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Global warming is the observed increase in the average temperature of the Earth's near-surface air and oceans in recent decades and its projected continuation.

Global average air temperature near Earth's surface rose 0.74 ± 0.18 °C (1.3 ± 0.32 °F) during the last century. The Intergovernmental Panel on Climate Change (IPCC) concludes, "most of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations," which leads to warming of the surface and lower atmosphere by increasing the greenhouse effect. These conclusions have been endorsed by more than 30 scientific societies and academies of science, including all of the national academies of science of the major industrialized states, but a small number of individual scientists disagree. The only scientific society that denies human-caused global warming is the American Association of Petroleum Geologists.

Models referenced by the IPCC predict that global temperatures are likely to increase by 1.1 to 6.4 °C (2.0 to 11.5 °F) between 1990 and 2100. The range of values reflects the use of differing scenarios of future greenhouse gas emissions as well as uncertainties regarding climate sensitivity. Although most studies focus on the period up to 2100, warming and sea level rise are expected to continue for more than a millennium even if no further greenhouse gases are released after this date. This reflects the long average atmospheric lifetime of carbon dioxide (CO₂).

An increase in global temperatures can in turn cause other changes, including a rising sea level and changes in the amount and pattern of precipitation. There may also be increases in the frequency and intensity of extreme weather events, though it is difficult to connect specific events to global warming. Other consequences include changes in agricultural yields, glacier retreat, reduced summer streamflows, species extinctions and increases in the ranges of disease vectors.

Remaining scientific uncertainties include the exact degree of climate change expected in the future, and especially how changes will vary from region to region across the globe. A hotly contested political and public debate also has yet to be resolved, regarding whether anything should be done, and what could be cost-effectively done to reduce or reverse future warming, or to deal with the expected consequences. Most national governments have signed and ratified the Kyoto Protocol aimed at combating greenhouse gas emissions.

Terminology

The term global warming is a specific example of the broader term climate change, which can also refer to global cooling. In principle, global warming is neutral as to the period or causes, but in both common and scientific usage the term generally refers to recent warming and implies a human influence. The United Nations Framework Convention on Climate Change (UNFCCC) uses the term "climate change" for human-caused change, and "climate variability" for other changes. The term "anthropogenic climate change" is sometimes used when focusing on human-induced changes.

Causes

The climate system varies through natural, internal processes and in response to variations in external "forcing" factors including solar activity, volcanic emissions, variations in the earth's orbit (orbital forcing) and greenhouse gases. The detailed causes of the recent warming remain an active field of research, but the scientific consensus identifies increased levels of greenhouse gases due to human activity as the main influence. This attribution is clearest for the most recent 50 years, for which the most detailed data are available.

Greenhouse gases create a natural greenhouse effect without which temperatures on Earth would be an estimated 30 °C (54 °F) lower, so that Earth would be uninhabitable. It is therefore not correct to say that there is a debate between those who "believe in" and "oppose" the greenhouse effect as such. Rather, the debate concerns the net effect of the addition of greenhouse gases when allowing for positive or negative feedback.

The primary greenhouse gases are water vapor, carbon dioxide, and methane. Water is the most abundant in the atmosphere by concentration, but it is a short-term greenhouse gas and in a dynamic equilibrium in the atmophere. Great quantities of water can be added to the atmoshphere by evaporation or subtracted by precipitation in a period of weeks. Methane is an intermediate-term greenhouse gas and in the atmosphere is converted to carbon dioxide in a period of months to years. Carbon dioxide is a long-term greenhouse gas and, once added to the atmosphere can remain in the atmosphere for hundreds of years.

Adding carbon dioxide (CO₂) or methane (CH₄) to Earth's atmosphere, with no other changes, will make the planet's surface warmer. The concentration of carbon dioxide in the atmosphere, currently 380 ppm, might be naively taken to be too low to have much effect. But the importance of carbon dioxide arises from a feedback effect: a little of the long-term carbon dioxide injected into the atmosphere causes a little warming, which causes a little more of the potent short-term water vapor to be evaporated into the atmosphere, which causes still more warming, which causes more of the potent water vapor to be evaporated, and so forth, until a new dynamic equilibrium concentration of water vapor is reached at a slightly higher humidity and with a much larger greenhouse effect than that due to carbon dioxide alone. This feedback effect is reversed only as the carbon dioxide is slowly removed from the atmosphere.

Another important feedback process is ice-albedo feedback. The increased CO₂ in the atmosphere warms the Earth's surface and leads to melting of ice near the poles. 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.

Feedback effects due to clouds are an area of ongoing research and debate. Seen from below, water aerosol clouds absorb infrared radiation and so exert a warming effect. Seen from above, the same clouds reflect sunlight and so exert a cooling effect. Increased global water vapor concentration may or may not cause an increase in global average cloud cover. The net effect of clouds thus has not been well modeled. Positive feedback due to release of carbon dioxide and methane from thawing permafrost is an additional mechanism contributing to warming. Possible positive feedback due to methane release from melting seabed ices is a further mechanism to be considered.

None of the effects of greenhouse gases are instantaneous. Due to the thermal inertia of the Earth's oceans and slow responses of other indirect effects, the Earth's current climate is not in equilibrium with the forcing imposed by increased greenhouse gases. Climate commitment studies indicate that, even if greenhouse gases were stabilized at present day levels, a further warming of about 0.5 °C (0.9 °F) would still occur.

Contrasting with the consensus view, other hypotheses have been proposed to explain all or most of the observed increase in global temperatures, including: the warming is within the range of natural variation; the warming is a consequence of coming out of a prior cool period, namely the Little Ice Age; the warming is primarily a result of variances in solar radiation; or the warming is primarily the result of increased activity of the solar magnetic field, which increases shielding of the Earth from cosmic rays which would otherwise cause raindrop nucleation in clouds, which would remove greenhouse-gas water vapor from the atmosphere.

Greenhouse gases in the atmosphere

The greenhouse effect was discovered by Joseph Fourier in 1824 and was first investigated quantitatively by Svante Arrhenius in 1896. It is the process by which absorbtion of infrared radiation by atmospheric gases warms a planet's atmosphere and surface.

On Earth, the major natural greenhouse gases are water vapor, which causes about 36–70% of the greenhouse effect (not including clouds); carbon dioxide, which causes 9–26%; methane, which causes 4–9%, and ozone, which causes 3–7%.

The atmospheric concentrations of CO₂ and methane (CH₄) have increased by 31% and 149% respectively above pre-industrial levels since 1750. This is considerably higher than at any time during the last 650,000 years, the period for which reliable data has been extracted from ice cores. From less direct geological evidence it is believed that CO₂ values this high were last attained 20 million years ago. About three-quarters of the anthropogenic (man-made) emissions of CO₂ to the atmosphere during the past 20 years are due to fossil fuel burning. The rest of the anthropogenic emissions are predominantly due to land-use change, especially deforestation.

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, 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 parts per million by the year 2100. Fossil fuel reserves are sufficient to reach this level and continue emissions past 2100, if coal, tar sands or methane clathrates are extensively used.

Carbon dioxide sink ecosystems (forests and oceans) are being degraded by pollutants. Degradation of major carbon sinks results in higher atmospheric CO₂ levels.

Positive feedback effects such as the expected release of methane from the melting of permafrost peat bogs in Siberia (possibly up to 70,000 million tonnes) may lead to significant additional sources of greenhouse gas emissions not included in IPCC's climate models.

Solar variation

Variations in solar output, possibly amplified by cloud feedbacks, have been suggested as a possible cause of recent warming.

A warming of the stratosphere, which has not been observed, would be expected if there were a significant increase in solar activity. The IPCC concludes that phenomena such as solar variation and volcanoes have probably had a warming effect from pre-industrial times to 1950, but a cooling effect since 1950. In 2005, researchers at Duke University have found that 10–30% of the warming over the last two decades may be due to increased solar output. Stott et al. conclude in 2003 that climate models overestimate the relative effect of greenhouse gases compared to other forcings, and that solar forcing may account for 16% or 36% of the recent warming due to the greenhouse effect. They also estimate that climate sensitivity with respect to the cooling effect of volcanic dust and sulfate aerosols has been underestimated, and that the absolute value of greenhouse warming is likely to be even larger than previously assumed.

Climate models

Scientists have studied global warming with computer models of the climate. These models are based on physical principles of fluid dynamics, radiative transfer, and other processes, with some simplifications being necessary because of limitations in computer power. These models predict that the net effect of adding greenhouse gases is to produce a warmer climate. However, even when the same assumptions of fossil fuel consumption and CO₂ emission are used, the amount of predicted warming varies between models and there still remains a considerable range of climate sensitivity.

Including uncertainties in the models and in future greenhouse gas concentrations, the IPCC anticipates a warming of 1.1 °C to 6.4 °C (2.0 °F to 11.5 °F) between 1990 and 2100. Models have also been used to help investigate the causes of recent climate change by comparing the observed changes to those that the models predict from various natural and human derived causes.

Climate models can produce a good match to observations of global temperature changes over the last century. 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.

Most global climate models, when run to predict future climate, are forced by imposed greenhouse gas scenarios, generally one from the IPCC Special Report on Emissions Scenarios (SRES). Less commonly, models may be run by adding a simulation of the carbon cycle; this generally shows a positive feedback, though this response is uncertain (under the A2 SRES scenario, responses vary between an extra 20 and 200 ppm of CO₂). Some observational studies also show a positive feedback.

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

Attributed and expected effects

Some effects on both the natural environment and human life are, at least in part, already being attributed to global warming. A 2001 report by the IPCC suggests that glacier retreat, ice shelf disruption such as the Larsen Ice Shelf, sea level rise, changes in rainfall patterns, increased intensity and frequency of extreme weather events, are being attributed in part to global warming. 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, changes in mountain snowpack, adverse health effects from warmer temperatures, and the spread of disease.

Increasing extreme weather catastrophes are primarily due to an increase in population, and are partly due to increasing severe weather. The World Meteorological Organization said that scientific assessments indicate as global temperatures continue to warm, the number and intensity of extreme events might increase. Hoyos et al. find that the increasing number of category 4 and 5 hurricanes is directly linked to increasing temperatures. Kerry Emmanuel in Nature writes that hurricane power dissipation is highly correlated with temperature, reflecting global warming. Thomas Knutson and Robert E. Tuleya of the NOAA stated in 2004 that warming induced by greenhouse gas may lead to increasing occurrence of highly destructive category-5 storms. A summary of probable effects and recent understanding can be found in the report of the IPCC Working Group II; the newer AR4 summary reports, "There is observational evidence for an increase of intense tropical cyclone activity in the North Atlantic since about 1970, correlated with increases of tropical sea surface temperatures. There are also suggestions of increased intense tropical cyclone activity in some other regions where concerns over data quality are greater. Multi-decadal variability and the quality of the tropical cyclone records prior to routine satellite observations in about 1970 complicate the detection of long-term trends in tropical cyclone activity. There is no clear trend in the annual numbers of tropical cyclones."

Additional anticipated effects include sea level rise of 110 to 770 mm (0.36 to 2.5 feet) by 2100, repercussions to agriculture, possible slowing of the thermohaline circulation, reductions in the ozone layer, increased intensity and frequency of hurricanes and extreme weather events, lowering of ocean pH, and the spread of diseases such as malaria and dengue fever. One study predicts 18 to 35% of a sample of 1,103 animal and plant species would be extinct by 2050, based on future climate projections. Mechanistic studies have documented extinctions due to recent climate change: McLaughlin et al. documented two populations of Bay checkerspot butterfly being threatened by precipitation change. Parmesan states, "Few studies have been conducted at a scale that encompasses an entire species" and McLaughlin et al. agree "few mechanistic studies have linked extinctions to recent climate change."

Two British scientists supporting the mainstream scientific opinion on global warming criticize what they call the "catastrophism and the 'Hollywoodisation'" of some of the expected effects. They argue that sensationalized claims cannot be justified by science.

Economics

In an October, 2006, report entitled the Stern Review by the former Chief Economist and Senior Vice-President of the World Bank, Nicholas Stern, he states that climate change could affect growth which could be cut by one-fifth unless drastic action is taken. Stern has warned that one percent of global GDP is required to be invested in order to mitigate the effects of climate change, and that failure to do so could risk a recession worth up to twenty percent of global GDP. Stern’s report suggests that climate change threatens to be the greatest and widest-ranging market failure ever seen. The report has had significant political effects: Australia reported two days after the report was released that they would allot AU$60 million to projects to help cut greenhouse gas emissions. The Stern Review has been criticized by economists, saying that Stern did not consider costs past 2200, that he used an incorrect discount rate in his calculations, and that stopping or significantly slowing climate change will require deep emission cuts everywhere.

According to a 2005 report from the Association of British Insurers, limiting carbon emissions could avoid 80% of the projected additional annual cost of tropical cyclones by the 2080s. A June 2004 report by the Association of British Insurers declared "Climate change is not a remote issue for future generations to deal with. It is, in various forms, here already, impacting on insurers' businesses now." It noted that weather risks for households and property were already increasing by 2–4 % per year due to changing weather, and that claims for storm and flood damages in the UK had doubled to over £6 billion over the period 1998–2003, compared to the previous five years. The results are rising insurance premiums, and the risk that in some areas flood insurance will become unaffordable for some.

In the U.S., according to Choi and Fisher (2003) each 1% increase in annual precipitation could enlarge catastrophe loss by as much as 2.8%. Financial institutions, including the world's two largest insurance companies, Munich Re and Swiss Re, warned in a 2002 study that "the increasing frequency of severe climatic events, coupled with social trends" could cost almost US$150 billion each year in the next decade. These costs would, through increased costs related to insurance and disaster relief, burden customers, taxpayers, and industry alike.

Many estimates of aggregate net economic costs of damages from climate change across the globe (i.e., the social cost of carbon (SCC), expressed in terms of future net benefits and costs that are discounted to the present) are now available. Peer-reviewed estimates of the SCC for 2005 have an average value of US$43 per tonne of carbon (tC) (i.e., US$12 per tonne of carbon dioxide) but the range around this mean is large. For example, in a survey of 100 estimates, the values ran from US$-10 per tonne of carbon (US$-3 per tonne of carbon dioxide) up to US$350/tC (US$95 per tonne of carbon dioxide.)

Mitigation, adaptation, and the Kyoto Protocol

The broad agreement among climate scientists that global temperatures will continue to increase has led nations, states, corporations and individuals to implement actions to try to curtail global warming. Many environmental groups encourage individual action against global warming, often aimed at the consumer, and there has been business action on climate change. The world's primary international agreement on combating global warming is the Kyoto Protocol, an amendment to the United Nations Framework Convention on Climate Change (UNFCCC).

History

Pre-human global warming

The earth has experienced natural global warming and cooling many times in the past. The recent Antarctic EPICA ice core spans 800,000 years, including eight glacial cycles with interglacial warming periods much hotter than current temperatures. The chart also shows the time of the last glacial maximum about 20,000 years ago.

A rapid buildup of greenhouse gases caused the Earth to experience global warming in the early Jurassic period, with average temperatures rising by 5 °C (9.0 °F). Research by the Open University indicates that this caused the rate of rock weathering to increase by 400%. As such weathering locks away carbon in calcite and dolomite, CO₂ levels dropped back to normal over roughly the next 150,000 years.

Sudden releases of methane from clathrate compounds (the clathrate gun hypothesis) have been hypothesized as a cause for other past global warming events, including the Permian-Triassic extinction event and the Paleocene-Eocene Thermal Maximum. However, warming at the end of the last glacial period is thought not to be due to methane release. Instead, natural variations in the Earth's orbit (Milankovitch cycles) are believed to have triggered the retreat of ice sheets by changing the amount of solar radiation received at high latitude and led to deglaciation.

Using paleoclimate data for the last 500 million years, Veizer et al. concluded that long-term temperature variations are only weakly related to CO₂ variations. Most paleoclimatologists believe this is because other factors, such as continental drift and mountain building have larger effects in determining very long-term climate. Shaviv and Veizer (2003) proposed that the largest long-term influence on temperature are variations in the flux of cosmic rays received by the Earth as the Solar System moves around the galaxy. They argued that over geologic time-scales a change in CO₂ concentrations comparable to doubling pre-industrial levels results in about 0.75 °C (1.35 °F) warming, less than the 1.5–4.5 °C (2.7–8.1 °F) reported by climate models. Shaviv and Veizer (2004) acknowledge that this conclusion may only be valid on multi-million year time scales when glacial and geological feedback have had a chance to establish themselves. Rahmstorf et al. argue that Shaviv and Veizer arbitrarily tuned their data, and that their conclusions are unreliable.

Pre-industrial global warming

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. He contends that forest clearing explains the rise in CO₂ levels in the current interglacial that started 8,000 years ago, contrasting with the decline in CO₂ levels seen in the previous three interglacials. He further contends that the spread of rice irrigation explains the breakdown in the last 5,000 years of the correlation between the Northern Hemisphere solar radiation and global methane levels, which had been maintained over at least the last eleven 22,000-year cycles. Ruddiman argues that without these effects, the Earth would be nearly 2 °C (3.6 °F) cooler and "well on the way" to a new ice age. Ruddiman's interpretation of the historical record, with respect to the methane data, has been disputed.

Past 200 years

In the past 200 years human industrial activity has injected carbon dioxide and other greenhouse gases into the atmosphere, and recently global average temperatures have been increasing. The scientific consensus is that these greenhouse gases have been responsible for most of the present warming trend. That consensus is not unanimous.

Global temperatures on both land and sea have increased by 0.75 °C (1.4 °F) relative to the period 1860–1900, according to the instrumental temperature record. This measured temperature increase is not significantly affected by the urban heat island. Since 1979, land temperatures have increased about twice as fast as ocean temperatures (0.25 °C/decade against 0.13 °C/decade). Temperatures in the lower troposphere have increased between 0.12 and 0.22 °C (0.22 and 0.4 °F) per decade since 1979, according to satellite temperature measurements. Temperature is believed to have been relatively stable over the one or two thousand years before 1850, with possibly regional fluctuations such as the Medieval Warm Period or the Little Ice Age.

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. Estimates prepared by the World Meteorological Organization and the Climatic Research Unit concluded that 2005 was the second warmest year, behind 1998.

Anthropogenic emissions of other pollutants—notably sulfate aerosols—can exert a cooling effect by increasing the reflection of incoming sunlight. This partially accounts for the cooling seen in the temperature record in the middle of the twentieth century, though the cooling may also be due in part to natural variability.

Controversy and politics

The scientific findings surrounding global warming have led to the involvement of politicians, energy industry funding of critics and skeptical politicians, participation by environmental groups, and active discussions by pundit and media personalities over the cause, effects, and mitigations. Governments have taken stances, often widely divergent at national and local levels (such as the U.S.). Fossil fuel companies have spent large sums of money for public relations to downplay its importance. Environmental groups have launched far-reaching campaigns.

Related issues

Ocean acidification

Increased atmospheric CO₂ increases the amount of CO₂ dissolved in the oceans. Carbon dioxide gas dissolved in the ocean reacts with water to form carbonic acid resulting in ocean acidification. Since biosystems are adapted to a narrow range of pH, this is a serious concern directly driven by increased atmospheric CO₂.

Global dimming

Scientists have stated with 66-90% confidence that the effects of volcanic and human-caused aerosols have offset some of global warming, and that greenhouse gases would have resulted in more warming than observed if not for this effect.

Ozone

Although global warming and ozone depletion often are linked in the media, the relationship between the two is not strong.

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53. Schmidt, Gavin (2004). "A note on the relationship between ice core methane concentrations and insolation". Geophysical Research Letters. 31. doi:10.1029/2004GL021083. ISSN 0094-8276. L23206. Retrieved 2007-03-05. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
54. Smith, Thomas M. (2005-05-15). "A Global Merged Land–Air–Sea Surface Temperature Reconstruction Based on Historical Observations (1880–1997)" (PDF). Journal of climate. 18 (12). American Meteorological Society: 2021–2036. ISSN 0894-8755. Retrieved 2007-03-14. {{cite journal}}: Check date values in: |date= (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)
55. "Goddard Institute for Space Studies, GISS Surface Temperature Analysis". NASA Goddard Institute for Space Studies. 2006-01-12. Retrieved 2007-01-17. {{cite web}}: Check date values in: |date= (help)
56. "The December Press Release 2005" (Word). Climactic Research Unit, School of Environmental Sciences, University of East Anglia. 2005-12-15. Retrieved 2007-04-13. {{cite web}}: Check date values in: |date= (help)
57. "WMO STATEMENT ON THE STATUS OF THE GLOBAL CLIMATE IN 2005". World Meteorological Organization. 2005-12-15. Retrieved 2007-04-13. {{cite web}}: Check date values in: |date= (help)
58. "Climate Change 2001: Working Group I: The Scientific Basis, Chapter 12.4.3.3". Intergovernmental Panel on Climate Change. 2001. Retrieved 2007-01-04. {{cite web}}: Check date values in: |year= (help)CS1 maint: year (link)
59. "The Ocean and the Carbon Cycle". NASA Oceanography (science@nasa). 2005-06-21. Retrieved 2007-03-04. {{cite web}}: External link in |work= (help)

Further reading

• Amstrup, Steven C. (2006-04-27). "Recent observations of intraspecific predation and cannibalism among polar bears in the southern Beaufort Sea". 29 (11): 997–1002. doi:10.1007/s00300-006-0142-5. {{cite journal}}: Cite journal requires |journal= (help); Unknown parameter |Journal= ignored (|journal= suggested) (help)
• Association of British Insurers (2005-06). Financial Risks of Climate Change (PDF). {{cite book}}: Check date values in: |year= (help)
• Barnett, Tim P. (2005-11-17). "Potential impacts of a warming climate on water availability in snow-dominated regions". Nature. 438 (7066): 303–309. doi:10.1038/nature04141. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
• Behrenfeld, Michael J. (2006-12-07). "Climate-driven trends in contemporary ocean productivity" (PDF). Nature. 444 (7120): 752-755. doi:10.1038/nature05317. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
• Choi, Onelack (2005-05). "The Impacts of Socioeconomic Development and Climate Change on Severe Weather Catastrophe Losses: Mid-Atlantic Region (MAR) and the U.S." Climate Change. 58: 149–170. doi:10.1023/A:1023459216609. {{cite journal}}: Check date values in: |date= (help); Unknown parameter |coauthors= ignored (|author= suggested) (help); Unknown parameter |issu e= ignored (help)
• Dyurgerov, Mark B. (2005). Glaciers and the Changing Earth System: a 2004 Snapshot (PDF). Institute of Arctic and Alpine Research Occasional Paper #58. ISSN 0069-6145. {{cite book}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
• Emanuel, Kerry A. (2005-08-04). "Increasing destructiveness of tropical cyclones over the past 30 years" (PDF). Nature. 436 (7051): 686–688. doi:10.1038/nature03906.
• Hansen, James (2005-06-03). "Earth's Energy Imbalance: Confirmation and Implications" (PDF). Science. 308 (5727): 1431–1435. doi:10.1126/science.1110252. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
• Hinrichs, Kai-Uwe (2003-02-21). "Molecular Fossil Record of Elevated Methane Levels in Late Pleistocene Coastal Waters". Science. 299 (5610): 1214–1217. doi:10.1126/science.1079601. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
• Hirsch, Time (2006-01-11). "Plants revealed as methane source". BBC.
• Hoyt, Douglas V. (1993-11). "A discussion of plausible solar irradiance variations, 1700–1992". Journal of Geophysical Research. 98 (A11): 18, 895–18, 906. {{cite journal}}: Check date values in: |year= (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)
• Kenneth, James P. (2003-02-14). Methane Hydrates in Quaternary Climate Change: The Clathrate Gun Hypothesis. American Geophysical Union. {{cite book}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)CS1 maint: year (link)
• Keppler, Frank (2006-01-18). "Global Warming - The Blame Is not with the Plants". Max Planck Society. {{cite news}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
• Kurzweil, Raymond (2006-07). "Nanotech Could Give Global Warming a Big Chill" (PDF). Forbes / Wolfe Nanotech Report. 5 (7). {{cite journal}}: Check date values in: |year= (help)
• Lean, Judith L. (2002-12). "The effect of increasing solar activity on the Sun's total and open magnetic flux during multiple cycles: Implications for solar forcing of climate". Geophysical Research Letters. 29 (24). doi:10.1029/2002GL015880. {{cite journal}}: Check date values in: |year= (help); Cite has empty unknown parameter: |1= (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)
• Lerner, K. Lee (2006-07-26). Environmental issues : essential primary sources. Thomson Gale. ISBN 1414406258. {{cite book}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
• McLaughlin, Joseph B. (2005-10-06). "Outbreak of Vibrio parahaemolyticus gastroenteritis associated with Alaskan oysters". New England Journal of Medicine. 353 (14). New England Medical Society: 1463–1470. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)(online version requires registration)
• Muscheler, Raimund (2005-07-28). "Climate: How unusual is today's solar activity?" (PDF). Nature. 436 (7012): 1084–1087. doi:10.1038/nature04045. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
• Oerlemans, J. (2005-04-29). "Extracting a Climate Signal from 169 Glacier Records" (PDF). Science. 308 (5722): 675–677. doi:10.1126/science.1107046.
• Oreskes, Naomi (2004-12-03). "Beyond the Ivory Tower: The Scientific Consensus on Climate Change" (PDF). Science. 306 (5702): 1686. doi:10.1126/science.1103618.
• Purse, Bethan V. (2005-02). "Climate change and the recent emergence of bluetongue in Europe". Nature Reviews Microbiology. 3 (2): 171–181. doi:10.1038/nrmicro1090. {{cite journal}}: Check date values in: |date= (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)
• Revkin, Andrew C (2005-11-05). "Rise in Gases Unmatched by a History in Ancient Ice". The New York Times.
• Ruddiman, William F. (2005-12-15). Earth's Climate Past and Future. New York: Princeton University Press. ISBN 0-7167-3741-8.
• Ruddiman, William F. (2005-08-01). Plows, Plagues, and Petroleum: How Humans Took Control of Climate. New Jersey: Princeton University Press. ISBN 0-691-12164-8.
• Smith, Thomas M. (2005-06). "A Global Merged Land-Air-Sea Surface Temperature Reconstruction Based on Historical Observations (1880-1997)". Journal of Climate. 18 (12): 2021–2036. {{cite journal}}: Check date values in: |year= (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)
• Solanki, Sami K. (2004-10-23). "Unusual activity of the Sun during recent decades compared to the previous 11,000 years" (PDF). Nature. 431: 1084–1087. doi:10.1038/nature02995. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
• Solanki, Sami K. (2005-07-28). "Climate: How unusual is today's solar activity? (Reply)" (PDF). Nature. 436: E4 – E5. doi:10.1038/nature04046. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
• Sowers, Todd (2006-02-10). "Late Quaternary Atmospheric CH₄ Isotope Record Suggests Marine Clathrates Are Stable". Science. 311 (5762): 838–840. doi:10.1126/science.1121235.
• Svensmark, Henrik (2007-02-08). "Experimental evidence for the role of ions in particle nucleation under atmospheric conditions". Proceedings of the Royal Society A. 463 (2078). FirstCite Early Online Publishing: 385–396. doi:10.1098/rspa.2006.1773. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)CS1 maint: year (link)(online version requires registration)
• "Climate risk to global economy" (PDF). UNEP Financial Initiative. 2002.
• Walter, K. M. (2006-09-07). "Methane bubbling from Siberian thaw lakes as a positive feedback to climate warming". Nature. 443 (7107): 71–75. doi:10.1038/nature05040. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
• Wang, Y.-M. (2005-05-20). "Modeling the sun's magnetic field and irradiance since 1713" (PDF). Astrophysical Journal. 625: 522–538. doi:10.1086/429689. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)

See also

External links

Scientific

• Intergovernmental Panel on Climate Change (IPCC)
• NOAA's Global Warming FAQ
• Discovery of Global Warming – An extensive introduction to the topic and the history of its discovery
• Max Planck Society: Global Warming - The Blame Is not with the Plants
• Caution urged on climate 'risks'
• NASA Finds Sun-Climate Connection in Old Nile Records, March 19, 2007

Educational

• The EdGCM (Educational Global Climate Modelling) Project free research-quality simulation for students, educators, and scientists alike, with a user-friendly interface that runs on desktop computers
• Daily global temperatures and trends from satellites Interactive graphics -- Nasa

Other

• UN: rearing cattle produces more greenhouse gases than driving cars
• Trends in Atmospheric Carbon Dioxide - Mauna Loa
• Science and Technology Librarianship: Global Warming and Climate Change Science – Extensive commented list of Internet resources – Science and Technology Sources on the Internet.
• 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
• Summary by "Physicians and Scientists for Responsible Application of Science and Technology"
• Newest reports on US EPA website
• IPS Inter Press Service – Independent news on global warming and its consequences.
• An online magazine discussing topics associated with global warming.
• Boffey, Philip (July 4 2006). "Talking Points: The Evidence for Global Warming". New York Times. {{cite news}}: Check date values in: |date= (help); Cite has empty unknown parameter: |coauthors= (help)
• Borenstein, Saul (August 2 2006). "Hot Summer Nights Getting Hotter". LiveScience.com. Retrieved 2006-08-06. {{cite news}}: Check date values in: |date= (help)

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• Climate change feedbacks and causes
• History of climate
• Global warming