Attribution of recent climate change is the effort to scientifically ascertain mechanisms responsible for relatively recent changes observed in the Earth's climate. The effort has focused on changes observed during the period of instrumental temperature record, when records are most reliable; particularly on the last 50 years, when human activity has grown fastest and observations of the upper atmosphere have become available. The dominant mechanisms to which recent climate change has been attributed all result from human activity. They are:^[1] Scientific method is a body of techniques for investigating phenomena and acquiring new knowledge, as well as for correcting and integrating previous knowledge. ... This article is about Earth as a planet. ... The instrumental temperature record shows the fluctuations of the temperature of the atmosphere and the oceans since the invention of thermometers. ...

• increasing atmospheric concentrations of greenhouse gases
• global changes to land surface, such as deforestation
• increasing atmospheric concentrations of aerosols.

Recent reports from the Intergovernmental Panel on Climate Change (IPCC) report have concluded that: View of Jupiters active atmosphere, including the Great Red Spot. ... Top: Increasing atmospheric CO2 levels as measured in the atmosphere and ice cores. ... Deforestation is the conversion of forested areas to non-forest land use such as arable land, pasture, urban use, logged area or wasteland. ... 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). ... 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...

• "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."^[2].
• "From new estimates of the combined anthropogenic forcing due to greenhouse gases, aerosols, and land surface changes, it is extremely likely that human activities have exerted a substantial net warming influence on climate since 1750."^[3]
• "It is virtually certain that anthropogenic aerosols produce a net negative radiative forcing (cooling influence) with a greater magnitude in the Northern Hemisphere than in the Southern Hemisphere.^[4]

The panel, which represents consensus in the scientific community, defines "very likely," "extremely likely," and "virtually certain" as indicating probabilities greater than 90%, 95%, and 99%, respectively.^[5] Look up anthropogenic in Wiktionary, the free dictionary. ... Top: Increasing atmospheric CO2 levels as measured in the atmosphere and ice cores. ... The generalised concept of radiative forcing in climate science is any change in the radiation (heat) entering the climate system or changes in radiatively active gases. ... 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). ... Land use is the pattern of construction and activity land is used for. ... Events March 2 - Small earthquake in London, England April 4 - Small earthquake in Warrington, England August 23 - Small earthquake in Spalding, England September 30 - Small earthquake in Northampton, England November 16 – Westminster Bridge officially opened Jonas Hanway is the first Englishman to use an umbrella James Gray reveals her sex... The generalised concept of radiative forcing in climate science is any change in the radiation (heat) entering the climate system or changes in radiatively active gases. ... The Northern Hemisphere is the half of a planets surface (or celestial sphere) that is north of the equator (the word hemisphere literally means half ball). On the Earth, the Northern Hemisphere contains most of the land and about 90% of the human population. ... southern hemisphere highlighted in yellow (Antarctica not depicted). ... National and international science academies and professional societies have assessed the current scientific opinion on climate change, in particular recent global warming. ... This article does not cite any references or sources. ...

Key attributions

Greenhouse gases

Scientific consensus has identified carbon dioxide as the dominant greenhouse gas; methane and nitrous oxide are also major contributors to the greenhouse effect. The Kyoto Protocol lists these together with Hydrofluorocarbons (HFCs), Perfluorocarbons (PFCs), and Sulphur hexafluoride (SF6),^[6] which contribute to climate change primarily by interfering with atmospheric ozone concentrations. The chart at right attributes greenhouse gas emissions to eight main economic sectors, of which the largest contributors are power stations (many of which burn coal or other fossil fuels), industrial processes (among which cement production is a dominant contributor^[7]), transportation fuels (generally fossil fuels), and agricultural byproducts (mainly methane from enteric fermentation and nitrous oxide from fertilizer use). Image File history File links Download high resolution version (650x603, 33 KB) Description This figure shows the relative fraction of man-made greenhouse gases coming from each of eight categories of sources, as estimated by the Emission Database for Global Atmospheric Research version 3. ... Image File history File links Download high resolution version (650x603, 33 KB) Description This figure shows the relative fraction of man-made greenhouse gases coming from each of eight categories of sources, as estimated by the Emission Database for Global Atmospheric Research version 3. ... In order to meet Wikipedias quality standards, this article requires cleanup. ... Methane is a chemical compound with the molecular formula CH4. ... R-phrases S-phrases Supplementary data page Structure and properties n, εr, etc. ... A schematic representation of the exchanges of energy between outer space, the Earths atmosphere, and the Earth surface. ... Kyoto Protocol Opened for signature December 11, 1997 in Kyoto, Japan Entered into force February 16, 2005. ... The haloalkanes (also known as halogenoalkanes) are a group of chemical compounds, consisting of alkanes, such as methane or ethane, with one or more halogens linked, such as chlorine or fluorine, making them a type of organic halide. ... Perfluorocarbons (or PFCs) are compounds derived from hydrocarbons by replacement of hydrogen atoms by fluorine atoms. ... Sulfur hexafluoride (SF6) is a gas that consists of one part sulfur and six parts fluorine. ... It has been suggested that Ozone generator be merged into this article or section. ... The word emission generally means sending something out. ... A power station (also power plant) is a facility for the generation of electric power. ... Coal Coal (IPA: ) is a fossil fuel formed in swamp ecosystems where plant remains were saved by water and mud from oxidization and biodegradation. ... Fossil fuels are hydrocarbons, primarily coal and petroleum (fuel oil or natural gas), formed from the fossilized remains of dead plants and animals[1] by exposure to heat and pressure in the Earths crust over hundreds of millions of years[2]. The theory that hydrocarbons were formed from these... In the most general sense of the word, cement is a binder, a substance which sets and hardens independently, and can bind other materials together. ... Fuel imports in 2005 Fuel is any material that is capable of releasing energy when its chemical or physical structure is altered. ... Fossil fuels are hydrocarbons, primarily coal and petroleum (fuel oil or natural gas), formed from the fossilized remains of dead plants and animals[1] by exposure to heat and pressure in the Earths crust over hundreds of millions of years[2]. The theory that hydrocarbons were formed from these... Enteric fermentation is fermentation that takes place in the digestive systems of animals. ... Spreading manure, an organic fertilizer Fertilizers (also spelled fertilisers) are compounds given to plants to promote growth; they are usually applied either via the soil, for uptake by plant roots, or by foliar feeding, for uptake through leaves. ...

Land use

Climate change is attributed to land use for two main reasons. While 66% of anthropogenic CO₂ emissions over the last 250 years have resulted from burning fossil fuels, 33% have resulted from changes in land use, primarily deforestation.^[8] Deforestation both reduces the amount of carbon dioxide absorbed by deforested regions and releases greenhouse gases directly, together with aerosols, through biomass burning that frequently accompanies it. A second reason that climate change has been attributed to land use is that the terrestrial albedo is often altered by use, which leads to radiative forcing. This effect is more significant locally than globally.^[9] Land use is the pattern of construction and activity land is used for. ... In order to meet Wikipedias quality standards, this article requires cleanup. ... Deforestation is the conversion of forested areas to non-forest land use such as arable land, pasture, urban use, logged area or wasteland. ... Assarting in Finland in 1892 Slash and burn (a specific practice that may be part of shifting cultivation or swidden-fallow agriculture) is an agricultural procedure widely used in forested areas. ... Albedo is the ratio of reflected to incident electromagnetic radiation. ... The generalised concept of radiative forcing in climate science is any change in the radiation (heat) entering the climate system or changes in radiatively active gases. ...

Livestock and land use

Worldwide, livestock production occupies 70% of all land used for agriculture, or 30% of the land surface of the Earth.^[10] Scientists attribute more than 18% of anthropogenic greenhouse gas emissions to livestock and livestock-related activities such as deforestation and increasingly fuel-intensive farming practices. Specific attributions to the livestock sector include:

• 9% of global carbon dioxide emissions
• 35-40% of global methane emissions (chiefly due to enteric fermentation and manure)
• 64% of global nitrous oxide emissions, chiefly as a result of fertilizer use.^[11]

In order to meet Wikipedias quality standards, this article requires cleanup. ... Methane is a chemical compound with the molecular formula CH4. ... Enteric fermentation is fermentation that takes place in the digestive systems of animals. ... Animal manure is often a mixture of animals feces and bedding straw, as in this example from a stable. ... R-phrases S-phrases Supplementary data page Structure and properties n, εr, etc. ... Spreading manure, an organic fertilizer Fertilizers (also spelled fertilisers) are compounds given to plants to promote growth; they are usually applied either via the soil, for uptake by plant roots, or by foliar feeding, for uptake through leaves. ...

Aerosols

With virtual certainty, scientific consensus has attributed various forms of climate change, chiefly cooling effects, to aerosols, which are small particles or droplets suspended in the atmosphere.^[12] Key sources to which anthropogenic aerosols are attributed^[13] include: 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). ...

• biomass burning such as slash and burn deforestation. Aerosols produced are primarily black carbon.
• industrial air pollution, which produces soot and airborne sulfates, nitrates, and ammonium
• dust produced by land use effects such as desertification

Assarting in Finland in 1892 Slash and burn (a specific practice that may be part of shifting cultivation or swidden-fallow agriculture) is an agricultural procedure widely used in forested areas. ... As explained by Goldberg (1985), black carbon (BC) is an impure form of carbon produced by incomplete combustion of fossil fuel and wood (forming soot) or biomass (forming charcoals). ... Air pollution is a chemical, particulate matter, or biological agent that modifies the natural characteristics of the atmosphere. ... Soot, also called lampblack, Pigment Black 7, carbon black or black carbon, is a dark powdery deposit of unburned fuel residues, usually composed mainly of amorphous carbon, that accumulates in chimneys, automobile mufflers and other surfaces exposed to smoke—especially from the combustion of carbon-rich organic fuels in the... In inorganic chemistry, a sulfate (IUPAC-recommended spelling; also sulphate in British English) is a salt of sulfuric acid. ... An electrostatic potential map of the nitrate ion. ... A ball-and-stick model of the ammonium cation Fumes from hydrochloric acid and ammonia forming a white cloud of ammonium chloride Ammonium is also an old name for the Siwa Oasis in western Egypt. ... Land use is the pattern of construction and activity land is used for. ... This article includes a list of works cited or a list of external links, but its sources remain unclear because it lacks in-text citations. ...

Attribution of 20th century climate change

One global climate model's reconstruction of temperature change during the 20th century as the result of five studied forcing factors and the amount of temperature change attributed to each.

Over the past 150 years human activities have released increasing quantities of greenhouse gases into the atmosphere. This has led to increases in mean global temperature, or global warming. Other human effects are relevant—for example, sulphate aerosols are believed to lead to cooling—and natural factors also contribute. According to the historical temperature record of the last century, the Earth's near-surface air temperature has risen around 0.74 ± 0.18 °Celsius (1.3 ± 0.32 °Fahrenheit). 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... The Intergovernmental Panel on Climate Change first assessment report was completed in 1990, and served as the basis of the United Nations Framework Convention on Climate Change (UNFCCC). ... The Intergovernmental Panel on Climate Change supplementary report of 1992 was published to contribute to the debate on the United Nations Framework Convention on Climate Change at the 1992 Earth Summit, held in Rio de Janeiro. ... The Second Assessment Report (SAR) of the Intergovernmental Panel on Climate Change was published in 1995. ... 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. ... UNFCCC logo. ... The World Meteorological Organization (WMO) is an intergovernmental organization with a membership of 187 Member States and Territories. ... Klaus Töpfer, former UNEP Exec. ... Image File history File links Climate_Change_Attribution. ... Image File history File links Climate_Change_Attribution. ... 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. ... Top: Increasing atmospheric CO2 levels as measured in the atmosphere and ice cores. ... Layers of Atmosphere—not to scale (NOAA) [1] Earths atmosphere is a layer of gases surrounding the planet Earth and retained by the Earths gravity. ... Global mean surface temperatures 1850 to 2006 Mean surface temperature anomalies during the period 1995 to 2004 with respect to the average temperatures from 1940 to 1980 Global warming is the observed increase in the average temperature of the Earths atmosphere and oceans in recent decades and the projected... Particulates, alternatively referred to as particulate matter (PM), aerosols or fine particles, are tiny particles of solid or liquid suspended in a gas. ... The historical temperature record shows the fluctuations of the temperature of the atmosphere and the oceans throughout history, and in particular since 1850. ... 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). ... Fahrenheit is a temperature scale named after the German-Dutch physicist Daniel Gabriel Fahrenheit (1686–1736), who proposed it in 1724. ...

A historically important question in climate change research has regarded the relative importance of human activity and non-anthropogenic causes during the period of instrumental record. In the 1995 second assessment report (SAR), the IPCC made the widely-quoted statement that "The balance of evidence suggests a discernible human influence on global climate". The phrase "balance of evidence" suggested the (English) common-law standard of proof required in civil as opposed to criminal courts: not as high as "beyond reasonable doubt". In 2001 the third assessment report (TAR) refined this, saying "There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities".^[14] The 2007 fourth assessment report (WG1 AR4) strengthened this finding: Look up anthropogenic in Wiktionary, the free dictionary. ... The instrumental temperature record shows the fluctuations of the temperature of the atmosphere and the oceans since the invention of thermometers. ... 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...

• "Anthropogenic warming of the climate system is widespread and can be detected in temperature observations taken at the surface, in the free atmosphere and in the oceans. Evidence of the effect of external influences, both anthropogenic and natural, on the climate system has continued to accumulate since the TAR."^[15]

Over the past five decades there has been a global warming of approximately 0.65 °C (1.17 °F) at the Earth's surface (see historical temperature record). Among the possible factors that could produce changes in global mean temperature are internal variability of the climate system, external forcing, an increase in concentration of greenhouse gases, or any combination of these. Current studies indicate that the increase in greenhouse gases, most notably CO₂, is mostly responsible for the observed warming. Evidence for this conclusion includes: The historical temperature record shows the fluctuations of the temperature of the atmosphere and the oceans throughout history, and in particular since 1850. ...

• Estimates of internal variability from climate models, and reconstructions of past temperatures, indicate that the warming is unlikely to be entirely natural.
• Climate models forced by natural factors and increased greenhouse gases and aerosols reproduce the observed global temperature changes; those forced by natural factors alone do not [13].
• "Fingerprint" methods indicate that the pattern of change is closer to that expected from greenhouse gas-forced change than from natural change.[14]
• The plateau in warming from the 1940s to 1960s can be attributed largely to sulphate aerosol cooling.[15]

In 2001, the U.S. National Academy of Sciences released a report supporting the IPCC’s conclusions regarding the causes of recent climate change. It stated, "Greenhouse gases are accumulating in Earth’s atmosphere as a result of human activities, causing surface air temperatures and subsurface ocean temperatures to rise. Temperatures are, in fact, rising. The changes observed over the last several decades are likely mostly due to human activities, but we cannot rule out that some significant part of these changes are also a reflection of natural variability."[16] [17][18] President Harding and the National Academy of Sciences at the White House, Washington, DC, April 1921 The National Academy of Sciences (NAS) is a corporation in the United States whose members serve pro bono as advisers to the nation on science, engineering, and medicine. ...

Detection vs. attribution

Detection and attribution of climate signals, as well as its common-sense meaning, has a more precise definition within the climate change literature, as expressed by the IPCC [19].

Detection of a signal requires demonstrating that an observed change is statistically significantly different from that which can be explained by natural internal variability.

Attribution requires demonstrating that a signal is:

• unlikely to be due entirely to internal variability;
• consistent with the estimated responses to the given combination of anthropogenic and natural forcing
• not consistent with alternative, physically plausible explanations of recent climate change that exclude important elements of the given combination of forcings.

Detection does not imply attribution, and is easier than attribution. Unequivocal attribution would require controlled experiments with multiple copies of the climate system, which is not possible. Attribution, as described above, can therefore only be done within some margin of error. For example, the IPCC's Fourth Assessment Report says "it is extremely likely that human activities have exerted a substantial net warming influence on climate since 1750," where "extremely likely" indicates a probability greater than 95%.^[16] 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. ... Events March 2 - Small earthquake in London, England April 4 - Small earthquake in Warrington, England August 23 - Small earthquake in Spalding, England September 30 - Small earthquake in Northampton, England November 16 – Westminster Bridge officially opened Jonas Hanway is the first Englishman to use an umbrella James Gray reveals her sex...

Following the publication of the Third Assessment Report (TAR) in 2001, "detection and attribution" of climate change has remained an active area of research. Some important results include:

• A review of detection and attribution studies by the International Ad Hoc Detection and Attribution Group^[17] found that "natural drivers such as solar variability and volcanic activity are at most partially responsible for the large-scale temperature changes observed over the past century, and that a large fraction of the warming over the last 50 yr can be attributed to greenhouse gas increases. Thus, the recent research supports and strengthens the IPCC Third Assessment Report conclusion that 'most of the global warming over the past 50 years is likely due to the increase in greenhouse gases.'"
• Multiple independent reconstructions of the temperature record of the past 1000 years confirm that the late 20th century is probably the warmest period in that time
• Two papers in Science in August 2005 ^{[18] [19]} resolve the problem, evident at the time of the TAR, of tropospheric temperature trends. The UAH version of the record contained errors, and there is evidence of spurious cooling trends in the radiosonde record, particularly in the tropics. See satellite temperature measurements for details; and the 2006 US CCSP report ^[20].
• Barnett and colleagues ^[21] say that the observed warming of the oceans "cannot be explained by natural internal climate variability or solar and volcanic forcing, but is well simulated by two anthropogenically forced climate models," concluding that "it is of human origin, a conclusion robust to observational sampling and model differences" ^[22]
• Bratcher and Giese ^[23] observed conditions that "could be an indication of a climate regime shift to pre-1976 conditions." Bratcher and Giese conclude: "The results presented here do not preclude the possibility that anthropogenic sources of greenhouse gases have contributed to global warming. However the results do indicate that the human forced portion of global warming may be less than previously described."

Ad hoc is a Latin phrase which means for this [purpose]. It generally signifies a solution that has been tailored to a specific purpose, such as a tailor-made suit, a handcrafted network protocol, and specific-purpose equation and things like that. ... The temperature record of the past 1000 years describes the reconstruction of temperature for the last 1000 years on the Northern Hemisphere. ... 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. ... Look up anthropogenic in Wiktionary, the free dictionary. ...

Scientific literature and opinion

Main article: Scientific opinion on climate change

Some examples of published and informal support for the consensus view: National and international science academies and professional societies have assessed the current scientific opinion on climate change, in particular recent global warming. ...

• The attribution of climate change is discussed extensively, with references to peer-reviewed research, in chapter 12 of the IPCC TAR, which discusses The Meaning of Detection and Attribution, Quantitative Comparison of Observed and Modelled Climate Change, Pattern Correlation Methods and Optimal Fingerprint Methods.
• An essay [20] in Science surveyed 928 abstracts related to climate change, and concluded that most journal reports accepted the consensus. This is discussed further in scientific opinion on climate change.
• A recent paper (Estimation of natural and anthropogenic contributions to twentieth century temperature change, Tett SFB et al., JGR 2002), says that "Our analysis suggests that the early twentieth century warming can best be explained by a combination of warming due to increases in greenhouse gases and natural forcing, some cooling due to other anthropogenic forcings, and a substantial, but not implausible, contribution from internal variability. In the second half of the century we find that the warming is largely caused by changes in greenhouse gases, with changes in sulphates and, perhaps, volcanic aerosol offsetting approximately one third of the warming." [21]
• In 1996, in a paper in Nature titled "A search for human influences on the thermal structure of the atmosphere", Benjamin D. Santer et al. wrote: "The observed spatial patterns of temperature change in the free atmosphere from 1963 to 1987 are similar to those predicted by state-of-the-art climate models incorporating various combinations of changes in carbon dioxide, anthropogenic sulphate aerosol and stratospheric ozone concentrations. The degree of pattern similarity between models and observations increases through this period. It is likely that this trend is partially due to human activities, although many uncertainties remain, particularly relating to estimates of natural variability." This earlier work only addressed the most recent period. Estimates of natural variability matter for assessing the significance of the trend.
• Some scientists noted for their somewhat skeptical view of global warming accept that recent climate change is mostly anthropogenic. John Christy has said that he supports the American Geophysical Union (AGU) declaration, and is convinced that human activities are the major cause of the global warming that has been measured. [22]

Some scientists do disagree with the consensus: see list of scientists opposing global warming consensus. For example Willie Soon and Richard Lindzen^[24] say that there is insufficient proof for anthropogenic attribution. Generally this position requires new physical mechanisms to explain the observed warming; for example "Climate hypersensitivity to solar forcing?", Soon W et al., 2000, Annales Geophysicae-Atmospheres Hydrospheres and Space Sciences 18(5). Science is the journal of the American Association for the Advancement of Science (AAAS). ... An abstract is a brief summary of a research article, thesis, review, conference proceeding or any in-depth analysis of a particular subject or discipline, and is often used to help the reader quickly ascertain the papers purpose. ... National and international science academies and professional societies have assessed the current scientific opinion on climate change, in particular recent global warming. ... National and international science academies and professional societies have assessed the current scientific opinion on climate change, in particular recent global warming. ... Simon Tett is a climatologist working at the Hadley Centre. ... Nature is one of the most prominent scientific journals, first published on 4 November 1869. ... Dr. Benjamin D. Santer Climate researcher, Lawrence Livermore National Laboratory. ... Dr. John Christy is a climate scientist whose chief interests are Global Climate Change, Satellite Sensing of Global Climate, and Paleoclimate. ... This article lists scientists, not necessarily involved in climate research, who have expressed doubt regarding the current scientific opinion on global warming. ... Willie Soon (Wei-Hock Soon) is an astrophysicist at the Solar and Stellar Physics Division of the Harvard-Smithsonian Center for Astrophysics. ... Richard Siegmund Lindzen (born 1940) is an atmospheric physicist and a professor of meteorology at MIT renowned for his research in dynamic meteorology - especially atmospheric waves. ...

Findings that complicate attribution to CO₂

Warming sometimes leads CO₂ increases

Factors other than increased CO₂ concentrations can initiate warming or cooling episodes (see e.g., orbital forcing). The ice core record shows that on some occasions temperature starts rising hundreds of years before CO₂ increases.^{[25] [26]} Such results confirm that the relationship between CO₂ and climate can go in both directions: changes in CO₂ concentrations affect climate, while changes in climate can affect CO₂ concentrations. One proposed mechanism for this effect is increased release of sequestered CO₂ from oceans as circulation patterns shift, perhaps abruptly, in response to climate change.^{[27] [28]} 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. ...

A more speculative and polemical inference sometimes drawn is that the causal relationship between temperature rises and global CO₂ concentrations are only one-way, so that historical increases in CO₂ have been nothing more than the product of independently rising temperatures.[23] However, a strictly "one-way" view of the relationship between CO₂ and temperature contradicts basic results in physics, specifically the fact that the absorption and emission of infrared radiation by CO₂ increases as its atmospheric concentration increases.^[29][30]

First principles as well as empirical observation suggest that positive feedbacks from CO₂ concentrations amplify warming initially caused by other factors:

Close analysis of the relationship between the two curves [i.e., temperature and CO₂] shows that, within the uncertainties of matching their timescales, the temperature led by a few centuries. This is expected, since it was changes in the Earth’s orbital parameters (including the shape of its orbit around the Sun, and the tilt of Earth’s axis) that caused the small initial temperature rise. This then raised atmospheric CO2 levels, in part by outgassing from the oceans, causing the temperature to rise further. By amplifying each other’s response, this “positive feedback” can turn a small initial perturbation into a large climate change. There is therefore no surprise that the temperature and CO2 rose in parallel, with the temperature initially in advance. In the current case, the situation is different, because human actions are raising the CO2 level, and we are starting to observe the temperature response. [24]

Present CO₂ levels greatly exceed the range found in the ice core data. Isotopic analysis of atmospheric CO₂ confirms that fossil fuel burning is the source of most of the CO₂ increase, unlike during prior interglacial periods.^[31] As noted above, models that include increased CO₂ levels when simulating recent climate match the observed data far better than those that do not.[25]

Solar variation

In the last 10 years evidence of local or planetary warming has been observed on Mars ^[32], Pluto ^[33], Jupiter ^[34], and Neptune's largest moon Triton ^[35]. It has sometimes been asserted in the popular press that this points to a solar explanation for the recent warming on Earth^[36]. Physicist K.I. Abdusamatov claims that solar variation has caused global warming on Earth, and that the coincident warmings "can only be a straightline consequence of the effect of the one same factor: a long-time change in solar irradiance."^[37] This view is not accepted by other scientists.^[38] Instead, scientific opinion is that these changes are caused by other factors, such as orbital irregularities or (in the case of Mars) changes in albedo as a result of dust storms^[39]. Adjectives: Martian Atmosphere Surface pressure: 0. ... Adjectives: Plutonian Atmosphere Surface pressure: 0. ... Adjectives: Jovian Atmosphere [4] Surface pressure: 20–200 kPa[8] (cloud layer) Scale height: 27 km Composition: Jupiter (IPA: or ) is the fifth planet from the Sun and the largest planet within the solar system. ... Note: This article contains special characters. ... Triton (trye-tÉ™n, IPA: , Greek Τρίτων), or Neptune I, is the planet Neptunes largest moon. ... Khabibullo Ismailovich Abdusamatov (Russian: ; with initials transliterated either H.I. or K.I.) is a mathematician and physicist at the laboratory of solar physics [1] at the Saint Petersburg-based Pulkovo Observatory (link, photo) of the Russian Academy of Sciences and the supervisor of the Astrometria project of the Russian... 400 year history of sunspot numbers. ... Albedo is the ratio of reflected to incident electromagnetic radiation. ...

Footnotes

Geophysical Research Letters is one of the scientific magazines dedicated to specialized aspects of geophysics, geology, climate science, and related disciplines. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... Geophysical Research Letters is one of the scientific magazines dedicated to specialized aspects of geophysics, geology, climate science, and related disciplines. ... Science is the journal of the American Association for the Advancement of Science (AAAS). ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... is the 61st day of the year (62nd in leap years) in the Gregorian calendar. ... The Pacific Northwest National Laboratory (PNNL) is a one of nine United States Department of Energy multiprogram national laboratories. ... This article needs to be cleaned up to conform to a higher standard of quality. ... Williams College is a private liberal arts college located in Williamstown, Massachusetts. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... is the 95th day of the year (96th in leap years) in the Gregorian calendar. ... Nature is one of the most prominent scientific journals, first published on 4 November 1869. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ...

References

• Le Quéré, How much of the recent CO₂ increase is due to human activities?, 2005 [26]

See also

Energy Portal

Image File history File links Crystal_128_energy. ...

External links

• RealClimate - Blog on current climate change issues by active climatologists
• "The Climate of Man", The New Yorker (2005): Part 1, Part 2, Part 3
• Anthropogenic or Solar? by Shaviv
• US EPA climate change and global warming website