Global mean surface temperature anomaly 1850 to 2006 relative to 1961–1990

Mean surface temperature anomalies during the period 1995 to 2004 with respect to the average temperatures from 1940 to 1980

Global warming refers to the increase in the average temperature of the Earth's near-surface air and oceans in recent decades and its projected continuation. Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... Instrumental global surface temperature measurements; see also [http://www. ... Animated map exhibiting the worlds oceanic waters. ...

The global average air temperature near the Earth's surface rose 0.74 ± 0.18 °C (1.33 ± 0.32 °F) during the last 100 years. The Intergovernmental Panel on Climate Change (IPCC) concludes, "most of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations"^[1] via the greenhouse effect. Natural phenomena such as solar variation combined with volcanoes probably had a small warming effect from pre-industrial times to 1950 and a small cooling effect from 1950 onward.^[2][3] These basic conclusions have been endorsed by at least 30 scientific societies and academies of science, including all of the national academies of science of the major industrialized countries. While individual scientists have voiced disagreement with some of the main conclusions of the IPCC, the overwhelming majority of scientists working on climate change are in agreement with them.^[4] The plus-minus sign (±) is a mathematical symbol commonly used to indicate the precision of an approximation, or as a convenient shorthand for a quantity which has two possible values opposite in sign. ... Celsius is, or relates to, the Celsius temperature scale (previously known as the centigrade scale). ... For other uses, see Fahrenheit (disambiguation). ... IPCC is the science authority for the UNFCCC The Intergovernmental Panel on Climate Change (IPCC) was established in 1988 by two United Nations organizations, the World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP), to evaluate the risk of climate change brought on by humans, based mainly on... Attribution of recent climate change is the effort to scientifically ascertain mechanisms responsible for relatively recent changes observed in the Earths climate. ... Look up anthropogenic in Wiktionary, the free dictionary. ... Wikinews has related news: Scientists warn thawing Siberia may trigger global meltdown A schematic representation of the exchanges of energy between outer space, the Earths atmosphere, and the Earth surface. ... 400 year history of sunspot numbers. ... Cleveland Volcano in the Aleutian Islands of Alaska photographed from the International Space Station For other uses, see Volcano (disambiguation). ... National and international science academies and professional societies have assessed the current scientific opinion on climate change, in particular recent global warming. ... Group of Eight redirects here. ... This article lists scientists and former scientists who have stated disagreement with one or more of the principal conclusions of the mainstream scientific assessment of global warming. ...

Climate model projections summarized by the IPCC indicate that average global surface temperature will likely rise a further 1.1 to 6.4 °C (2.0 to 11.5 °F) during the 21st century.^[1] The range of values results from the use of differing scenarios of future greenhouse gas emissions as well as models with differing climate sensitivity. Although most studies focus on the period up to 2100, warming and sea level rise are expected to continue for more than a millennium even if greenhouse gas levels are stabilized. The delay in reaching equilibrium is a result of the large heat capacity of the oceans.^[1] Climate models use quantitative methods to simulate the interactions of the atmosphere, oceans, land surface, and ice. ... The Special Report on Emissions Scenarios was a report, prepared for the IPCC TAR, on future emission scenarios to be used for driving global circulation models to develop climate change scenarios. ... Top: Increasing atmospheric CO2 levels as measured in the atmosphere and ice cores. ... In IPCC reports, equilibrium climate sensitivity refers to the equilibrium change in global mean surface temperature following a doubling of the atmospheric (equivalent) CO2 concentration. ...

Increasing global temperatures will cause sea level to rise, and is expected to increase the intensity of extreme weather events and to change the amount and pattern of precipitation. Other effects of global warming include changes in agricultural yields, glacier retreat, species extinctions and increases in the ranges of disease vectors. Sea level measurements from 23 long tide gauge records in geologically stable environments show a rise of around 20 centimeters per century (2 mm/year). ... Trends in natural disasters, Pascal Peduzzi (2004) Is climate change increasing the frequency of hazardous events? Environment Times UNEP/GRID-Arendal Extreme weather includes weather phenomena that are at the extremes of the historical distribution, especially severe or unseasonal weather. ... The net impact of global warming so far has been modest, but near-future effects are likely to become significantly negative, with large-scale extreme impacts possible by the end of the century. ... In agriculture, crop yield (also known as agricultural output) is not only a measure of the yield of cereal per unit area of land under cultivation, it is also the seed generation of the plant itself, i. ... Global glacial mass balance in the last fifty years, reported to the WGMS and NSIDC. The downward trend in the late 1980s is symptomatic of the increased rate and number of retreating glaciers. ... The extinction risk of climate change -- that is, the expected number of species expected to become extinct due to the effects of global warming -- has been estimated in a 2004 Nature study to be between 15 and 37 percent of known species by 2050. ... In epidemiology, a vector is an organism that does not cause disease itself but which spreads infection by conveying pathogens from one host to another. ...

Remaining scientific uncertainties include the amount of warming expected in the future, and how warming and related changes will vary from region to region around the globe. There is ongoing political and public debate worldwide regarding what, if any, action should be taken to reduce or reverse future warming or to adapt to its expected consequences. Most national governments have signed and ratified the Kyoto Protocol, aimed at reducing greenhouse gas emissions. “Uncertain” redirects here. ... The politics of global warming looks at the current political issues relating to global warming, as well as the historical rise of global warming as a political issue. ... The global warming controversy is a dispute regarding the nature and consequences of global warming. ... Global carbon dioxide emissions 1800–2000 Global average surface temperature 1850 to 2006 Mitigation of global warming involves taking actions aimed at reducing the extent of global warming. ... Adaptation to global warming covers all actions aimed at reducing the negative effects of global warming. ... // Participation in the Kyoto Protocol, where dark green indicates countries that have signed and ratified the treaty. ... Kyoto Protocol Opened for signature December 11, 1997 in Kyoto, Japan Entered into force February 16, 2005. ...

Terminology

The term "global warming" is a specific example of the broader term climate change, which can also refer to global cooling. In common usage, the term refers to recent warming and implies a human influence.^[5] The United Nations Framework Convention on Climate Change (UNFCCC) uses the term "climate change" for human-caused change, and "climate variability" for other changes.^[6] The term "anthropogenic global warming" is sometimes used when focusing on human-induced changes. Variations in CO2, temperature and dust from the Vostok ice core over the last 450,000 years For current global climate change, see Global warming. ... Global cooling in general can refer to a cooling of the Earth. ... UNFCCC logo. ...

Causes

Carbon dioxide during the last 400,000 years and (inset above) the rapid rise since the Industrial Revolution; changes in the Earth's orbit around the Sun, known as Milankovitch cycles, are believed to be the pacemaker of the 100,000 year ice age cycle.

Recent increases in atmospheric carbon dioxide (CO₂). The monthly CO₂ measurements display small seasonal oscillations in an overall yearly uptrend; each year's maximum is reached during the Northern Hemisphere's late spring, and declines during the Northern Hemisphere growing season as plants remove some CO₂ from the atmosphere.

The change from May to May in parts per million of CO₂ at Mauna Loa. May is the month with the highest concentrations of CO₂.

Main articles: Attribution of recent climate change and scientific opinion on climate change

The Earth's climate changes in response to external forcing, including variations in its orbit around the sun (orbital forcing),^[7][8][9] volcanic eruptions, and atmospheric greenhouse gas concentrations. The detailed causes of the recent warming remain an active field of research, but the scientific consensus^[10][11] identifies elevated levels of greenhouse gases due to human activity as the main influence. This attribution is clearest for the most recent 50 years, for which the most detailed data are available. In contrast to the scientific consensus that recent warming is mainly attributable to elevated levels of greenhouse gases, other hypotheses have been suggested to explain the observed increase in mean global temperature. One such hypothesis proposes that warming may be the result of variations in solar activity.^{[12][13][14][15]} Image File history File links Carbon_Dioxide_400kyr-2. ... Image File history File links Carbon_Dioxide_400kyr-2. ... Carbon dioxide is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. ... A Watt steam engine, the steam engine that propelled the Industrial Revolution in Britain and the world. ... Milankovitch cycles are the collective effect of changes in the Earths movements upon its climate, named after Serbian civil engineer and mathematician Milutin Milanković. The eccentricity, axial tilt, and precession of the Earths orbit vary in several patterns, resulting in 100,000 year ice age cycles of the... Variations in CO2, temperature and dust from the Vostok ice core over the last 400 000 years For the animated movie, see Ice Age (movie). ... Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... Northern hemisphere highlighted in yellow. ... Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... Attribution of recent climate change is the effort to scientifically ascertain mechanisms responsible for relatively recent changes observed in the Earths climate. ... National and international science academies and professional societies have assessed the current scientific opinion on climate change, in particular recent global warming. ... Orbital forcing, or Milankovitch theory, describes the effect on climate of slow changes in the tilt of the Earths axis and shape of the orbit. ... Cleveland Volcano in the Aleutian Islands of Alaska photographed from the International Space Station For other uses, see Volcano (disambiguation). ... Top: Increasing atmospheric CO2 levels as measured in the atmosphere and ice cores. ... Attribution of recent climate change is the effort to scientifically ascertain mechanisms responsible for relatively recent changes observed in the Earths climate. ... National and international science academies and professional societies have assessed the current scientific opinion on climate change, in particular recent global warming. ...

None of the effects of forcing are instantaneous. The thermal inertia of the Earth's oceans and slow responses of other indirect effects mean that the Earth's current climate is not in equilibrium with the forcing imposed. Climate commitment studies indicate that even if greenhouse gases were stabilized at 2000 levels, a further warming of about 0.5 °C (0.9 °F) would still occur.^[16] Volumetric heat capacity (VHC) describes the ability of a given volume of a substance to store heat while undergoing a given temperature change, but without undergoing a phase change. ... Climate commitment describes the fact that climate reacts with a delay to influencing factors (climate forcings) such as the presence of green house gases. ...

Greenhouse gases in the atmosphere

Main article: Greenhouse effect

The greenhouse effect was discovered by Joseph Fourier in 1824 and was first investigated quantitatively by Svante Arrhenius in 1896. It is the process by which absorption and emission of infrared radiation by atmospheric gases warms a planet's atmosphere and surface. Wikinews has related news: Scientists warn thawing Siberia may trigger global meltdown A schematic representation of the exchanges of energy between outer space, the Earths atmosphere, and the Earth surface. ... Jean Baptiste Joseph Fourier (March 21, 1768 - May 16, 1830) was a French mathematician and physicist who is best known for initiating the investigation of Fourier series and their application to problems of heat flow. ... Svante August Arrhenius (February 19, 1859 – October 2, 1927) was a Swedish chemist and one of the founders of the science of physical chemistry. ... In physics, absorption is the process by which the energy of a photon is taken up by another entity, for example, by an atom whose valence electrons make transition between two electronic energy levels. ... For other uses, see Infrared (disambiguation). ... For other uses, see Atmosphere (disambiguation). ... This article is about the astronomical term. ...

Existence of the greenhouse effect as such is not disputed. Naturally occurring greenhouse gases have a mean warming effect of about 33 °C (59 °F), without which Earth would be uninhabitable.^[17][18] The debate centers on how the strength of the greenhouse effect is changed when human activity increases the atmospheric concentrations of some greenhouse gases.

On Earth, the major greenhouse gases are water vapor, which causes about 36–70% of the greenhouse effect (not including clouds); carbon dioxide (CO₂), which causes 9–26%; methane (CH₄), which causes 4–9%; and ozone, which causes 3–7%.^[19][20] Some other naturally occurring gases contribute very small fractions of the greenhouse effect; one of these, nitrous oxide (N₂O), is increasing in concentration owing to human activity such as agriculture. The atmospheric concentrations of CO₂ and CH₄ have increased by 31% and 149% respectively above pre-industrial levels since 1750. These levels are considerably higher than at any time during the last 650,000 years, the period for which reliable data has been extracted from ice cores. From less direct geological evidence it is believed that CO₂ values this high were last attained 20 million years ago.^[21] 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, in particular deforestation.^[22] Water vapor or water vapour (see spelling differences), also aqueous vapor, is the gas phase of water. ... Cloud forcing (sometimes described as cloud radiative forcing) is the difference between the radiation budget components for average cloud conditions and cloud-free conditions. ... Carbon dioxide is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. ... Methane is a chemical compound with the molecular formula . ... For other uses, see Ozone (disambiguation). ... For other uses, see Nitrous oxide (disambiguation). ... Top: Increasing atmospheric CO2 levels as measured in the atmosphere and ice cores. ... Ice Core sample taken from drill. ... Fossil fuels or mineral fuels are fossil source fuels, this is, hydrocarbons found within the top layer of the earth’s crust. ... This article is about the process of deforestation in the environment. ...

The present atmospheric concentration of CO₂ is about 383 parts per million (ppm) by volume.^[23] Future CO₂ levels are expected to rise due to ongoing burning of fossil fuels and land-use change. The rate of rise will depend on uncertain economic, sociological, technological, and natural developments, but may be ultimately limited by the availability of fossil fuels. The IPCC Special Report on Emissions Scenarios gives a wide range of future CO₂ scenarios, ranging from 541 to 970 ppm by the year 2100.^[24] Fossil fuel reserves are sufficient to reach this level and continue emissions past 2100, if coal, tar sands or methane clathrates are extensively used.^[25] The Special Report on Emissions Scenarios was a report, prepared for the IPCC TAR, on future emission scenarios to be used for driving global circulation models to develop climate change scenarios. ... Burning ice. Methane, released by heating, burns; water drips (USGS). ...

Feedbacks

Main article: Effects of global warming#Further global warming (positive feedback)

The effects of forcing agents on the climate are complicated by various feedback processes. The net impact of global warming so far has been modest, but near-future effects are likely to become significantly negative, with large-scale extreme impacts possible by the end of the century. ...

One of the most pronounced feedback effects relates to the evaporation of water. In the case of warming by the addition of long-lived greenhouse gases such as CO₂, the initial warming will cause more water to be evaporated into the atmosphere. Since water vapor itself acts as a greenhouse gas, this causes still more warming; the warming causes more water vapor to be evaporated, and so forth until a new dynamic equilibrium concentration of water vapor is reached with a much larger greenhouse effect than that due to CO₂ alone. Although this feedback process involves an increase in the absolute moisture content of the air, the relative humidity stays nearly constant or even decreases slightly because the air is warmer.^[26] This feedback effect can only be reversed slowly as CO₂ has a long average atmospheric lifetime. A hygrometer used to measure the humidity of air. ... Top: Increasing atmospheric CO2 levels as measured in the atmosphere and ice cores. ...

Feedback effects due to clouds are an area of ongoing research. Seen from below, clouds emit infrared radiation back to the surface, and so exert a warming effect; seen from above, clouds reflect sunlight and emit infrared radiation to space, and so exert a cooling effect. Whether the net effect is warming or cooling depends on details such as the type and altitude of the cloud. These details are difficult to represent in climate models, in part because clouds are much smaller than the spacing between points on the computational grids of climate models. Nevertheless, cloud feedback is second only to water vapor feedback and is positive in all the models that were used in the IPCC Fourth Assessment Report.^[26] Climate Change 2007, the Fourth Assessment Report (AR4) of the United Nations Intergovernmental Panel on Climate Change (IPCC), is the fourth in a series of such reports. ...

Another important feedback process is ice-albedo feedback.^[27] When global temperatures increase, ice near the poles melts at an increasing rate. As the ice melts, land or open water takes its place. Both land and open water are on average less reflective than ice, and thus absorb more solar radiation. This causes more warming, which in turn causes more melting, and this cycle continues.

Positive feedback due to release of CO₂ and CH₄ from thawing permafrost, such as the frozen peat bogs in Siberia, is an additional mechanism contributing to warming.^[28] A massive release of CH₄ from methane clathrates could cause rapid warming, according to the clathrate gun hypothesis. While these two men dig in Alaska to study soil, the hard permafrost requires the use of a jackhammer In geology, permafrost or permafrost soil is soil at or below the freezing point of water (0 °C or 32 °F) for two or more years. ... Peat in Lewis, Scotland Peat is an accumulation of partially decayed vegetation matter. ... Lütt-Witt Moor, a bog in Henstedt-Ulzburg in northern Germany. ... This article is about Siberia as a whole. ... Burning ice. Methane, released by heating, burns; water drips (USGS). ... The clathrate gun hypothesis states that as sea temperatures rise the sudden release of methane from methane clathrate compounds buried in the seabeds will cause a drastic alteration of the ocean enviornment and the atmosphere of earth, as recent analysis concerning the Permian extinction event indicates may have happened in...

The ocean's ability to sequester carbon is expected to decline as it warms, because the resulting low nutrient levels of the mesopelagic zone limits the growth of diatoms in favor of smaller phytoplankton that are poorer biological pumps of carbon.^[29] The pelagic zone is the part of the open sea or ocean comprising the water column, i. ... Orders Centrales Pennales Diatoms (Greek: (dia) = through + (temnein) = to cut, i. ... Diagrams of some typical phytoplankton Phytoplankton are the autotrophic component of plankton. ... In oceanic biogeochemistry, the biological pump is the sum of a suite of biologically-mediated processes that transport carbon from the surface euphotic zone to the oceans interior. ...

Solar variation

Solar variation over the last 30 years.

Main article: Solar variation

A few papers suggest that the Sun's contribution may have been underestimated. Two researchers at Duke University, Bruce West and Nicola Scafetta, have estimated that the Sun may have contributed about 45–50% of the increase in the average global surface temperature over the period 1900–2000, and about 25–35% between 1980 and 2000.^[30] A paper by Peter Stott and other researchers suggests that climate models overestimate the relative effect of greenhouse gases compared to solar forcing; they also suggest that the cooling effects of volcanic dust and sulfate aerosols have been underestimated.^[31] They nevertheless conclude that even with an enhanced climate sensitivity to solar forcing, most of the warming since the mid-20th century is likely attributable to the increases in greenhouse gases. Image File history File links Pic of 20 years of solar output data. ... Image File history File links Pic of 20 years of solar output data. ... 400 year history of sunspot numbers. ... Duke University is a private coeducational research university located in Durham, North Carolina, USA. Founded by Methodists and Quakers in the present-day town of Trinity in 1838, the school moved to Durham in 1892. ...

A different hypothesis is that variations in solar output, possibly amplified by cloud seeding via galactic cosmic rays, may have contributed to recent warming.^[32] It suggests magnetic activity of the sun is a crucial factor which deflects cosmic rays that may influence the generation of cloud condensation nuclei and thereby affect the climate.^[33] 400 year history of sunspot numbers. ... Galactic cosmic rays are high-energy charged particles that enter the solar system from the outside. ...

One predicted effect of an increase in solar activity would be a warming of the stratosphere; however, the observed effect since at least 1960 has been a cooling of the lower stratosphere, which is one of the predicted results of greenhouse gas warming.^[34] Reduction of stratospheric ozone also has a cooling influence, although substantial ozone depletion did not occur until the late 1970s. Solar variation combined with changes in volcanic activity probably did have a warming effect from pre-industrial times to 1950, but a cooling effect since.^[1] In 2006, Peter Foukal and other researchers from the United States, Germany, and Switzerland found no net increase of solar brightness over the last thousand years. Solar cycles lead to a small increase of 0.07% in brightness over the last 30 years. This effect is far too small to contribute significantly to global warming.^[35][36] A paper by Mike Lockwood and Claus Fröhlich found no relation between global warming and solar radiation since 1985, whether through variations in solar output or variations in cosmic rays.^[37] Henrik Svensmark and Eigil Friis-Christensen, the main proponents of cloud seeding by galactic cosmic rays, disputed the findings of Lockwood and Fröhlich.^[38] Atmosphere diagram showing stratosphere. ... Global monthly average total ozone amount Ozone depletion describes two distinct, but related observations: a slow, steady decline of about 4 percent per decade in the total amount of ozone in Earths stratosphere since around 1980; and a much larger, but seasonal, decrease in stratospheric ozone over Earths... Cleveland Volcano in the Aleutian Islands of Alaska photographed from the International Space Station For other uses, see Volcano (disambiguation). ... Henrik Svensmark is an atmospheric scientist at the Danish National Space Center in Copenhagen who studies the effects of cosmic rays on cloud formation. ... Dr Eigil Friis-Christensen is a director in the management department of the Danish Space Research Institute (Danmarks Meteorologiske Institut) [1], [2]. His work with Knud Lassen on Solar Activity/Solar Cycle Length was referenced in The Great Global Warming Swindle. ...

Temperature changes

Two millennia of mean surface temperatures according to different reconstructions, each smoothed on a decadal scale. The unsmoothed, annual value for 2004 is also plotted for reference.

Main article: Temperature record

Image File history File links 2000_Year_Temperature_Comparison. ... Image File history File links 2000_Year_Temperature_Comparison. ... The temperature record shows the fluctuations of the temperature of the atmosphere and the oceans through various spans of time. ...

Recent

Global temperatures on both land and sea have increased by 0.75 °C (1.35 °F) relative to the period 1860–1900, according to the instrumental temperature record. This measured temperature increase is not significantly affected by the urban heat island effect. Since 1979, land temperatures have increased about twice as fast as ocean temperatures (0.25 °C per decade against 0.13 °C per decade).^[39] Temperatures in the lower troposphere have increased between 0.12 and 0.22 °C (0.22 and 0.4 °F) per decade since 1979, according to satellite temperature measurements. Temperature is believed to have been relatively stable over the one or two thousand years before 1850, with possibly regional fluctuations such as the Medieval Warm Period or the Little Ice Age. Instrumental global surface temperature measurements; see also [http://www. ... Tokyo, a case of Urban Heat Island. ... Atmosphere diagram showing the mesosphere and other layers. ... Comparison of ground based (blue) and satellite based (red: UAH; green: RSS) records of temperature variations since 1979. ... The temperature record of the past 1000 years describes the reconstruction of temperature for the last 1000 years on the Northern Hemisphere. ... The Medieval Warm Period (MWP) or Medieval Climate Optimum theorizes that there was a time of unusually warm climate in the North Atlantic region, lasting from about the tenth century to about the fourteenth century. ... The Little Ice Age (LIA) was a period of cooling occurring after a warmer era known as the Medieval climate optimum. ...

Sea temperatures increase more slowly than those on land both because of the larger effective heat capacity of the oceans and because the ocean can lose heat by evaporation more readily than the land.^[40] Since the Northern Hemisphere has more land mass than the Southern Hemisphere it warms faster; also there are extensive areas of seasonal snow cover subject to the snow-albedo feedback. Although more greenhouse gases are emitted in the Northern than Southern Hemisphere this does not contribute to the asymmetry of warming as the major gases are essentially well-mixed between hemispheres. Northern hemisphere highlighted in yellow. ... southern hemisphere highlighted in yellow (Antarctica not depicted). ...

Based on estimates by NASA's Goddard Institute for Space Studies, 2005 was the warmest year since reliable, widespread instrumental measurements became available in the late 1800s, exceeding the previous record set in 1998 by a few hundredths of a degree.^[41] Estimates prepared by the World Meteorological Organization and the Climatic Research Unit concluded that 2005 was the second warmest year, behind 1998.^[42][43] The National Aeronautics and Space Administration (NASA) (IPA [ˈnæsə]) is an agency of the United States government, responsible for the nations public space program. ... Goddard Institute for Space Studies building. ... WMO flag The World Meteorological Organization (WMO, French: , OMM) is an intergovernmental organization with a membership of 188 Member States and Territories. ... The Climatic Research Unit is a component of the University of East Anglia. ...

Anthropogenic emissions of other pollutants—notably sulfate aerosols—can exert a cooling effect by increasing the reflection of incoming sunlight. This partially accounts for the cooling seen in the temperature record in the middle of the twentieth century,^[44] though the cooling may also be due in part to natural variability. Many of the compounds which are dangerous to the environment can also be harmful to humans in the long-term range and come from mineral and fossil sources or are produced by humans themselves. ... Aerosol, is a term derived from the fact that matter floating in air is a suspension (a mixture in which solid or liquid or combined solid-liquid particles are suspended in a fluid). ...

Paleoclimatologist William Ruddiman has argued that human influence on the global climate began around 8,000 years ago with the start of forest clearing to provide land for agriculture and 5,000 years ago with the start of Asian rice irrigation.^[45] Ruddiman's interpretation of the historical record, with respect to the methane data, has been disputed.^[46] William F. Ruddiman is a palaeoclimatologist and Professor Emeritus at the university of Virginia. ...

Pre-human climate variations

Curves of reconstructed temperature at two locations in Antarctica and a global record of variations in glacial ice volume. Today's date is on the left side of the graph.

Further information: Paleoclimatology

See also: Snowball Earth

Earth has experienced warming and cooling many times in the past. The recent Antarctic EPICA ice core spans 800,000 years, including eight glacial cycles timed by orbital variations with interglacial warm periods comparable to present temperatures.^[47] Description Expanded record of temperature change since the end of the last glacial period Extended record of climate change during the last 5 Myr This figure shows the Antarctic temperature changes during the last several glacial/interglacial cycles of the present ice age and a comparison to changes in global... Description Expanded record of temperature change since the end of the last glacial period Extended record of climate change during the last 5 Myr This figure shows the Antarctic temperature changes during the last several glacial/interglacial cycles of the present ice age and a comparison to changes in global... Paleoclimatology is the study of climate change taken on the scale of the entire history of the Earth. ... One computer simulation of conditions during the Snowball Earth period. ... The European Project for Ice Coring in Antarctica (EPICA) is a multinational European project for deep ice core drilling in Antarctica. ... Milankovitch cycles are the collective effect of changes in the Earths movements upon its climate, named after Serbian civil engineer and mathematician Milutin Milanković. The eccentricity, axial tilt, and precession of the Earths orbit vary in several patterns, resulting in 100,000 year ice age cycles of the... Glaciation, often called an ice age, is a geological phenomenon in which massive ice sheets form in the Arctic and Antarctic and advance toward the equator. ...

A rapid buildup of greenhouse gases caused warming in the early Jurassic period (about 180 million years ago), with average temperatures rising by 5 °C (9 °F). Research by the Open University indicates that the warming caused the rate of rock weathering to increase by 400%. As such weathering locks away carbon in calcite and dolomite, CO₂ levels dropped back to normal over roughly the next 150,000 years.^[48][49] The Jurassic Period is a major unit of the geologic timescale that extends from about 199. ... Affiliations Alliance of Non-Aligned Universities, Association of Commonwealth Universities, European Association of Distance Teaching Universities, Middle States Association of Colleges and Schools Website http://www. ... Weathering is the decomposition of rocks, soils and their minerals through direct contact with the Earths atmosphere. ... Doubly refracting Calcite from Iceberg claim, Dixon, New Mexico. ... For other uses, see Dolomite (disambiguation). ...

Sudden releases of methane from clathrate compounds (the clathrate gun hypothesis) have been hypothesized as a cause for other warming events in the distant past, including the Permian-Triassic extinction event (about 251 million years ago) and the Paleocene-Eocene Thermal Maximum (about 55 million years ago). A clathrate or clathrate compound or cage compound is a chemical substance consisting of a lattice of one type of molecule trapping and containing a second type of molecule. ... The clathrate gun hypothesis states that as sea temperatures rise the sudden release of methane from methane clathrate compounds buried in the seabeds will cause a drastic alteration of the ocean enviornment and the atmosphere of earth, as recent analysis concerning the Permian extinction event indicates may have happened in... The Permian-Triassic (P-T or PT) extinction event, sometimes informally called the Great Dying, was an extinction event that occurred approximately 251 million years ago (mya), forming the boundary between the Permian and Triassic geologic periods. ... Climate change during the last 65 million years. ...

Climate models

The projected temperature increase for a range of stabilization scenarios (the colored bands). The black line in middle of the shaded area indicates 'best estimates'; the red and the blue lines the likely limits. From the work of IPCC AR4.

Calculations of global warming prepared in or before 2001 from a range of climate models under the SRES A2 emissions scenario, which assumes no action is taken to reduce emissions.

The geographic distribution of surface warming during the 21^st century calculated by the HadCM3 climate model if a business as usual scenario is assumed for economic growth and greenhouse gas emissions. In this figure, the globally averaged warming corresponds to 3.0 °C (5.4 °F).

Main article: Global climate model

Scientists have studied global warming with computer models of the climate. These models are based on physical principles of fluid dynamics, radiative transfer, and other processes, with some simplifications being necessary because of limitations in computer power. These models predict that the effect of adding greenhouse gases is to produce a warmer climate.^[50] However, even when the same assumptions of future greenhouse gas levels are used, there still remains a considerable range of climate sensitivity. Image File history File links Size of this preview: 800 × 409 pixelsFull resolution (1431 × 731 pixel, file size: 122 KB, MIME type: image/png) File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Image File history File links Size of this preview: 800 × 409 pixelsFull resolution (1431 × 731 pixel, file size: 122 KB, MIME type: image/png) File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Climate Change 2007, the Fourth Assessment Report (AR4) of the United Nations Intergovernmental Panel on Climate Change (IPCC), is the fourth in a series of such reports. ... Image File history File links Global_Warming_Predictions. ... Image File history File links Global_Warming_Predictions. ... Climate models use quantitative methods to simulate the interactions of the atmosphere, oceans, land surface, and ice. ... The Special Report on Emissions Scenarios was a report, prepared for the IPCC TAR, on future emission scenarios to be used for driving global circulation models to develop climate change scenarios. ... Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... HadCM3 (Hadley Centre Coupled Model, version 3) is a coupled atmosphere-ocean general circulation model (AOGCM) developed at the Hadley Centre in the United Kingdom and described by Gordon et al (2000) and Pope et al (2000). ... General Circulation Models (GCMs) are a class of computer-driven models for weather forecasting and predicting climate change, where they are commonly called Global Climate Models. ... A computer simulation or a computer model is a computer program that attempts to simulate an abstract model of a particular system. ... The equation of radiative transfer describes the propagation of electromagnetic radiation through an atmosphere which is itself emitting radiation, absorbing radiation and scattering radiation. ... In IPCC reports, equilibrium climate sensitivity refers to the equilibrium change in global mean surface temperature following a doubling of the atmospheric (equivalent) CO2 concentration. ...

Including uncertainties in future greenhouse gas concentrations and climate modeling, 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.^[1] Models have also been 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. Attribution of recent climate change is the effort to scientifically ascertain mechanisms responsible for relatively recent changes observed in the Earths climate. ...

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.^[51] These models do not unambiguously attribute the warming that occurred from approximately 1910 to 1945 to either natural variation or human effects; however, they suggest that the warming since 1975 is dominated by man-made greenhouse gas emissions. Top: Increasing atmospheric CO2 levels as measured in the atmosphere and ice cores. ...

Most global climate models, when run to project future climate, are forced by imposed greenhouse gas scenarios, generally one from the IPCC Special Report on Emissions Scenarios (SRES). Less commonly, models may be run by adding a simulation of the carbon cycle; this generally shows a positive feedback, though this response is uncertain (under the A2 SRES scenario, responses vary between an extra 20 and 200 ppm of CO₂). Some observational studies also show a positive feedback.^[52][53][54] The Special Report on Emissions Scenarios was a report, prepared for the IPCC TAR, on future emission scenarios to be used for driving global circulation models to develop climate change scenarios. ... For the thermonuclear reaction involving carbon that helps power stars, see CNO cycle. ...

The representation of clouds is one of the main sources of uncertainty in present-generation models, though progress is being made on this problem.^[55] There is also an ongoing discussion as to whether climate models are neglecting important indirect and feedback effects of solar variability. 400 year history of sunspot numbers. ...

Attributed and expected effects

Main article: Effects of global warming

Sparse records indicate that glaciers have been retreating since the early 1800s. In the 1950s measurements began that allow the monitoring of glacial mass balance, reported to the WGMS and the NSIDC.

Though it is difficult to connect specific weather events to global warming, an increase in global temperatures may in turn cause other changes, including glacial retreat and worldwide sea level rise. Changes in the amount and pattern of precipitation may result in flooding and drought. There may also be changes in the frequency and intensity of extreme weather events. Other effects may include changes in agricultural yields, reduced summer streamflows, species extinctions and increases in the range of disease vectors. The net impact of global warming so far has been modest, but near-future effects are likely to become significantly negative, with large-scale extreme impacts possible by the end of the century. ... Image File history File links Glacier_Mass_Balance. ... Image File history File links Glacier_Mass_Balance. ... The World Glacier Monitoring Service (WGMS) was started in 1986, combining the two former services PSFG (Permanent Service on Fluctuations of Glaciers) and TTS/WGI (Temporal Technical Secretary/World Glacier Inventory). ... The National Snow and Ice Data Center, or NSIDC, is a United States information and referral center in support of polar and cryospheric research. ... The net impact of global warming so far has been modest, but near-future effects are likely to become significantly negative, with large-scale extreme impacts possible by the end of the century. ... Global glacial mass balance in the last fifty years, reported to the WGMS and NSIDC. The downward trend in the late 1980s is symptomatic of the increased rate and number of retreating glaciers. ... Sea level measurements from 23 long tide gauge records in geologically stable environments show a rise of around 20 centimeters per century (2 mm/year). ... A flood (in Old English flod, a word common to Teutonic languages; compare German Flut, Dutch vloed from the same root as is seen in flow, float) is an overflow of water, an expanse of water submerging land, a deluge. ... Fields outside Benambra, Victoria, Australia suffering from drought conditions A drought is an extended period of months or years when a region notes a deficiency in its water supply. ... Trends in natural disasters, Pascal Peduzzi (2004) Is climate change increasing the frequency of hazardous events? Environment Times UNEP/GRID-Arendal Extreme weather includes weather phenomena that are at the extremes of the historical distribution, especially severe or unseasonal weather. ... Streamflow, or channel runoff, is the flow of water in streams, rivers, and other channels, and is a major element of the water cycle. ... The extinction risk of climate change -- that is, the expected number of species expected to become extinct due to the effects of global warming -- has been estimated in a 2004 Nature study to be between 15 and 37 percent of known species by 2050. ... In epidemiology, a vector is an organism that does not cause disease itself but which spreads infection by conveying pathogens from one host to another. ...

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 the Larsen Ice Shelf, sea level rise, changes in rainfall patterns, increased intensity and frequency of extreme weather events, are being attributed in part to global warming.^[56] While changes are expected for overall patterns, intensity, and frequencies, it is difficult to attribute specific events to global warming. Other expected effects include water scarcity in some regions and increased precipitation in others, changes in mountain snowpack, and adverse health effects from warmer temperatures.^[57] This article is about the natural environment. ... Central New York City. ... A view down the Whitechuck Glacier in North Cascades National Park in 1973 The same view as seen in 2006, where this branch of glacier retreated 1. ... Ross Ice Shelf An ice shelf is a thick, floating platform of ice that forms where a glacier or ice sheet flows down to a coastline and onto the ocean surface. ... Larsen A and Larsen B iceshelves marked in red The Larsen Ice Shelf () is a long, fringing ice shelf in the northwest part of the Weddell Sea, extending along the east coast of Antarctic Peninsula from Cape Longing to the area just southward of Hearst Island. ... Sea level measurements from 23 long tide gauge records in geologically stable environments show a rise of around 20 centimeters per century (2 mm/year). ... The net impact of global warming so far has been modest, but near-future effects are likely to become significantly negative, with large-scale extreme impacts possible by the end of the century. ...

Increasing deaths, displacements, and economic losses projected due to extreme weather attributed to global warming may be exacerbated by growing population densities in affected areas, although temperate regions are projected to experience some minor benefits, such as fewer deaths due to cold exposure.^[58] 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.^[56] 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, 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.^[1] Trends in natural disasters, Pascal Peduzzi (2004) Is climate change increasing the frequency of hazardous events? Environment Times UNEP/GRID-Arendal Extreme weather includes weather phenomena that are at the extremes of the historical distribution, especially severe or unseasonal weather. ... The Third Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) was issued in 2001. ... Climate Change 2007, the Fourth Assessment Report (AR4) of the United Nations Intergovernmental Panel on Climate Change (IPCC), is the fourth in a series of such reports. ... Cyclone Catarina, a rare South Atlantic tropical cyclone viewed from the International Space Station on March 26, 2004 Hurricane and Typhoon redirect here. ...

Additional anticipated effects include sea level rise of 110 to 770 millimeters (0.36 to 2.5 ft) between 1990 and 2100,^[59] repercussions to agriculture, possible slowing of the thermohaline circulation, reductions in the ozone layer, increased intensity of hurricanes and extreme weather events, lowering of ocean pH, and the spread of diseases such as malaria and dengue fever. One study predicts 18% to 35% of a sample of 1,103 animal and plant species would be extinct by 2050, based on future climate projections.^[60] Two populations of Bay checkerspot butterfly are being threatened by changes in precipitation, though few mechanistic studies have documented extinctions due to recent climate change.^[61] This article or section does not cite any references or sources. ... Shutdown or slowdown of the thermohaline circulation is a possible effect of global warming. ... The ozone layer is a layer in Earths atmosphere which contains relatively high concentrations of ozone (O3). ... The net impact of global warming so far has been modest, but near-future effects are likely to become significantly negative, with large-scale extreme impacts possible by the end of the century. ... Change in sea surface pH caused by anthropogenic CO2 between the 1700s and the 1990s Ocean acidification is the name given to the ongoing decrease in the pH of the Earths oceans, caused by their uptake of anthropogenic carbon dioxide from the atmosphere. ... For other uses, see PH (disambiguation). ... Malaria is a vector-borne infectious disease caused by protozoan parasites. ... “Dengue Fever” redirects here. ... The extinction risk of climate change -- that is, the expected number of species expected to become extinct due to the effects of global warming -- has been estimated in a 2004 Nature study to be between 15 and 37 percent of known species by 2050. ... Trinomial name Euphydryas editha bayensis Sternitsky, 1937 & Dos Passos, 1964 The Bay checkerspot butterfly (Euphydryas editha bayensis) is a federally threatened insect species which is native to the U.S. State of California. ...

Economic

Main articles: Economics of global warming and Low-carbon economy

Some economists have tried to estimate the aggregate net economic costs of damages from climate change across the globe. Such estimates have so far failed to reach conclusive findings; in a survey of 100 estimates, the values ran from US$-10 per tonne of carbon (tC) (US$-3 per tonne of carbon dioxide) up to US$350/tC (US$95 per tonne of carbon dioxide), with a mean of US$43 per tonne of carbon (US$12 per tonne of carbon dioxide).^[58] One widely-publicized report on potential economic impact is the Stern Review; it suggests that extreme weather might reduce global gross domestic product by up to 1%, and that in a worst case scenario global per capita consumption could fall 20%.^[62] The report's methodology, advocacy and conclusions have been criticized by many economists, primarily around the Review's assumptions of discounting and its choices of scenarios,^[63] while others have supported the general attempt to quantify economic risk, even if not the specific numbers.^[64][65] As recent estimates of the rate of global warming have increased, so have the financial estimates of the damage costs. ... A low-carbon economy is an economy in which carbon dioxide emissions from the use of carbon based fuels (coal, oil and gas) are significantly reduced. ... USD redirects here. ... Sir Nicholas Stern, author of the report. ... This article is about GDP in the context of economics. ... In finance, discounting is the process of finding the current value of an amount of cash at some future date, and along with compounding cash form the basis of time value of money calculations. ...

In a summary of economic cost associated with climate change, the United Nations Environment Programme emphasizes the risks to insurers, reinsurers, and banks of increasingly traumatic and costly weather events. Other economic sectors likely to face difficulties related to climate change include agriculture and transport. Developing countries, rather than the developed world, are at greatest economic risk.^[66] Klaus Töpfer, former UNEP Exec. ... Insurance, in law and economics, is a form of risk management primarily used to hedge against the risk of a contingent loss. ... Reinsurance is a means by which an insurance company can protect itself against the risk of losses with other insurance companies. ... For other uses, see Bank (disambiguation). ...

Security

In November 2007, the Center for Strategic and International Studies and the Center for a New American Security published a report highlighting the national security effects of climate change.^[67] These security effects include increased competition for resources between countries, mass migration from the worst affected areas, challenges to the cohesion of major states threatened by the rise in sea levels, and, as a consequence of these factors, an increased risk of armed conflict, including even nuclear conflicts. The Center for Strategic and International Studies (CSIS) is a Washington, D.C.-based foreign policy think tank. ... The Center for a New American Security (CNAS) is a Washington, D.C.-based national security think tank established in 2007. ...

Adaptation and mitigation

Main articles: Adaptation to global warming, Mitigation of global warming, and Kyoto Protocol

The broad agreement among climate scientists that global temperatures will continue to increase has led nations, states, corporations and individuals to implement actions to try to curtail global warming or adjust to it. Many environmental groups encourage action against global warming, often by the consumer, but also by community and regional organizations. There has also been business action on climate change, including efforts at increased energy efficiency and limited moves towards use of alternative fuels. One important innovation has been the development of greenhouse gas emissions trading through which companies, in conjunction with government, agree to cap their emissions or to purchase credits from those below their allowances. Adaptation to global warming covers all actions aimed at reducing the negative effects of global warming. ... Global carbon dioxide emissions 1800–2000 Global average surface temperature 1850 to 2006 Mitigation of global warming involves taking actions aimed at reducing the extent of global warming. ... Kyoto Protocol Opened for signature December 11, 1997 in Kyoto, Japan Entered into force February 16, 2005. ... National and international science academies and professional societies have assessed the current scientific opinion on climate change, in particular recent global warming. ... The issue of human-caused, or anthropogenic, climate change (global warming) is becoming a central focus of the Green movement. ... Business action on climate change includes a range of activities relating to combatting global warming, and to influencing political decisions on global-warming-related regulation, such as the Kyoto Protocol. ... Alternative fuel refers to methods of powering an engine that do not involve petroleum (oil). ... Emissions trading (or cap and trade) is an administrative approach used to control pollution by providing economic incentives for achieving reductions in the emissions of pollutants. ...

The world's primary international agreement on combating global warming is the Kyoto Protocol, an amendment to the United Nations Framework Convention on Climate Change (UNFCCC) negotiated in 1997. The Protocol now covers more than 160 countries globally and over 55% of global greenhouse gas emissions.^[68] Only the United States, Australia, and Kazakhstan have not ratified the treaty, with the United States historically being the world's largest emitter of greenhouse gas. This treaty expires in 2012, and international talks began in May 2007 on a future treaty to succeed the current one.^[69] Kyoto Protocol Opened for signature December 11, 1997 in Kyoto, Japan Entered into force February 16, 2005. ... UNFCCC logo. ... Atmospheric Carbon Dioxide versus Time The United States is historically the worlds largest greenhouse gas emitter. ...

Citing "serious harm" to its economy, as well as the exemption of developing nations from the treaty, the Uni