Global mean surface temperature anomaly relative to 1961–1990

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

Global warming is the increase in the average temperature of the Earth's near-surface air and oceans since the mid-twentieth century, and its projected continuation. Climate change is any long-term significant change in the “average weather” that a given region experiences See also Temperature record. The instrumental temperature record shows the fluctuations of the Temperature of the atmosphere and the oceans as An ocean (from Greek, ''Okeanos'' (Oceanus) is a major body of saline water, and a principal component of the Hydrosphere.

The average global air temperature near the Earth's surface increased 0. 74 ± 0. ± The 18 °C (1. The Celsius Temperature scale was previously known as the centigrade scale. 33 ± 0. 32 °F) during the hundred years ending in 2005. Fahrenheit is a temperature scale named after Daniel Gabriel Fahrenheit (1686–1736 a German Physicist who proposed it in 1724 ^[1] The Intergovernmental Panel on Climate Change (IPCC) concludes "most of the observed increase in globally averaged temperatures since the mid-twentieth century is very likely due to the observed increase in anthropogenic (man-made) greenhouse gas concentrations"^[1] via an enhanced greenhouse effect. See also Global warming, Climate change, Climate change denial Attribution of recent climate change is the effort to scientifically ascertain Anthropogenic effects processes objects or materials are those that are derived from Human activities as opposed to those occurring in Natural environments without The Greenhouse effect refers to the change in the Thermal equilibrium temperature of a planet or moon by the presence of an Atmosphere containing gas that absorbs 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. Solar variations are changes in the amount of Solar radiation emitted by the Sun. Plate tectonics and hotspots Divergent plate boundaries At the ^[2][3]

These basic conclusions have been endorsed by at least thirty scientific societies and academies of science,^[4] including all of the national academies of science of the major industrialized countries. National and international science academies and professional societies have assessed the current scientific opinion on climate change, in particular recent Global warming. ^[5][6][7] While individual scientists have voiced disagreement with some findings of the IPCC,^[8] the overwhelming majority of scientists working on climate change agree with the IPCC's main conclusions. This article lists scientists and former scientists who have stated disagreement with one or more of the principal conclusions of the mainstream scientific opinion on global warming ^[9][10]

Climate model projections summarized by the IPCC indicate that average global surface temperature will likely rise a further 1. This article is about the theories and mathematics of climate modeling 1 to 6. 4 °C (2. 0 to 11. 5 °F) during the twenty-first century. ^[1] This range of values results from the use of differing scenarios of future greenhouse gas emissions as well as models with differing climate sensitivity. The Special Report on Emissions Scenarios (SRES was a report prepared by the Intergovernmental Panel on Climate Change (IPCC for the Third Assessment Report Greenhouse gases are gaseous constituents of the atmosphere bothnatural and anthropogenic that absorb and emit radiation at specific wavelengths within the spectrum of thermal infrared In Intergovernmental Panel on Climate Change (IPCC reports equilibrium climate sensitivity refers to the equilibrium change in global mean surface temperature following Although most studies focus on the period up to 2100, warming and sea level rise are expected to continue for more than a thousand years even if greenhouse gas levels are stabilized. The delay in reaching equilibrium is a result of the large heat capacity of the oceans. ^[1]

Increasing global temperature 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. Sea-level rise is an increase in Sea level. Multiple complex factors may influence this change See also List of extreme weather events Extreme weather includes Weather phenomena that are at the extremes of the historical distribution especially In Meteorology, precipitation (also known as one class of hydrometeors, which are atmospheric water phenomena is any product of the condensation of atmospheric Other effects of global warming include changes in agricultural yields, trade routes, glacier retreat, species extinctions and increases in the ranges of disease vectors. effects of Global warming on the environment and human life are numerous varied accelerating and taking scientists studying global warming by surprise 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 whitechuck glacier 2006jpg|right|thumb|320px|The same view as seen in 2006 where this branch of glacier retreated 1 The extinction risk of climate change is the risk Species have of becoming Extinct due to the Effects of global warming. In Epidemiology, a vector is an Organism that does not cause Disease itself but which transmits Infection by conveying Pathogens from

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. Uncertainty is a term used in subtly different ways in a number of fields including Philosophy, Statistics, Economics, Finance, Insurance Most national governments have signed and ratified the Kyoto Protocol aimed at reducing greenhouse gas emissions, but 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. Kyoto Protocol As of April 2008 178 states have signed and ratified the Kyoto Protocol to the United Nations Framework Convention on Climate Change, aimed at The Kyoto Protocol is a protocol to the international Framework Convention on Climate Change with the objective of reducing Greenhouse gases in an effort The politics of global warming have involved policy decisions legislation and political debate over the science of and response to Global warming. The global warming controversy is a dispute regarding the nature and consequences of Global warming. Mitigation of global warming involves taking actions to reduce Greenhouse gas emissions and to enhance sinks aimed at reducing the extent of Global warming Adaptation to global warming consists of initiatives and measures to reduce the vulnerability of natural and human systems against actual or expected climate change effects.

Terminology

The term "global warming" refers to the warming in recent decades and its projected continuation, and implies a human influence. ^[11][12] The United Nations Framework Convention on Climate Change (UNFCCC) uses the term "climate change" for human-caused change, and "climate variability" for other changes. Annex I and Annex II Countries and Developing Countries Signatories to the UNFCCC are split into three groups Annex I countries (industrialized countries ^[13] The term "anthropogenic global warming" (AGW) is sometimes used when focusing on human-induced changes.

Causes

Components of the current radiative forcing as estimated by the IPCC Fourth Assessment Report. In Climate science radiative forcing is (loosely defined as the change in net Irradiance at the Tropopause. Climate Change 2007, the Fourth Assessment Report (AR4 of the United Nations Intergovernmental Panel on Climate Change ( IPCC) is the fourth

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),^[14][15][16], changes in solar luminosity, volcanic eruptions,^[17] and atmospheric greenhouse gas concentrations. See also Global warming, Climate change, Climate change denial Attribution of recent climate change is the effort to scientifically ascertain National and international science academies and professional societies have assessed the current scientific opinion on climate change, in particular recent Global warming. The Sun (Sol is the Star at the center of the Solar System. Orbital forcing describes the effect on Climate of slow changes in the tilt of the Earth 's axis and shape of the Orbit (see Milankovitch cycles The solar luminosity, L_\odot is a unit of Luminosity ( power emitted in the form of Photons conventionally used by Astronomers to Plate tectonics and hotspots Divergent plate boundaries At the Greenhouse gases are gaseous constituents of the atmosphere bothnatural and anthropogenic that absorb and emit radiation at specific wavelengths within the spectrum of thermal infrared The detailed causes of the recent warming remain an active field of research, but the scientific consensus^[18][19] is that the increase in atmospheric greenhouse gases due to human activity caused most of the warming observed since the start of the industrial era. See also Global warming, Climate change, Climate change denial Attribution of recent climate change is the effort to scientifically ascertain National and international science academies and professional societies have assessed the current scientific opinion on climate change, in particular recent Global warming. This attribution is clearest for the most recent 50 years, for which the most detailed data are available. Some other hypotheses departing from the consensus view have been suggested to explain most of the temperature increase. One such hypothesis proposes that warming may be the result of variations in solar activity. ^[20][21][22]

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. Volumetric heat capacity ( VHC) describes the ability of a given Volume of a substance to store Internal energy while undergoing a given Temperature Climate commitment studies indicate that even if greenhouse gases were stabilized at 2000 levels, a further warming of about 0. Climate commitment describes the fact that Climate reacts with a delay to influencing factors (" Climate forcings quot such as the presence of Greenhouse 5 °C (0. 9 °F) would still occur. ^[23]

Greenhouse gases in the atmosphere

Main articles: Greenhouse gas and Greenhouse effect

The greenhouse effect was discovered by Joseph Fourier in 1824 and was first investigated quantitatively by Svante Arrhenius in 1896. Greenhouse gases are gaseous constituents of the atmosphere bothnatural and anthropogenic that absorb and emit radiation at specific wavelengths within the spectrum of thermal infrared The Greenhouse effect refers to the change in the Thermal equilibrium temperature of a planet or moon by the presence of an Atmosphere containing gas that absorbs Jean Baptiste Joseph Fourier ( March 21, 1768 &ndash May 16, 1830) was a French Mathematician and Physicist Svante August Arrhenius ( February 19, 1859 &ndash October 2, 1927) was a Swedish Scientist, originally a Physicist It is the process by which absorption and emission of infrared radiation by atmospheric gases warm a planet's lower atmosphere and surface. In Physics, absorption of electromagnetic radiation is the process by which the Energy of a Photon is taken up by matter typically the electrons of an Infrared ( IR) radiation is Electromagnetic radiation whose Wavelength is longer than that of Visible light, but shorter than that of An atmosphere (from Greek ατμός - atmos, " Vapor " + σφαίρα - sphaira, " Sphere " A planet, as defined by the International Astronomical Union (IAU is a celestial body Orbiting a Star or stellar remnant that is

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. Northern Hemisphere is the half of a Planet that is North of the Equator —the word hemisphere literally means 'half ball'

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. ^[24][25] 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%. General properties of water vapor Evaporation/sublimation Whenever a water molecule leaves a surface it is said to have evaporated Cloud forcing (sometimes described as cloud radiative forcing) is the difference between the radiation budget components for average Cloud conditions and cloud-free Carbon dioxide ( Chemical formula:) is a Chemical compound composed of two Oxygen Atoms covalently bonded to a single Methane is a Chemical compound with the molecular formula. It is the simplest Alkane, and the principal component of Natural gas. OZONE is an object oriented Operating system written in the C programming language. ^[26][27] The issue is how the strength of the greenhouse effect changes when human activity increases the atmospheric concentrations of some greenhouse gases.

Human activity since the industrial revolution has increased the concentration of various greenhouse gases, leading to increased radiative forcing from CO₂, methane, tropospheric ozone, CFCs and nitrous oxide. In Climate science radiative forcing is (loosely defined as the change in net Irradiance at the Tropopause. Methane is a Chemical compound with the molecular formula. It is the simplest Alkane, and the principal component of Natural gas. OZONE is an object oriented Operating system written in the C programming language. Nitrous oxide, commonly known as " laughing gas," is a Chemical compound with the Chemical formula N 2 O. Molecule for molecule, methane is a more effective greenhouse gas than carbon dioxide, but its concentration is much smaller so that its total radiative forcing is only about a fourth of that from carbon dioxide. Methane is a Chemical compound with the molecular formula. It is the simplest Alkane, and the principal component of Natural gas. Carbon dioxide ( Chemical formula:) is a Chemical compound composed of two Oxygen Atoms covalently bonded to a single In Climate science radiative forcing is (loosely defined as the change in net Irradiance at the Tropopause. Some other naturally occurring gases contribute small fractions of the greenhouse effect; one of these, nitrous oxide (N₂O), is increasing in concentration owing to human activity such as agriculture. Nitrous oxide, commonly known as " laughing gas," is a Chemical compound with the Chemical formula N 2 O. The atmospheric concentrations of CO₂ and CH₄ have increased by 31% and 149% respectively since the beginning of the industrial revolution in the mid-1700s. Greenhouse gases are gaseous constituents of the atmosphere bothnatural and anthropogenic that absorb and emit radiation at specific wavelengths within the spectrum of thermal infrared The Industrial Revolution was a period in the late 18th and early 19th centuries when major changes in agriculture manufacturing and transportation had a profound effect on the 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. An ice core is a Core sample from the accumulation of snow and ice over many years that have re-crystallized and have trapped air bubbles from previous time periods ^[28] From less direct geological evidence it is believed that CO₂ values this high were last attained 20 million years ago. ^[29] Fossil fuel burning has produced approximately three-quarters of the increase in CO₂ from human activity over the past 20 years. Fossil fuels or mineral fuels are fossil source Fuels that is Hydrocarbons found within the top layer of the Earth’s crust. Most of the rest is due to land-use change, in particular deforestation. Deforestation is the conversion of Forested areas to non-forest land for use such as Arable land, Pasture, urban use logged area or wasteland ^[30]

Yearly increase of atmospheric CO₂: In the 1960s, the average annual increase was 37% of what it was in 2000 through 2007. ^[31]

The present atmospheric concentration of CO₂ is about 385 parts per million (ppm) by volume. "Parts-per" notation is used especially in Science and Engineering, to denote Ratios (relative proportions in measured quantities particularly ^[32] 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. The Special Report on Emissions Scenarios (SRES was a report prepared by the Intergovernmental Panel on Climate Change (IPCC for the Third Assessment Report ^[33] Fossil fuel reserves are sufficient to reach this level and continue emissions past 2100, if coal, tar sands or methane clathrates are extensively used. Methane clathrate, also called methane hydrate or methane ice, is a solid form of water that contains a large amount of Methane within its Crystal ^[34]

Feedbacks

Main article: Effects of global warming

The effects of forcing agents on the climate are complicated by various feedback processes. effects of Global warming on the environment and human life are numerous varied accelerating and taking scientists studying global warming by surprise

One of the most pronounced feedback effects relates to the evaporation of water. Warming by the addition of long-lived greenhouse gases such as CO₂ will cause more water to evaporate into the atmosphere. Since water vapor itself acts as a greenhouse gas, the atmosphere warms further; this warming causes more water vapor to evaporate (a positive feedback), and so on until other processes stop the feedback loop. Positive feedback, sometimes referred to as "cumulative causation" is a Feedback loop system in which the system responds to perturbation in the same direction The result is a much larger greenhouse effect than that due to CO₂ alone. Although this feedback process causes an increase in the absolute moisture content of the air, the relative humidity stays nearly constant or even decreases slightly because the air is warmer. Relative humidity is a measurement of the amount of Water vapor that exists in a gaseous mixture of air and water ^[35] This feedback effect can only be reversed slowly as CO₂ has a long average atmospheric lifetime. Greenhouse gases are gaseous constituents of the atmosphere bothnatural and anthropogenic that absorb and emit radiation at specific wavelengths within the spectrum of thermal infrared

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. Clouds form when the Dewpoint of Water is reached in the presence of Condensation nuclei in the Troposphere. 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. Climate Change 2007, the Fourth Assessment Report (AR4 of the United Nations Intergovernmental Panel on Climate Change ( IPCC) is the fourth ^[35]

A subtler feedback process relates to changes in the lapse rate as the atmosphere warms. The lapse rate is defined as the negative of the rate of change in an atmospheric variable usually Temperature, with height in an atmosphere The atmosphere's temperature decreases with height in the troposphere. The troposphere is the lowest portion of Earth's atmosphere. It contains approximately 75% of the atmosphere's mass and almost all of its Water vapor and Since emission of infrared radiation varies with the fourth power of temperature, longwave radiation emitted from the upper atmosphere is less than that emitted from the lower atmosphere. Most of the radiation emitted from the upper atmosphere escapes to space, while most of the radiation emitted from the lower atmosphere is re-absorbed by the surface or the atmosphere. Thus, the strength of the greenhouse effect depends on the atmosphere's rate of temperature decrease with height: if the rate of temperature decrease is greater the greenhouse effect will be stronger, and if the rate of temperature decrease is smaller then the greenhouse effect will be weaker. Both theory and climate models indicate that warming will reduce the decrease of temperature with height, producing a negative lapse rate feedback that weakens the greenhouse effect. Measurements of the rate of temperature change with height are very sensitive to small errors in observations, making it difficult to establish whether the models agree with observations. ^[36]

Northern Hemisphere ice trends

Southern Hemisphere ice trends

Another important feedback process is ice-albedo feedback. ^[37] 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 that could contribute to warming. Positive feedback, sometimes referred to as "cumulative causation" is a Feedback loop system in which the system responds to perturbation in the same direction This article is about frozen ground For other meanings see Permafrost (disambiguation. Peat is an accumulation of partially Decayed Vegetation matter. A bog or mire is a Wetland type that accumulates Acidic Peat, a deposit of dead plant material &ndash usually Mosses but also Siberia (Сиби́рь Sibir) is the name given to the vast region constituting almost all of Northern Asia and for the most part currently serving ^[38] Similarly a massive release of CH₄ from methane clathrates in the ocean could cause rapid warming, according to the clathrate gun hypothesis. Methane clathrate, also called methane hydrate or methane ice, is a solid form of water that contains a large amount of Methane within its Crystal The clathrate gun hypothesis is the popular name given to the hypothesis that rises in sea temperatures (and/or falls in sea level can trigger the sudden release of Methane

The ocean's ability to sequester carbon is expected to decline as it warms. This is because the resulting low nutrient levels of the mesopelagic zone (about 200 to 1000 m depth) limits the growth of diatoms in favor of smaller phytoplankton that are poorer biological pumps of carbon. The mesopelagic ( Greek μέσον middle (also known as the middle pelagic or twilight zone) is a Pelagic zone extending from 200 m (650 ft Diatoms ( Greek: (dia = "through" + (temnein = "to cut" i Phytoplankton are the Autotrophic component of the Plankton community In Oceanic Biogeochemistry, the biological pump is the sum of a suite of biologically-mediated processes that transport Carbon from the surface ^[39]

Solar variation

Solar variation over the last thirty years.

Main article: Solar variation

A few papers suggest that the Sun's contribution may have been underestimated. Solar variations are changes in the amount of Solar radiation emitted by the Sun. 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. Duke University is a private Research University located in Durham, North Carolina, United States. ^[40] 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. ^[41] 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.

A different hypothesis is that variations in solar output, possibly amplified by cloud seeding via galactic cosmic rays, may have contributed to recent warming. Solar variations are changes in the amount of Solar radiation emitted by the Sun. Galactic cosmic rays ( GCRs) consist of those Cosmic rays that enter the solar system from the outside ^[42] 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. ^[43]

One predicted effect of an increase in solar activity would be a warming of most of the stratosphere, whereas greenhouse gas theory predicts cooling there. The stratosphere is the second major layer of Earth's atmosphere, just above the Troposphere, and below the Mesosphere. ^[44] The observed trend since at least 1960 has been a cooling of the lower stratosphere. ^[45] Reduction of stratospheric ozone also has a cooling influence, but substantial ozone depletion did not occur until the late 1970s. 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 Earth's ^[46] 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. Plate tectonics and hotspots Divergent plate boundaries At the ^[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 led to a small increase of 0. 07% in brightness over the last thirty years. This effect is too small to contribute significantly to global warming. ^[47][48] One paper by Mike Lockwood and Claus Fröhlich found no relation between global warming and solar radiation since 1985, whether through variations in solar output or variations in cosmic rays. ^[49] Henrik Svensmark and Eigil Friis-Christensen, the main proponents of cloud seeding by galactic cosmic rays, disputed this criticism of their hypothesis. Henrik Svensmark is a Physicist at the Danish National Space Center in Copenhagen who studies the effects of cosmic rays on cloud formation Eigil Friis-Christensen is an expert in space physics and Director of the Danish National Space Center. ^[50] A 2007 paper found that in the last 20 years there has been no significant link between changes in cosmic rays coming to Earth and cloudiness and temperature. ^[51][52][53]

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

Recent

Global temperatures on both land and sea have increased by 0. For extreme records instead of records as a set of data see Temperature extremes The temperature record shows the fluctuations of the 75 °C (1. 35 °F) relative to the period 1860–1900, according to the instrumental temperature record. See also Temperature record. The instrumental temperature record shows the fluctuations of the Temperature of the atmosphere and the oceans as This measured temperature increase is not significantly affected by the urban heat island effect. An urban heat island ( UHI) is a metropolitan area which is significantly warmer than its surrounding rural areas ^[54] Since 1979, land temperatures have increased about twice as fast as ocean temperatures (0. 25 °C per decade against 0. 13 °C per decade). ^[55] Temperatures in the lower troposphere have increased between 0. The troposphere is the lowest portion of Earth's atmosphere. It contains approximately 75% of the atmosphere's mass and almost all of its Water vapor and 12 and 0. 22 °C (0. 22 and 0. 4 °F) per decade since 1979, according to satellite temperature measurements. Satellite temperature measurements have been obtained from the Troposphere since 1978 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. 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 was a time of unusually Warm Climate in the North Atlantic region lasting from about The Little Ice Age (LIA was a period of cooling occurring after a warmer era known as the Medieval Warm Period or 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. ^[56] The Northern Hemisphere has more land than the Southern Hemisphere, so it warms faster. Northern Hemisphere is the half of a Planet that is North of the Equator —the word hemisphere literally means 'half ball' Southern Hemisphere is the half of a Planet that is South of the Equator —the word hemisphere literally means 'half ball' The Northern Hemisphere also has extensive areas of seasonal snow and sea-ice cover subject to the ice-albedo feedback. More greenhouse gases are emitted in the Northern than Southern Hemisphere, but this does not contribute to the difference in warming because the major greenhouse gases persist long enough to mix between hemispheres.

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. The National Aeronautics and Space Administration ( NASA, ˈnæsə is an agency of the United States government, responsible for the nation's public space program The NASA Goddard Institute for Space Studies (GISS at Columbia University in New York City, is a component laboratory of NASA's Goddard Space Flight ^[57] Estimates prepared by the World Meteorological Organization and the Climatic Research Unit concluded that 2005 was the second warmest year, behind 1998. The Climatic Research Unit is a component of the University of East Anglia and is a leading institution concerned with the study of natural and anthropogenic Climate ^[58][59] Temperatures in 1998 were unusually warm because the strongest El Niño in the past century occurred during that year. El Niño-Southern Oscillation ( ENSO; commonly referred to as simply El Niño) is a global coupled ocean-atmosphere phenomenon ^[60]

Anthropogenic emissions of other pollutants—notably sulfate aerosols—can exert a cooling effect by increasing the reflection of incoming sunlight. Pollution is the introduction of contaminants into an environment that causes instability disorder harm or discomfort to the physical systems or living organisms they are in Technically an aerosol is a suspension of fine solid particles or liquid droplets in a gas This partially accounts for the cooling seen in the temperature record in the middle of the twentieth century,^[61] though the cooling may also be due in part to natural variability. James Hansen and colleagues have proposed that the effects of the products of fossil fuel combustion—CO₂ and aerosols—have largely offset one another, so that warming in recent decades has been driven mainly by non-CO₂ greenhouse gases. This is about the American scientist/administrator For others see James Hansen (disambiguation. ^[62]

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. William F Ruddiman is a palaeoclimatologist and Professor Emeritus at the University of Virginia. ^[63] Ruddiman's interpretation of the historical record, with respect to the methane data, has been disputed. ^[64]

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. Paleoclimatology (also Palaeoclimatology) is the study of Climate change taken on the scale of the entire History of Earth. The Snowball Earth Hypothesis as it was originally proposed]] Evidence The Snowball Earth hypothesis was originally devised to explain the apparent presence of 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. 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 Earth 's movements upon its climate named after Serbian civil engineer and Mathematician An interglacial is a geological interval of warmer global average temperature that separates Glacial periods within an Ice age. ^[65]

A rapid buildup of greenhouse gases amplified warming in the early Jurassic period (about 180 million years ago), with average temperatures rising by 5 °C (9 °F). The Jurassic is a geologic period and system that extends from about Ma (million years ago to  Ma that is from the end of the Triassic to the beginning Research by the Open University indicates that the warming caused the rate of rock weathering to increase by 400%. Open University is also the name of other institutions See Distance education or the Open Universities category for a list Weathering is the decomposition of earth rocks, Soils and their Minerals through direct contact with the planet's Atmosphere. As such weathering locks away carbon in calcite and dolomite, CO₂ levels dropped back to normal over roughly the next 150,000 years. Calcite is a carbonate mineral and the most stable polymorph of Calcium carbonate ( Ca[[carbon C]] O 3 Dolomite (ˈdɒləmaɪt is the name of a Sedimentary Carbonate rock and a Mineral, both composed ^[66][67]

Sudden releases of methane from clathrate compounds (the clathrate gun hypothesis) have been hypothesized as both a cause for and an effect of other warming events in the distant past, including the Permian–Triassic extinction event (about 251 million years ago) and the Paleocene–Eocene Thermal Maximum (about 55 million years ago). A clathrate or clathrate compound or cage compound is a Chemical substance consisting of a lattice of one type of molecule trapping The clathrate gun hypothesis is the popular name given to the hypothesis that rises in sea temperatures (and/or falls in sea level can trigger the sudden release of Methane The Permian–Triassic (P–Tr extinction event, informally known as the Great Dying, was an Extinction event that occurred, and 70 percent of terrestrial The Paleocene /Eocene boundary, was marked by the most rapid and significant climatic disturbance of the Cenozoic Era.

Climate models

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. This article is about the theories and mathematics of climate modeling The Special Report on Emissions Scenarios (SRES was a report prepared by the Intergovernmental Panel on Climate Change (IPCC for the Third Assessment Report

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. 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 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. This article is about computer-driven prediction of Earth's climate for the theories and mathematics of climate modeling please see Climate model. A computer simulation, a computer model or a computational model is a Computer program, or network of computers that attempts to simulate an These models are based on physical principles of fluid dynamics, radiative transfer, and other processes, with simplifications being necessary because of limitations in computer power and the complexity of the climate system. The term radiative transfer refers to the physical phenomena of energy transfer in the form of electromagnetic radiation This article describes complex system as a type of system For other meanings see Complex systems. All modern climate models include an atmospheric model that is coupled to an ocean model and models for ice cover on land and sea. Some models also include treatments of chemical and biological processes. ^[68]These models predict that the effect of adding greenhouse gases is to produce a warmer climate. ^[69] However, even when the same assumptions of future greenhouse gas levels are used, there still remains a considerable range of climate sensitivity. In Intergovernmental Panel on Climate Change (IPCC reports equilibrium climate sensitivity refers to the equilibrium change in global mean surface temperature following

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. See also Global warming, Climate change, Climate change denial Attribution of recent climate change is the effort to scientifically ascertain

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. ^[70] 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. Greenhouse gases are gaseous constituents of the atmosphere bothnatural and anthropogenic that absorb and emit radiation at specific wavelengths within the spectrum of thermal infrared

Global climate model projections of future climate are forced by imposed greenhouse gas emission scenarios, most often from the IPCC Special Report on Emissions Scenarios (SRES). The Special Report on Emissions Scenarios (SRES was a report prepared by the Intergovernmental Panel on Climate Change (IPCC for the Third Assessment Report Less commonly, models may also include a simulation of the carbon cycle; this generally shows a positive feedback, though this response is uncertain (under the A2 SRES scenario, responses vary between an extra 20 and 200 ppm of CO₂). The carbon cycle is the biogeochemical cycle by which carbon is exchanged among the Biosphere, Pedosphere, Geosphere, Hydrosphere, and Some observational studies also show a positive feedback. ^[71][72][73]

The representation of clouds is one of the main sources of uncertainty in present-generation models, though progress is being made on this problem. ^[74]

A recent study by David Douglass, John Christy, Benjamin Pearson and Fred Singer comparing the composite output of 22 leading global climate models with actual climate data finds that the models do not accurately predict observed changes to the temperature profile in the tropical troposphere. David H Douglass is an American Physicist at the University of Rochester. John R Christy is a climate scientist whose chief interests are global climate change satellite sensing of global climate and paleoclimate Siegfried Frederick Singer (born September 27, 1924 in Vienna) is an American atmospheric physicist. The authors note that their conclusions contrast strongly with those of recent publications based on essentially the same data. ^[75]

Attributed and expected effects

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. 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 The National Snow and Ice Data Center, or NSIDC, is a United States information and referral center in support of polar and cryospheric

Main article: Effects of global warming

Although it is difficult to connect specific weather events to global warming, an increase in global temperatures may in turn cause broader changes, including glacial retreat, Arctic shrinkage, and worldwide sea level rise. effects of Global warming on the environment and human life are numerous varied accelerating and taking scientists studying global warming by surprise effects of Global warming on the environment and human life are numerous varied accelerating and taking scientists studying global warming by surprise See also Retreat of glaciers since 1850 Crucial to the survival of a Glacier is its mass balance, the difference between accumulation Arctic shrinkage is the marked decrease in Arctic sea ice and the observed melting of the Greenland Ice Sheet in recent years Sea-level rise is an increase in Sea level. Multiple complex factors may influence this change Changes in the amount and pattern of precipitation may result in flooding and drought. In Meteorology, precipitation (also known as one class of hydrometeors, which are atmospheric water phenomena is any product of the condensation of atmospheric A flood is an overflow of an expanse of water that submerges land a deluge A drought is an extended period of months or years when a region notes a deficiency in its water supply There may also be changes in the frequency and intensity of extreme weather events. See also List of extreme weather events Extreme weather includes Weather phenomena that are at the extremes of the historical distribution especially Other effects may include changes in agricultural yields, addition of new trade routes,^[76] reduced summer streamflows, species extinctions, and increases in the range of disease vectors. Streamflow, or channel runoff, is the flow of Water in Streams Rivers and other channels and is a major element of the Water The extinction risk of climate change is the risk Species have of becoming Extinct due to the Effects of global warming. In Epidemiology, a vector is an Organism that does not cause Disease itself but which transmits Infection by conveying Pathogens from

Some effects on both the natural environment and human life are, at least in part, already being attributed to global warming. See also Nature The natural environment, commonly referred to simply as the environment, is a terminology that is comprised of all living and A Civilization is a society in which large numbers of people share a variety of common elements 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 being attributed in part to global warming. whitechuck glacier 2006jpg|right|thumb|320px|The same view as seen in 2006 where this branch of glacier retreated 1 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 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 Sea-level rise is an increase in Sea level. Multiple complex factors may influence this change effects of Global warming on the environment and human life are numerous varied accelerating and taking scientists studying global warming by surprise ^[77] 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. ^[78]

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 benefits, such as fewer deaths due to cold exposure. See also List of extreme weather events Extreme weather includes Weather phenomena that are at the extremes of the historical distribution especially ^[79] 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. The IPCC Third Assessment Report, Climate Change 2001, is an assessment of available scientific and socio-economic information on climate change by an intergovermental panel ^[77] 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. Climate Change 2007, the Fourth Assessment Report (AR4 of the United Nations Intergovernmental Panel on Climate Change ( IPCC) is the fourth A tropical cyclone is a storm system characterized by a low pressure center and numerous Thunderstorms that produce strong winds and Flooding The summary also states that there is no clear trend in the annual worldwide number of tropical cyclones. ^[1]

Additional anticipated effects include sea level rise of 110 to 770 millimeters (0. 36 to 2. 5 ft) between 1990 and 2100,^[80] repercussions to agriculture, possible slowing of the thermohaline circulation, reductions in the ozone layer, increased intensity (but less frequent)^[81] of hurricanes and extreme weather events, lowering of ocean pH, and the spread of diseases such as malaria and dengue fever. Climate change and Agriculture are interrelated processes both of which take place on a global scale Shutdown or slowdown of the Thermohaline circulation is a postulated effect of global warming. The photochemical mechanisms that give rise to the ozone layer were worked out by the British physicist Sidney Chapman in 1930 effects of Global warming on the environment and human life are numerous varied accelerating and taking scientists studying global warming by surprise pH is the measure of the acidity or alkalinity of a Solution. Malaria is a vector -borne Infectious disease caused by Protozoan Parasites It is widespread in tropical and subtropical regions including 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. The extinction risk of climate change is the risk Species have of becoming Extinct due to the Effects of global warming. ^[82] However, few mechanistic studies have documented extinctions due to recent climate change^[83] and one study suggests that projected rates of extinction are uncertain. ^[84]

Economic

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. Climate Change 2007, the Fourth Assessment Report (AR4 of the United Nations Intergovernmental Panel on Climate Change ( IPCC) is the fourth

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. The economics of global warming refers to the projected size and distribution of the economic costs and benefits of Global warming, and to the economic A Low-Carbon Economy (LCE or Low Fossil Fuel Economy (LFFEis a popular term that refers to an Economy which has a minimal output of Greenhouse Gas (GHG emissions into the 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). The United States dollar ( sign: $; code: USD) is the unit of Currency of the United States; it has also been ^[79] 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%. The Stern Review on the Economics of Climate Change is a 700-page report released on October 30, 2006 by economist Lord Stern of Brentford for the ^[85] 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,^[86] while others have supported the general attempt to quantify economic risk, even if not the specific numbers. Discounts and allowancesIn Finance and Economics, discounting is the process of finding the present value of an amount of cash at some future date and along with ^[87][88]

Preliminary studies suggest that costs and benefits of mitigating global warming are broadly comparable in magnitude. ^[89]

According to United Nations Environment Programme (UNEP), economic sectors likely to face difficulties related to climate change include banks, agriculture, transport and others. The UN Environment Programme (or UNEP) coordinates United Nations environmental activities assisting developing countries in implementing environmentally sound policies A banker or bank is a Financial institution whose primary activity is to act as a payment agent for customers and to borrow and lend money Climate change and Agriculture are interrelated processes both of which take place on a global scale ^[90] Developing countries dependent upon agriculture will be particularly harmed by global warming. ^[91]

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 some nations, states, corporations and individuals to implement actions to try to curtail global warming or adjust to it. Adaptation to global warming consists of initiatives and measures to reduce the vulnerability of natural and human systems against actual or expected climate change effects. Mitigation of global warming involves taking actions to reduce Greenhouse gas emissions and to enhance sinks aimed at reducing the extent of Global warming The Kyoto Protocol is a protocol to the international Framework Convention on Climate Change with the objective of reducing Greenhouse gases in an effort National and international science academies and professional societies have assessed the current scientific opinion on climate change, in particular recent Global warming. Many environmental groups encourage individual action against global warming, often by the consumer, but also by community and regional organizations. The issue of human-caused or anthropogenic Climate change ( Global warming) is becoming a central focus of the Green movement. Others have suggested a quota on worldwide fossil fuel production, citing a direct link between fossil fuel production and CO₂ emissions. ^[92][93]

There has also been business action on climate change, including efforts at increased energy efficiency and limited moves towards use of alternative fuels. Business action on climate change includes a range of activities relating to combatting Global warming, and to influencing political decisions on global-warming-related Alternative fuels, also known as non-conventional Fuels are any Materials or substances that can be used as a Fuel, other than conventional 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. Emissions trading (or emission trading) is an administrative approach used to control Pollution by providing economic Incentives for

The world's primary international agreement on combating global warming is the Kyoto Protocol, an amendment to the UNFCCC negotiated in 1997. The Kyoto Protocol is a protocol to the international Framework Convention on Climate Change with the objective of reducing Greenhouse gases in an effort Annex I and Annex II Countries and Developing Countries Signatories to the UNFCCC are split into three groups Annex I countries (industrialized countries The Protocol now covers more than 160 countries globally and over 55% of global greenhouse gas emissions. ^[94] Only the United States and Kazakhstan have not ratified the treaty, with the United States historically being the world's largest emitter of greenhouse gas. The United States of America —commonly referred to as the Kazakhstan, also Kazakstan ( Қазақстан, Qazaqstan, qɑzɑqˈstɑn Казахстан, Kazakhstán,) officially the See also Climate change in the United States Until recently the United States was the largest emitter of carbon dioxide emissions This treaty expires in 2012, and international talks began in May 2007 on a future treaty to succeed the current one. ^[95]

Claiming "serious harm" to the United States economy and the exemption of "80 percent of the world, including major population centers" like China and India from the treaty, George W. Bush contends that the Kyoto Protocol is an unfair and ineffective means of addressing global climate change concerns. China ( Wade-Giles ( Mandarin) Chung¹kuo² is a cultural region, an ancient Civilization, and depending on perspective a National India, officially the Republic of India (भारत गणराज्य inc-Latn Bhārat Gaṇarājya; see also other Indian languages) is a country George Walker Bush ( born July 6 1946 is the forty-third and current President of the United States. ^[96] Bush has promoted improved energy technology as a means to combat climate change,^[97] and various state and city governments within the United States have begun their own initiatives to indicate support and compliance with the Kyoto Protocol on a local basis; an example of this being the Regional Greenhouse Gas Initiative. Regional Greenhouse Gas Initiative ( RGGI, or ReGGIe) is a regional initiative by states in the Northeastern United States region to reduce Greenhouse ^[98]

China and India, though exempt from its provisions as developing countries, have ratified the Kyoto Protocol. Developing countries are countries that haven't reached Western-style standards of democratic government free market economy industrialization social programs and human rights guaranties China may have passed the U. S. in total annual greenhouse gas emissions according to some recent studies^[99]. Chinese Premier Wen Jiabao has called on the nation to redouble its efforts to tackle pollution and global warming. This is a Chinese name; the family name is Wen. Wen Jiabao ( (born 15 September 1942 is the Premier of the Pollution is the introduction of contaminants into an environment that causes instability disorder harm or discomfort to the physical systems or living organisms they are in ^[100]

The IPCC's Working Group III is responsible for crafting reports that deal with the mitigation of global warming and analyzing the costs and benefits of different approaches. In the 2007 IPCC Fourth Assessment Report, they conclude that no one technology or sector can be completely responsible for mitigating future warming. Climate Change 2007, the Fourth Assessment Report (AR4 of the United Nations Intergovernmental Panel on Climate Change ( IPCC) is the fourth 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. Energy supply is the delivery of fuels or transformed fuels to point of consumption Transport or transportation is the movement of people and goods from one place to another For other uses of this term see Industry (disambiguation An industry (from Latin industrius, "diligent industrious" Agriculture refers to the production of goods through the growing of plants and fungi and the raising of domesticated Animals The study of agriculture They estimate that stabilization of carbon dioxide equivalent between 445 and 710 ppm by 2030 will result in between a 0. Carbon dioxide equivalent ( CDE) and Equivalent carbon dioxide (or CO2e) are two related but distinct measures for describing how much Global 6% increase and 3% decrease in global gross domestic product. ^[101] According to Working Group III, to limit temperature rise to 2 Degrees Centigrade, "developed countries as a group would need to reduce their emissions to below 1990 levels in 2020 (on the order of –10% to 40% below 1990 levels for most of the considered regimes) and to still lower levels by 2050 (40% (Sic. 80% in Box 13. 7, p776) to 95% below 1990 levels), even if developing countries make substantial reductions. "^[102]

Social and political debate

Main articles: Global warming controversy, Politics of global warming, and Economics of global warming

See also: Climate change denial

Per capita greenhouse gas emissions in 2000, including land-use change. The global warming controversy is a dispute regarding the nature and consequences of Global warming. The politics of global warming have involved policy decisions legislation and political debate over the science of and response to Global warming. The economics of global warming refers to the projected size and distribution of the economic costs and benefits of Global warming, and to the economic Climate change denial describes efforts to counter all or part of the theory of global climate change when those involved are believed to be acting out of vested interests rather Land use, land-use change and Forestry (LULUCF all have impacts on the global Carbon cycle and as such these activities can add or remove Carbon dioxide

Per country greenhouse gas emissions in 2000, including land-use change.

Since the last decades of the 20th century, increased awareness 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] At the same time, developing country exemptions from provisions of the Kyoto Protocol have been criticized by the United States and Australia, and used as part of a rationale for continued non-ratification by the U. Developing countries are countries that haven't reached Western-style standards of democratic government free market economy industrialization social programs and human rights guaranties The Kyoto Protocol is a protocol to the international Framework Convention on Climate Change with the objective of reducing Greenhouse gases in an effort The United States of America —commonly referred to as the For a topic outline on this subject see List of basic Australia topics. S. ^[105] In the Western world, the idea of human influence on climate has gained wider public acceptance in Europe than in the United States. The term Western world, the West or the Occident ( Latin: occidens -sunset -west as distinct from the Orient) can have multiple meanings ^[106][107]

The issue of climate change has sparked debate weighing the benefits of limiting industrial emissions of greenhouse gases against the costs that such changes would entail. Industrial processes are procedures involving chemical or mechanical steps to aid in the Manufacture of an item or items usually carried out on a very Air pollution is the human introduction into the atmosphere of Chemicals Particulate matter, or Biological materials that cause harm or discomfort Greenhouse gases are gaseous constituents of the atmosphere bothnatural and anthropogenic that absorb and emit radiation at specific wavelengths within the spectrum of thermal infrared The economics of global warming refers to the projected size and distribution of the economic costs and benefits of Global warming, and to the economic There has been discussion in several countries about the cost and benefits of adopting alternative energy sources in order to reduce carbon emissions. Alternative energy is typically defined as coming from sources that do not deplete natural resources or harm. ^[108] Organizations and companies such as the Competitive Enterprise Institute and ExxonMobil have emphasized more conservative climate change scenarios while highlighting the potential economic cost of stricter controls. The Competitive Enterprise Institute (CEI is a Non-profit public policy organization founded in 1984 by Fred L The Exxon Mobil Corporation, or ExxonMobil, is an American oil and gas Corporation and a direct descendant of John D ^{[109][110][111][112]} Likewise, various environmental lobbies and a number of public figures have launched campaigns to emphasize the potential risks of climate change and promote the implementation of stricter controls. effects of Global warming on the environment and human life are numerous varied accelerating and taking scientists studying global warming by surprise Some fossil fuel companies have scaled back their efforts in recent years,^[113] or called for policies to reduce global warming. ^[114]

Another point of contention is the degree to which emerging economies such as India and China should be expected to constrain their emissions. The category of newly industrialized country ( NIC) is a socioeconomic classification applied to several countries around the world by Political scientists India, officially the Republic of India (भारत गणराज्य inc-Latn Bhārat Gaṇarājya; see also other Indian languages) is a country China ( Wade-Giles ( Mandarin) Chung¹kuo² is a cultural region, an ancient Civilization, and depending on perspective a National According to recent reports, China's gross national CO₂ emissions may now exceed those of the U. This is a list of sovereign states by carbon dioxide emissions due to human activity S. ^[115] China has contended that it has less of an obligation to reduce emissions since its per capita emissions are roughly one-fifth that of the United States. This is a list of countries by Carbon dioxide emissions Per capita from 1990 through 2004 ^[116] India, also exempt from Kyoto restrictions and another of the biggest sources of industrial emissions, has made similar assertions. ^[117] However, the U. S. contends that if they must bear the cost of reducing emissions, then China should do the same. ^[118]

Related climatic issues

Main articles: Ocean acidification, global dimming, and ozone depletion

A variety of issues are often raised in relation to global warming. Global dimming is the gradual reduction in the amount of global direct Irradiance at the Earth 's surface that was observed for several decades after the start of systematic 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 Earth's One is ocean acidification. Increased atmospheric CO₂ increases the amount of CO₂ dissolved in the oceans. ^[119] CO₂ dissolved in the ocean reacts with water to form carbonic acid, resulting in acidification. Carbonic acid (ancient name acid of air or aerial acid) has the formula H2CO3 Ocean surface pH is estimated to have decreased from 8. pH is the measure of the acidity or alkalinity of a Solution. 25 near the beginning of the industrial era to 8. 14 by 2004,^[120] and is projected to decrease by a further 0. 14 to 0. 5 units by 2100 as the ocean absorbs more CO₂. ^[1][121] Since organisms and ecosystems are adapted to a narrow range of pH, this raises extinction concerns, directly driven by increased atmospheric CO₂, that could disrupt food webs and impact human societies that depend on marine ecosystem services. In Biology and Ecology, extinction is the cessation of existence of a Species or group of taxa. Food chains, also called food networks and/or trophic networks, describe the feeding relationships between species within an Ecosystem. ^[122]

Global dimming, the gradual reduction in the amount of global direct irradiance at the Earth's surface, may have partially mitigated global warming in the late twentieth century. Global dimming is the gradual reduction in the amount of global direct Irradiance at the Earth 's surface that was observed for several decades after the start of systematic Irradiance, radiant emittance, and radiant exitance are Radiometry terms for the power of Electromagnetic radiation at a surface per unit From 1960 to 1990 human-caused aerosols likely precipitated this effect. Scientists have stated with 66–90% confidence that the effects of human-caused aerosols, along with volcanic activity, have offset some of the global warming, and that greenhouse gases would have resulted in more warming than observed if not for these dimming agents. ^[1]

Ozone depletion, the steady decline in the total amount of ozone in Earth's stratosphere, is frequently cited in relation to global warming. 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 Earth's OZONE is an object oriented Operating system written in the C programming language. The stratosphere is the second major layer of Earth's atmosphere, just above the Troposphere, and below the Mesosphere. Although there are areas of linkage, the relationship between the two is not strong. 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 Earth's

See also

• Glossary of climate change

Notes and references

Further reading

External links

Scientific

• Intergovernmental Panel on Climate Change and UN Climate Panel Report's Key Findings.
• Nature Reports Climate Change
• The UK Met Office Hadley Centre site
• NOAA's Global Warming FAQ
• Discovery of Global Warming – An extensive introduction to the topic and the history of its discovery, written by Spencer R. Weart
• Caution urged on climate 'risks'
• Impact of Livestock on Global Warming (UN Report)

Educational

• Global warming at HowStuffWorks
• What Is Global Warming? – Shockwave presentation from National Geographic
• The EdGCM (Educational Global Climate Modelling) Project – A free research-quality simulation for students, educators, and scientists alike, with a user-friendly interface that runs on desktop computers
• DISCOVER Satellite-based ocean and climate data since 1979 from NASA
• The Pew Center on global climate change
• Video of a talk by Warren Washington titled "The Evolution of Global Warming Science: From Ideas to Scientific Facts"
• Best Effort Global Warming Trajectories by Harvey Lam (Princeton University), The Wolfram Demonstrations Project. Spencer R Weart is the director of the Center for History of Physics of the American Institute of Physics. Overview The NGS's historical mission is "to increase and diffuse geographic knowledge while promoting the conservation of the world's cultural historical and natural The National Aeronautics and Space Administration ( NASA, ˈnæsə is an agency of the United States government, responsible for the nation's public space program

Other

• Science and Technology Sources on the Internet – Extensive commented list of Internet resources
• Union of Concerned Scientists Global Warming page
• Watch and read 'Tipping Point', Australian science documentary about effects of global warming on rare, common, and endangered wildlife
• Gateway to the UN System's Work on Climate Change