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| == '''[[Global warming]]''' ==
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| ''by [[User:Gareth Leng|Gareth Leng]], [[User:Raymond Arritt|Raymond Arritt]], [[User:Robert Badgett|Robert Badgett]], [[User:Milton Beychok|Milton Beychok]], [[User:Greg Harris|Greg Harris]], [[User:Ed Poor|Ed Poor]], [[User:Nereo Preto|Nereo Preto]], [[User:Anthony Sebastian|Anthony Sebastian]], [[User:Benjamin Seghers|Benjamin Seghers]], and [[User:Paul Wormer|Paul Wormer]] <small>(and [[User:David Finn|David Finn]], [[User:Larry Sanger|Larry Sanger]], and [[User:John Stephenson|John Stephenson]])</small>''
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| | ==Footnotes== |
| [[Image:105582main GlobalWarming 2060 lg.jpg|right|thumb|Annual average global warming by the year 2060 simulated and plotted as color differences using EdGCM|250px]]
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| '''[[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.
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| Global average air temperature near the Earth's surface rose by 0.74 ± 0.18 °[[Celsius|C]] (1.33 ± 0.32 °F) from 1906 to 2005. The prevailing scientific view,
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| <ref name = Doran>See [http://tigger.uic.edu/~pdoran/012009_Doran_final.pdf Doran (2009)] 'Examining the Scientific Consensus
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| 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</ref> as represented by the science academies of the major industrialized nations<ref name = "academies">[http://nationalacademies.org/onpi/06072005.pdf Joint science academies’ statement: Global response to climate change]
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| *"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."</ref>
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| and the ''[http://www.ipcc.ch/ Intergovernmental Panel on Climate Change]'',<ref name=grida7>{{cite web | url=http://www.ipcc.ch/publications_and_data/ar4/wg1/en/spm.html|title=Summary for Policymakers|work=Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change|date=2007}}
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| *"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" </ref> 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.<ref name=grida7/> 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.<ref name=grida7/>
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| 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] (CO<sub>2</sub>),”<ref name=walker2007>Walker G (2007) [http://dx.doi.org/10.1038/446718a Climate Change 2007: A world melting from the top down] ''Nature'' 446:718-21</ref> possibly as much as 25 times that of CO<sub>2</sub> per unit mass.<ref name=simpson2009>Simpson (2009) [http://www.ScientificAmerican.com/Earth3 "The Peril Below the Ice"] ''Scientific American Earth 3.0'' pp 30-7</ref>
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| 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.<ref>[http://www.ipcc.ch/publications_and_data/ar4/wg2/en/ch19s19-3-6.html Schneider ''et al.'' (2007)]. [http://www.ipcc.ch/publications_and_data/ar4/wg2/en/ch19.html Assessing key vulnerabilities and the risk from climate change]. In Parry ML ''et al.'' (eds) ''[http://www.ipcc.ch/publications_and_data/ar4/wg2/en/contents.html 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
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| *"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).
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| *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).
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| *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." </ref> 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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| ''[[Global warming|.... (read more)]]''
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| === [[Global warming/References|notes]] ===
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| {{reflist|2}} | | {{reflist|2}} |
| | </small> |
Nuclear weapons proliferation is one of the four big issues that have held back worldwide deployment of peaceful nuclear power. This article will address the proliferation questions raised in Nuclear power reconsidered.
As of 2022, countries with nuclear weapons have followed one or both of two paths in producing fissile materials for nuclear weapons: enrichment of uranium to very high fractions of U-235, or extraction of fissile plutonium (Pu-239) from irradiated uranium nuclear reactor fuel. The US forged the way on both paths during its World War II Manhattan Project. The fundamental aspects of both paths are well understood, but both are technically challenging. Even relatively poor countries can be successful if they have sufficient motivation, financial investment, and, in some cases, direct or illicit assistance from more technologically advanced countries.
The International Non-proliferation Regime
The International Atomic Energy Agency (IAEA) has a vigorous program to prevent additional countries from acquiring nuclear weapons. The Treaty on the Non-Proliferation of Nuclear Weapons (NPT) is the cornerstone arrangement under which strategic rivals can trust, by independent international verification, that their rivals are not developing a nuclear weapons threat. The large expense of weapons programs makes it very unlikely that a country would start its own nuclear weapons program, if it knows that its rivals are not so engaged. With some notable and worrying exceptions, this program has been largely successful.
Paths to the Bomb
It is frequently claimed that building a civil nuclear power program adds to the weapons proliferation risk. There is an overlap in the two distinct technologies, after all. To build a bomb, one needs Highly Enriched Uranium (HEU) or weapons-grade plutonium (Pu-239).
Existing reactors running on Low Enriched Uranium (LEU, under 5% U-235) or advanced reactors running on High Assay LEU (HALEU,up to 20% U-235) use the same technology that can enrich uranium to very high levels, but configured differently. Enrichment levels and centrifuge configurations can be monitored using remote cameras, on-site inspections, and installed instrumentation -- hence the value of international inspections by the IAEA. Using commercial power reactors as a weapons plutonium source is an extremely ineffective, slow, expensive, and easily detectable way to produce Pu. Besides the nuclear physics issues, refueling pressurized water reactors is both time-consuming and obvious to outside observers. That is why the US and other countries developed specialized Pu production reactors and/or uranium enrichment to produce fissile cores for nuclear weapons.
Future Threats and Barriers
Minimizing the risk of future proliferation in states that want to buy nuclear reactors or fuel might require one or more barriers:
1) Insisting on full transparency for all nuclear activities in buyer states, including monitoring and inspections by the International Atomic Energy Agency (IAEA).
2) Limiting fuel processing to just a few supplier states that already have weapons or are approved by the IAEA.
3) Ensuring that fuel at any stage after initial fabrication has an isotopic composition unsuitable for weapons. "Spiking" the initial fuel with non-fissile isotopes, if necessary.
4) Limiting the types of reactors deployed to buyer states. In general, breeders are less secure than burners. Sealed reactor modules are more secure than reactors with on-site fuel processing.
5) Providing incentives and assurances for buyer states to go along with all of the above.
6) Application of diplomatic pressure, sanctions, and other economic measures to non-compliant states.
7) Agreement that any reactor declared rogue by the IAEA will be "fair game" for any state feeling threatened.