< CZ:Featured articleRevision as of 19:19, 27 November 2011 by imported>Anthony.Sebastian
by Gareth Leng, Raymond Arritt, Robert Badgett, Nereo Preto, Anthony.Sebastian, and Benjamin Seghers (and Milton Beychok, David Finn, Greg Harris, Ed Poor, Larry Sanger, John Stephenson and Paul Wormer)
Annual average global warming by the year 2060 simulated and plotted as color differences using EdGCM
Global warming is the increase in the average temperature of the Earth's near-surface air and oceans in recent decades and its projected continuation. There is strong evidence that significant global warming is occurring; this evidence comes from direct measurements of rising surface air temperatures and subsurface ocean temperatures and from phenomena such as increases in average global sea levels, retreating glaciers, and changes to many physical and biological systems. It is likely that most of the warming in recent decades is attributable to human activity, particularly the burning of fossil fuels and deforestation.
Global average air temperature near the Earth's surface rose by 0.74 ± 0.18 °C (1.33 ± 0.32 °F) from 1906 to 2005. The prevailing scientific view, [1] as represented by the science academies of the major industrialized nations[2]
and the Intergovernmental Panel on Climate Change,[3] it is very likely that most of the temperature increase since the mid-20th century has been caused by increases in atmospheric greenhouse gas concentrations produced by human activity. Climate models predict that average global surface temperatures will increase by a further 1.1 to 6.4 °C (2.0 to 11.5 °F) by the end of the century, relative to 1980–1999.[3] The range of values reflects differing assumptions of future greenhouse gas emissions and results of models that differ in their sensitivity to increases in greenhouse gases.[3]
Scientists have not yet quantitatively assessed the potential self-accelerating effects of global-warming itself, either on threshold or rate. Melting of permafrost, for example, causes increased production and atmospheric release of such newly produced as well as anciently stored methane gas, which “….packs a far greater warming punch than [carbon dioxide] (CO2),”[4] possibly as much as 25 times that of CO2 per unit mass.[5]
An increase in global temperatures will cause the sea level to rise, glaciers to retreat, sea ice to melt, and changes in the amount, geographical distribution and seasonal pattern of precipitation. There may also be changes in the frequency and intensity of extreme weather events. These will have many practical consequences, including changes in agricultural yields and impacts on human health.[6] Scientific uncertainties include the extent of climate change expected in the future, and how changes will vary around the globe. There is political and public debate about what action should be taken to reduce future warming or to adapt to its consequences. The Kyoto Protocol, an international agreement aimed at reducing greenhouse gas emissions, was adopted by 169 nations.
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- ↑ See Doran (2009) 'Examining the Scientific Consensus
on Climate Change' for information on a poll of research-active climate scientists, other researchers and the public regarding the scientific consensus on global warming Eos 90: 21-2
- ↑ Joint science academies’ statement: Global response to climate change
- "There will always be uncertainty in understanding a system as complex as the world’s climate. However there is now strong evidence that significant global warming is occurring. The evidence comes from direct measurements of rising surface air temperatures and subsurface ocean temperatures and from phenomena such as increases in average global sea levels, retreating glaciers, and changes to many physical and biological systems. It is likely that most of the warming in recent decades can be attributed to human activities (IPCC 2001). This warming has already led to changes in the Earth's climate."
- ↑ 3.0 3.1 3.2 Summary for Policymakers. Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (2007).
- "Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations...Discernible human influences now extend to other aspects of climate, including ocean warming, continental-average temperatures, temperature extremes and wind patterns"
- ↑ Walker G (2007) Climate Change 2007: A world melting from the top down Nature 446:718-21
- ↑ Simpson (2009) "The Peril Below the Ice" Scientific American Earth 3.0 pp 30-7
- ↑ Schneider et al. (2007). Assessing key vulnerabilities and the risk from climate change. In Parry ML et al. (eds) Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change Cambridge University Press pp 779-810
- "There is new and stronger evidence of observed impacts of climate change on unique and vulnerable systems (such as polar and high-mountain communities and ecosystems), with increasing levels of adverse impacts as temperatures increase (very high confidence).
- There is new evidence that observed climate change is likely to have already increased the risk of certain extreme events such as heatwaves, and it is more likely than not that warming has contributed to the intensification of some tropical cyclones, with increasing levels of adverse impacts as temperatures increase (very high confidence).
- The distribution of impacts and vulnerabilities is still considered to be uneven, and low-latitude, less-developed areas are generally at greatest risk due to both higher sensitivity and lower adaptive capacity; but there is new evidence that vulnerability to climate change is also highly variable within countries, including developed countries."
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