], where ] release gases such as ] which eventually becomes ] to ] in the atmosphere. Disruption to the oceans as a result of ] or disruptions to the ] may result in disruption of the ], thus reducing its cooling effect on the planet through the creation of ].

===Geology===
====Volcanoes====
{{see also|Post-glacial rebound}}
The retreat of glaciers and ice caps can cause increased ]. Reduction in ice cover reduces the ] exerted on the volcano, increasing ]es and potentially causing the volcano to erupt. This reduction of pressure can also cause ] of material in the mantle, resulting in the generation of more magma.<ref>{{cite journal|doi=10.1029/2008GL033510|title=Will present day glacier retreat increase volcanic activity? Stress induced by recent glacier retreat and its effect on magmatism at the Vatnajökull ice cap, Iceland|year=2008|last1=Pagli|first1=Carolina|last2=Sigmundsson|first2=Freysteinn|journal=Geophysical Research Letters|volume=35|pages=L09304|bibcode=2008GeoRL..3509304P|issue=9}}</ref> Researchers in Iceland have shown that the rate of volcanic rock production there following deglaciation (10,000 to 4500 years ]) was 20–30 times greater than that observed after 2900 years before present.<ref>{{cite journal|doi=10.1007/BF00312320|title=Effect of glacier loading/deloading on volcanism: postglacial volcanic production rate of the Dyngjufj�ll area, central Iceland|year=1992|last1=Sigvaldason|first1=Gudmundur E|last2=Annertz|first2=Kristian|last3=Nilsson|first3=Magnus|journal=Bulletin of Volcanology|volume=54|pages=385|bibcode=1992BVol...54..385S|issue=5}}</ref> While the original study addresses the first reason for increased volcanism (reduced confining pressure), scientists have more recently shown that these lavas have unusually high ] concentrations, indicative of increased melting in the mantle.<ref>{{cite journal|doi=10.1016/S0012-821X(98)00200-3|title=Deglaciation effects on mantle melting under Iceland: results from the northern volcanic zone|year=1998|last1=Slater|first1=L|last2=Jull|first2=M|last3=McKenzie|first3=D|last4=Gronvöld|first4=K|journal=Earth and Planetary Science Letters|volume=164|pages=151|bibcode=1998E&PSL.164..151S}}</ref> This work in Iceland has been corroborated by a study in California, in which scientists found a strong correlation between volcanism and periods of global deglaciation.<ref>{{cite journal|doi=10.1029/2004JB002978|title=Did melting glaciers cause volcanic eruptions in eastern California? Probing the mechanics of dike formation|year=2004|last1=Jellinek|first1=A. Mark|journal=Journal of Geophysical Research|volume=109|pages=B09206|bibcode=2004JGRB..10909206J}}</ref> The effects of ] could include increased ] stress at the base of coastal volcanoes from a rise in the volcano's ] (and the associated ]), while the mass from extra water could activate dormant ]s around volcanoes. In addition, the wide-scale displacement of water from melting in places such as ] is likely to slightly alter the Earth's ] and may shift its ] on the scale of hundreds of metres, inducing further crustal stress changes.<ref>{{cite book|last=McGuire|first=Bill|title=Raging planet: earthquakes, volcanoes, and the tectonic threat to life on earth|year=2002|publisher=Quarto Inc|isbn=0-7641-1969-9|editor=Nicolette Linton|location=Hauppauge, New York}}</ref><ref>{{cite web|last=University of Toronto|first=ScienceDaily|title=Collapse Of Antarctic Ice Sheet Would Likely Put Washington, D.C. Largely Underwater|url=http://www.sciencedaily.com/releases/2009/02/090205142132.htm|work=ScienceDaily LLC|publisher=ScienceDaily|accessdate=19 November 2010|date=February 6, 2009}}</ref>

Current melting of ice is predicted to increase the size and frequency of volcanic eruptions.<ref name="rs_volc">{{cite journal|last1=Tuffen|first1=H.|title=How will melting of ice affect volcanic hazards in the twenty-first century?|journal=Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences|volume=368|issue=1919|pages=2535–58|year=2010|pmid=20403841|doi=10.1098/rsta.2010.0063|bibcode = 2010RSPTA.368.2535T }}</ref> In particular, lateral collapse events at ]es are likely to increase,<ref name="rs_volc"/><ref>{{cite journal|last1=Deeming|first1=K. R.|last2=McGuire|first2=B.|last3=Harrop|first3=P.|title=Climate forcing of volcano lateral collapse: evidence from Mount Etna, Sicily|journal=Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences|volume=368|issue=1919|pages=2559–77|year=2010|pmid=20403842|doi=10.1098/rsta.2010.0054|bibcode = 2010RSPTA.368.2559D }}</ref> and there are potential positive feedbacks between the removal of ice and magmatism.<ref name="rs_volc"/>

====Earthquakes====

A ]ing study has demonstrated that ] increases during unloading, such as that due to the removal of ice.<ref>{{cite journal|last1=Hampel|first1=A.|last2=Hetzel|first2=R.|last3=Maniatis|first3=G.|title=Response of faults to climate-driven changes in ice and water volumes on Earth's surface|journal=Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences|volume=368|issue=1919|pages=2501–17|year=2010|pmid=20403839|doi=10.1098/rsta.2010.0031|bibcode = 2010RSPTA.368.2501H }}</ref>

==See also==
{{portal|Global warming}}
*] (university program)
*]
<br>

==References==
{{Reflist|2}}

==External links==
===Scientific===
*. ].
*. This body assesses the physical scientific aspects of the climate system and climate change.
* - ]

====Specific topics====

*], June 30, 2005,
*]'s Environmental Science Seminar Series (Oct 2005):
** (])
** (])
** (])
*Videos:
**. A lecture given by ], ], at the "Summit on America's Climate Choices: Developing the Framework for a National Response to Climate Change", ], 2101 Constitution Avenue NW, Washington, D.C. March 30, 2009.
**Grantham Institute for Climate Change Annual Lecture, 11 June 2009, "Shifting rainfall patterns: lessons from the past", presented by Professor ]. Available as a or (116mb). ] website.

===Popular media===

* "The Climate of Man", '']'' (2005): , ,

{{Global warming}}

{{DEFAULTSORT:Physical Impacts Of Climate Change}}
]

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