Climate change: Difference between revisions
Frendinius (talk | contribs) Undid revision 347802243 by William M. Connolley (talk) This is accurate and appears appropriate |
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[[File:Solar-cycle-data.png|thumb|Solar variation over the last thirty years.]] |
[[File:Solar-cycle-data.png|thumb|Solar variation over the last thirty years.]] |
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Variations in solar output have been the cause of past |
Variations in solar output have been the cause of past climate changes,<ref>National Research Council (1994). Solar Influences On Global Change. Washington, D.C.: National Academy Press. p. 36. ISBN 0-309-05148-7. http://books.nap.edu/openbook.php?record_id=4778&page=R1.</ref> but climate models predict that solar forcing is too small to account for a significant part of global warming during the industrial era.<ref>Hansen, J. (2002). "Climate". Journal of Geophysical Research 107: 4347. doi:10.1029/2001JD001143</ref><ref>Hansen, J. (2005). "Efficacy of climate forcings". Journal of Geophysical Research 110: D18104. doi:10.1029/2005JD005776</ref> Recent empirical analyses confirm potentially significant variations of solar luminosity on climate timescales <ref>Nicola Scafetta and Richard Willson, “ACRIM-gap and Total Solar Irradiance (TSI) trend issue resolved using a surface magnetic flux TSI proxy model”, Geophysical Research Letter 36, L05701, doi:10.1029/2008GL036307 (2009)</ref> and indicate the contribution of solar forcing may be underestimated by current climate models.<ref>Scafetta, N. (2007). "Phenomenological reconstructions of the solar signature in the Northern Hemisphere surface temperature records since 1600". Journal of Geophysical Research 112: D24S03. doi:10.1029/2007JD008437</ref> |
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Greenhouse gases and solar forcing affect temperatures in different ways. While both increased solar activity and increased greenhouse gases are expected to warm the [[troposphere]], an increase in solar activity should warm the [[stratosphere]] while an increase in greenhouse gases should cool the stratosphere.<ref name=Hegerl-2001/> Observations show that temperatures in the stratosphere have been cooling since 1979, when satellite measurements became available. [[Radiosonde]] (weather balloon) data from the pre-satellite era show cooling since 1958, though there is greater uncertainty in the early radiosonde record.<ref name=Randel2009>{{Cite journal|doi=10.1029/2008JD010421|title=An update of observed stratospheric temperature trends|year=2009|author=Randel, William J.|journal=Journal of Geophysical Research|volume=114|pages=D02107|last2=Shine|first2=Keith P.|last3=Austin|first3=John|last4=Barnett|first4=John|last5=Claud|first5=Chantal|last6=Gillett|first6=Nathan P.|last7=Keckhut|first7=Philippe|last8=Langematz|first8=Ulrike|last9=Lin|first9=Roger}}</ref> |
Greenhouse gases and solar forcing affect temperatures in different ways. While both increased solar activity and increased greenhouse gases are expected to warm the [[troposphere]], an increase in solar activity should warm the [[stratosphere]] while an increase in greenhouse gases should cool the stratosphere.<ref name=Hegerl-2001/> Observations show that temperatures in the stratosphere have been cooling since 1979, when satellite measurements became available. [[Radiosonde]] (weather balloon) data from the pre-satellite era show cooling since 1958, though there is greater uncertainty in the early radiosonde record.<ref name=Randel2009>{{Cite journal|doi=10.1029/2008JD010421|title=An update of observed stratospheric temperature trends|year=2009|author=Randel, William J.|journal=Journal of Geophysical Research|volume=114|pages=D02107|last2=Shine|first2=Keith P.|last3=Austin|first3=John|last4=Barnett|first4=John|last5=Claud|first5=Chantal|last6=Gillett|first6=Nathan P.|last7=Keckhut|first7=Philippe|last8=Langematz|first8=Ulrike|last9=Lin|first9=Roger}}</ref> |
Revision as of 07:36, 5 March 2010
Global warming is the increase in the average temperature of Earth's near-surface air and oceans since the mid-20th century and its projected continuation. Global surface temperature increased 0.74 ± 0.18 °C (1.33 ± 0.32 °F) between the start and the end of the 20th century.[3][A] The Intergovernmental Panel on Climate Change (IPCC) concludes that most of the observed temperature increase since the middle of the 20th century was very likely caused by increasing concentrations of greenhouse gases resulting from human activity such as fossil fuel burning and deforestation.[3] The IPCC also concludes that variations in natural phenomena such as solar radiation and volcanic eruptions had a small cooling effect after 1950.[4][5] These basic conclusions have been endorsed by more than 40 scientific societies and academies of science,[B] including all of the national academies of science of the major industrialized countries.[6]
Climate model projections summarized in the latest IPCC report indicate that the global surface temperature is likely to rise a further 1.1 to 6.4 °C (2.0 to 11.5 °F) during the 21st century.[3] The uncertainty in this estimate arises from the use of models with differing sensitivity to greenhouse gas concentrations and the use of differing estimates of future greenhouse gas emissions. Most studies focus on the period leading up to the year 2100. However, warming is expected to continue beyond 2100 even if emissions stop, because of the large heat capacity of the oceans and the long lifetime of carbon dioxide in the atmosphere.[7][8]
An increase in global temperature will cause sea levels to rise and will change the amount and pattern of precipitation, probably including expansion of subtropical deserts.[9] Warming is expected to be strongest in the Arctic and would be associated with continuing retreat of glaciers, permafrost and sea ice. Other likely effects include changes in the frequency and intensity of extreme weather events, species extinctions, and changes in agricultural yields. Warming and related changes will vary from region to region around the globe, though the nature of these regional variations are uncertain.
Political and public debate continues regarding global warming, and what actions to take in response. The available options are mitigation to reduce further emissions; adaptation to reduce the damage caused by warming; and, more speculatively, geoengineering to reverse global warming. Most national governments have signed and ratified the Kyoto Protocol aimed at reducing greenhouse gas emissions.
Temperature changes
![](http://upload.wikimedia.org/wikipedia/commons/thumb/c/c1/2000_Year_Temperature_Comparison.png/220px-2000_Year_Temperature_Comparison.png)
The most common measure of global warming is the trend in globally averaged temperature near the Earth's surface. Expressed as a linear trend, this temperature rose by 0.74 ± 0.18 °C over the period 1906–2005. The rate of warming over the last half of that period was almost double that for the period as a whole (0.13 ± 0.03 °C per decade, versus 0.07 °C ± 0.02 °C per decade). The urban heat island effect is estimated to account for about 0.002 °C of warming per decade since 1900.[10] Temperatures in the lower troposphere have increased between 0.13 and 0.22 °C (0.22 and 0.4 °F) per decade since 1979, according to satellite temperature measurements. Temperature is believed to have been relatively stable over the one or two thousand years before 1850, with regionally varying fluctuations such as the Medieval Warm Period and the Little Ice Age.[11]
Estimates by NASA's Goddard Institute for Space Studies and the National Climatic Data Center show that 2005 was the warmest year since reliable, widespread instrumental measurements became available in the late 1800s, exceeding the previous record set in 1998 by a few hundredths of a degree.[12][13] Estimates prepared by the World Meteorological Organization and the Climatic Research Unit show 2005 as the second warmest year, behind 1998.[14][15] Temperatures in 1998 were unusually warm because the strongest El Niño in the past century occurred during that year.[16] Global temperature is subject to short-term fluctuations that overlay long term trends and can temporarily mask them. The relative stability in temperature from 2002 to 2009 is consistent with such an episode.[17][18]
Temperature changes vary over the globe. Since 1979, land temperatures have increased about twice as fast as ocean temperatures (0.25 °C per decade against 0.13 °C per decade).[19] Ocean temperatures increase more slowly than land temperatures because of the larger effective heat capacity of the oceans and because the ocean loses more heat by evaporation.[20] The Northern Hemisphere warms faster than the Southern Hemisphere because it has more land and because it has extensive areas of seasonal snow and sea-ice cover subject to ice-albedo feedback. Although more greenhouse gases are emitted in the Northern than Southern Hemisphere this does not contribute to the difference in warming because the major greenhouse gases persist long enough to mix between hemispheres.[21]
The thermal inertia of the oceans and slow responses of other indirect effects mean that climate can take centuries or longer to adjust to changes in forcing. Climate commitment studies indicate that even if greenhouse gases were stabilized at 2000 levels, a further warming of about 0.5 °C (0.9 °F) would still occur.[22]
External forcings
External forcing refers to processes external to the climate system (though not necessarily external to Earth) that influence climate. Climate responds to several types of external forcing, such as radiative forcing due to changes in atmospheric composition (mainly greenhouse gas concentrations), changes in solar luminosity, volcanic eruptions, and variations in Earth's orbit around the Sun.[4] Attribution of recent climate change focuses on the first three types of forcing. Orbital cycles vary slowly over tens of thousands of years and thus are too gradual to have caused the temperature changes observed in the past century.
Greenhouse gases
The greenhouse effect is the process by which absorption and emission of infrared radiation by gases in the atmosphere warm a planet's lower atmosphere and surface. It was discovered by Joseph Fourier in 1824 and was first investigated quantitatively by Svante Arrhenius in 1896.[23] Existence of the greenhouse effect as such is not disputed, even by those who do not agree that the recent temperature increase is attributable to human activity. The question is instead how the strength of the greenhouse effect changes when human activity increases the concentrations of greenhouse gases in the atmosphere.
Naturally occurring greenhouse gases have a mean warming effect of about 33 °C (59 °F).[24][C] The major greenhouse gases are water vapor, which causes about 36–70 percent of the greenhouse effect; carbon dioxide (CO2), which causes 9–26 percent; methane (CH4), which causes 4–9 percent; and ozone (O3), which causes 3–7 percent.[25][26][27] Clouds also affect the radiation balance, but they are composed of liquid water or ice and so are considered separately from water vapor and other gases.
Human activity since the Industrial Revolution has increased the amount of greenhouse gases in the atmosphere, leading to increased radiative forcing from CO2, methane, tropospheric ozone, CFCs and nitrous oxide. The concentrations of CO2 and methane have increased by 36% and 148% respectively since 1750.[28] These levels are much higher than at any time during the last 650,000 years, the period for which reliable data has been extracted from ice cores.[29][30][31] Less direct geological evidence indicates that CO2 values higher than this were last seen about 20 million years ago.[32] Fossil fuel burning has produced about three-quarters of the increase in CO2 from human activity over the past 20 years. Most of the rest is due to land-use change, particularly deforestation.[33]
CO2 concentrations are continuing to rise due to burning of fossil fuels and land-use change. The future rate of rise will depend on uncertain economic, sociological, technological, and natural developments. Accordingly, the IPCC Special Report on Emissions Scenarios gives a wide range of future CO2 scenarios, ranging from 541 to 970 ppm by the year 2100 (an increase by 90-250% since 1750).[34] Fossil fuel reserves are sufficient to reach these levels and continue emissions past 2100 if coal, tar sands or methane clathrates are extensively exploited.[35]
The destruction of stratospheric ozone by chlorofluorocarbons is sometimes mentioned in relation to global warming. Although there are a few areas of linkage, the relationship between the two is not strong. Reduction of stratospheric ozone has a cooling influence, but substantial ozone depletion did not occur until the late 1970s.[36] Ozone in the troposphere (the lowest part of the Earth's atmosphere) does contribute to surface warming.[37]
Aerosols and soot
![](http://upload.wikimedia.org/wikipedia/commons/thumb/e/ee/ShipTracks_MODIS_2005may11.jpg/220px-ShipTracks_MODIS_2005may11.jpg)
Global dimming, a gradual reduction in the amount of global direct irradiance at the Earth's surface, has partially counteracted global warming from 1960 to the present.[38] The main cause of this dimming is aerosols produced by volcanoes and pollutants. These aerosols exert a cooling effect by increasing the reflection of incoming sunlight. James E. Hansen and colleagues have proposed that the effects of the products of fossil fuel combustion—CO2 and aerosols—have largely offset one another in recent decades, so that net warming has been driven mainly by non-CO2 greenhouse gases.[39]
In addition to their direct effect by scattering and absorbing solar radiation, aerosols have indirect effects on the radiation budget.[40] Sulfate aerosols act as cloud condensation nuclei and thus lead to clouds that have more and smaller cloud droplets. These clouds reflect solar radiation more efficiently than clouds with fewer and larger droplets.[41] This effect also causes droplets to be of more uniform size, which reduces growth of raindrops and makes the cloud more reflective to incoming sunlight.[42]
Soot may cool or warm, depending on whether it is airborne or deposited. Atmospheric soot aerosols directly absorb solar radiation, which heats the atmosphere and cools the surface. Regionally (but not globally), as much as 50% of surface warming due to greenhouse gases may be masked by atmospheric brown clouds.[43] When deposited, especially on glaciers or on ice in arctic regions, the lower surface albedo can also directly heat the surface.[44] The influences of aerosols, including black carbon, are most pronounced in the tropics and sub-tropics, particularly in Asia, while the effects of greenhouse gases are dominant in the extratropics and southern hemisphere.[45]
Solar variation
![](http://upload.wikimedia.org/wikipedia/commons/thumb/0/0d/Solar-cycle-data.png/220px-Solar-cycle-data.png)
Variations in solar output have been the cause of past climate changes,[46] but climate models predict that solar forcing is too small to account for a significant part of global warming during the industrial era.[47][48] Recent empirical analyses confirm potentially significant variations of solar luminosity on climate timescales [49] and indicate the contribution of solar forcing may be underestimated by current climate models.[50]
Greenhouse gases and solar forcing affect temperatures in different ways. While both increased solar activity and increased greenhouse gases are expected to warm the troposphere, an increase in solar activity should warm the stratosphere while an increase in greenhouse gases should cool the stratosphere.[4] Observations show that temperatures in the stratosphere have been cooling since 1979, when satellite measurements became available. Radiosonde (weather balloon) data from the pre-satellite era show cooling since 1958, though there is greater uncertainty in the early radiosonde record.[51]
A related hypothesis, proposed by Henrik Svensmark, is that magnetic activity of the sun deflects cosmic rays that may influence the generation of cloud condensation nuclei and thereby affect the climate.[52] Other research has found no relation between warming in recent decades and cosmic rays.[53][54] A recent study concluded that the influence of cosmic rays on cloud cover is about a factor of 100 lower than needed to explain the observed changes in clouds or to be a significant contributor to present-day climate change.[55]
Feedback
Feedback is a process in which changing one quantity changes a second quantity, and the change in the second quantity in turn changes the first. Positive feedback amplifies the change in the first quantity while negative feedback reduces it. Feedback is important in the study of global warming because it may amplify or diminish the effect of a particular process. The main positive feedback in global warming is the tendency of warming to increase the amount of water vapor in the atmosphere, which in turn leads to further warming. The main negative feedback is that according to the Stefan–Boltzmann law, the amount of heat radiated from the Earth into space increases with the temperature of Earth's surface and atmosphere. Imperfect understanding of feedbacks is a major cause of uncertainty and concern about global warming.
Climate models
The main tools for projecting future climate changes are mathematical models based on physical principles including fluid dynamics, thermodynamics and radiative transfer. Although they attempt to include as many processes as possible, simplifications of the actual climate system are inevitable because of the constraints of available computer power and limitations in knowledge of the climate system. All modern climate models are in fact combinations of models for different parts of the Earth. These include an atmospheric model for air movement, temperature, clouds, and other atmospheric properties; an ocean model that predicts temperature, salt content, and circulation of ocean waters; models for ice cover on land and sea; and a model of heat and moisture transfer from soil and vegetation to the atmosphere. Some models also include treatments of chemical and biological processes.[56] Warming due to increasing levels of greenhouse gases is not an assumption of the models; rather, it is an end result from the interaction of greenhouse gases with radiative transfer and other physical processes in the models.[57] Although much of the variation in model outcomes depends on the greenhouse gas emissions used as inputs, the temperature effect of a specific greenhouse gas concentration (climate sensitivity) varies depending on the model used. The representation of clouds is one of the main sources of uncertainty in present-generation models.[58]
Global climate model projections of future climate most often have used estimates of greenhouse gas emissions from the IPCC Special Report on Emissions Scenarios (SRES). In addition to human-caused emissions, some models also include a simulation of the carbon cycle; this generally shows a positive feedback, though this response is uncertain. Some observational studies also show a positive feedback.[59][60][61] Including uncertainties in future greenhouse gas concentrations and climate sensitivity, the IPCC anticipates a warming of 1.1 °C to 6.4 °C (2.0 °F to 11.5 °F) by the end of the 21st century, relative to 1980–1999.[3]
Models are also used to help investigate the causes of recent climate change by comparing the observed changes to those that the models project from various natural and human-derived causes. Although these models do not unambiguously attribute the warming that occurred from approximately 1910 to 1945 to either natural variation or human effects, they do indicate that the warming since 1970 is dominated by man-made greenhouse gas emissions.[4]
The physical realism of models is tested by examining their ability to simulate current or past climates.[62] Current climate models produce a good match to observations of global temperature changes over the last century, but do not simulate all aspects of climate.[33] Not all effects of global warming are accurately predicted by the climate models used by the IPCC. For example, observed Arctic shrinkage has been faster than that predicted.[63]
Attributed and expected effects
Environmental
![](http://upload.wikimedia.org/wikipedia/commons/thumb/e/e5/Glacier_Mass_Balance.png/220px-Glacier_Mass_Balance.png)
It is usually impossible to connect specific weather events to global warming. Instead, global warming is expected to cause changes in the overall distribution and intensity of events, such as changes to the frequency and intensity of heavy precipitation. Broader effects are expected to include glacial retreat, Arctic shrinkage including long-term shrinkage of Greenland ice sheet[64], and worldwide sea level rise. Some effects on both the natural environment and human life are, at least in part, already being attributed to global warming. A 2001 report by the IPCC suggests that glacier retreat, ice shelf disruption such as that of the Larsen Ice Shelf, sea level rise, changes in rainfall patterns, and increased intensity and frequency of extreme weather events are attributable in part to global warming.[65] Other expected effects include water scarcity in some regions and increased precipitation in others, changes in mountain snowpack, and some adverse health effects from warmer temperatures.[66]
Social and economic effects of global warming may be exacerbated by growing population densities in affected areas. Temperate regions are projected to experience fewer cold-related deaths but many more deaths from heat exposure.[67] A summary of probable effects and recent understanding can be found in the report made for the IPCC Third Assessment Report by Working Group II.[65] The newer IPCC Fourth Assessment Report summary reports that there is observational evidence for an increase in intense tropical cyclone activity in the North Atlantic Ocean since about 1970, in correlation with the increase in sea surface temperature (see Atlantic Multidecadal Oscillation), but that the detection of long-term trends is complicated by the quality of records prior to routine satellite observations. The summary also states that there is no clear trend in the annual worldwide number of tropical cyclones.[3]
Additional anticipated effects include sea level rise of 0.18 to 0.59 meters (0.59 to 1.9 ft) in 2090–2100 relative to 1980–1999,[3] new trade routes resulting from arctic shrinkage,[68] possible thermohaline circulation slowing, increasingly intense, in some locations, (but less frequent) hurricanes [69]and extreme weather events,[70] reductions in the ozone layer, changes in agriculture yields, changes in the range of climate-dependent disease vectors,[71] which have been linked to increases in the prevalence of malaria and dengue fever,[72] and ocean oxygen depletion.[73] Increased atmospheric CO2 increases the amount of CO2 dissolved in the oceans.[74] CO2 dissolved in the ocean reacts with water to form carbonic acid, resulting in ocean acidification. Ocean surface pH is estimated to have decreased from 8.25 near the beginning of the industrial era to 8.14 by 2004,[75] and is projected to decrease by a further 0.14 to 0.5 units by 2100 as the ocean absorbs more CO2.[3][76] Heat and carbon dioxide trapped in the oceans may still take hundreds of years to be re-emitted, even after greenhouse gas emissions are eventually reduced.[8] Since organisms and ecosystems are adapted to a narrow range of pH, this raises extinction concerns and disruptions in food webs.[77] One study predicts 18% to 35% of a sample of 1,103 animal and plant species would be extinct by 2050, based on future climate projections.[78] However, few mechanistic studies have documented extinctions due to recent climate change,[79] and one study suggests that projected rates of extinction are uncertain.[80]
Economic
In a literature assessment, Smith and others concluded, with medium confidence,[D] that:
- climate change would increase income inequalities between and within countries
- a small increase in global mean temperature (up to 2 °C by 2100, measured against 1990 levels) would result in net negative market sector impacts in many developing countries and net positive market sector impacts in many developed countries
- the aggregate market sector impact (i.e., total impacts across all regions) of a small increase in global mean temperature would amount to plus or minus a few percent of world GDP.
With high confidence, Smith and others concluded that a medium (2-3 °C) to high (above 3 °C) level of warming would result in more intense negative impacts, and that net positive impacts would begin to decline and eventually become negative.[81] They found that most studies showed aggregate net damages at a global scale above a medium temperature increase, with further damages at higher temperatures.
Depending on underlying assumptions, studies of the economic impacts of a doubling in atmospheric carbon dioxide (CO2) from pre-industrial levels conclude that this would have a slightly negative to moderately positive aggregate effect on the agricultural sector.[81] This aggregate effect hides substantial regional differences, with benefits mostly predicted in the developed world and strongly negative impacts for populations poorly connected to regional and global trading systems.
A number of other sectors will be affected by climate change, including the livestock, forestry, and fisheries industries. Other sectors sensitive to climate change include the energy, construction, insurance, tourism and recreation industries. The aggregate impact of climate change on most of these sectors is highly uncertain.[82]
Stern in 2007 assessed climate change impacts using the basic economics of risk premiums.[83] He found that unmitigated climate change could result in a reduction in welfare equivalent to a persistent average fall in global per-capita consumption of at least 5%. The study by Stern has received both criticism and support from other economists (see Stern Review). The IPCC in 2007 concluded that "Aggregate estimates of costs mask significant differences in impacts across sectors, regions and populations and very likely underestimate damage costs because they cannot include many non-quantifiable impacts."[84]
Responses to global warming
The broad agreement among climate scientists that global temperatures will continue to increase has led some nations, states, corporations and individuals to implement responses. These responses to global warming can be divided into mitigation of the causes and effects of global warming, adaptation to the changing global environment, and geoengineering to reverse global warming.
Mitigation
![](http://upload.wikimedia.org/wikipedia/commons/thumb/b/b5/Carbon_sequestration-2009-10-07.svg/220px-Carbon_sequestration-2009-10-07.svg.png)
The IPCC's Working Group III is responsible for crafting reports on mitigation of global warming and the costs and benefits of different approaches. The 2007 IPCC Fourth Assessment Report concludes that no one technology or sector can be completely responsible for mitigating future warming. They find there are key practices and technologies in various sectors, such as energy supply, transportation, industry, and agriculture that should be implemented to reduced global emissions. They estimate that stabilization of carbon dioxide equivalent between 445 and 710 ppm by 2030 will result in between a 0.6 percent increase and three percent decrease in global gross domestic product.[85]
Mitigation of global warming is accomplished through reductions in the rate of anthropogenic greenhouse gas release. The world's primary international agreement on reducing greenhouse gas emissions, the Kyoto Protocol, now covers more than 160 countries and over 55 percent of global greenhouse gas emissions.[86] As of February 2010, only the United States, historically the world's largest emitter of greenhouse gases, has refused to ratify the treaty. The treaty expires in 2012. International talks began in May 2007 on a future treaty to succeed the current one.[87] The 2009 United Nations Climate Change Conference met in Copenhagen in December 2009 to agree on a framework for climate change mitigation.[88] No binding agreement was made.
There has also been business action on climate change, including efforts to improve energy efficiency and limited moves towards use of alternative fuels. In January 2005 the European Union introduced its European Union Emission Trading Scheme, through which companies in conjunction with government agree to cap their emissions or to purchase credits from those below their allowances. Australia announced its Carbon Pollution Reduction Scheme in 2008. United States President Barack Obama has announced plans to introduce an economy-wide cap and trade scheme.[89]
Adaptation
A wide variety of measures have been suggested for adaptation to global warming, from the installation of air-conditioning equipment, to major infrastructure projects, such as abandoning settlements threatened by sea level rise.
Measures including water conservation,[90] water rationing, adaptive agricultural practices[91] including diversification, construction of flood defenses,[92] changes to medical care,[93] and interventions to protect threatened species[94] have all been suggested. A wide-ranging study of the possible opportunities for adaptation of infrastructure has been published by the Institute of Mechanical Engineers.[95]
Geoengineering
Geoengineering is the concept of planetary engineering applied to Earth: The deliberate modification of Earth's natural environment on a large scale to suit human needs.[96] An example is greenhouse gas remediation, which removes greenhouse gases from the atmosphere, usually through carbon sequestration techniques such as carbon dioxide air capture.[97] Solar radiation management reduces absorbed solar radiation, such as by the addition of stratospheric sulfur aerosols[98] or cool roof techniques.[99] No geoengineering projects of significant scale have been implemented, and detailed study has largely been the work of small numbers of scientists; but various significant institutions such as the Royal Society and IMechE have recently suggested that further study is warranted. Their various externalities and other costs are seen as major issues, and the idea or concern that one country could act unilaterally has also been raised.[100][101][102]
Debate and skepticism
Increased publicity of the scientific findings surrounding global warming has resulted in political and economic debate.[103] Poor regions, particularly Africa, appear at greatest risk from the projected effects of global warming, while their emissions have been small compared to the developed world.[104] The exemption of developing countries from Kyoto Protocol restrictions has been used to justify non-ratification by the U.S. and a previous Australian Government.[105] (Australia has since ratified the Kyoto protocol.)[106] Another point of contention is the degree to which emerging economies such as India and China should be expected to constrain their emissions.[107] The U.S. contends that if it must bear the cost of reducing emissions, then China should do the same[108][109] since China's gross national CO2 emissions now exceed those of the U.S.[110][111][112] China has contended that it is less obligated to reduce emissions since its per capita responsibility and per capita emissions are less that of the U.S.[113] India, also exempt, has made similar contentions.[114]
In 2007–2008 Gallup Polls surveyed 127 countries. Over a third of the world's population was unaware of global warming, with developing countries less aware than developed, and Africa the least aware. Of those aware, Latin America leads in belief that temperature changes are a result of human activities while Africa, parts of Asia and the Middle East, and a few countries from the Former Soviet Union lead in the opposite belief.[115] In the Western world, opinions over the concept and the appropriate responses are divided. Nick Pidgeon of Cardiff University finds that "results show the different stages of engagement about global warming on each side of the Atlantic"; where Europe debates the appropriate responses while the United States debates whether climate change is happening.[116]
Debates weigh the benefits of limiting industrial emissions of greenhouse gases against the costs that such changes would entail.[85] Using economic incentives, alternative and renewable energy have been promoted to reduce emissions while building infrastructure.[117][118] Organizations such as the libertarian Competitive Enterprise Institute, conservative commentators, and companies such as ExxonMobil have challenged IPCC climate change scenarios, funded scientists who disagree with the scientific consensus, and provided their own projections of the economic cost of stricter controls.[119][120][121][122] Environmental organizations and public figures have emphasized changes in the current climate and the risks they entail, while promoting adaptation to changes in infrastructural needs and emissions reductions.[123] Some fossil fuel companies have scaled back their efforts in recent years,[124] or called for policies to reduce global warming.[125] Many studies link population growth with emissions and the effect of climate change.[126][127][128]
Some global warming skeptics in the science or political communities dispute all or some of the global warming scientific consensus, questioning whether global warming is actually occurring, whether human activity has contributed significantly to the warming, and the magnitude of the threat posed by global warming.
See also
Notes
- ^ Increase is for years 1905 to 2005. Global surface temperature is defined in the IPCC Fourth Assessment Report as the average of near-surface air temperature over land and sea surface temperature. These error bounds are constructed with a 90% confidence interval.
- ^ The 2001 joint statement was signed by the national academies of science of Australia, Belgium, Brazil, Canada, the Caribbean, the People's Republic of China, France, Germany, India, Indonesia, Ireland, Italy, Malaysia, New Zealand, Sweden, and the UK. The 2005 statement added Japan, Russia, and the U.S. The 2007 statement added Mexico and South Africa. The Network of African Science Academies, and the Polish Academy of Sciences have issued separate statements. Professional scientific societies include American Astronomical Society, American Chemical Society, American Geophysical Union, American Institute of Physics, American Meteorological Society, American Physical Society, American Quaternary Association, Australian Meteorological and Oceanographic Society, Canadian Foundation for Climate and Atmospheric Sciences, Canadian Meteorological and Oceanographic Society, European Academy of Sciences and Arts, European Geosciences Union, European Science Foundation, Geological Society of America, Geological Society of Australia, Geological Society of London-Stratigraphy Commission, InterAcademy Council, International Union of Geodesy and Geophysics, International Union for Quaternary Research, National Association of Geoscience Teachers, National Research Council (US), Royal Meteorological Society, and World Meteorological Organization.
- ^ Note that the greenhouse effect produces an average worldwide temperature increase of about 33 °C (59 °F) compared to black body predictions without the greenhouse effect, not an average surface temperature of 33 °C (91 °F). The average worldwide surface temperature is about 14 °C (57 °F).
- ^ These confidence levels are Bayesian probabilities, and represent the degree of belief that Smith and his co-authors had in the validity of their conclusions. As a percentage chance of the conclusion being correct: high confidence ranges 67-95%, medium confidence ranges 33-67%.[129]
References
- ^ Attention: This template ({{cite doi}}) is deprecated. To cite the publication identified by doi:10.1073/pnas.0606291103, please use {{cite journal}} (if it was published in a bona fide academic journal, otherwise {{cite report}} with
|doi=10.1073/pnas.0606291103
instead. - ^ 2009 Ends Warmest Decade on Record. NASA Earth Observatory Image of the Day, January 22, 2010.
- ^ a b c d e f g IPCC (2007-05-04). "Summary for Policymakers" (PDF). Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Retrieved 2009-07-03.
- ^ a b c d
Hegerl, Gabriele C. (2007). "Understanding and Attributing Climate Change" (PDF). Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. IPCC.
Recent estimates indicate a relatively small combined effect of natural forcings on the global mean temperature evolution of the second half of the 20th century, with a small net cooling from the combined effects of solar and volcanic forcings.
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Ammann, Caspar (2007). "Solar influence on climate during the past millennium: Results from transient simulations with the NCAR Climate Simulation Model" (PDF). Proceedings of the National Academy of Sciences of the United States of America. 104 (10): 3713–3718. doi:10.1073/pnas.0605064103. PMC 1810336. PMID 17360418.
Simulations with only natural forcing components included yield an early 20th century peak warming of ≈0.2 °C (≈1950 AD), which is reduced to about half by the end of the century because of increased volcanism
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suggested) (help) - ^ Royal Society (2005). "Joint science academies' statement: Global response to climate change". Retrieved 19 April 2009.
- ^
Archer, David (2005). "Fate of fossil fuel CO
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(help) - ^ Attention: This template ({{cite doi}}) is deprecated. To cite the publication identified by doi:10.1007/s00382-009-0646-0, please use {{cite journal}} (if it was published in a bona fide academic journal, otherwise {{cite report}} with
|doi=10.1007/s00382-009-0646-0
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- ^ ftp://texmex.mit.edu/pub/emanuel/PAPERS/Emanuel_etal_2008.pdf
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- ^ Caldeira, Ken (2005-09-21). "Ocean model predictions of chemistry changes from carbon dioxide emissions to the atmosphere and ocean". Journal of Geophysical Research. 110 (C09S04): 1–12. doi:10.1029/2004JC002671. Retrieved 2006-02-14.
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ignored (help) - ^ a b
Smith, J.B., Schellnhuber, H., Mirza, M.M.Q., Fankhauser, S., Leemans, R., Erda, L., Ogallo, L., Pittock, B., Richels, R., Rosenzweig, C., Safriel, U., Tol, R.S.J., Weyant, J., Yohe, G. (2001). "Chapter 19: Vulnerability to Climate Change and Reasons for Concern: A Synthesis". In Hope C. and Sinha S.K. (eds.) (ed.). Climate Change 2001: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Third Assessment Report of the Intergovernmental Panel on Climate Change (Full free text). Cambridge, United Kingdom: Cambridge University Press. pp. 957–958.
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Schneider, S.H., S. Semenov, A. Patwardhan, I. Burton, C.H.D. Magadza, M. Oppenheimer, A.B. Pittock, A. Rahman, J.B. Smith, A. Suarez and F. Yamin (2007). "Chapter 19: Assessing key vulnerabilities and the risk from climate change". In M.L. Parry, O.F. Canziani, J.P. Palutikof, P.J. van der Linden and C.E. Hanson (eds.) (ed.). Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (Full free text). Cambridge, United Kingdom: Cambridge University Press. p. 790.
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Yohe, G.W., R.D. Lasco, Q.K. Ahmad, N.W. Arnell, S.J. Cohen, C. Hope, A.C. Janetos and R.T. Perez (2007). "Chapter 20: Perspectives on climate change and sustainability". In M.L. Parry, O.F. Canziani, J.P. Palutikof, P.J. van der Linden and C.E. Hanson (eds.) (ed.). Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (Full free text). Cambridge, United Kingdom: Cambridge University Press. p. 821.
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- ^ "Group: China surpassed US in carbon emissions in 2006: Dutch report". livemint.com. Reuters. 2007-06-20. Retrieved 2007-10-16.
- ^ Casey, Michael (2007-12-07). "China Says West Should Deal With Warming". Newsvine. Retrieved 2009-06-06.
- ^ IANS (2009-02-05). "India can't be exempt from mandatory greenhouse gas emission cap: John Kerry". Thaindian.com. Retrieved 2009-06-24.
- ^ Pelham, Brett (2009-04-22). "Awareness, Opinions About Global Warming Vary Worldwide". Gallup. Retrieved 2009-07-14.
- ^ "Summary of Findings". Little Consensus on Global Warming. Partisanship Drives Opinion. Pew Research Center. 2006-07-12. Retrieved 2007-04-14.
- ^ Blair, Tony (2009-07-03). "Breaking the Climate Deadlock". Kosovo Times. Retrieved 2009-07-03.
- ^ Richards, Holly (2009-07-02). "Energy bill causing some tension among U.S. officials". Coshocton Tribune. Retrieved 2009-07-03.
- ^ Begley, Sharon (2007-08-13). "The Truth About Denial". Newsweek. Retrieved 2007-08-13.
- ^ Adams, David (2006-09-20). "Royal Society tells Exxon: stop funding climate change denial". The Guardian. Retrieved 2007-08-09.
- ^ "Exxon cuts ties to global warming skeptics". MSNBC. 2007-01-12. Retrieved 2007-05-02.
- ^ Sandell, Clayton (2007-01-03). "Report: Big Money Confusing Public on Global Warming". ABC. Retrieved 2007-04-27.
- ^ "New Report Provides Authoritative Assessment of National, Regional Impacts of Global Climate Change" (PDF) (Press release). U.S. Global Change Research Program. June 6, 2009. Retrieved 2009-06-27.
- ^ Reuters (May 18, 2007). "Greenpeace: Exxon still funding climate skeptics". USA Today. Retrieved Jan 21, 2010.
{{cite news}}
:|author=
has generic name (help) - ^ "Global Warming Resolutions at U.S. Oil Companies Bring Policy Commitments from Leaders, and Record High Votes at Laggards" (Press release). Ceres. May 13, 2004. Retrieved 2010-03-04.
- ^ "Does Population Growth Impact Climate Change?". Scientific American. July 29, 2009. Retrieved Jan 21, 2010.
- ^ Gray, Louise (December 8, 2009). "Copenhagen climate summit issues: population growth". Telegraph.co.uk. Retrieved Jan 21, 2010.
- ^ "Once taboo, population enters climate debate". The Independent. December 5, 2009. Retrieved Jan 21, 2010.
- ^
Schneider, S., J. Sarukhan, J. Adejuwon, C. Azar, W. Baethgen, C. Hope,
R. Moss, N. Leary, R. Richels, J.-P. van Ypersele, K. Kuntz-Duriseti and R.N. Jones (2001). "Chapter 1: Overview of Impacts, Adaptation, and Vulnerability to Climate Change". In J. Bruce and B. Walker (eds.) (ed.). Climate Change 2001: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Third Assessment Report of the Intergovernmental Panel on Climate Change (Full free text). Cambridge, United Kingdom: Cambridge University Press. p. 79.
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Further reading
- Association of British Insurers (2005–06). Financial Risks of Climate Change (PDF).
{{cite book}}
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(help) - Barnett, Tim P.; Adam, JC; Lettenmaier, DP (2005-11-17). "Potential impacts of a warming climate on water availability in snow-dominated regions" (abstract). Nature. 438 (7066): 303–309. doi:10.1038/nature04141. PMID 16292301.
{{cite journal}}
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and|first=
specified (help); More than one of|last1=
and|last=
specified (help); Unknown parameter|coauthors=
ignored (|author=
suggested) (help) - Behrenfeld, Michael J.; O'malley, RT; Siegel, DA; Mcclain, CR; Sarmiento, JL; Feldman, GC; Milligan, AJ; Falkowski, PG; Letelier, RM (2006-12-07). "Climate-driven trends in contemporary ocean productivity" (PDF). Nature. 444 (7120): 752–755. doi:10.1038/nature05317. PMID 17151666.
{{cite journal}}
: More than one of|first1=
and|first=
specified (help); More than one of|last1=
and|last=
specified (help); Unknown parameter|coauthors=
ignored (|author=
suggested) (help) - Choi, Onelack (2005). "The Impacts of Socioeconomic Development and Climate Change on Severe Weather Catastrophe Losses: Mid-Atlantic Region (MAR) and the U.S." Climate Change. 58 (1–2): 149–170. doi:10.1023/A:1023459216609.
{{cite journal}}
: Unknown parameter|coauthors=
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suggested) (help); Unknown parameter|month=
ignored (help) - Dyurgerov, Mark B. (2005). Glaciers and the Changing Earth System: a 2004 Snapshot (PDF). Institute of Arctic and Alpine Research Occasional Paper #58. ISSN 0069-6145.
{{cite book}}
: Unknown parameter|coauthors=
ignored (|author=
suggested) (help) - Emanuel, Kerry A. (2005-08-04). "Increasing destructiveness of tropical cyclones over the past 30 years" (PDF). Nature. 436 (7051): 686–688. doi:10.1038/nature03906. PMID 16056221.
{{cite journal}}
: More than one of|first1=
and|first=
specified (help); More than one of|last1=
and|last=
specified (help) - Hansen, James (2005-06-03). "Earth's Energy Imbalance: Confirmation and Implications" (PDF). Science. 308 (5727): 1431–1435. doi:10.1126/science.1110252. PMID 15860591.
{{cite journal}}
: Unknown parameter|coauthors=
ignored (|author=
suggested) (help) - Hinrichs, Kai-Uwe (2003-02-21). "Molecular Fossil Record of Elevated Methane Levels in Late Pleistocene Coastal Waters". Science. 299 (5610): 1214–1217. doi:10.1126/science.1079601. PMID 12595688.
{{cite journal}}
: Unknown parameter|coauthors=
ignored (|author=
suggested) (help) - Hirsch, Tim (2006-01-11). "Plants revealed as methane source". BBC.
- Hoyt, Douglas V. (1993–11). "A discussion of plausible solar irradiance variations, 1700–1992". Journal of Geophysical Research. 98 (A11): 18, 895–18, 906. doi:10.1029/93JA01944.
{{cite journal}}
: Check date values in:|year=
(help); Unknown parameter|coauthors=
ignored (|author=
suggested) (help) - Karnaukhov, A. V. (2001). "Role of the Biosphere in the Formation of the Earth's Climate: The Greenhouse Catastrophe" (PDF). Biophysics. 46 (6).
- Kenneth, James P. (2003-02-14). Methane Hydrates in Quaternary Climate Change: The Clathrate Gun Hypothesis. American Geophysical Union.
{{cite book}}
: Unknown parameter|coauthors=
ignored (|author=
suggested) (help) - Keppler, Frank (2006-01-18). "Global Warming – The Blame Is not with the Plants". Max Planck Society.
{{cite news}}
: Unknown parameter|coauthors=
ignored (|author=
suggested) (help) - Lean, Judith L. (2002–12). "The effect of increasing solar activity on the Sun's total and open magnetic flux during multiple cycles: Implications for solar forcing of climate" (abstract). Geophysical Research Letters. 29 (24): 2224. doi:10.1029/2002GL015880.
{{cite journal}}
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(help); Unknown parameter|coauthors=
ignored (|author=
suggested) (help) - Lerner, K. Lee (2006-07-26). Environmental issues: essential primary sources. Thomson Gale. ISBN 1414406258.
{{cite book}}
: Unknown parameter|coauthors=
ignored (|author=
suggested) (help) - Muscheler, Raimund, R; Joos, F; Müller, SA; Snowball, I (2005-07-28). "Climate: How unusual is today's solar activity?" (PDF). Nature. 436 (7012): 1084–1087. doi:10.1038/nature04045. PMID 16049429.
{{cite journal}}
: More than one of|last1=
and|last=
specified (help); Unknown parameter|coauthors=
ignored (|author=
suggested) (help) - Oerlemans, J. (2005-04-29). "Extracting a Climate Signal from 169 Glacier Records" (PDF). Science. 308 (5722): 675–677. doi:10.1126/science.1107046. PMID 15746388.
- Oreskes, Naomi (2004-12-03). "Beyond the Ivory Tower: The Scientific Consensus on Climate Change" (PDF). Science. 306 (5702): 1686. doi:10.1126/science.1103618. PMID 15576594.
{{cite journal}}
: More than one of|first1=
and|first=
specified (help); More than one of|last1=
and|last=
specified (help) - Purse, Bethan V.; Mellor, PS; Rogers, DJ; Samuel, AR; Mertens, PP; Baylis, M (2005). "Climate change and the recent emergence of bluetongue in Europe" (abstract). Nature Reviews Microbiology. 3 (2): 171–181. doi:10.1038/nrmicro1090. PMID 15685226.
{{cite journal}}
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and|first=
specified (help); More than one of|last1=
and|last=
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ignored (help) - Revkin, Andrew C (2005-11-05). "Rise in Gases Unmatched by a History in Ancient Ice". The New York Times.
- Ruddiman, William F. (2005-12-15). Earth's Climate Past and Future. New York: Princeton University Press. ISBN 0-7167-3741-8.
- Ruddiman, William F. (2005-08-01). Plows, Plagues, and Petroleum: How Humans Took Control of Climate. New Jersey: Princeton University Press. ISBN 0-691-12164-8.
- Solanki, Sami K.; Usoskin, IG; Kromer, B; Schüssler, M; Beer, J (2004-10-23). "Unusual activity of the Sun during recent decades compared to the previous 11,000 years" (PDF). Nature. 431 (7012): 1084–1087. doi:10.1038/nature02995. PMID 15510145.
{{cite journal}}
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and|first=
specified (help); More than one of|last1=
and|last=
specified (help); Unknown parameter|coauthors=
ignored (|author=
suggested) (help) - Solanki, Sami K. (2005-07-28). "Climate: How unusual is today's solar activity? (Reply)" (PDF). Nature. 436: E4–E5. doi:10.1038/nature04046.
{{cite journal}}
: Unknown parameter|coauthors=
ignored (|author=
suggested) (help) - Sowers, Todd (2006-02-10). "Late Quaternary Atmospheric CH4 Isotope Record Suggests Marine Clathrates Are Stable". Science. 311 (5762): 838–840. doi:10.1126/science.1121235. PMID 16469923.
- Svensmark, Henrik (2007-02-08). "Experimental evidence for the role of ions in particle nucleation under atmospheric conditions". Proceedings of the Royal Society A. 463 (2078). FirstCite Early Online Publishing: 385–396. doi:10.1098/rspa.2006.1773.
{{cite journal}}
: Unknown parameter|coauthors=
ignored (|author=
suggested) (help)(online version requires registration) - Walter, K. M.; Zimov, SA; Chanton, JP; Verbyla, D; Chapin Fs, 3rd (2006-09-07). "Methane bubbling from Siberian thaw lakes as a positive feedback to climate warming". Nature. 443 (7107): 71–75. doi:10.1038/nature05040. PMID 16957728.
{{cite journal}}
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and|first=
specified (help); More than one of|last1=
and|last=
specified (help); Unknown parameter|coauthors=
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suggested) (help)CS1 maint: numeric names: authors list (link) - Wang, Y.-M. (2005-05-20). "Modeling the sun's magnetic field and irradiance since 1713" (PDF). Astrophysical Journal. 625: 522–538. doi:10.1086/429689.
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External links
Research
- Intergovernmental Panel on Climate Change — collection of IPCC reports
- Climate Change at the National Academies — repository for reports, workshops, and meetings
- Nature Reports Climate Change — free-access web resource
- Met Office: Climate change — UK National Weather Service
- Global Science and Technology Sources on the Internet — extensive commented list of internet resources
- Educational Global Climate Modelling (EdGCM) — research-quality climate change simulator
- DISCOVER — satellite-based ocean and climate data since 1979 from NASA
- Global Warming Art — collection of figures and images
Educational
- What Is Global Warming? — by National Geographic
- Global Warming Frequently Asked Questions — from NOAA
- Understanding Climate Change – Frequently Asked Questions — from UCAR
- Global Climate Change: NASA's Eyes on the Earth — from NASA's JPL and Caltech
- OurWorld 2.0 — from the United Nations University
- Pew Center on Global Climate Change — business and politics
- Best Effort Global Warming Trajectories – Wolfram Demonstrations Project — by Harvey Lam
- Koshland Science Museum – Global Warming Facts and Our Future — graphical introduction from National Academy of Sciences
- The Discovery of Global Warming – A History — by Spencer R. Weart from The American Institute of Physics
- Climate Change: Coral Reefs on the Edge — A video presentation by Prof. Ove Hoegh-Guldberg, University of Auckland
- Understanding and Responding to Climate Change — National Academies Reports 2008
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