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User:Towerman/translation/政府间气候变化专门委员会第四次评估报告

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政府间气候变化专门委员会第四次评估报告是政府间气候变化专门委员会（IPCC）针对气候变化及其影响的第四个综合评估报告。该报告的全名是《气候变化2007：联合国政府间气候变化专门委员会第四次评估报告》（Climate Change 2007, the Fourth Assessment Report (AR4) of the United Nations Intergovernmental Panel on Climate Change），因此常被简称“IPCC第四次评估报告”，或“气候变化2007”报告，或“AR4”报告。IPCC的任务是对全球范围内有关气候变化及其影响、气候变化减缓和适应措施的科学、技术、社会、经济方面的信息进行评估，并根据需求为《联合国气候变化框架公约》（UNFCCC）实施提供科学技术咨询。作为IPCC的主要工作，此前于1990年、1995年和2001年，IPCC已经相继完成了三次评估报告，下一份报告计划于2014年出版。IPCC不直接评估政策问题，但所评估的科学问题均与政策相关。此次发布的评估报告，在吸纳了此前开展的各项评估以及过去6年最新科研成果的基础上，阐述了当前对气候变化主要原因、气候变化观测事实、气候的多种过程和归因以及一系列未来气候变化预估结果的科学认识水平[1]。该报告是迄今以来有关气候变化的最长和最详细的总结，来自几十个国家的上千名专家参与了该报告的写作，编辑和评审等工作，报告共引用了6000多篇同行评议的科学文献。报告已成为国际社会认识和了解气候变化问题的主要科学依据，对气候变化国际谈判产生了重要影响。该报告的首要发现或结论是：“气候系统正在变暖是毫不含糊的（unequivocal）[2]”，以及“自20世纪中期以来所观测到的全球平均气温的上升非常可能（very likely）是由于观测到的人为温室气体排放的增加造成的”[3]。尽管该报告是全世界大多数科学家对气候变化的共识，但还是有一些批评意见出现[4]。

概况

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IPCC第四次评估报告共有四个部分，于2007年不同时间分别发行[5]。前三个部分是IPCC的三个工作小组对不同议题的分别报告，第四个报告是一个总结报告。这四个报告为：

  • 第一工作组报告（WGI）：《气候变化2007: 科学基础》
  • 第二工作组报告（WGII）：《气候变化2007: 影响、适应性和脆弱性》
  • 第三工作组报告（WGIII）：《气候变化2007: 减缓气候变化》
  • 综合报告（SYR）：《气候变化2007: 综合报告》

每个报告又由两大部分组成：决策者摘要和主报告。

第一工作组报告（WGI）：科学基础

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使用第四次评估报告中的四个SRES（英语：Special Report on Emissions Scenarios）排放方案[6][7][8]得到的相应的全球平均地面温度在2100年的预测值
AR4
(决策者摘要; PDF)
更多的经济考虑
更多的环境考虑
全球化
（同一化的世界） 		A1
快速的经济发展
（分组：A1T；A1B；A1Fl）
1.4～6.4 °C 		B1
全球环境可持续性 
1.1～2.9 °C
区域化
（多样化的世界） 		A2
区域定向的经济发展
2.0～5.4 °C 		B2
本地的环境可持续性
1.4～3.8 °C

第一工作组的决策者摘要（SPM）[9]于2007年2月2日出版，2007年2月5日再版。完整的第一工作组报告[10]于3月出版，9月5日最后一次更新。一份34页长的“常见问题”文档[11]也已经被提供。

第一工作组的报告（《气候变化2007：科学基础》）“评估了有关气候变化的人为和自然驱动力、观测到的气候变化、将这些变化归因到不同原因的能力、预测未来的气候变化等方面的当前科学认识”。

有来自40个国家的大约600名作者（英语：List of authors of Climate Change 2007: The Physical Science Basis）合作写出了这个报告。超过620个专家或政府审阅了该报告。报告引用了超过6000份科学文献[12]。

正式通过该报告之前，在法国巴黎于1月29日到2月1日召开了第一工作组的第10次工作会议。在这次会议上，来自113个国家的代表逐行审议了该报告的决策者摘要。[13]

对于全球变暖及其原因，该摘要（SPM）认为：[9]

  • “气候系统的变暖是毫无疑问的。”
  • “自20世纪中期以来，绝大部分被观测到的全球平均地面温度的升高非常可能是因为观测到的人为排放的温室气体的浓度增加而引起的。”

该摘要在第3页的脚注6解释，非常可能和可能分别意味着“通过专家们的判断，被评估的可能性”是90%和66%以上。

观测

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这份报告提到了许多观测到的地球气候系统的变化，包括有大气成分，全球平均温度，海洋状况，以及其他气候变化。

大气的变化

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二氧化碳，甲烷和氧化亚氮都是长寿命的温室气体。

  • “由于1750年以来的人类活动，二氧化碳、甲烷以及氧化亚氮已经显著的增加，并远远超过工业化前的水平。”
  • 2005年二氧化碳在大气中的含量已经超过了(379 ppm)，这个值已经高于最近650,000年来的自然变动范围（180－300ppm）。
  • 2005年大气中的甲烷含量（1774ppb）已经远远超过最近65万年的自然变化范围（320～790ppb）。
  • 二氧化碳增加的首要来源是化石燃料，但土地利用的变化也是很大的原因。
  • 甲烷增加的首要来源非常可能是人类农业活动和使用化石燃料。但每个因素具体贡献多少甲烷增加还没有很确定的数字。
  • 氧化亚氮的浓度已经由工业化以前的270ppb上升到319ppb（2005年）。至少三分之一的甲烷增加是因为人类活动，其中农业活动又占到首位。

地球变暖

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冷天已经变得少些了，热天和热浪出现的跟频繁了。另外：

  • 在最近的12年里（1995至2006年），有11年的都排在仪器测量到的温度记录（自1880年）里的最热的12个年份里。
  • 最近100年来的变暖以经使得全球平均气温上升了大约0.74°C。第三次气候评估报告（AR3）估计的100年里增加的温度还只是0.6°C。
  • 热岛效应已经被证明对全球平均气温的影响十分微小（平均每10年造成陆地升温少于0.0006°C，对海洋的影响为0）。
  • 自1961年以来的观测记录显示，加入气候系统的热量中超过80%的部分被海洋吸收。海洋温度的上升已经使得海洋深度达到至少3000米（9800英尺）。
  • “北极的平均气温在过去100年里的上升速度是全球气温上升速度的大致2倍。”
  • 如果没有火山喷发及人为产生的气溶胶的冷却效应，排放的温室气体可能会造成更大的升温。（参见全球黯化）
  • 20世纪后50年的北半球平均气温很有可能比过去500年来其他任意一个50年的气温都高，甚至有可能是至少过去1300年（接近小冰期的开始）来最高的。

Ice, snow, permafrost, rain, and the oceans

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The SPM documents increases in wind intensity, decline of permafrost coverage, and increases of both drought and heavy precipitation events. Additionally:

  • "Mountain glaciers and snow cover have declined on average in both hemispheres."
  • Losses from the land-based ice sheets of Greenland and Antarctica have very likely (>90%) contributed to sea level rise between 1993 and 2003.
  • Ocean warming causes seawater to expand, which contributes to sea level rising.
  • Sea level rose at an average rate of about 1.8 mm/year during the years 1961-2003. The rise in sea level during 1993-2003 was at an average rate of 3.1 mm/year. It is not clear whether this is a long-term trend or just variability.
  • Antarctic sea ice shows no significant overall trend, consistent with a lack of warming in that region.

飓风

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  • There has been an increase in hurricane intensity in the North Atlantic since the 1970s, and that increase correlates with increases in sea surface temperature.
  • The observed increase in hurricane intensity is larger than climate models predict for the sea surface temperature changes we have experienced.
  • There is no clear trend in the number of hurricanes.
  • Other regions appear to have experienced increased hurricane intensity as well, but there are concerns about the quality of data in these other regions.
  • It is more likely than not (>50%) that there has been some human contribution to the increases in hurricane intensity.
  • It is likely (>66%) that we will see increases in hurricane intensity during the 21st century.

Table SPM-2 lists recent trends along with certainty levels for the trend having actually occurred, for a human contribution to the trend, and for the trend occurring in the future. In relation to changes (including increased hurricane intensity) where the certainty of a human contribution is stated as "more likely than not" footnote f to table SPM-2 notes "Magnitude of anthropogenic contributions not assessed. Attribution for these phenomena based on expert judgment rather than formal attribution studies."

使地球变暖或变冷的因素

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Changes in radiative forcings between 1750 and 2005 as estimated by the IPCC.

AR4 describes warming and cooling effects on the planet in terms of radiative forcing — the rate of change of energy in the system, measured as power per unit area (in SI units, W/m²). The report shows in detail the individual warming contributions (positive forcing) of carbon dioxide, methane, nitrous oxide, halocarbons, other human warming factors, and the warming effects of changes in solar activity. Also shown are the cooling effects (negative forcing) of aerosols, land-use changes, and other human activities. All values are shown as a change from pre-industrial conditions.

  • Total radiative forcing from the sum of all human activities is a warming force of about +1.6 watts/m²
  • Radiative forcing from an increase of solar intensity since 1750 is about +0.12 watts/m²
  • Radiative forcing from carbon dioxide, methane, and nitrous oxide combined is very likely (>90%) increasing more quickly during the current era (1750-present) than at any other time in the last 10,000 years.

Climate sensitivity

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Climate sensitivity is defined as the amount of global average surface warming following a doubling of carbon dioxide concentrations. It is likely to be in the range of 2 to 4.5 °C, with a best estimate of about 3 °C. This range of values is not a projection of the temperature rise we will see in the 21st century, since the future change in carbon dioxide concentrations is unknown, and factors besides carbon dioxide concentrations affect temperature.

Model-based projections for the future

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Model projections are made based on an analysis of various computer climate models running within different SRES scenarios. As a result, predictions for the 21st century are as shown below.

  • Surface air warming in the 21st century:
    • Best estimate for a "low scenario"[14] is 1.8 °C with a likely range of 1.1 to 2.9 °C (3.2 °F with a likely range of 2.0 to 5.2 °F)
    • Best estimate for a "high scenario"[15] is 4.0 °C with a likely range of 2.4 to 6.4 °C (7.2 °F with a likely range of 4.3 to 11.5 °F)
    • A temperature rise of about 0.1 °C per decade would be expected for the next two decades, even if greenhouse gas and aerosol concentrations were kept at year 2000 levels.
    • A temperature rise of about 0.2 °C per decade is projected for the next two decades for all SRES scenarios.
    • Confidence in these near-term projections is strengthened because of the agreement between past model projections and actual observed temperature increases.
  • Based on multiple models that all exclude ice sheet flow due to a lack of basis in published literature,[16] it is estimated that sea level rise will be:
    • in a low scenario[14] 18 to 38 cm (7 to 15 inches)
    • in a high scenario[15] 26 to 59 cm (10 to 23 inches)
  • It is very likely that there will be an increase in frequency of warm spells, heat waves and events of heavy rainfall.
  • It is likely that there will be an increase in areas affected by droughts, intensity of tropical cyclones (which include hurricanes and typhoons) and the occurrence of extreme high tides.
  • "Sea ice is projected to shrink in both the Arctic and Antarctic … In some projections, Arctic late-summer sea ice disappears almost entirely by the latter part of the 21st century."

Scenario-specific projections are based on analysis of multiple runs by multiple climate models, using the various SRES Scenarios. "Low scenario" refers to B1, the most optimistic scenario family. "High scenario" refers to A1FI, the most pessimistic scenario family.

Temperature and sea level rise for each SRES scenario family

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There are six families of SRES Scenarios, and AR4 provides projected temperature and sea level rises for each scenario family.

  • Scenario B1
    • Best estimate temperature rise of 1.8 °C with a likely range of 1.1 to 2.9 °C (3.2 °F with a likely range of 2.0 to 5.2 °F)
    • Sea level rise likely range [18 to 38 cm] (7 to 15 inches)
  • Scenario A1T
    • Best estimate temperature rise of 2.4 °C with a likely range of 1.4 to 3.8 °C (4.3 °F with a likely range of 2.5 to 6.8 °F)
    • Sea level rise likely range [20 to 45 cm] (8 to 18 inches)
  • Scenario B2
    • Best estimate temperature rise of 2.4 °C with a likely range of 1.4 to 3.8 °C (4.3 °F with a likely range of 2.5 to 6.8 °F)
    • Sea level rise likely range [20 to 43 cm] (8 to 17 inches)
  • Scenario A1B
    • Best estimate temperature rise of 2.8 °C with a likely range of 1.7 to 4.4 °C (5.0 °F with a likely range of 3.1 to 7.9 °F)
    • Sea level rise likely range [21 to 48 cm] (8 to 19 inches)
  • Scenario A2
    • Best estimate temperature rise of 3.4 °C with a likely range of 2.0 to 5.4 °C (6.1 °F with a likely range of 3.6 to 9.7 °F)
    • Sea level rise likely range [23 to 51 cm] (9 to 20 inches)
  • Scenario A1FI
    • Best estimate temperature rise of 4.0 °C with a likely range of 2.4 to 6.4 °C (7.2 °F with a likely range of 4.3 to 11.5 °F)
    • Sea level rise likely range [26 to 59 cm] (10 to 23 inches)

Selected quotes from the WGI Summary for Policymakers

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  • "Both past and future anthropogenic carbon dioxide emissions will continue to contribute to warming and sea level rise for more than a millennium, due to the timescales required for removal of this gas from the atmosphere."

对WGI报告的反应

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在第一工作组的报告出版前几周，对于报告所预计的未来海平面的变化就有了争议。正式报告中有关海平面变化的估计值小于之前的几次估计值。正式报告中警告说这个海平面变化的估计值可能太低：“有关冰流的一些动态过程没有被包括在当前的模式里，但是一些最近的观测表明这些过程可能会使得面对全球变暖时冰面的脆弱性加大，从而加大未来海平面得上升。”这些海平面上升的估计值的中点是在IPCC第三次评估报告（TAR）的估计值的±10%以内，但是这个范围已经缩小了。

英国皇家学会主席里斯勋爵说，“这个报告比以往更令人信服的清楚地指出，人类活动对我们正看到的和将看到的气候改变有很大责任。IPCC强烈的强调，真实的气候改变是不可避免的，我们将不得不去适应这个改变。这必将迫使包括世界领导人、商界人士和个人在内的我们所有人开始行动，而不是恐惧得瘫痪。我们不仅仅需要减少我们排放的温室气体，还应为气候变化的影响做好准备。那些声称有不同意见的人将无法以科学为接口来支持他们的论调了。”[17]

美国能源部部长塞缪尔·博德曼（Samuel Bodman）在一次新闻发布会上说，这份报告“科学合理”，并且，“像总统一直在说的一样，该报告清楚的阐明了，人类活动对我们地球的气候改变有贡献，这个问题已经不需要再争论了。”[18]美国负责欧洲和欧亚事务的副助理国务卿科特·沃尔克（Kurt Volker）说，“我们支持这份由美国科学家领导写出的最近的IPCC报告。”[19]

基于这份报告，在由法国总统希拉克宣读的“巴黎行动宣言”（Paris Call for Action）中，46个国家号召创立一个联合国环境组织（United Nations Environment Organization；UNEO），并赋予其比现有的联合国环境署（UNEP）更多的权力，将类似于有较多权力的世界卫生组织。 这46个国家包括了欧盟，但没有包括美国、中国、俄罗斯和印度这四个最主要的温室气体排放国。[20]

第二工作组报告（WGII）：影响、适应和脆弱性

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第二工作组[21]报告（WGII）的决策者摘要[22]于2007年4月6日发布。全报告[23]于2007年9月18日发布。

WGII认为“来自于所有大陆和大部分海洋的证据表明许多自然系统正在被区域气候的变化所影响，特别是升高的温度的影响。”

Observations

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Some observed changes have been associated with climate change at varying levels of confidence.

With a High Confidence (about an 8 in 10 chance to be correct) WGII asserts that climate change has resulted in:

  • More and larger glacial lakes.
  • Increasing ground instability in permafrost regions.
  • Increasing rock avalanches in mountain regions.
  • Changes in some Arctic and Antarctic ecosystems.
  • Increased run-off and earlier spring peak discharge in many glacier and snow-fed rivers.
  • Changes affecting algae, plankton, fish and zooplankton because rising water temperatures and changes in:
    • ice cover
    • salinity
    • oxygen levels
    • water circulation

With a Very High Confidence (about a 9 in 10 chance to be correct) WGII asserts that climate change is affecting terrestrial biological systems in that:

  • Spring events such as the unfolding of leaves, laying of eggs, and migration are happening earlier.
  • There are poleward and upward (to higher altitude) shifts in ranges of plant and animal species.

WGII also states that the ocean has become more acidic because it has absorbed human-caused carbon dioxide. Ocean pH has dropped by 0.1, but how this affects marine life is not documented.

Attribution of Changes

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WGII acknowledges some of the difficulties of attributing specific changes to human-caused global warming, stating that "Limitations and gaps prevent more complete attribution of the causes of observed system responses to anthropogenic warming." but found that the agreement between observed and projected changes was "Nevertheless ... sufficient to conclude with high confidence that anthropogenic warming over the last three decades has had a discernible influence on many physical and biological systems."

Projections

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WGII describes some of what might be expected in the coming century, based on studies and model projections.

Fresh Water

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It is projected with High Confidence that:

  • Dry regions are projected to get drier, and wet regions are projected to get wetter: "By mid-century, annual average river runoff and water availability are projected to increase by 10-40% at high latitudes and in some wet tropical areas, and decrease by 10-30% over some dry regions at mid-latitudes and in the dry tropics..."
  • Drought-affected areas will become larger.
  • Heavy precipitation events are very likely to become more common and will increase flood risk.
  • Water supplies stored in glaciers and snow cover will be reduced over the course of the century.

Ecosystems

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It is projected with High Confidence that:

  • The resilience of many ecosystems is likely to be exceeded this century by a combination of climate change and other stressors.
  • Carbon removal by terrestrial ecosystems is likely to peak before mid-century and then weaken or reverse. This would amplify climate change.

Food

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It is projected with Medium Confidence (about 5 in 10 chance to be correct) that globally, potential food production will increase for temperature rises of 1-3 °C, but decrease for higher temperature ranges. Fortunately, temperatures are not expected to rise to these ranges in the near future.

Coastal Systems

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It is projected with Very High Confidence that:

  • Coasts will be exposed to increasing risks such as coastal erosion due to climate change and sea-level rise.
  • "Increases in sea-surface temperature of about 1-3 °C are projected to result in more frequent coral bleaching events and widespread mortality unless there is thermal adaptation or acclimatisation by corals."
  • "Many millions more people are projected to be flooded every year due to sea-level rise by the 2080s."

Objections to original WGII language

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U.S. negotiators managed to eliminate language calling for cuts in greenhouse gas emissions, according to Patricia Romero Lankao, a lead author from the National Center for Atmospheric Research (NCAR). The original draft read: "However, adaptation alone is not expected to cope with all the projected effects of climate change, and especially not over the long run as most impacts increase in magnitude. Mitigation measures will therefore also be required." The second sentence does not appear in the final version of the report.[24]

China objected to wording that said "based on observed evidence, there is very high confidence that many natural systems, on all continents and in most oceans, are being affected by regional climate changes, particularly temperature increases." When China asked that the word "very" be stricken, three scientific authors balked, and the deadlock was broken only by a compromise to delete any reference to confidence levels.[24]

第三工作组报告（WGIII）：减缓气候变化

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参见：减缓全球变暖

第三工作组[25]的决策者摘要（SPM）[26]于2007年5月4日在该组的第26次工作会议上发布。[27] The full WG III report was published online in September, 2007.[28]

IPCC召集会议于4月30日在曼谷开始讨论该组报告的决策者摘要的草稿。有来自大约120个国家的超过400位科学家和专家参加了此次会议。[29]在5月4日的IPCC全体会议上，这2000多位代表的大多数同意了该摘要。会议上主要的一个争议是有关一个限制温室气体浓度的提案。为了避免危险的气候变化，该提案建议到2030年将温室气体浓度限制于445～650ppm之间，但发展中国家施压提高低限浓度。尽管如此，来自于原始提案的图表还是被写入决策者摘要中。[30]该摘要下结论说，温室气体浓度的稳定将需要一个适度的代价，比如浓度稳定于445ppm～535ppm将花费少于3%的全球GDP。[31]

第三工作组报告分析了对于主要部门在近期可选的减缓气候变化的方式，同时也提到了一些有关跨部门的事情，比如合作，互利，和交易。报告也根据不同的稳定浓度目标给出了相应的减缓气候变化的长期战略，同时也强调了应用不同的短期战略来达到长期目标。[32]

短期和中期减缓（至2030年）

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The Summary for Policymakers concludes that there was a high level of agreement and much evidence that 'there is substantial economic potential for the mitigation of global greenhouse gas emissions over the coming decades, that could offset the projected growth of global emissions or reduce emissions below current levels',[33] taking into account financial and social costs and benefits.[34] The technologies with the largest economic potential within this timescale are considered to be:[35]

Key mitigation technologies and practices by sector
Sector Key mitigation technologies and practices currently commercially available Key mitigation technologies and practices projected to be commercialized before 2030
Energy Supply Improved supply and distribution efficiency; fuel switching from coal to gas; nuclear power; renewable heat and power (hydropower, solar, wind, geothermal and bioenergy); combined heat and power; early applications of CCS (e.g. storage of removed CO2 from natural gas) Carbon Capture and Storage (CCS) for gas, biomass and coal-fired electricity generating facilities; advanced nuclear power; advanced renewable energy, including tidal and waves energy, concentrating solar, and solar PV.
Transport More fuel efficient vehicles; hybrid vehicles; cleaner diesel vehicles; biofuels; modal shifts from road transport to rail and public transport systems; non-motorised transport (cycling, walking); land-use and transport planning Second generation biofuels; higher efficiency aircraft; advanced electric and hybrid vehicles with more powerful and reliable batteries
Buildings Efficient lighting and daylighting; more efficient electrical appliances and heating and cooling devices; improved cook stoves, improved insulation; passive and active solar design for heating and cooling; alternative refrigeration fluids, recovery and recycle of fluorinated gases Integrated design of commercial buildings including technologies, such as intelligent meters that provide feedback and control; solar PV integrated in buildings
Industry More efficient end-use electrical equipment; heat and power recovery; material recycling and substitution; control of non-CO2 gas emissions; and a wide array of process-specific technologies Advanced energy efficiency; CCS for cement, ammonia, and iron manufacture; inert electrodes for aluminium manufacture
Agriculture Improved crop and grazing land management to increase soil carbon storage; restoration of cultivated peaty soils and degraded lands; improved rice cultivation techniques and livestock and manure management to reduce CH4 emissions; improved nitrogen fertilizer application techniques to reduce N2O emissions; dedicated energy crops to replace fossil fuel use; improved energy efficiency Improvements of crop yields
Forestry/forests Afforestation; reforestation; forest management; reduced deforestation; harvested wood product management; use of forestry products for bio-energy to replace fossil fuel use Tree species improvement to increase biomass productivity and carbon sequestration. Improved remote sensing technologies for analysis of vegetation/ soil carbon sequestration potential and mapping land use change
Waste Landfill methane recovery; waste incineration with energy recovery; composting of organic waste; controlled waste water treatment; recycling and waste minimization Biocovers and biofilters to optimize CH4 oxidation

The IPCC estimates that stabilizing atmospheric greenhouse gases at between 445-535ppm CO2 equivalent would result in a reduction of average annual GDP growth rates of less than 0.12%. stabilizing at 535 to 590ppm would reduce average annual GDP growth rates by 0.1%, while stabilization at 590 to 710ppm would reduce rates by 0.06%.[36] There was high agreement and much evidence that a substantial fraction of these mitigation costs may be offset by benefits to health as a result of reduced air pollution, and that there would be further cost savings from other benefits such as increased energy security, increased agricultural production, and reduced pressure on natural ecosystems as well as, in certain countries, balance of trade improvements, provision of modern energy services to rural areas and employment.[37]

The IPCC considered that achieving these reductions would require a 'large shift in the pattern of investment, although the net additional investment required ranges from negligible to 5-10%'.They also concluded that it is often more cost effective to invest in end-use energy efficiency improvement than in increasing energy supply.[38]

In terms of electricity generation, the IPCC envisage that renewable energy can provide 30 to 35% of electricity by 2030 (up from 18% in 2005) at a carbon price of up to US$50/t, and that nuclear power can rise from 16% to 18%. They also warn that higher oil prices might lead to the exploitation of high-carbon alternatives such as oil sands, oil shales, heavy oils, and synthetic fuels from coal and gas, leading to increasing emissions, unless carbon capture and storage technologies are employed.[39]

In the transport sector there was a medium level of agreement and evidence that the multiple mitigation options may be counteracted by increased use, and that there were many barriers and a lack of government policy frameworks.[40]

There was high agreement and much evidence that, despite many barriers (particularly in the developing countries), new and existing buildings could reduce emissions considerably, and that this would also provide other benefits in terms of improved air quality, social welfare and energy security.[41]

长期减缓（2030年后）

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The IPCC reported that the effectiveness of mitigation efforts over the next two or three decades would have a large impact on the ability to stabilize atmospheric greenhouse gases at lower levels, and that the lower the ultimate stabilization levels, the more quickly emissions would need to peak and decline.[42] For example, to stabilize at between 445 and 490ppm (resulting in an estimate global temperature 2 to 2.4oC above the pre-industrial average) emissions would need to peak before 2015, with 50 to 85% reductions on 2000 levels by 2050.[43]

There was high agreement and much evidence that stabilization could be achieved by 2050 using currently available technologies, provided appropriate and effective incentives were put in place for their development, acquisition, deployment and diffusion, and that barriers were removed.[44] For stabilization at lower levels the IPCC agreed that improvements of carbon intensity need to be made much faster than has been the case in the past, and that there would be a greater need for efficient public and private research, development & demonstration efforts and investment in new technologies during the next few decades.[45] The IPCC points out that government funding in real absolute terms for most energy research programmes has been flat or declining for nearly 20 years, and is now about half the 1980 level.[46] Delays in cutting emissions would lead to higher stabilization levels and increase the risk of more severe climate change impacts, as more of the current high-emission technologies would have been deployed.[47]

Among the measures that might be used, there was high agreement and much evidence that policies that put a price on the cost of carbon emissions could provide incentives for consumers and producers. Carbon prices of 5 to 65 US$/tCO2 in 2030 and 15 to 130 US$/tCO2 by 2050 are envisaged for stabilization at around 550 ppm by 2100.[48]

综合报告

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A draft version of the AR4 Synthesis Report, Summary for Policymakers (SPM)PDF（1.92 MB）, "Subject to final copyedit", was published 16 November, 2007.

The Synthesis Report goes one step further [than the first three Climate Change 2007 Working Group Reports]: it is the decisive effort to integrate and compact this wealth of information into a readable and concise document explicitly targeted to the policymakers.

The Synthesis Report also brings in relevant parts some material [sic] contained in the full Working Group Reports over and above what is included in the Summary for Policymakers in these three Reports. It is designed to be a powerful, scientifically authoritative document of high policy relevance, which will be a major contribution to the discussions at the 13th Conference of the Parties in Bali during December 2007. In fact, this Conference was postponed to December to allow the IPCC Synthesis Report to come out first.
— Undated IPCC press release

The six topics[49][50] addressed in the Synthesis Report are:

  1. Observed changes in climate and its effects (Working Groups 1-2).
  2. Causes of change (WGs 1, 3).
  3. Climate change and its impacts in the near and long term under different scenarios (WGs 1-3).
  4. Adaptation and mitigation options and responses, and the inter-relationship with sustainable development, at global and regional levels (WGs 2-3).
  5. The long term perspective: scientific and socio-economic aspects relevant to adaptation and mitigation, consistent with the objectives and provisions of the Convention [sic], and in the context of sustainable development (WGs 1-3).
  6. Robust findings, key uncertainties (WGs 1-3).

The "Convention" mentioned in Topic 5 is the UN Framework Convention on Climate Change (UNFCCC).

The key findings from the AR4 Synthesis Report will be discussed Wednesday 13 December 2007[51] at the United Nations Climate Change Conference (UNFCCC COP 13--CMP 3) in Bali, Indonesia, which takes place 3-14 December (see UNFCCC home page[52]).

人为的变暖可能导致一些突变或不可逆转的影响

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The SPM states that "Anthropogenic warming could lead to some impacts that are abrupt or irreversible, depending upon the rate and magnitude of the climate change."

  • "There is medium confidence that approximately 20-30% of species assessed so far are likely to be at increased risk of extinction if increases in global average warming exceed 1.5-2.5°C (relative to 1980-1999). As global average temperature increase exceeds about 3.5°C,

model projections suggest significant extinctions (40-70% of species assessed) around the globe."

  • "Partial loss of ice sheets on polar land could imply metres of sea level rise, major changes in coastlines and inundation of low-lying areas, with greatest effects in river deltas and low-lying islands. Such changes are projected to occur over millennial time scales, but more rapid sea level rise on century time scales cannot be excluded."

批评

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主条目：对IPCC第四次评估报告的批评

第四次评估报告已经受到批评。对人为引起全球变暖持怀疑者声称他们的意见没有被充分的包括在这份报告中。也有些人认为IPCC对气候变化带来的潜在危害估计的过于保守。

因为和全球变暖这个大主题有关，第四次评估报告已经被许多方面评论过，比如政府官员、特殊利益团体、科学组织。有关围绕全球变暖的政治以及各团体对之的态度的全面讨论，可参看文章“全球变暖的政治”。

See also

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Template:EnergyPortal

參考資料

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  1. ^ 国务院新闻办召开IPCC第四次评估报告发布会. 中国气象局网站. 2007-2-06 [2008-12-18] （中文（简体））. 
  2. ^ 原文为“warming of the climate system is unequivocal”
  3. ^ 原文为“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”。
  4. ^ 专家称联合国过于“轻描淡写”气候变化. 人民网. 2007-11-26 [2008-12-18] （中文（简体））. 
  5. ^ 国家气候委员会举行新闻发布会介绍IPCC第四次评估报告综合报告及中国的行动. 中国气象报. 2007-11-22 [2008-12-18] （中文（简体））. 
  6. ^ according to: Canadian Institute for Climate Studies, CCIS project: Frequently Asked Questions
  7. ^ IPCC Special Report on Emissions Scenarios, Chapter 4: An Overview of Scenarios / 4.2. SRES Scenario Taxonomy / Table 4- 2: Overview of SRES scenario quantifications.
  8. ^ Figure 2.11: Schematic illustration of SRES scenarios (IPCC)
  9. ^ 9.0 9.1 Climate Change 2007: The Physical Science Basis. Summary for PolicymakersPDF（3.7 MB）
  10. ^ Climate Change 2007: The Physical Sciences Basis, IPCC, [2007-04-30] 
  11. ^ Frequently Asked Questions (from the Report Accepted by Working Group I of the Intergovernmental Panel on Climate Change) (PDF), IPCC, [2007-10-12] 
  12. ^ IPCC website: Summary Description of the IPCC Process。
  13. ^ IPCC adopts major assessment of climate change science
  14. ^ 14.0 14.1 "... a convergent world with the same global population, that peaks in mid-century and declines thereafter, ... but with rapid change in economic structures toward a service and information economy, with reductions in material intensity and the introduction of clean and resource efficient technologies. The emphasis is on global solutions to economic, social and environmental sustainability, including improved equity, but without additional climate initiatives."
  15. ^ 15.0 15.1 "... a future world of very rapid economic growth, global population that peaks in mid-century and declines thereafter, and the rapid introduction of new and more efficient technologies. Major underlying themes are convergence among regions, capacity building and increased cultural and social interactions, with a substantial reduction in regional differences in per capita income. ... technological emphasis: fossil intensive"
  16. ^ This contrasts with the TAR, which included these ice dynamics, and had a higher top end sea level rise estimate. The report states that recent observations suggest that ice flow dynamics could lead to additional rise: "Dynamical processes related to ice flow not included in current models but suggested by recent observations could increase the vulnerability of the ice sheets to warming, increasing future sea level rise. Understanding of these processes is limited and there is no consensus on their magnitude."
  17. ^ UK scientists' IPCC reaction. BBC新闻. 2007-02-02 （英语）. 
  18. ^ Duray, Dan. Bush endorses climate study. Monterey County Herald. 2007-02-03 （英语）. 
  19. ^ Volker, Kurt. Post-Kyoto Surprise: America's Quiet Efforts to Cut Greenhouse Gases Are Producing Results. 美国国务院. 2007-02-12 [2009-01-02] （英语）. 
  20. ^ Doyle, Alister. 46 nations call for tougher U.N. environment role. 路透社. 2007-02-03 （英语）. 
  21. ^ IPCC WGII web site
  22. ^ Working Group II Contribution to the Intergovernmental Panel on Climate Change Fourth Assessment Report Climate Change 2007: Climate Change Impacts, Adaptation and VulnerabilityPDF（547 KB）
  23. ^ http://www.gtp89.dial.pipex.com/chpt.htm
  24. ^ 24.0 24.1 U.S., China Got Climate Warnings Toned Down. [2007-04-09]. 
  25. ^ Intergovernmental Panel on Climate Change
  26. ^ Climate Change 2007: Mitigation of Climate Change. Summary for PolicymakersPDF（631 KB）
  27. ^ IPCC meetings in 2007. IPCC. [2007-05-01]. 
  28. ^ IPCC AR4 Working Group III Final Report. IPCC. 2007-09 [2007-09-12]. 
  29. ^ Bangkok hosts key climate summit. BBC. 2007-04-30 [2007-05-01]. 
  30. ^ Deal reached on climate change report. CNN. 2007-05-04 [2007-05-04]. 
  31. ^ Climate change 'can be tackled'. BBC. 2007-05-04 [2007-05-04]. 
  32. ^ IPCC. Principles Governing IPCC WorkPDF（8.38 KB）
  33. ^ Climate Change 2007: Mitigation of Climate Change, Summary for Policymakers (PDF). Working Group III, IPCC: Item 5, page 11. 2007-05-04 [2007-05-10]. 
  34. ^ Climate Change 2007: Mitigation of Climate Change, Summary for Policymakers (PDF). Working Group III, IPCC: Box SPM 2, page 10. 2007-05-04 [2007-05-10]. 
  35. ^ Climate Change 2007: Mitigation of Climate Change, Summary for Policymakers (PDF). Working Group III, IPCC: Table SPM 3, page 14. 2007-05-04 [2007-05-10]. 
  36. ^ Climate Change 2007: Mitigation of Climate Change, Summary for Policymakers (PDF). Working Group III, IPCC: Table SPM4, page 16. 2007-05-04 [2007-05-10]. 
  37. ^ Climate Change 2007: Mitigation of Climate Change, Summary for Policymakers (PDF). Working Group III, IPCC: Item 30, page 17; Item 10, page 18. 2007-05-04 [2007-05-10]. 
  38. ^ Climate Change 2007: Mitigation of Climate Change, Summary for Policymakers (PDF). Working Group III, IPCC: Items 15, 20 & 25, page 18. 2007-05-04 [2007-05-10]. 
  39. ^ Climate Change 2007: Mitigation of Climate Change, Summary for Policymakers (PDF). Working Group III, IPCC: Items 25, 30, 35, page 18. 2007-05-04 [2007-05-10]. 
  40. ^ Climate Change 2007: Mitigation of Climate Change, Summary for Policymakers (PDF). Working Group III, IPCC: Item 11, page 19. 2007-05-04 [2007-05-10]. 
  41. ^ Climate Change 2007: Mitigation of Climate Change, Summary for Policymakers (PDF). Working Group III, IPCC: Item 12, page 19. 2007-05-04 [2007-05-10]. 
  42. ^ Climate Change 2007: Mitigation of Climate Change, Summary for Policymakers (PDF). Working Group III, IPCC: Item 18, page 22. 2007-05-04 [2007-05-10]. 
  43. ^ Climate Change 2007: Mitigation of Climate Change, Summary for Policymakers (PDF). Working Group III, IPCC: Table SPM.5, page 23. 2007-05-04 [2007-05-10]. 
  44. ^ Climate Change 2007: Mitigation of Climate Change, Summary for Policymakers (PDF). Working Group III, IPCC: Item 19, page 25. 2007-05-04 [2007-05-10]. 
  45. ^ Climate Change 2007: Mitigation of Climate Change, Summary for Policymakers (PDF). Working Group III, IPCC: Item 25, page 25, and Item 5 page 26. 2007-05-04 [2007-05-10]. 
  46. ^ Climate Change 2007: Mitigation of Climate Change, Summary for Policymakers (PDF). Working Group III, IPCC: Item 10, page 32. 2007-05-04 [2007-05-10]. 
  47. ^ Climate Change 2007: Mitigation of Climate Change, Summary for Policymakers (PDF). Working Group III, IPCC: Item 10, page 28. 2007-05-04 [2007-05-10]. 
  48. ^ Climate Change 2007: Mitigation of Climate Change, Summary for Policymakers (PDF). Working Group III, IPCC: Item 23 & 25, page 29. 2007-05-04 [2007-05-10]. 
  49. ^ Core Writing Team For the AR4 Synthesis ReportPDF（121 KB）
  50. ^ AR4 Synthesis Report - Outline of Topics
  51. ^ IPCC home page. [2007-11-17]. 
  52. ^ UNFCCC home page. [2007-11-17]. 


外部链接

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Category:气候变化

zh:政府间气候变化专门委员会第四次评估报告 en:IPCC Fourth Assessment Report

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