Effects of global warming 2119174 226171346 2008-07-17T03:51:11Z SEWilco 18620 Reverted 2 edits by [[Special:Contributions/Nallan|Nallan]]; Rv ad for anecdotal site. ([[WP:TW|TW]]) {{pp-semi-protected|small=yes}} [[Image:Risks and Impacts of Global Warming.png|thumb|350px|Graphical description of risks and impacts from global warming from the [[Third Assessment Report]] of the [[Intergovernmental Panel on Climate Change]].]]The predicted '''effects of [[global warming]]''' on the [[natural environment|environment]] and for [[civilization|human life]] are numerous and varied. It is generally difficult to attribute specific natural phenomena to long-term causes, but some effects of recent [[climate change]] may already be occurring. [[Sea level rise|Raising sea levels]], [[Retreat of glaciers since 1850|glacier retreat]], [[Arctic shrinkage]], and altered patterns of [[Climate change and agriculture|agriculture]] are cited as direct consequences, but predictions for secondary and regional effects include [[extreme weather]] events, an expansion of [[tropical diseases]], [[phenology|changes in the timing of seasonal patterns in ecosystems]], and drastic [[Economics of global warming|economic impact]]. Concerns have led to [[Politics of global warming|political]] activism advocating proposals to [[Mitigation of global warming|mitigate]], [[zero-carbon|eliminate]], or [[Adaptation to global warming|adapt]] to it. The 2007 [[IPCC Fourth Assessment Report|Fourth Assessment Report]] by the [[Intergovernmental Panel on Climate Change]] (IPCC) includes a summary of the expected effects. ==Overview== Potential climate changes due to [[global warming]] may lead to future large-scale and possibly irreversible effects at continental and global scales. The likelihood, magnitude, and timing is uncertain and [[Global warming controversy|controversial]], but some examples of projected climate changes include significant slowing of the ocean circulation that transports warm water to the [[Atlantic Ocean|North Atlantic]], large reductions in the [[Greenland ice sheet|Greenland]] and [[West Antarctic Ice Sheet]]s, accelerated global warming due to carbon cycle feedbacks in the terrestrial [[biosphere]], and releases of terrestrial carbon from [[permafrost]] regions and methane from hydrates in coastal sediments. The probability of one or more of these changes occurring is likely to increase with the rate, magnitude, and duration of climate change. Additionally, the [[United States National Academy of Sciences]] has stated, "greenhouse warming and other human alterations of the earth system may increase the possibility of large, abrupt, and unwelcome regional or global climatic events. . . . Future abrupt changes cannot be predicted with confidence, and climate surprises are to be expected."<ref>{{cite web |url=http://books.nap.edu/openbook.php?record_id=10136&page=1 |title= Executive Summary |accessdate=2007-05-07 |format= [[PHP]] |work= Abrupt Climate Change: Inevitable Surprises |publisher= [[United States National Academy of Sciences]] |month= June |year= 2002}}</ref> The IPCC reports that the effects of global warming will be mixed across regions. For smaller values of warming (1 to 3&nbsp;°[[Celsius|C]]), changes are expected to produce net benefits in some regions and for some activities, and net costs for others. Greater warming may produce net costs (or to reduce the benefits from smaller warming) in all regions. Developing countries are vulnerable to reduced economic growth as a result of warming.<ref name="WG2 AR4 SPM">{{cite book | url=http://www.ipcc.ch/pdf/assessment-report/ar4/wg2/ar4-wg2-spm.pdf | format=[[Portable Document Format|PDF]] | title=Summary for Policymakers. 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=[[Intergovernmental Panel on Climate Change]] |editors=M.L. Parry, O.F. Canziani, J.P. Palutikof, P.J. van der Linden and C.E.Hanson| publisher=[[Cambridge University Press]], Cambridge, UK |pages=7-22}}</ref> Most of the consequences of global warming would result from one of three physical changes: sea level rise, higher local temperatures, and changes in rainfall patterns. Sea level is generally expected to [[sea level rise|rise]] 18 to 59&nbsp;cm (7.1 to 23.2&nbsp;inches) by the end of the 21st century.<ref name="WGI AR4 SPM">{{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]]}}</ref> ==Physical impacts== ===Effects on weather=== [[Image:Trends in natural disasters.jpg|thumb|right|Global warming is responsible in part for some trends in natural disasters such as [[extreme weather]].]] Increasing temperature is likely to lead to increasing precipitation <ref name=ar4wg1a>{{cite web |publisher= [[Intergovernmental Panel on Climate Change]] |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. Human influences will continue to change atmospheric composition throughout the 21st century. |url=http://www.grida.no/climate/ipcc_tar/wg1/008.htm |format= |accessdate= 2007-12-03 |accessyear= |year=2001}}</ref><ref>{{cite web |publisher= [[Intergovernmental Panel on Climate Change]] |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 |format= |accessdate= 2007-12-03 |accessyear= |year=2001}}</ref> but the effects on storms are less clear. Extratropical storms partly depend on the [[temperature gradient]], 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= [[Intergovernmental Panel on Climate Change]] |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 |format= |accessdate= 2007-12-03 |accessyear= |year=2001}}</ref> ====Extreme weather==== 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> [[Kerry Emanuel]] writes that hurricane power dissipation is highly correlated with temperature, reflecting global warming.<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=[[Nature (journal)|Nature]] |year=2005 |volume=436 |pages=686–688 |doi=10.1038/nature03906|format=PDF}}</ref>. However, a further study by Emanuel using current model output has 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=[[Bulletin of the American Meteorological Society]] |year=2008 |volume=89 |pages=347–367 |doi=10.1175/BAMS-89-3-347|format=PDF}}</ref>. Hurricane modeling has produced similar results, finding that hurricanes, simulated under warmer, high-CO<sub>2</sub> conditions, are more intense; models also show that 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=3|pages=11}}</ref> Worldwide, the proportion of [[hurricane]]s reaching [[Saffir-Simpson Hurricane Scale|categories 4 or 5]] – 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= [[New Scientist]] |date=2005-09-15 |accessdate=2007-12-03}}</ref> Precipitation hitting the US from hurricanes has increased by 7% over the twentieth 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=[[NOAA]] 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=[[Time (magazine)|Time]] |Date= 2005-09-26 |accessdate=2007-12-03}}</ref> The extent to which this is due to global warming as opposed to the [[Atlantic Multidecadal Oscillation]] is unclear. Some studies have found that the increase in [[sea surface temperature]] may be offset by an increase in wind shear, 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> 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. | authorlink = | coauthors = ''et al.'' | year = 2008 | month = | title = Normalized Hurricane Damage in the United States: 1900–2005 | journal = Natural Hazards Review | volume = 9 | issue = 1 | pages = 29&ndash;42 | doi = 10.1061/(ASCE)1527-6988(2008)9:1(29) | url = http://forecast.mssl.ucl.ac.uk/shadow/docs/Pielkeetal2006a.pdf | accessdate = | quote = |format=PDF}}</ref> The [[World Meteorological Organization]] 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 |language= |accessdate= |quote= }}</ref> They also clarified that “no individual tropical cyclone can be directly attributed to climate change.”<ref name="WMO-IWTC" /> However, 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. |authorlink= |coauthors= |year=2006 |month= |title=Deconvolution of the Factors Contributing to the Increase in Global Hurricane Intensity |journal=Science |volume=312 |issue=5770 |pages=94&ndash;97 |doi=10.1126/science.1123560 |url= |accessdate= |quote=|pmid=16543416 }}</ref> {{Highest ACE Atlantic hurricane seasons|align=right}} [[Image:Hurricane Intensity Shift.png|thumb|left|This image shows the conclusions of Knutson and Tuleya (2004) that maximum intensity reached by tropical storms is likely to undergo an increase, with a significant increase in the number of highly destructive category 5 storms.]] [[Thomas Knutson]] and Robert E. Tuleya of [[NOAA]] stated in 2004 that warming induced by [[greenhouse gas]] 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=3477–3494 |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}}</ref> Vecchi and Soden find that [[wind shear]], the increase of which acts to inhibit [[tropical cyclones]], also changes in model-projections of global warming. There are projected increases of [[wind shear]] in the tropical Atlantic and East Pacific associated with the deceleration of the [[Walker circulation]], 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= [[Geophysical Research Letters]] |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}}</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 |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}}</ref> Stephen Mwakifwamba, national co-ordinator of the Centre for Energy, Environment, Science and Technology — which prepared the Tanzanian government's climate change report to the UN — says that change is happening in [[Tanzania]] right now. "In the past, we had a drought about every 10 years", he says. "Now we just don't know when they will come. They are more frequent, but then so are floods. The climate is far less predictable. We might have floods in May or droughts every three years. Upland areas, which were never affected by mosquitoes, now are. Water levels are decreasing every day. The rains come at the wrong time for farmers and it is leading to many problems"<ref>{{cite news|url=http://www.guardian.co.uk/climatechange/story/0,12374,1517935,00.html |title=In the land where life is on hold |author=John Vidal |publisher=[[The Guardian]] |date=2005-06-30| accessdate=2007-12-06}}</ref>. Greg Holland, director of the Mesoscale and Microscale Meteorology Division at the [[National Center for Atmospheric Research]] in Boulder, Colorado, said on April 24, 2006, "The hurricanes we are seeing are indeed a direct result of climate change," and that the wind and warmer water conditions that fuel storms when they form in the Caribbean are, "increasingly due to greenhouse gases. There seems to be no other conclusion you can logically draw." Holland said, "The large bulk of the scientific community say what we are seeing now is linked directly to greenhouse gases." <ref>{{cite web|url=http://globalwarmingfacts.blogspot.com/2006_04_01_archive.html|publisher=Global Warming blog (from [[Reuters]])|accessdate=2007-12-06|title= Global warming behind record 2005 storms: experts|date=2006-04-25}}</ref> (See also "Global warming?" in [[tropical cyclone]]) ====Increased evaporation==== [[Image:BAMS climate assess boulder water vapor 2002.gif|thumb|200px|Increasing water vapor at Boulder, Colorado.]] 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 (magazine)| Nature]]|date= [[October 26]], [[2002]]|volume=377|pages=687–688| doi=10.1038/377687b0| format=abstract}}</ref>; this is thought by many to be explained by [[global dimming]]. As the climate grows warmer and the causes of global dimming are reduced, [[evaporation]] will increase due to warmer oceans. Because the world is a closed system this will cause heavier [[rainfall]], with more [[erosion]]. This erosion, in turn, can in vulnerable tropical areas (especially in Africa) lead to [[desertification]]. 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 [[weather]] 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 [[Antarctica]] 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= [[Intergovernmental Panel on Climate Change]] |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 |format= |accessdate= 2007-12-03 |accessyear= |year=2001}}</ref> ====Cost of more extreme weather==== {{Costliest U.S. Atlantic hurricanes by wealth normalization}} As the [[World Meteorological Organization]] 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 [[1926 Miami hurricane]], 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: [http://www.insurancejournal.com/news/national/2006/04/18/67389.htm Sound Risk Management, Strong Investment Results Prove Positive for P/C Industry], 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 |date=June 2005|format=PDF}}</ref> ====Destabilization of local climates==== [[Image:Cyclone Catarina 2004.jpg|thumb|left|The first recorded South Atlantic hurricane, [[Cyclone Catarina|"Catarina"]], which hit Brazil in March 2004]] In the northern hemisphere, the southern part of the [[Arctic]] 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. [[Canada]], [[Alaska]] and [[Russia]] are experiencing initial melting of [[permafrost]]. This may disrupt ecosystems and by increasing bacterial activity in the soil lead to these areas becoming carbon sources instead of [[carbon sink]]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 [[Siberia]]'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 [[Effects of global warming#Methane release from melting permafrost peat bogs|methane release from melting permafrost peat bogs]]. [[Tropical cyclone|Hurricane]]s were thought to be an entirely North Atlantic phenomenon. In late March 2004, the first [[Cyclone Catarina|Atlantic cyclone]] to form south of the [[equator]] hit [[Brazil]] with 40 m/s (144 km/h) winds, although some Brazilian meteorologists deny that it was a hurricane.<ref>{{cite news |url=http://www.usatoday.com/weather/news/2004-03-28-brazil-storm_x.htm |title=First South Atlantic hurricane hits Brazil |publisher= [[USA Today]] |date= 2004-03-28}}</ref> Monitoring systems may have to be extended 1,600 km (1,000 miles) further south. There is no agreement as to whether this hurricane is linked to climate change,<ref name="Henson2005">{{cite web |url=http://www.ucar.edu/communications/quarterly/summer05/catarina.html |title=What was Catarina? |accessdate=2008-06-22 |last=Henson |first=Bob |coauthors= |date=2005 |work=UCAR Quarterly |publisher=}}</ref><ref>{{cite journal |last=Pezza |first=Alexandre B. |coauthors=Simmonds, Ian |date=2006-04-28 |title=Catarina: The first South Atlantic hurricane and its association with vertical wind shear and high latitude blocking |journal=Proceedings of 8th International Conference on Southern Hemisphere Meteorology and Oceanography |pages=353–364 |isbn=85-17-00023-4 |accessdate=}}</ref> but at least one climate model exhibits increased tropical cyclone genesis in the South Atlantic under global warming by the end of the 21st century.<ref>{{cite web |url=http://www2.metoffice.gov.uk/weather/tropicalcyclone/catarina.html |title=South Atlantic Hurricane breaks all the rules|publisher= U. K. [[Met Office]] |accessdate=2007-12-06}}</ref> ===Glacier retreat and disappearance === {{main|Retreat of glaciers since 1850}} [[Image:Glacier Mass Balance Map.png|300px|right|thumb|A map of the change in thickness of mountain glaciers since 1970. Thinning in orange and red, thickening in blue.]] [[Image:Lewist.jpg|right|thumb|300px|Lewis Glacier, North Cascades, WA USA is one of five glaciers in the area that melted away]] In historic times, glaciers grew during a cool period from about 1550 to 1850 known as the [[Little Ice Age]]. Subsequently, until about 1940, glaciers around the world retreated as the climate warmed. [[Retreat of glaciers since 1850|Glacier retreat]] 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 | work= | url=http://www.geo.unizh.ch/wgms/fog.html | accessdate=December 20 | accessyear=2005 }}</ref> Excluding the [[ice cap]]s and [[ice sheet]]s of the Arctic and Antarctic, the total surface area of [[glacier]]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 [[Andes]], [[Alps]], [[Himalayas]], [[Rocky Mountains]] and [[North Cascades]]. The loss of glaciers not only directly causes landslides, flash floods and [[glacial lake]] overflow,<ref>{{cite web |url=http://www.rrcap.unep.org/issues/glof/ |title=Glacial Lake Outburst Flood Monitoring and Early Warning System|publisher=[[United Nations Environment Programme]] |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 [[Hindu Kush]] and [[Himalaya]]n glacial melts that comprise the principal dry-season water source of many of the major rivers of the [[Central Asia|Central]], [[South Asia|South]], [[East Asia|East]] and [[Southeast Asia]]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 (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=[[17 November]] [[2005]] | volume=438 | pages=303–309 | accessdate=2008-02-18 | doi= 10.1038/nature04141 }}</ref> According to a UN climate report, the [[Himalayas|Himalayan]] glaciers that are the sources of [[Asia]]'s biggest rivers&mdash;[[Ganges]], [[Indus]], [[Brahmaputra]], [[Yangtze]], [[Mekong]], [[Salween]] and [[Yellow]]&mdash;could disappear by 2035 as temperatures rise.<ref>{{cite web | author= | title=Vanishing Himalayan Glaciers Threaten a Billion | publisher=[[Reuters]] | url=http://www.planetark.com/dailynewsstory.cfm/newsid/42387/story.htm | date=2007-06-05 | accessdate=December 21 | accessyear=2007 }}</ref> Approximately 2.4 billion people live in the [[drainage basin]] 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}}</ref> [[India]], [[China]], [[Pakistan]], [[Bangladesh]], [[Nepal]] and [[Myanmar]] could experience floods followed by [[droughts]] in coming decades. In [[India]] alone, the Ganges provides water for drinking and farming for more than 500 million people.<ref>{{cite web | author= | 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 | accessyear=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 | accessyear=2007 }}</ref><ref>{{cite web | author=Navin Singh Khadka | title=Himalaya glaciers melt unnoticed | publisher=[[BBC]] | url=http://news.bbc.co.uk/2/hi/science/nature/3998967.stm | date=2004-11-10 | accessdate=December 21 | accessyear=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 |authorlink= |coauthors=''et al.'' |year=2006 |month= |title=Accelerated melting of Himalayan snow and ice triggers pronounced changes in a valley peatland from northern India |journal=Geophysical Research Letters |volume=33 |issue= |pages=L15709 |doi=10.1029/2006GL026704 |url= |accessdate= |quote= }}</ref> The recession of mountain glaciers, notably in Western North America, Franz-Josef Land, Asia, the Alps, 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 glacierized areas. The [[Lewis Glacier]], North Cascades pictured at right after melting away in 1990 is one of the 47 North Cascade glaciers observed and 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 [[world population|human populations]], 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|abbr=off|lk=off}} 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. [[Image:Retreat of the Helheim Glacier, Greenland.jpg|thumb|300px|left|Retreat of the Helheim Glacier, Greenland]] Glacier retreat has been observed in these outlet glaciers, resulting in an increase of the ice flow rate. In [[Greenland]] 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, Jakobshavns and Kangerdlugssuaq Glaciers, jointly drain more than 16% of the [[Greenland Ice Sheet]]. 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|lk=off}} between 2001 and 2005. It has also accelerated from {{convert|20|m|ft|abbr=on|lk=off}}/day to {{convert|32|m|ft|abbr=on|lk=off}}/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 west Greenland is generally considered the fastest moving glacier in the world. It had been moving continuously at speeds of over {{convert|24|m|ft|abbr=on|lk=off}}/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 doubled to over {{convert|30|m|ft|abbr=on|lk=off}}/day.<ref>{{cite web |url=http://www.nasa.gov/vision/earth/lookingatearth/jakobshavn.html |title=Fastest Glacier in Greenland Doubles Speed |publisher=[[NASA]] |date=2004-12-01 | author=Krishna Ramanujan |accessdate=2007-12-28}}</ref> Glacier retreat and acceleration is also apparent on two important outlet glaciers of the [[West Antarctic Ice Sheet]]. [[Pine Island Glacier]], which flows into the [[Amundsen Sea]] thinned {{convert|3.5|+/-|0.9|m|ft|abbr=on|lk=off}} per year and retreated {{convert|5|km|mi|abbr=off|lk=off}} in 3.8 years. The [[Glacier terminus|terminus]] of the glacier is a floating ice shelf and the point at which it is afloat is retreating {{convert|1.2|km|mi|abbr=on|lk=off}}/year. This glacier drains a substantial portion of the West Antarctic Ice Sheet and has been referred to as the weak underbelly of this ice sheet.<ref>{{cite journal |journal = [[Science (journal)|Science]] |url=http://www.sciencemag.org/cgi/content/abstract/281/5376/549 |title=Fast Recession of a West Antarctic Glacier | last=Rignot |first=E.J. |volume=281 |number=5376 |ages=549-551 |date=[[July 24]], [[1998]] |accessdate=2007-12-28 |format=abstract |pmid=9677195 |doi=10.1126/science.281.5376.549 |pages=549}}</ref> This same pattern of thinning is evident on the neighboring Thwaites Glacier cliff. ===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 [[ocean acidification]]. 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 level rise==== {{Double image stack|right|Holocene Sea Level.png|Recent Sea Level Rise.png|200|Sea leve rise during the Holocene.|Sea level has been rising {{#expr: 20/120 round 1}} cm/year, based on measurements of [[sea level rise]] from 23 long [[tide gauge]] records in geologically stable environments.}} {{main|Sea level rise}} With increasing average global temperature, the [[water]] in the oceans expands in volume, and additional water enters them which had previously been locked up on land in glaciers, for example, the [[Greenland ice sheet|Greenland]] and the [[Antarctic ice sheet]]s. For most glaciers worldwide, an average volume loss of 60% until 2050 is predicted.<ref name="Schneeberger2993">{{cite journal |last=Schneeberger |first=Christian |authorlink= |coauthors=''et al.'' |year=2003 |month= |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&ndash;4 |pages=145&ndash;163 |doi=10.1016/S0022-1694(03)00260-9 |url= |accessdate= |quote= }}</ref> Meanwhile, the estimated total ice melting rate over Greenland is –239 ± 23 cubic kilometers per year, mostly from East Greenland.<ref name="Chen2006">{{cite journal |last=Chen |first=J. L. |authorlink= |coauthors=Wilson, C. R.; Tapley, B. D. |year=2006 |month= |title=Satellite Gravity Measurements Confirm Accelerated Melting of Greenland Ice Sheet |journal=Science |volume=313 |issue=5795 |pages=1958&ndash;1960 |doi=10.1126/science.1129007 |url= |accessdate= |quote= }}</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 Scenarios (SRES) A1B scenario by the mid-2090s, for instance, global sea level reaches 0.22 to 0.44 m above 1990 levels, and is rising at about 4 mm 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 |accessyear= |year=2007}}</ref> Since 1900, the sea level has risen at an average of 1.7 mm/yr.;<ref name="ar4wg1ch5" /> since 1993, [[satellite]] altimetry from [[TOPEX/Poseidon]] indicates a rate of about 3 mm/yr.<ref name="ar4wg1ch5" /> The sea level has risen more than 120 metres since the [[Last Glacial Maximum]] about 20,000 years ago. The bulk of that occurred before 7000 years ago.<ref name="Fleming1998">{{cite journal |last=Fleming |first=Kevin |authorlink= |coauthors=''et al.'' |year=1998 |month= |title=Refining the eustatic sea-level curve since the Last Glacial Maximum using far- and intermediate-field sites |journal=Earth and Planetary Science Letters |volume=163 |issue=1&ndash;4 |pages=327&ndash;342 |doi=10.1016/S0012-821X(98)00198-8 |url= |accessdate= |quote= }}</ref> Global temperature declined after the [[Holocene Climatic Optimum]], causing a sea level lowering of 0.7 ± 0.1 m between 4000 and 2500 years before present.<ref name="Goodwin1998">{{cite journal |last=Goodwin |first=Ian D. |authorlink= |coauthors= |year=1998 |month= |title=Did changes in Antarctic ice volume influence late Holocene sea-level lowering? |journal=Quaternary Science Reviews |volume=17 |issue=4&ndash;5 |pages=319&ndash;332 |doi=10.1016/S0277-3791(97)00051-6 |url= |accessdate= |quote= }}</ref> From 3000 years ago to the start of the 19th century, sea level was almost constant, with only minor fluctuations. However, the [[Medieval Warm Period]] may have caused some sea level rise; evidence has been found in the [[Pacific Ocean]] for a rose to perhaps 0.9 m above present level in 700 BP.<ref>{{cite journal |last=Nunn |first=Patrick D. |authorlink= |coauthors= |year=1998 |month= |title=Sea-Level Changes over the Past 1,000 Years in the Pacific |journal=Journal of Coastal Research |volume=14 |issue=1 |pages=23&ndash;30 |doi=10.2112%2F0749-0208(1998)014%5B0023%3ASLCOTP%5D2.3.CO%3B2 |url= |accessdate= |quote= }}</ref> In a paper published in 2007, the climatologist [[James Hansen]] ''et al.'' claimed that ice at the poles does not melt in a gradual and linear fashion, but flips suddenly from one state to another according to the geological record. 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.'' | date = 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 | volume = 365 | pages = 1925–1954 | format = [[Portable Document Format|PDF]] |doi = 10.1098/rsta.2007.2052 }}</ref></blockquote> ====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 [[Southern Ocean]] 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= [[Science (journal)|Science]] |date=[[February 15]], [[2002]]|volume=295|number=5558pages=1275-1277 |doi=10.1126/science.1065863 |pages=1275 |pmid=11847337}}</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>. {{Fact|date=June 2008}} ====Acidification==== {{main|Ocean acidification}} The world’s oceans soak up much of the carbon dioxide 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. |authorlink= |coauthors=''et al.'' |year=2004 |month= |title=The Oceanic Sink for Anthropogenic CO<sub>2</sub> |journal=Science |volume=385 |issue=5682 |pages=367&ndash;371 |doi=10.1126/science.1097403 |url= |accessdate= |quote=|pmid=15256665 }}</ref> But in water, carbon dioxide becomes a weak [[carbonic acid]], and the increase in the greenhouse gas since the [[industrial revolution]] has already lowered the average [[pH]] (the laboratory measure of acidity) of seawater by 0.1 units, to 8.2. Predicted emissions could lower it 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=[[BBC]] |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=[[Royal Society]]|date=2005-06-30|accessdate=2008-06-22}}</ref> There are concerns that increasing acidification could have a particularly detrimental effect on [[coral]]s <ref>{{cite web |url=http://www.opendemocracy.net/globalization-climate_change_debate/2558.jsp |title=Global warming and coral reefs|auithor=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 |authorlink= |coauthors=''et al.'' |year=2002 |month= |title=Ecological responses to recent climate change |journal=Nature |volume=416 |issue=6879 |pages=389&ndash;395 |doi=10.1038/416389a |url= |accessdate= |quote= }}</ref> which coincidentally was the warmest year ever recorded) and other marine organisms with [[calcium carbonate]] 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> ====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. This would affect in particular areas like [[Scandinavia]] and [[United Kingdom|Britain]] that are warmed by the [[North Atlantic drift]]. More significantly, it could lead to an [[oceanic anoxic event]]. 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. 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. ==Abrupt and irreversible effects== The scientific consensus in the [[IPCC Fourth Assessment Report]] is that "Anthropogenic warming could lead to some effects that are abrupt or irreversible, depending upon the rate and magnitude of the climate change." ====Abrupt effects==== Partial loss of ice sheets on polar land could imply metres of sea level rise, major changes in coastlines and inundation of low-lying areas, with greatest effects in river deltas and low-lying islands. Such changes are projected to occur over millennial time scales, but more rapid sea level rise on century time scales cannot be excluded.<ref>Intergovernmental Panel on Climate Change, Fourth Assessment Report, Working Group II Report "Impacts, Adaptation and Vulnerability". Chapter 6: Coastal Systems and Low Lying Areas. http://www.ipcc.ch/pdf/assessment-report/ar4/wg2/ar4-wg2-chapter6.pdf</ref> ====Irreversible effects==== Climate change is likely to lead to some irreversible effects. There is medium confidence that approximately 20- 30% of species assessed so far are likely to be at increased risk of extinction if increases in global average warming exceed 1.5-2.5°C (relative to 1980-1999). As global average temperature increase exceeds about 3.5°C,model projections suggest significant extinctions (40-70% of species assessed) around the globe. At the scale of 7°C temperature increase, emissions of [[hydrogen sulfide]] caused by [[sulfate-reducing bacteria]] may cause by a severe [[anoxic event]]. This will adversely affect marine ecologies. ==Positive feedback effects== Some of the observed and potential effects of global warming are [[positive feedback]]s, contributing directly to further global warming. ====Methane release from melting permafrost peat bogs==== {{wikinews|Scientists warn thawing Siberia may trigger global meltdown}} Western Siberia is the world's largest [[peat bog]], a one million square kilometer region of [[permafrost]] peat bog that was formed 11,000 years ago at the end of the last [[ice age]]. The melting of its permafrost is likely to lead to the release, over decades, of large quantities of [[methane]]. As much as 70,000 million [[tonne]]s of methane, an extremely effective greenhouse gas, might be released over the next few decades, creating an additional source of greenhouse gas emissions <ref>{{cite web |url=http://www.newscientist.com/article.ns?id=mg18725124.500 |title=Climate warning as Siberia melts |author=Fred Pearce |publisher=New Scientist |date= 2005-08-11|accessdate=2007-12-30}}</ref>. Similar melting has been observed in eastern [[Siberia]] <ref>{{cite web| url=http://www.zmag.org/content/showarticle.cfm?SectionID=56&ItemID=8482 |title=Warming Hits 'Tipping Point' |author=Ian Sample |publisher=Guardian |date=2005-08-11 |accessdate=2007-12-30}}</ref>. ====Methane release from hydrates==== {{main|Clathrate gun hypothesis}} [[Methane clathrate]], also called methane hydrate, is a form of [[water (molecule)|water]] [[ice]] that contains a large amount of [[methane]] within its [[crystal]] structure. Extremely large deposits of methane clathrate have been found under sediments on the ocean floors of Earth. The sudden release of large amounts of natural gas from methane clathrate deposits, in a [[runaway greenhouse effect#Positive feedback and runaway greenhouse effect|runaway greenhouse effect]], has been hypothesized as a cause of past and possibly future climate changes. The release of this trapped methane is a potential major outcome of a rise in temperature; it is thought that this might increase the global temperature by an additional 5° in itself, as methane is much more powerful as a greenhouse gas than carbon dioxide. The theory also predicts this will greatly affect available oxygen content of the atmophere. This theory has been proposed to explain the most severe mass extinction event on earth known as the [[Permian-Triassic extinction event]]. ====Carbon cycle feedbacks==== There have been predictions, and some evidence, that global warming might cause loss of carbon from terrestrial ecosystems, leading to an increase of atmospheric CO<sub>2</sub> levels. Several climate models indicate that global warming through the 21st century could be accelerated by the response of the terrestrial carbon cycle to such warming <ref>{{cite journal |url=http://www.nature.com/nature/journal/v408/n6809/abs/408184a0.html |journal =[[Nature (journal)|Nature]] |title=Acceleration of global warming due to carbon-cycle feedbacks in a coupled climate model |first=Peter M. |last=Cox |coauthors=Richard A. Betts, Chris D. Jones, Steven A. Spall and Ian J. Totterdell |volume=408 |number=6809 |date=[[November 9]], [[2000]] |accessdate=2008-01-02 |format=abstract |doi=10.1038/35041539 |pages=184}}</ref>. All 11 models in the [[C4MIP]] study found that a larger fraction of anthropogenic CO<sub>2</sub> will stay airborne if climate change is accounted for. By the end of the twenty-first century, this additional CO<sub>2</sub> varied between 20 and 200 ppm for the two extreme models, the majority of the models lying between 50 and 100 ppm. The higher CO<sub>2</sub> levels led to an additional climate warming ranging between 0.1° and 1.5 °C. However, there was still a large uncertainty on the magnitude of these sensitivities. Eight models attributed most of the changes to the land, while three attributed it to the ocean <ref>{{cite journal |url=http://ams.allenpress.com/amsonline/?request=get-document&doi=10.1175%2FJCLI3800.1 |journal=Journal of Climate |title=Climate–Carbon Cycle Feedback Analysis: Results from the C4MIP Model Intercomparison |volume=19 |number =14 |pages=3337–3353 |year=2006 | first=P. |last=Friedlingstein |coauthors= P. Cox, R. Betts, L. Bopp, W. von Bloh, V. Brovkin, P. Cadule, S. Doney, M. Eby, I. Fung, G. Bala, J. John, C. Jones, F. Joos, T. Kato, M. Kawamiya, W. Knorr, K. Lindsay, H.D. Matthews, T. Raddatz, P. Rayner, C. Reick, E. Roeckner, K.G. Schnitzler, R. Schnur, K. Strassmann, A.J. Weaver, C. Yoshikawa, and N. Zeng |accessdate=2008-01-02 |doi=10.1175/JCLI3800.1 |format=subscription required}}</ref>. The strongest feedbacks in these cases are due to increased respiration of carbon from soils throughout the high latitude [[taiga|boreal forests]] of the Northern Hemisphere. One model in particular ([[HadCM3]]) indicates a secondary carbon cycle feedback due to the loss of much of the [[Amazon rainforest]] in response to significantly reduced precipitation over tropical South America<ref>{{cite web |url=http://education.guardian.co.uk/higher/research/story/0,,965721,00.html |title=5.5C temperature rise in next century| publisher=The Guardian |date=2003-05-29|accessdate=2008-01-02}}</ref>. While models disagree on the strength of any terrestrial carbon cycle feedback, they each suggest any such feedback would accelerate global warming. Observations show that soils in England have been losing carbon at the rate of four million tonnes a year for the past 25 years<ref>{{cite web |url=http://www.guardian.co.uk/life/science/story/0,12996,1565050,00.html |title= Loss of soil carbon 'will speed global warming' |author=Tim Radford |publisher=The Guardian |date=2005-09-08 |accessdate=2008-01-02}}</ref> according to a paper in Nature by Bellamy et al. in September 2005, who note that these results are unlikely to be explained by land use changes. Results such as this rely on a dense sampling network and thus are not available on a global scale. Extrapolating to all of the United Kingdom, they estimate annual losses of 13 million tons per year. This is as much as the annual reductions in carbon dioxide emissions achieved by the UK under the Kyoto Treaty (12.7 million tons of carbon per year).<ref>{{cite journal |journal=[[Nature (journal)|Nature]] |title= Environmental science: Carbon unlocked from soils |first=E. Detlef |last= Schulze |coauthors= Annette Freibauer |url=http://www.nature.com/nature/journal/v437/n7056/full/437205a.html |volume=437|number=7056 |pages=205–206 |date=[[September 8]], [[2005]] |accessdate=2008-01-02 |doi= 10.1038/437205a}}</ref> ====Forest fires==== The IPCC Fourth Assessment Report predicts that many mid-latitude regions, such as Mediterranean Europe, will experience decreased rainfall and an increased risk of drought, which in turn would allow forest fires to occur on larger scale, and more regularly. This releases more stored carbon into the atmosphere than the carbon cycle can naturally re-absorb, as well as reducing the overall forest area on the planet, creating a positive feedback loop. Part of that feedback loop is more rapid growth of replacement forests and a northward migration of forests as northern latitudes become more suitable climates for sustaining forests. There is a question of whether the burning of renewable fuels such as forests should be counted as contributing to global warming.<ref>{{cite web | url=http://www.davidsuzuki.org/Forests/Forests_101/FIRE/Climate_Change.asp | title=Climate Change and Fire | publisher=[[David Suzuki Foundation]] | accessdate=2007-12-02}}</ref><ref>{{cite web | url=http://yosemite.epa.gov/oar/globalwarming.nsf/content/ImpactsForests.html | title=Global warming : Impacts : Forests | accessdate=2007-05-17 | publisher=[[United States Environmental Protection Agency]] | date=2000-01-07 | accessdate=2007-12-02}}</ref><ref>{{cite web | url= http://www.whrc.org/southamerica/fire_savann/FeedbackCycles.htm | title= Feedback Cycles: linking forests, climate and landuse activities | publisher=[[Woods Hole Research Center]] | accessdate=2007-12-02}}</ref> ====Retreat of sea ice==== [[Image:Northern Hemisphere Sea Ice Extent Anomalies.png|right|thumb|Northern Hemisphere ice trends]] [[Image:Southern Hemisphere Sea Ice Extent Anomalies.png|right|thumb|Southern Hemisphere ice trends]] The sea absorbs heat from the sun, while the ice largely reflects the sun rays back to space. Thus, retreating sea ice will allow the sun to warm the now exposed sea water, contributing to further warming. The mechanism is the same as when a black car heats up faster in sunlight than a white car. This [[albedo]] change is also the main reason why [[IPCC]] predict polar temperatures in the northern hemisphere to rise up to twice as much as those of the rest of the world. In September 2007, the [[Polar ice packs#Extent and trends of polar ice packs|Arctic sea ice area]] reached about half the size of the average summer minimum area between 1979 to 2000. <ref>{{cite web |url=http://arctic.atmos.uiuc.edu/cryosphere/ |title=The cryosphere today |publisher=University of Illinois at Urbana-Champagne Polar Research Group |accessdate=2008-01-02}}</ref><ref> {{cite web |url=http://www.nsidc.org/news/press/2007_seaiceminimum/20070810_index.html |title=Arctic Sea Ice News Fall 2007 |publisher= National Snow and Ice Data Center |accessdate=2008-01-02 }}. </ref> Based on the accelerated loss, predictions are that by 2030 the Arctic could be ice-free part of the year. <ref>{{cite web |url=http://www.guardian.co.uk/environment/2007/sep/05/climatechange.sciencenews |publisher=The Guardian |date=2007-09-05 |title=Ice-free Arctic could be here in 23 years |author=David Adam |accessdate=2008-01-02}}</ref> Also in September 2007, Arctic sea ice retreated far enough for the Northwest Passage to become navigable to shipping for the first time in recorded history.<ref>{{Citation | title=Arctic ice levels at record low opening Northwest Passage | newspaper=Wikinews | url=http://en.wikinews.org/wiki/Arctic_ice_levels_at_record_low_opening_Northwest_Passage |date = September 16, 2007}}</ref> The [[polar amplification]] of global warming is not predicted to occur in the southern hemisphere.<ref>{{cite web |url=http://www.realclimate.org/index.php?p=18 |title=Antarctic cooling, global warming? |author= Eric Steig and Gavin Schmidt |publisher=RealClimate |accessdate=2008-01-20}}</ref> The Antarctic sea ice reached its greatest extent on record since the beginning of observation in 1979,<ref>{{cite web |url=http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/current.area.south.jpg |title=Southern hemisphere sea ice area |publisher=Cryosphere Today |accessdate=2008-01-20}}</ref> but the gain in ice in the south is exceeded by the loss in the north. The trend for global sea ice, northern hemisphere and southern hemisphere combined is clearly a decline.<ref>{{cite web |url=http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/global.daily.ice.area.withtrend.jpg |title=Global sea ice area |publisher=Cryosphere Today |accessdate=2008-01-20}}</ref> ==Negative feedback effects== {{Refimprove|date=May 2008}} Following [[Le Chatelier's principle]], the chemical equilibrium of the Earth's [[carbon cycle]] will shift in response to anthropogenic CO<sub>2</sub> emissions. The primary driver of this is the ocean, which absorbs anthropogenic CO<sub>2</sub> via the so-called [[solubility pump]]. At present this accounts for only about one third of the current emissions, but ultimately most (~75%) of the CO<sub>2</sub> emitted by human activities will dissolve in the ocean over a period of centuries: "A better approximation of the lifetime of fossil fuel CO<sub>2</sub> for public discussion might be 300 years, plus 25% that lasts forever"<ref>{{cite journal |last=Archer|first=David|year=2005|title= Fate of fossil fuel CO<sub>2</sub> in geologic time |journal=[[Journal of Geophysical Research]]|volume=110 |doi=10.1029/2004JC002625|pages= C09S05}} </ref>. However, the rate at which the ocean will take it up in the future is less certain, and will be affected by [[stratification (water)|stratification]] induced by warming and, potentially, changes in the ocean's [[thermohaline circulation]]. Also, the [[thermal radiation]] of the Earth rises in proportion to the fourth power of temperature, increasing the amount of outgoing radiation as the Earth warms. The impact of this negative feedback effect is included in [[global climate model]]s summarized by the [[IPCC]]. ==Other consequences== [[Image:Edccc.jpg|right|thumb|300px|As recent estimates of the rate of global warming have increased, so have the financial estimates of the damage costs.<ref>Adapted from a portion of Figure 1 in Tol and Yohe (2006) "A Review of the Stern Review" ''World Economics'' '''7'''(4): 233-50.</ref>]] ===Economic and social=== {{seealso|Economics of global warming}} Many estimates of aggregate net economic costs of damages from climate change across the globe, the social cost of carbon (SCC), expressed in terms of future net benefits and costs that are discounted to the present, are now available. Peer-reviewed estimates of the SCC for 2005 have an average value of US$43 per tonne of carbon (tC) (i.e., US$12 per tonne of carbon dioxide) but the range around this mean is large. For example, in a survey of 100 estimates, the values ran from US$-10 per tonne of carbon (US$-3 per tonne of carbon dioxide) up to US$350/tC (US$95 per tonne of carbon dioxide.)<ref name="WG2 AR4 SPM"/> [[Nicholas Stern]], the former [[World Bank Chief Economist|Chief Economist]] and Senior Vice-President of the [[World Bank]], states in an [[October 29]], [[2006]], [[Stern Review|review]] that climate change could affect [[Economic growth|growth]], which could be cut by one-fifth unless drastic action is taken. <ref>{{cite web |url=http://news.bbc.co.uk/1/hi/business/6096594.stm |title=Report's stark warning on climate |date=2006-10-29|accessdate=2008-01-22 |author=Robert Peston |publisher=[[BBC News]]}}</ref> Stern has warned that one percent of global [[GDP]] is required to be invested in order to mitigate the effects of climate change, and that failure to do so could risk a [[recession]] worth up to twenty percent of global [[GDP]].<ref>{{cite web |publisher=[[BBC News]] |date=2006-10-30|url=http://news.bbc.co.uk/2/hi/business/6098362.stm |title=At-a-glance: The Stern Review |accessdate=2008-01-22}}</ref> Stern’s report<ref>{{cite web | url=http://news.bbc.co.uk/1/shared/bsp/hi/pdfs/30_10_06_exec_sum.pdf |title=Stern Review executive summary | author=Nicholas Stern | date=[[30 October]] [[2006]] | publisher=[[New Economics Foundation]]|accessdate=2008-01-22|format=PDF}}</ref> suggests that climate change threatens to be the greatest and widest-ranging market failure ever seen. The report has had significant political effects: [[Australia]] reported two days after the report was released that they would allott AU$60 million to projects to help cut greenhouse gas emissions.<ref>{{cite web |publisher=News.com.au |date=2006-11-01 |url=http://www.news.com.au/story/0,23599,20682039-421,00.html |title=$60m to help cut emissions |accessdate=2008-01-22}}</ref> The ''Stern Review'' has been criticized by some economists, saying that Stern did not consider costs past 2200, that he used an incorrect [[discount rate]] in his calculations, and that stopping or significantly slowing climate change will require deep emission cuts everywhere.<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> Other economists have supported Stern's approach <ref>{{web cite|url=http://delong.typepad.com/sdj/2006/12/do_unto_others.html|title= Do unto others...|author=[[Brad DeLong]] |date=December 18, 2006 |accessdate=2008-01-22}}</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]] |date=December 20, 2006 |accessdate=2008-01-22}}</ref>, or argued that Stern's estimates are reasonable, even if the method by which he reached them is open to criticism. <ref>{{web cite|url=http://www.economics.harvard.edu/faculty/weitzman/files/JELSternReport.pdf|title=The Stern Review of the Economics of Climate Change|author=[[Martin Weitzman]]|date=April 2007|accessdate=2008-01-22}}</ref>. In a 2004 comment on the economic effect of global warming in [[Copenhagen Consensus]], Professor [[Robert O. Mendelsohn]] of Yale School of Forestry and Environmental Studies, stated that :"A series of studies on the impacts of climate change have systematically shown that the older literature overestimated climate damages by failing to allow for adaptation and for climate benefits (see Fankhauser et al 1997; Mendelsohn and Newmann 1999; Tol 1999; Mendelsohn et al 2000; Mendelsohn 2001;Maddison 2001; Tol 2002; Sohngen et al 2002; Pearce 2003; Mendelsohn and Williams 2004). These new studies imply that impacts depend heavily upon initial temperatures (latitude). Countries in the polar region are likely to receive large benefits from warming, countries in the mid-latitudes will at first benefit and only begin to be harmed if temperatures rise above 2.5C (Mendelsohn et al 2000). Only countries in the tropical and subtropical regions are likely to be harmed immediately by warming and be subject to the magnitudes of impacts first thought likely (Mendelsohn et al 2000). Summing these regional impacts across the globe implies that warming benefits and damages will likely offset each other until warming passes 2.5C and even then it will be far smaller on net than originally thought (Mendelsohn and Williams 2004)."<ref>{{cite web |url=http://www.copenhagenconsensus.com/Default.aspx?ID=165 |title=Opponent paper on climate change |publisher= Copenhagen Consensus 2004|author=Robert Mendelsohn |accessdate=2008-01-22}}</ref> ====Insurance==== An industry very directly affected by the risks is the [[insurance]] industry; the number of major natural disasters has tripled since the 1960s, and insured losses increased fifteenfold in real terms (adjusted for inflation).<ref>[http://www.aaisonline.com/viewpoint/AAISviewpointSp05.pdf Viewpoint] American Association of Insurance Services</ref> According to one study, 35&ndash;40% of the worst catastrophes have been climate change related. Over the past three decades, the proportion of the global population affected by weather-related disasters has doubled in linear trend, rising from roughly 2% in 1975 to 4% in 2001. <ref>Climate change (html version) [http://72.14.253.104/search?q=cache:fiFPaQwpYD8J:www.odi.org.uk/iedg/publications/climate_change_web.pdf+%22ERM,+2002%22+%22climate+change%22&hl=en&ct=clnk&cd=2&gl=us ''www.odi.org.uk'']</ref> According to a 2005 report from the Association of British Insurers, limiting carbon emissions could avoid 80% of the projected additional annual cost of tropical cyclones by the 2080s.<ref>Association of British Insurers (2005) [http://www.abi.org.uk/Display/File/Child/552/Financial_Risks_of_Climate_Change.pdf "Financial Risks of Climate Change"] summary report</ref> A June 2004 report by the Association of British Insurers declared "Climate change is not a remote issue for future generations to deal with. It is, in various forms, here already, impacting on insurers' businesses now."<ref>Association of British Insurers (June 2005) [http://www.abi.org.uk/Display/File/364/SP_Climate_Change5.pdf "A Changing Climate for Insurance:] A Summary Report for Chief Executives and Policymakers"</ref> It noted that weather risks for households and property were already increasing by 2-4 % per year due to changing weather, and that claims for storm and flood damages in the UK had doubled to over £6 billion over the period 1998&ndash;2003, compared to the previous five years. The results are rising insurance premiums, and the risk that in some areas [[flood insurance]] will become unaffordable for some. Financial institutions, including the world's two largest insurance companies, [[Munich Re]] and [[Swiss Re]], warned in a 2002 study that "the increasing frequency of severe climatic events, coupled with social trends" could cost almost US$ 150 billion each year in the next decade.<ref>UNEP (2002) [http://www.unepfi.org/fileadmin/documents/CEO_briefing_climate_change_2002_en.pdf "Key findings of UNEP’s Finance Initiatives study"] ''CEObriefing''</ref> These costs would, through increased costs related to insurance and disaster relief, burden customers, taxpayers, and industry alike. In the United States, insurance losses have also greatly increased. According to Choi and Fisher (2003) each 1% increase in annual precipitation could enlarge catastrophe loss by as much as 2.8%.<ref name=choifisher>{{cite journal|last=Choi|first=O. |coauthors=A. Fisher |year=2003 | url= http://www.ingentaconnect.com/content/klu/clim/2003/00000058/F0020001/05109227 |title=The Impacts of Socioeconomic Development and Climate Change on Severe Weather Catastrophe Losses: Mid-Atlantic Region (MAR) and the U.S.|journal=Climatic Change| volume=58|number=(1-2)|pages=149–170 |doi=10.1023/A:1023459216609}}</ref> Gross increases are mostly attributed to increased population and property values in vulnerable coastal areas, though there was also an increase in frequency of weather-related events like heavy rainfalls since the 1950s <ref>{{cite journal|journal=[[Science]]|volume=284|pages=1943–1947| year=1999|number=5422|title=Mitigation Emerges as Major Strategy for Reducing Losses Caused by Natural Disasters|author=Board on Natural Disasters|doi=10.1126/science.284.5422.1943|pmid=10373106}}</ref>. ====Transport==== Roads, airport runways, railway lines and pipelines, (including [[oil pipeline]]s, [[sewer]]s, [[water main]]s etc) may require increased maintenance and renewal as they become subject to greater temperature variation. Regions already adversely affected include areas of [[permafrost]], which are subject to high levels of [[subsidence]], resulting in buckling roads, sunken foundations, and severely cracked runways. <ref>[http://www.airportbusiness.com/article/article.jsp?id=2258&siteSection=4 Studies Show Climate Change Melting Permafrost Under Runways in Western Arctic] ''Weber, Bob'' ''Airportbusiness.com'' October 2007</ref> ====Effects on agriculture==== {{main|Climate change and agriculture}} For some time it was hoped that a positive effect of global warming would be increased agricultural yields, because of the role of carbon dioxide in [[photosynthesis]], especially in preventing [[photorespiration]], which is responsible for significant destruction of several crops. In [[Iceland]], rising temperatures have made possible the widespread sowing of [[barley]], which was untenable twenty years ago. Some of the warming is due to a local (possibly temporary) effect via ocean currents from the Caribbean, which has also affected fish stocks.<ref>{{cite web |url=http://www.guardian.co.uk/climatechange/story/0,12374,1517939,00.html |title=Frozen assets|author=Paul Brown|publisher=[[The Guardian]]|date=2005-06-30|accessdate=2008-01-22}}</ref> While local benefits may be felt in some regions (such as [[Siberia]]), recent evidence is that global yields will be negatively affected. "Rising atmospheric temperatures, longer droughts and side-effects of both, such as higher levels of ground-level ozone gas, are likely to bring about a substantial reduction in crop yields in the coming decades, large-scale experiments have shown" <ref>''[[The Independent]]'', [[April 27]], 2005, "Climate change poses threat to food supply, scientists say" - report on [http://www.royalsoc.ac.uk/event.asp?id=2844 this event]</ref>. Moreover, the region likely to be worst affected is [[Africa]], both because its geography makes it particularly vulnerable, and because seventy per cent of the population rely on rain-fed agriculture for their livelihoods. Tanzania's official report on climate change suggests that the areas that usually get two rainfalls in the year will probably get more, and those that get only one rainy season will get far less. The net result is expected to be that 33% less maize&mdash;the country's staple crop&mdash;will be grown.<ref>{{cite web |url=http://www.guardian.co.uk/climatechange/story/0,12374,1517935,00.html| title=In the land where life is on hold |author= John Vidal |publisher=[[The Guardian]]|date=2005-06-30 |accessdate=2008-01-22}}</ref> [[Climate change]] may be one of the causes of the [[Darfur conflict]]. The combination of decades of [[drought]], [[desertification]] and [[overpopulation]] are among the causes of the conflict, because the [[Arab]] [[Baggara]] [[nomads]] searching for water have to take their livestock further south, to land mainly occupied by farming peoples.<ref>{{cite web |url=http://www.alertnet.org/db/blogs/1265/2007/06/30-100806-1.htm |title=Looking to water to find peace in Darfur|publisher=Reuters AlertNet|author=Nina Brenjo |date=2007-07-30|accessdate=2008-01-22}}</ref> :"The scale of historical climate change, as recorded in Northern [[Darfur]], is almost unprecedented: the reduction in rainfall has turned millions of hectares of already marginal semi-desert grazing land into desert. The impact of climate change is considered to be directly related to the conflict in the region, as desertification has added significantly to the stress on the livelihoods of pastoralist societies, forcing them to move south to find pasture," the [[UNEP]] report states.<ref>{{cite web|url=http://www.irinnews.org/Report.aspx?ReportId=72985|title= Climate change - only one cause among many for Darfur conflict|publisher=IRIN|date=2007-06-28|accessdate=2008-01-22}}</ref> In 2007, higher incentives for farmers to grow non-food [[biofuel]] crops<ref>[http://www.sundayherald.com/news/heraldnews/display.var.2104849.0.2008_the_year_of_global_food_crisis.php 2008: The year of global food crisis]</ref> combined with other factors (such as rising transportation costs, [[climate change]], growing consumer demand in [[China]] and [[India]], and [[population growth]])<ref>[http://www.csmonitor.com/2008/0118/p08s01-comv.html The global grain bubble]</ref> to cause [[Oil price increases of 2004 and 2005#Food security|food shortages]] in [[Asia]], the [[Middle East]], [[Africa]], and [[Mexico]], as well as rising food prices around the globe.<ref>[http://news.bbc.co.uk/1/hi/world/7284196.stm The cost of food: Facts and figures]</ref><ref>[http://www.time.com/time/world/article/0,8599,1717572,00.html The World's Growing Food-Price Crisis]</ref> As of December 2007, 37 countries faced food crises, and 20 had imposed some sort of food-price controls. Some of these shortages resulted in [[2007–2008 world food price crisis|food riots]] and even deadly stampedes.<ref>[http://www.timesonline.co.uk/tol/news/environment/article3500975.ece Already we have riots, hoarding, panic: the sign of things to come?]</ref><ref>[http://www.guardian.co.uk/world/2007/dec/04/china.business Riots and hunger feared as demand for grain sends food costs soaring]</ref><ref>[http://www.guardian.co.uk/environment/2008/feb/26/food.unitednations Feed the world? We are fighting a losing battle, UN admits]</ref> {{See also|Food security|Food vs fuel|2007–2008 world food price crisis}} ====Flood defense==== For historical reasons to do with [[trade]], many of the world's largest and most prosperous cities are on the coast, and the cost of building better [[coastal defenses]] (due to the rising sea level) is likely to be considerable. Some countries will be more affected than others &mdash; low-lying countries such as [[Bangladesh]] and the [[Netherlands]] would be worst hit by any sea level rise, in terms of [[floods]] or the cost of preventing them. In developing countries, the poorest often live on flood plains, because it is the only available space, or fertile agricultural land. These settlements often lack infrastructure such as dykes and early warning systems. Poorer communities also tend to lack the insurance, savings or access to credit needed to recover from disasters.<ref>[http://lnweb18.worldbank.org/ESSD/envext.nsf/46ParentDoc/ClimateChange?Opendocument The World Bank’s Approach to Clean Energy & Climate Change]</ref> ====Migration==== Some [[Pacific Ocean]] island nations, such as [[Tuvalu]], are concerned about the possibility of an eventual evacuation, as flood defense may become economically unviable for them. Tuvalu already has an ad hoc agreement with [[New Zealand]] to allow phased relocation.<ref>[http://www.guardian.co.uk/climatechange/story/0,12374,1063181,00.html Unnatural disasters] ''Andrew Simms'' The Guardian October 2003</ref> In the 1990s a variety of estimates placed the number of environmental refugees at around 25 million. (Environmental refugees are not included in the official definition of [[refugee]]s, which only includes migrants fleeing persecution.) The Intergovernmental Panel on Climate Change (IPCC), which advises the world’s governments under the auspices of the UN, estimated that 150 million environmental refugees will exist in the year 2050, due mainly to the effects of coastal flooding, shoreline erosion and agricultural disruption (150 million means 1.5% of 2050’s predicted 10 billion [[world population]]).<ref>[http://www.risingtide.nl/greenpepper/envracism/refugees.html Hidden statistics: environmental refugees]</ref><ref>[http://web.archive.org/web/20050223042051/http://www.risingtide.nl/greenpepper/envracism/refugees.html Hidden statistics: environmental refugees] Archived version</ref> ====Northwest Passage==== [[Image:Arctic Ice Thickness.gif|250px|right|thumb|Arctic ice thicknesses changes from 1950s to 2050s simulated in one of [[Geophysical Fluid Dynamics Laboratory|GFDL]]'s R30 atmosphere-ocean [[general circulation model]] experiments]] Melting [[Arctic]] ice may open the [[Northwest Passage]] in summer, which would cut 5,000 [[nautical mile]]s (9,000 km) from shipping routes between Europe and Asia. This would be of particular benefit for [[supertanker]]s which are too big to fit through the [[Panama Canal]] and currently have to go around the tip of South America. According to the Canadian Ice Service, the amount of ice in Canada's eastern [[Canadian Arctic Archipelago|Arctic Archipelago]] decreased by 15% between 1969 and 2004.<ref>[http://www.washingtontimes.com/specialreport/20050612-123835-3711r.htm ''www.washingtontimes.com'']</ref> In September 2007, the Arctic Ice Cap retreated far enough for the Northwest Passage to become navigable to shipping for the first time in recorded history.<ref>{{Citation | title=Arctic ice levels at record low opening Northwest Passage | newspaper=Wikinews | url=http://en.wikinews.org/wiki/Arctic_ice_levels_at_record_low_opening_Northwest_Passage}}</ref> ====Development==== The combined effects of global warming may have particularly harsh effects on people and countries without the resources to [[mitigation of global warming|mitigate]] those effects. This may slow [[economic development]] and [[poverty reduction]], and make it harder to achieve the [[Millennium Development Goals]].<ref>{{cite web|url=http://www.odi.org.uk/iedg/publications/climate_change_web.pdf |title=Poverty Reduction, Equity and Climate Change: Global Governance Synergies or Contradictions?|author=Richards, Michael|publisher=Overseas Development Institute|accessdate=2007-12-01|format=PDF}}</ref> In October 2004 the Working Group on Climate Change and Development, a coalition of development and environment [[Non-governmental organization|NGO]]s, issued a report [http://www.iied.org/pubs/display.php?o=9512IIED Up in Smoke] on the effects of climate change on development. This report, and the July 2005 report [http://www.iied.org/pubs/display.php?o=9560IIED Africa - Up in Smoke?] predicted increased hunger and disease due to decreased rainfall and severe weather events, particularly in [[Africa]]. These are likely to have severe impacts on development for those affected. ===Ecosystems=== Unchecked global warming could affect most [[terrestrial ecoregions]]. Increasing global temperature means that ecosystems will change; some [[species]] are being forced out of their habitats ([[extinction risk from climate change|possibly to extinction]]) because of changing conditions, while others are flourishing. Secondary effects of global warming, such as lessened snow cover, rising sea levels, and weather changes, may influence not only human activities but also the [[ecosystem]]. Studying the association between Earth climate and extinctions over the past 520 million years, scientists from [[University of York]] write, "The global temperatures predicted for the coming centuries may trigger a new ‘mass extinction event’, where over 50 per cent of animal and plant species would be wiped out."<ref>{{cite journal | last = Mayhew | first = Peter J | coauthors = Gareth B. Jenkins, Timothy G. Benton | date = [[October 23]], [[2007]] | title = A long-term association between global temperature and biodiversity, origination and extinction in the fossil record | journal = Proceedings of the Royal Society B | volume = 275| issue = | pages = 47| publisher = Royal Society Publishing | doi = 10.1098/rspb.2007.1302 | url = http://www.journals.royalsoc.ac.uk/content/3x081w5n5358qj01/ | accessdate = 2007-10-30}}</ref> Many of the species at risk are Arctic and Antarctic fauna such as [[Polar Bear|polar bears]]<ref>{{cite journal | last = Amstrup | first=Steven C. | coauthors = [[Ian Stirling]], Tom S. Smith, Craig Perham, Gregory W. Thiemann | date = [[2006-04-27]] | title = Recent observations of intraspecific predation and cannibalism among polar bears in the southern Beaufort Sea | journal = Polar Biology | volume = 29 | issue = 11 | pages = 997–1002 | doi = 10.1007/s00300-006-0142-5}} </ref> and [[emperor penguin]]s<ref>{{cite journal | last = Le Bohec | first = Céline | coauthors = Joël M. Durant, Michel Gauthier-Clerc, Nils C. Stenseth, Young-Hyang Park, Roger Pradel, David Grémillet, Jean-Paul Gendner, and Yvon Le Maho | title = King penguin population threatened by Southern Ocean warming | journal = [[Proceedings of the National Academy of Sciences]] | volume = 105| issue = | pages = 2493| date = [[2008-02-11]] | url = http://www.pnas.org/cgi/content/abstract/0712031105v1 | doi = 10.1073/pnas.0712031105 | accessdate = 2008-02-13 | format = abstract | pmid = 18268328}}</ref>. In the Arctic, the waters of [[Hudson Bay]] are ice-free for three weeks longer than they were thirty years ago, affecting [[Polar Bear|polar bears]], which prefer to hunt on sea ice.<ref>[http://www.lrb.co.uk/v27/n01/byer01_.html On Thinning Ice] ''Michael Byers'' London Review of Books January 2005</ref>. Species that rely on cold weather conditions such as [[gyrfalcon]]s, and [[snowy owl]]s that prey on lemmings that use the cold winter to their advantage may be hit hard.<ref>{{cite web |url=http://ec.europa.eu/environment/nature/conservation/wildbirds/action_plans/docs/falco_rusticolis.pdf |title=International Species Action Plan for the Gyrfalcon Falco rusticolis |publisher=BirdLife International |date=1999 |author=Pertti Koskimies (compiler) |accessdate=2007-12-28|format=PDF}}</ref> <ref>{{cite web|url=http://aknhp.uaa.alaska.edu/zoology/species_ADFG/ADFG_PDFs/Birds/Snowy%20Owl_ADFG_final_2006.pdf |title=Snowy Owl |publisher=University of Alaska |date=2006 |accessdate=2007-12-28|format=PDF}}</ref>Marine invertebrates enjoy peak growth at the temperatures they have adapted to, regardless of how cold these may be, and [[cold-blooded]] animals found at greater [[latitude]]s and [[altitude]]s generally grow faster to compensate for the short growing season.<ref>{{cite journal |author=Arendt, J.D. |title=Adaptive intrinsic growth rates: an integration across taxa |year=1997 |journal=[[Q. Rev. Biol.]] |volume=72 |issue=2 |pages=149–177 |url=http://links.jstor.org/sici?sici=0033-5770%28199706%2972%3A2%3C149%3AAIGRAI%3E2.0.CO%3B2-X |doi=10.1086/419764}} </ref> Warmer-than-ideal conditions result in higher [[metabolism]] and consequent reductions in body size despite increased foraging, which in turn elevates the risk of [[predation]]. Indeed, even a slight increase in temperature during development impairs growth efficiency and survival rate in [[rainbow trout]].<ref> {{cite journal |author=Biro, P.A., ''et al.'' |year=2007 |month=June |title=Mechanisms for climate-induced mortality of fish populations in whole-lake experiments |journal=[[Proc. Nat. Acad. Sci.]] |volume=104 |issue=23 |pages=9715–9719 |doi=10.1073/pnas.0701638104 |issn=1091-6490 |pmid=17535908}} </ref> Rising temperatures are beginning to have a noticeable impact on birds<ref>{{cite web |url=http://news.bbc.co.uk/2/hi/science/nature/4313726.stm |title=Animals 'hit by global warming'| author=Time Hirsch |publisher=[[BBC]] News |date=2005-10-05 |accessdate=2007-12-29}}</ref>, and [[Butterfly|butterflies]] have shifted their ranges northward by 200 km in Europe and North America. Plants lag behind, and larger animals' migration is slowed down by cities and highways. In Britain, spring butterflies are appearing an average of 6 days earlier than two decades ago <ref>{{cite journal |url=http://www.nature.com/nature/journal/v416/n6879/pdf/416389a.pdf |title= Ecological responses to recent climate change |journal=[[Nature (journal)| Nature]] |last=Walther |first=Gian-Reto |coauthors=Eric Post, Peter Convey, Annette Menzel, Camille Parmesan, Trevor J. C. Beebee, Jean-Marc Fromentin, Ove Hoegh-Guldberg, Franz Bairlein |volume=416 |number= |pages=389–395|date=[[March 28]], [[2002]] |doi= 10.1038/416389a|format=PDF}}</ref>. A 2002 article in ''[[Nature (journal)|Nature]]''<ref>{{cite journal | last = Root | first = Terry L. | coauthors = Jeff T. Price, Kimberly R. Hall, Stephen H. Schneider, Cynthia Rosenzweig & Alan Pounds | title = Fingerprints of global warming on animals and plants | journal = [[Nature (journal)|Nature]] | volume = 421 | issue = 6918 | pages = 57–59 | date = [[2003-01-02]] | url = http://cesp.stanford.edu/publications/fingerprints_of_global_warming_on_animals_and_plants/index.html | accessdate = 2008-02-13 | doi = 10.1038/nature01333}}</ref> surveyed the scientific literature to find recent changes in range or seasonal behaviour by plant and animal species. Of species showing recent change, 4 out of 5 shifted their ranges towards the poles or higher altitudes, creating "[[refugee species]]". Frogs were breeding, flowers blossoming and birds migrating an average 2.3 days earlier each decade; butterflies, birds and plants moving towards the poles by 6.1 km per decade. A 2005 study concludes human activity is the cause of the temperature rise and resultant changing species behaviour, and links these effects with the predictions of [[climate model]]s to provide validation for them <ref>[http://iis-db.stanford.edu/pubs/20887/PNAS_5_16_05.pdf ''www.stanford.edu'']</ref>. Scientists have observed that [[Antarctic hair grass]] is colonizing areas of Antarctica where previously their survival range was limited. <ref>[http://www.heatisonline.org/contentserver/objecthandlers/index.cfm?id=5014&method=full Grass flourishes in warmer Antarctic] originally from [[The Times]], December 2004</ref> Mechanistic studies have documented extinctions due to recent climate change: McLaughlin ''et al.'' documented two populations of [[Bay checkerspot butterfly]] being threatened by precipitation change.<ref name="McLaughlin"> {{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> Parmesan states, "Few studies have been conducted at a scale that encompasses an entire species"<ref> {{cite journal |last= Permesan |first= Camille |date= [[2006-08-24]] |title= Ecological and Evolutionary Responses to Recent Climate Change |journal= [[Annual Review of Ecology, Evolution, and Systematics]] |volume= 37 |pages= 637–669 |doi= 10.1146/annurev.ecolsys.37.091305.110100 |url= http://cns.utexas.edu/communications/File/AnnRev_CCimpacts2006.pdf |format= [[Portable Document Format|PDF]] |accessdate= 2007-03-30}} </ref> and McLaughlin ''et al.'' agreed "few mechanistic studies have linked extinctions to recent climate change."<ref name="McLaughlin"/> Daniel Botkin and other authors in one study believe that projected rates of extinction are overestimated.<ref>{{cite journal |last=Botkin |first=Daniel B. |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> Many species of freshwater and saltwater plants and animals are dependent on glacier-fed waters to ensure a cold water habitat that they have adapted to. Some species of freshwater fish need cold water to survive and to reproduce, and this is especially true with [[Salmon]] and [[Cutthroat trout]]. Reduced glacier runoff can lead to insufficient stream flow to allow these species to thrive. Ocean [[krill]], a cornerstone species, prefer cold water and are the primary food source for aquatic mammals such as the [[Blue whale]]<ref>{{cite news | last = Lovell | first = Jeremy | title = Warming Could End Antarctic Species | publisher = CBS News | date = 2002-09-09 | url = http://www.cbsnews.com/stories/2002/09/09/tech/main521258.shtml | accessdate = 2008-01-02 }}</ref>. Alterations to the [[ocean currents]], due to increased freshwater inputs from glacier melt, and the potential alterations to [[thermohaline circulation]] of the worlds oceans, may affect existing fisheries upon which humans depend as well. ====Forests==== [[Image:Northern Forest Trend in Photosynthetic Activity.gif|thumb|250px|right]] Pine forests in [[British Columbia]] have been devastated by a [[pine beetle]] infestation, which has expanded unhindered since 1998 at least in part due to the lack of severe winters since that time; a few days of extreme cold kill most mountain pine beetles and have kept outbreaks in the past naturally contained. The infestation, which will have killed 50% of the lodgepole pines by 2008 <ref> [http://mpb.cfs.nrcan.gc.ca/index_e.html Natural Resources Canada] </ref> has passed to Alberta and will spread further East and eventually into America given continued milder winters. Besides the immediate ecological and economic impact, the huge dead forests provide a fire risk as well. Forests in some regions potentially face an increased risk of [[forest fire]]s. The 10-year average of boreal forest burned in North America, after several decades of around 10,000 km² (2.5 million acres), has increased steadily since 1970 to more than 28,000 km² (7 million acres) annually.<ref>[http://www.usgcrp.gov/usgcrp/nacc/education/alaska/ak-edu-5.htm US National Assessment of the Potential Consequences of Climate Variability and Change] Regional Paper: Alaska</ref>. This change may be due in part to changes in forest management practices. In the western U. S., since 1986, longer, warmer summers have resulted in a fourfold increase of major wildfires and a sixfold increase in the area of forest burned, compared to the period from 1970 to 1986. A similar increase in wildfire activity has been reported in Canada from 1920 to 1999.<ref>[http://www.sciencemag.org/cgi/content/short/313/5789/927 Science Magazine - August 2006 "Is Global Warming Causing More, Larger Wildfires?" - Steven W. Running]</ref> Also note forest fires since 1997 in Indonesia. The fires are started to clear forest for agriculture. These occur from time to time and can set fire to the large peat bogs in that region. The CO<sub>2</sub> released by these peat bog fires has been estimated, in an average year, to release 15% of the quantity of CO<sub>2</sub> produced by fossil fuel combustion. <ref> BBC News: [http://news.bbc.co.uk/2/hi/science/nature/4208564.stm Asian peat fires add to warming]</ref> ====Mountains==== [[Mountains]] cover approximately 25 percent of earth's surface and provide a home to more than one-tenth of global human population. Changes in global climate pose a number of potential risks to mountain habitats<ref>[http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VFV-4MY0TS1-1&_user=4225319&_coverDate=10%2F31%2F2007&_rdoc=12&_fmt=summary&_orig=browse&_srch=doc-info(%23toc%236020%232007%23999829996%23668309%23FLA%23display%23Volume)&_cdi=6020&_sort=d&_docanchor=&_ct=17&_acct=C000048559&_version=1&_urlVersion=0&_userid=4225319&md5=b28529ce89b28da5f49792dfebeef70b&errMsg=1 Exposure of global mountain systems to climate warming during the 21st Century] Science Direct</ref>. Researchers expect that over time, climate change will affect mountain and lowland ecosystems, the frequency and intensity of [[forest fires]], the diversity of wildlife, and the distribution of water. Studies suggest that a warmer climate in the United States would cause lower-elevation habitats to expand into the higher alpine zone.<ref>[http://www.epa.gov/climatechange/effects/downloads/potential_effects.pdf The Potential Effects Of Global Climate Change On The United States] Report to Congress Editors: Joel B. Smith and Dennis Tirpak US-EPA December 1989</ref> Such a shift would encroach on the rare alpine meadows and other high-altitude habitats. High-elevation plants and animals have limited space available for new habitat as they move higher on the mountains in order to adapt to long-term changes in regional climate. Changes in climate will also affect the depth of the mountains snowpacks and glaciers. Any changes in their seasonal melting can have powerful impacts on areas that rely on freshwater [[surface runoff|runoff]] from mountains. Rising temperature may cause snow to melt earlier and faster in the spring and shift the timing and distribution of runoff. These changes could affect the availability of freshwater for natural systems and human uses.<ref>{{cite press release | title = Freshwater Issues at ‘Heart of Humankind’S Hopes for Peace and Development’ | publisher = [[United Nations]] | date = [[2002-12-12]] | url = http://www.un.org/News/Press/docs/2002/ENVDEV713.doc.htm | accessdate = 2008-02-13}}</ref> ====Ecological productivity==== Increasing average temperature and carbon dioxide may have the effect of improving ecosystems' productivity. In [[photorespiration]], carbon dioxide that oxygen can enter a plant's [[chloroplasts]] and take the place of carbon dioxide in the [[Calvin cycle]]. This causes the sugars being made to be destroyed, suppressing growth. Higher carbon dioxide concentrations tend to reduce photorespiration. Satellite data shows that the productivity of the northern hemisphere has increased since 1982 (although attribution of this increase to a specific cause is difficult). IPCC models predict that higher CO<sub>2</sub> concentrations would only spur growth of flora up to a point, because in many regions the limiting factors are water or nutrients, not temperature or CO<sub>2</sub>; after that, greenhouse effects and warming would continue but there would be no compensatory increase in growth. Research done by the [http://pages.unibas.ch/botschoen/scc/index.shtml Swiss Canopy Crane Project] suggests that slow-growing trees only are stimulated in growth for a short period under higher CO<sub>2</sub> levels, while faster growing plants like [[liana]] benefit in the long term. In general, but especially in [[rain forest]]s, this means that liana become the prevalent species; and because they decompose much faster than trees their carbon content is more quickly returned to the atmosphere. Slow growing trees incorporate atmospheric carbon for decades. ===Water scarcity=== {{seealso|Water crisis}} Sea level rise is projected to increase salt-water intrusion into [[groundwater]] in some regions, affecting drinking water and agriculture in coastal zones.<ref>[http://yosemite.epa.gov/oar/GlobalWarming.nsf/content/ResourceCenterPublicationsSeaLevelRiseIndex.html EPA : Global Warming : Resource Center : Publications : Sea Level Rise : Sea Level Rise Reports<!-- Bot generated title -->]</ref> Increased evaporation will reduce the effectiveness of reservoirs. Increased extreme weather means more water falls on hardened ground unable to absorb it, leading to flash floods instead of a replenishment of soil moisture or groundwater levels. In some areas, shrinking glaciers threaten the water supply.<ref>[http://www.opendemocracy.net/globalization-climate_change_debate/kazakhstan_2551.jsp Kazakhstan: glaciers and geopolitics] ''Stephan Harrison'' Open Democracy May 2005</ref> The continued retreat of glaciers will have a number of different effects. In areas that are heavily dependent on water runoff from glaciers that melt during the warmer summer months, a continuation of the current retreat will eventually deplete the glacial ice and substantially reduce or eliminate runoff. A reduction in runoff will affect the ability to [[irrigation|irrigate]] crops and will reduce summer stream flows necessary to keep dams and reservoirs replenished. This situation is particularly acute for irrigation in South America, where numerous artificial lakes are filled almost exclusively by glacial melt.{{ref_harv|peru2|BBC|BBC}} Central Asian countries have also been historically dependent on the seasonal glacier melt water for irrigation and drinking supplies. In Norway, the Alps, and the Pacific Northwest of North America, glacier runoff is important for hydropower. Higher temperatures will also increase the demand for water for the purposes of cooling and hydration. In the [[Sahel]], there has been an unusually wet period from 1950 until 1970, followed by [[Sahel drought|extremely dry years]] from 1970 to 1990. From 1990 until 2004 rainfall returned to levels slightly below the 1898–1993 average, but year-to-year variability was high.<ref name="Mitchell">[http://jisao.washington.edu/data_sets/sahel/ Sahel rainfall index (20-10N, 20W-10E), 1900–2007]</ref><ref>{{cite web | title=Temporary Drought or Permanent Desert? | url=http://earthobservatory.nasa.gov/Study/Desertification/desertification2.html | publisher=[[NASA]] Earth Observatory | accessdate=2008-06-23 }}</ref> ===Health=== ====Direct effects of temperature rise==== The most direct effect of climate change on humans might be the impacts of hotter temperatures themselves. Extreme high temperatures increase the number of people who die on a given day for many reasons: people with heart problems are vulnerable because one's cardiovascular system must work harder to keep the body cool during hot weather, heat exhaustion, and some respiratory problems increase. Global warming could mean more [[cardiovascular disease]]s, doctors warn<ref>[http://www.iht.com/articles/ap/2007/09/05/europe/EU-MED-Global-Warming-Hearts.php Global warming could mean more heart problems, doctors warn] September 2007 Associated Press</ref>. Higher air temperature also increase the concentration of ozone at ground level. In the lower atmosphere, ozone is a harmful pollutant. It damages lung tissues and causes problems for people with asthma and other lung diseases. <ref>{{cite web|author=McMichael, A.J., Campbell-Lendrum, D.H., Corvalán, C.F., Ebi, K.L., Githeko, A., Scheraga, J.D. and Woodward, A. |year=2003|url=http://www.who.int/globalchange/climate/summary/en/index.html |title=Climate Change and Human Health – Risk and Responses |publisher=[[World Health Organization]], Geneva}}</ref> Rising temperatures have two opposing direct effects on [[death|mortality]]: higher temperatures in winter reduce deaths from cold; higher temperatures in summer increase heat-related deaths. The net local impact of these two direct effects depends on the current climate in a particular area. Palutikof ''et al.'' (1996) calculate that in England and Wales for a 1°C temperature rise the reduced deaths from cold outweigh the increased deaths from heat, resulting in a reduction in annual average mortality of 7000,<ref>{{cite journal |author=J.P. Palutikof, S. Subak and M.D. Agnew |title=Impacts of the exceptionally hot weather in 1995 in the UK |journal=Climate Monitor|volume= 25|number=3 |year=1996}}</ref> while Keatinge ''et al.'' (2000) “suggest that any increases in mortality due to increased temperatures would be outweighed by much larger short term declines in cold related mortalities.”<ref name="Keatinge2000">{{ cite journal | last = Keatinge | first = W. R. | authorlink = | coauthors = ''et al.'' | year = 2000 | month = | title = Heat related mortality in warm and cold regions of Europe: observational study | journal = British Medical Journal | volume = 321 | issue = 7262 | pages = 670&ndash;673 | id = | url = | accessdate = | quote =| doi = 10.1136/bmj.321.7262.670| pmid = 10987770 }}</ref> A government report shows decreased mortality due to recent warming and predicts increased mortality due to future warming in the United Kingdom.<ref> {{Citation | last = Department of Health and Health Protection Agency | title = Health effects of climate change in the UK 2008: an update of the Department of Health report 2001/2002 | year = 12 February 2008 | url = http://www.dh.gov.uk/en/Publicationsandstatistics/Publications/PublicationsPolicyAndGuidance/DH_080702}}</ref> The [[European heat wave of 2003]] killed 22,000&ndash;35,000 people, based on normal mortality rates<ref name=Schär2004>{{cite journal | author = Schär, C. | coauthors = Jendritzky, G. | year = 2004 | title = Hot news from summer 2003 | journal = Nature | volume = 432 | issue = 7017 | pages = 559–60 | issn = | doi = 10.1038/432559a | url = | accessdate = | format = }}</ref>. Peter A. Stott from the [[Hadley Centre for Climate Prediction and Research]] estimated with 90% confidence that past human influence on climate was responsible for at least half the risk of the 2003 European summer heat-wave.<ref name=Stott2004>{{cite journal| author = Peter A. Stott | coauthors = D.A. Stone, M.R. Allen | year = 2004 | title = Human contribution to the European heatwave of 2003 | journal = Nature | volume = 432 | pages = 610–614 | issn = 0028-0836 | doi = 10.1038/nature03089 | url = | accessdate = | format = }}</ref> In the United States, more than 1000 people die from the cold each year, while twice that number die from the heat.<ref>[http://www.epa.gov/climatechange/effects/health.html Climate Change - Health and Environmental Effects] US-EPA</ref> ====Spread of disease==== {{seealso|Tropical disease}} Global warming may extend the favourable zones for [[Vector (biology)|vectors]] conveying [[infectious disease]] such as [[dengue fever]]<ref>{{cite journal |title = Potential effect of population and climate changes on global distribution of dengue fever: an empirical model |url = http://image.thelancet.com/extras/01art11175web.pdf |format = [[Portable Document Format|PDF]] |journal = The Lancet |last = Hales |first = Simon |coauthors = ''et al.'' |volume = 360 |issue = 9336 |pages = 830–834 |date= [[2002-09-14]] |accessdate=2007-05-02 |doi = 10.1016/S0140-6736(02)09964-6}}</ref> and [[malaria]]<ref>{{cite journal | last = Rogers | first = D. | coauthors = S. Randolph | title = The global spread of malaria in a future warmer world | journal = Science | volume = 289 | issue = 5485 | pages = 1763–6 | date = [[2000-09-08]] | url = http://www.sciencemag.org/cgi/content/full/289/5485/1763 | accessdate = 2008-01-04 }}</ref><ref>{{cite news | last = Boseley | first = Sarah | title = Health hazard | publisher = The Guardian | date = June 2005 | url = http://www.guardian.co.uk/climatechange/story/0,12374,1517940,00.html | accessdate = 2008-01-04 }}</ref> In poorer countries, this may simply lead to higher incidence of such diseases. In richer countries, where such diseases have been eliminated or kept in check by [[vaccination]], draining swamps and using pesticides, the consequences may be felt more in economic than health terms. The [[World Health Organisation]] (WHO) says global warming could lead to a major increase in insect-borne diseases in Britain and Europe, as northern Europe becomes warmer, ticks&mdash;which carry [[encephalitis]] and [[lyme disease]]&mdash;and [[sandflies]]&mdash;which carry [[visceral leishmaniasis]]&mdash;are likely to move in.<ref> BBC News: [http://news.bbc.co.uk/2/hi/science/nature/372219.stm Global Warming disease warning]</ref> However, Malaria has always been a common threat in European past, with the last epidemic occuring in the [[Netherlands]] during the 1950s. In the United States, Malaria has been endemic in as much as 36 states (including Washington, North Dakota, Michigan and New York) until the [[1940s]].<ref>{{cite journal |last=Reiter |first=Paul |authorlink= |coauthors=''et al.'' |year=2004 |month= |title=Global warming and malaria: a call for accuracy |journal=The Lancet Infectious Deseases |volume=4 |issue=6 |pages=323&ndash;324 |doi=10.1016/S1473-3099(04)01038-2 |url= |accessdate= |quote= }}</ref> By 1949, the country was declared free of malaria as a significant public health problem, after more than 4,650,000 house [[DDT]] spray applications had been made.<ref>{{cite web |url=http://www.cdc.gov/malaria/history/eradication_us.htm |title=Eradication of Malaria in the United States (1947-1951) |accessdate=2008-07-12 |work= |publisher=Centers for Disease Control and Prevention |date=[[April 23]], [[2004]] }}</ref> The World Health Organisation estimates 150,000 deaths annually "as a result of climate change", of which half in the [[Asia]]-[[Pacific]] region.<ref>[http://www.abc.net.au/ra/news/stories/200804/s2211161.htm?tab=latest "Malaria found in PNG highlands"], ABC Radio Australia, April 8, 2008</ref> In [[April 2008]], it reported that, as a result of increased temperatures, [[malaria]] is appearing in the [[Highland (geography)|highland]] areas of [[Papua New Guinea]], where it has always been too cold for disease-spreading mosquitoes.<ref>[http://www.irinnews.org/Report.aspx?ReportId=77993 PAPUA NEW GUINEA: Climate change challenge to combat malaria] ''UN Office for the Coordination of Humanitarian Affairs''</ref> === Security === {{seealso|Military Advisory Board}} The [[Military Advisory Board]], a panel of retired U.S. generals and admirals released a report entitled "National Security and the Threat of Climate Change." The report predicts that global warming will have security implications, in particular serving as a "threat multiplier" in already volatile regions.<ref>[http://securityandclimate.cna.org/report/ "National Security and the Threat of Climate Change]". Military Advisory Board, April 15, 2007.</ref> Britain's [[Foreign Secretary]] [[Margaret Beckett]] argues that “An unstable climate will exacerbate some of the core drivers of conflict, such as migratory pressures and competition for resources.”<ref>Reuters. [http://www.nytimes.com/2007/04/18/world/18nations.html?ex=1334548800en=599119af2640e7b1ei=5088partner=rssnytemc=rss U.N. Council Hits Impasse Over Debate on Warming]. The New York Times, April 17, 2007. Retrieved on May 29, 2007.</ref> And several weeks earlier, U.S. Senators [[Chuck Hagel]] (R-NB) and [[Richard Durbin]] (D-IL) introduced a bill in the U.S. Congress that would require federal intelligence agencies to collaborate on a [[National Intelligence Estimate]] to evaluate the security challenges presented by climate change.<ref>[http://www.salon.com/news/feature/2007/04/09/muckraker/ Will global warming threaten national security?]. ''Salon,'' April 9, 2007. Retrieved on May 29, 2007.</ref> In November 2007, two Washington think tanks, the established [[Center for Strategic and International Studies]] and the newer [[Center for a New American Security]], published a report analysing the worldwide security implications of three different global warming scenarios. The report considers three different scenarios, two over a roughly 30 year perspective and one covering the time up to 2100. Its general results include:<ref>{{cite web|author=Kurt M. Campbell, Jay Gulledge, J.R. McNeill, John Podesta, Peter Ogden, Leon Fuerth, R. James Woolsey, Alexander T.J. Lennon, Julianne Smith, Richard Weitz, Derek Mix|title=The Age of Consequences: The Foreign Policy and National Security Implications of Global Climate Change|url=http://www.cnas.org/attachments/contentmanagers/1278/CSIS-CNAS_AgeofConsequences_October07.pdf|format=PDF|date=Oktober 2007|accessdate=2007-11-06}}</ref> * "There is a lack of rigorously tested data or reliable modeling to determine with any sense of certainty the ultimate path and pace of temperature increase or sea level rise associated with climate change in the decades ahead", "most scientific predictions in the overall arena of climate change over the last two decades, when compared with ultimate outcomes, have been consistently below what has actually transpired" and "this tendency should provide some context when examining current predictions of future climate parameters". * "A few countries may benefit from climate change in the short term, but there will be no "winners...While growing seasons might lengthen in some areas, or frozen seaways might open to new maritime traffic in others, the negative offsetting consequences -- such as a collapse of ocean systems and their fisheries -- could easily negate any perceived local or national advantages." * "Perhaps the most worrisome problems associated with rising temperatures and sea levels are from large-scale migrations of people -- both inside nations and across existing national borders. " * "Poor and underdeveloped areas are likely to have fewer resources and less stamina to deal with climate change -- in even its very modest and early manifestations." *"The flooding of coastal communities around the world, especially in the Netherlands, the United States, South Asia, and China, has the potential to challenge regional and even national identities. Armed conflict between nations over resources, such as the Nile and its tributaries, is likely..." === Children === On [[2008-04-29]], a [[UNICEF]] UK Report found that global warming is already reducing the quality of the world's most vulnerable children's lives and making it more difficult to meet the UN [[Millennium Development Goals]]. Global warming will reduce access to [[clean water]] and [[food supply|food supplies]], particularly in Africa and Asia. Disasters, violence and disease are expected to be more frequent and intense, making the future of the world's poorest children more bleak. <ref>[http://www.unicef.org.uk/press/news_detail_full_story.asp?news_id=1120 UNICEF UK News :: News item :: The tragic consequences of climate change for the world’s children :: 29 April 2008 00:00]</ref> ==References== {{reflist|2}} <!--Please cite these in the text if they are being used as sources, per relevant policies and guidelines. --> ==See also== {| style="background-color: transparent; width: {{{width|100%}}}" | width="50%" align="{{{align|left}}}" valign="{{{valign|top}}}" | * [[National Assessment on Climate Change]] for the [[United States]] * [[Effects of global warming on Australia]] * [[Arctic Climate Impact Assessment]] * [[Loop Current]] of the Gulf of Mexico * [[Oceanic anoxic event]] * [[List of topics related to global warming]] | width="50%" align="{{{align|left}}}" valign="{{{valign|top}}}" | * [[EdGCM]] &mdash; a [[global climate model]] for students * [[Biological pump]] * [[Solubility pump]] * [[Avoiding Dangerous Climate Change]] * [[Military Advisory Board]] * [[Risks to civilization, humans and planet Earth]] |} ==External links== * [http://www.epa.gov/climatechange/effects/index.html EPA: Health and Environmental Effects of Global Warming] *[http://www.human-global-warming.co.uk/ Human Global Warming] *[http://www.nature.org/initiatives/climatechange/issues/ The Impacts of Global Warming and Climate Change] from [[The Nature Conservancy]] *[http://www.whoi.edu/institutes/occi/viewTopic.do?o=read&id=521 Global Warming Information from the Ocean & Climate Change Institute], [[Woods Hole Oceanographic Institution]] * [http://wind.mit.edu/~emanuel/anthro2.htm#Essay "Anthropogenic Effects on Tropical Cyclone Activity"] ([[Kerry Emanuel]]) * "The Climate of Man", ''The New Yorker'' (2005): [http://www.newyorker.com/printables/fact/050425fa_fact3 Part 1], [http://www.newyorker.com/printables/fact/050502fa_fact3 Part 2], [http://www.newyorker.com/printables/fact/050509fa_fact3 Part 3] * Pezza, Alexandre Bernardes and Ian Simmonds (Aug 2005). [http://www.earthsci.unimelb.edu.au/~apezza/climate.dir/papers/Pezza_and_Simmonds_2005.GRL.pdf "The first South Atlantic hurricane: Unprecedented blocking, low shear and climate change"]. ''[[Geophysical Research Letters]]'' 32 (L15712). * [http://www.sbmet.org.br/internas/publicacoes/informativo/2005_07/index_en.html Workshop on the Phenomenon Catarina] (Brazilian Society of Meteorology) * [[American Meteorological Society]]'s Environmental Science Seminar Series (Oct 2005): [http://ametsoc.org/atmospolicy/documents/October252005-Hurricanes_000.pdf "Hurricanes: Are They Changing and Are We Adequately Prepared for the Future?"] ** [http://ametsoc.org/atmospolicy/documents/October252005KevinTrenberth.pdf "How are hurricanes changing with global warming?"] ([[Kevin Trenberth]]) ** [http://ametsoc.org/atmospolicy/documents/October252005JudithCurry.pdf "Changes in hurricane intensity in a warming environment"] (Judith Curry) ** [http://ametsoc.org/atmospolicy/documents/October252005KerryEmanuel.pdf "Hurricanes and Climate"] (Kerry Emanuel) * [http://www.munichre.com/pages/03/georisks/geo_desasters/worldmap_of_natural_hazards_en.aspx Munich Re: World Map of Natural Hazards] * [[Oliver James]], ''[[The Guardian]]'', [[June 30]], 2005 [http://www.guardian.co.uk/climatechange/story/0,12374,1517953,00.html Face the facts: For many people climate change is too depressing to think about, and some prefer to simply pretend it doesn't exist] * Mark Lynas, ''The Guardian'', [[March 31]], 2004, [http://society.guardian.co.uk/environment/story/0,14124,1181198,00.html "Vanishing worlds"] * The ecological crisis on the verge of a catastrophe by Takis Fotopoulos, (Inclusive Democracy Journal, vol 2, no 4, 11/2006)[http://www.inclusivedemocracy.org/journal/newsletter/ecological_catastrophe.htm] * See the impacts of climate change happening now on three Australian ecosystems: [http://www.abc.net.au/catalyst/stories/s1647466.htm 'Tipping Point', Catalyst, ABC-TV] * Peter Schwartz and Doug Randall, Global Business Network, [http://www.environmentaldefense.org/documents/3566_AbruptClimateChange.pdf "An Abrupt Climate Change Scenario and Its Implications for United States National Security"], A report commissioned by the U.S. Defense Department, October 2003 [http://www.ems.org/climate/exec_pentagon_climatechange.pdf (executive summary)] * [http://pistehors.com/backcountry/wiki/Weather/The-Effects-Of-Global-Warming-On-Skiing Effects of global warming on skiing] * [http://www.stabilisation2005.com/impacts/impacts_human.pdf Stabilisation 2005 conference: survey of scientific papers] * [http://www.alternet.org/envirohealth/23686/ Elevated levels of atmospheric CO<sub>2</sub> decrease the nutritional value of plants] * [[Royal Society]], [[30 June]] 2005, [http://www.royalsoc.ac.uk/document.asp?tip=0&id=3249 "Ocean acidification due to increasing atmospheric carbon dioxide"] * [http://www.time.com/time/magazine/article/0,9171,1109337,00.html Time Magazine's "Global Warming: The Culprit?"] (Time Magazine, October 3, 2005, pages 42-46) *[http://pubs.acs.org/subscribe/journals/esthag-w/2005/oct/policy/pt_curry.html The Evidence Linking Hurricanes and Climate Change: Interview with Judith Curry] *[http://zfacts.com/p/49.html Hurricanes and Global Warming] Review of most recent ''Nature'' and ''Science'' data. *[http://www.bjerknes.uib.no/pages.asp?kat=2&id=170&lang=2 Recent ice sheet growth in the interior of Greenland] *[http://www.bjerknes.uib.no/pages.asp?id=169&kat=2&lang=2 Increased temperature and salinity in the Nordic Seas] *[http://www.chez.com/170585 Effect of global warmng on the Gulf Stream (in French)] *[http://yosemite.epa.gov/oar/globalwarming.nsf/content/newsandeventsScienceandPolicyNews.html Newest reports on US EPA website] *[http://www.sciencedaily.com/releases/2007/02/070212182131.htm Glaciers Not On Simple, Upward Trend Of Melting] sciencedaily.com, Feb. 21, 2007 "Two of Greenland's largest glaciers (Kangerdlugssuaq and Helheim) shrank dramatically ... between 2004 and 2005. And then, less than two years later, they returned to near their previous rates of discharge. {{Global warming}} [[Category:Climate change feedbacks and causes]] [[Category:Effects of global warming| ]] {{Link FA|de}} [[de:Folgen der globalen Erwärmung]] [[es:Efectos potenciales del calentamiento global]] [[fr:Enjeux du réchauffement climatique]] [[ja:地球温暖化の影響]] [[fi:Ilmaston lämpenemisen vaikutukset]] [[sv:Följder av en global uppvärmning]] [[zh:全球变暖的效应]]