IPCC Fourth Assessment Report

IPCC Fourth Assessment Report

Overview
Climate Change 2007, the Fourth Assessment Report (AR4) of the United Nations
United Nations
The United Nations is an international organization whose stated aims are facilitating cooperation in international law, international security, economic development, social progress, human rights, and achievement of world peace...

 Intergovernmental Panel on Climate Change (IPCC
Intergovernmental Panel on Climate Change
The Intergovernmental Panel on Climate Change is a scientific intergovernmental body which provides comprehensive assessments of current scientific, technical and socio-economic information worldwide about the risk of climate change caused by human activity, its potential environmental and...

), is the fourth in a series of reports intended to assess scientific, technical and socio-economic information concerning climate change
Climate change
Climate change is a significant and lasting change in the statistical distribution of weather patterns over periods ranging from decades to millions of years. It may be a change in average weather conditions or the distribution of events around that average...

, its potential effects, and options for adaptation and mitigation. The report is the largest and most detailed summary of the climate change situation ever undertaken, produced by thousands of authors, editors, and reviewer from dozens of countries, citing over 6,000 peer-reviewed scientific studies.
It supersedes the Third Assessment Report
IPCC Third Assessment Report
The IPCC Third Assessment Report, Climate Change 2001, is an assessment of available scientific and socio-economic information on climate change by the IPCC. The IPCC was established in 1988 by the United Nations Environment Programme and the UN's World Meteorological Organization ".....

 (2001), and will in turn be superseded by the Fifth Assessment Report
IPCC Fifth Assessment Report
The Fifth Assessment Report of the United Nations Intergovernmental Panel on Climate Change , will be the fifth in a series of such reports...

 (expected in 2014).
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Climate Change 2007, the Fourth Assessment Report (AR4) of the United Nations
United Nations
The United Nations is an international organization whose stated aims are facilitating cooperation in international law, international security, economic development, social progress, human rights, and achievement of world peace...

 Intergovernmental Panel on Climate Change (IPCC
Intergovernmental Panel on Climate Change
The Intergovernmental Panel on Climate Change is a scientific intergovernmental body which provides comprehensive assessments of current scientific, technical and socio-economic information worldwide about the risk of climate change caused by human activity, its potential environmental and...

), is the fourth in a series of reports intended to assess scientific, technical and socio-economic information concerning climate change
Climate change
Climate change is a significant and lasting change in the statistical distribution of weather patterns over periods ranging from decades to millions of years. It may be a change in average weather conditions or the distribution of events around that average...

, its potential effects, and options for adaptation and mitigation. The report is the largest and most detailed summary of the climate change situation ever undertaken, produced by thousands of authors, editors, and reviewer from dozens of countries, citing over 6,000 peer-reviewed scientific studies.
It supersedes the Third Assessment Report
IPCC Third Assessment Report
The IPCC Third Assessment Report, Climate Change 2001, is an assessment of available scientific and socio-economic information on climate change by the IPCC. The IPCC was established in 1988 by the United Nations Environment Programme and the UN's World Meteorological Organization ".....

 (2001), and will in turn be superseded by the Fifth Assessment Report
IPCC Fifth Assessment Report
The Fifth Assessment Report of the United Nations Intergovernmental Panel on Climate Change , will be the fifth in a series of such reports...

 (expected in 2014). Among its notable findings:
  • "Warming of the climate system is unequivocal."
  • "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."

Climate Change 2007: Report Overview


The Fourth Assessment Report (Climate Change 2007) was released in four principal sections:
  • Contribution of Working Group I (WGI): Climate Change 2007: The Physical Science Basis.
  • Contribution of Working Group II (WGII): Climate Change 2007: Impacts, Adaptation and Vulnerability.
  • Contribution of Working Group III (WGIII): Climate Change 2007: Mitigation of Climate Change.
  • Contribution of Working Groups I, II, and III: The Synthesis Report (SYR).


Working Group I (WGI): The Physical Science Basis

The four SRES
Special Report on Emissions Scenarios
The Special Report on Emissions Scenarios was prepared by the Intergovernmental Panel on Climate Change in 2000, based on data developed at the Earth Institute at Columbia University. The emissions scenarios described in the Report have been used to make projections of possible future climate...

scenario families of the Fourth Assessment Report vs. projected global average surface warming until 2100
AR4
(Summary; PDF)

More economic focus

More environmental focus
Globalisation
(homogeneous world)
A1
rapid economic growth
(groups: A1T; A1B; A1Fl)
1.4 - 6.4 °C
B1
global environmental sustainability 
1.1 - 2.9 °C
Regionalisation
Regionalisation
Regionalization is the tendency to form regions, or the process of doing so.Regionalization can be observed in various disciplines:*In geography, it has two ways: the process of delineating the Earth, its small areas or other units into regions and a state of such a delineation.*In globalization...


(heterogeneous world)
A2
regionally oriented
economic development

2.0 - 5.4 °C
B2
local environmental sustainability
1.4 - 3.8 °C

The full WGI report was published in March, and last updated on 5 September 2007. It includes a Summary for Policymakers (SPM)(published 2 February 2007 and revised 5 February 2007), and a Frequently Asked Questions section.

Climate Change 2007: The Physical Science Basis "assesses the current scientific knowledge of the natural and human drivers of climate change, observed changes in climate, the ability of science to attribute changes to different causes, and projections for future climate change". It was produced by 152 lead authors, 26 review edtiors, and 498 contributing authors (see list) from 40 countries (citing over 6,000 peer-reviewed publications), then reviewed by over 625 expert reviewers. Before being approved, the summary was reviewed line-by-line by representatives from 113 governments during the 10th Session of Working Group I, which took place in Paris
Paris
Paris is the capital and largest city in France, situated on the river Seine, in northern France, at the heart of the Île-de-France region...

, France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

, between 29 January and 1 February 2007.

On the issue of global warming and its causes, the SPM states that:
  • "Warming of the climate system is unequivocal."
  • "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."


Very likely and likely mean "the assessed likelihood, using expert judgment" are over 90% and over 66%, respectively.

Observations


The report notes many observed changes in the Earth's climate including atmospheric composition, global average temperatures, ocean conditions, and other climate changes.

Changes in the atmosphere


Carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

, methane
Methane
Methane is a chemical compound with the chemical formula . It is the simplest alkane, the principal component of natural gas, and probably the most abundant organic compound on earth. The relative abundance of methane makes it an attractive fuel...

, and nitrous oxide
Nitrous oxide
Nitrous oxide, commonly known as laughing gas or sweet air, is a chemical compound with the formula . It is an oxide of nitrogen. At room temperature, it is a colorless non-flammable gas, with a slightly sweet odor and taste. It is used in surgery and dentistry for its anesthetic and analgesic...

 are all long-lived greenhouse gases.
  • "Carbon dioxide, methane, and nitrous oxide have increased markedly as a result of human activities since 1750 and now far exceed pre-industrial values."
  • The amount of carbon dioxide in the atmosphere in 2005 (379 ppm) exceeds by far the natural range of the last 650,000 years (180 to 300 ppm).
  • The amount of methane in the atmosphere in 2005 (1774 ppb) exceeds by far the natural range of the last 650,000 years (320 to 790 ppb).
  • The primary source of the increase in carbon dioxide is fossil fuel
    Fossil fuel
    Fossil fuels are fuels formed by natural processes such as anaerobic decomposition of buried dead organisms. The age of the organisms and their resulting fossil fuels is typically millions of years, and sometimes exceeds 650 million years...

     use, but land-use changes also make a contribution.
  • The primary source of the increase in methane is very likely to be a combination of human agricultural activities
    Agriculture
    Agriculture is the cultivation of animals, plants, fungi and other life forms for food, fiber, and other products used to sustain life. Agriculture was the key implement in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that nurtured the...

     and fossil fuel use. How much each contributes is not well determined.
  • Nitrous oxide concentrations have risen from a pre-industrial value of 270 ppb to a 2005 value of 319 ppb. More than a third of this rise is due to human activity, primarily agriculture.

Warming of the planet


Cold days, cold nights, and frost events have become less frequent. Hot days, hot nights, and heat waves have become more frequent. Additionally:
  • Eleven of the twelve years in the period (1995–2006) rank among the top 12 warmest years in the instrumental record (since 1880).
  • Warming in the last 100 years has caused about a 0.74 °C increase in global average temperature. This is up from the 0.6 °C increase in the 100 years prior to the Third Assessment Report.
  • Urban heat island
    Urban heat island
    An urban heat island is a metropolitan area which is significantly warmer than its surrounding rural areas. The phenomenon was first investigated and described by Luke Howard in the 1810s, although he was not the one to name the phenomenon. The temperature difference usually is larger at night...

     effects were determined to have negligible influence (less than 0.0006 °C per decade over land and zero over oceans) on these measurements.
  • Observations since 1961 show that the ocean has been absorbing more than 80% of the heat added to the climate system, and that ocean temperatures have increased to depths of at least 3000 m (9800 ft).
  • "Average Arctic temperatures increased at almost twice the global average rate in the past 100 years."
  • It is likely that greenhouse gases would have caused more warming than we have observed if not for the cooling effects of volcanic and human-caused aerosols. See global dimming
    Global dimming
    Global dimming is the gradual reduction in the amount of global direct irradiance at the Earth's surface that was observed for several decades after the start of systematic measurements in the 1950s. The effect varies by location, but worldwide it has been estimated to be of the order of a 4%...

    .
  • Average Northern Hemisphere temperatures during the second half of the 20th century were very likely higher than during any other 50-year period in the last 500 years and likely the highest in at least the past 1300 years (including both the Medieval Warm Period
    Medieval Warm Period
    The Medieval Warm Period , Medieval Climate Optimum, or Medieval Climatic Anomaly was a time of warm climate in the North Atlantic region, that may also have been related to other climate events around the world during that time, including in China, New Zealand, and other countries lasting from...

     and the Little Ice Age
    Little Ice Age
    The Little Ice Age was a period of cooling that occurred after the Medieval Warm Period . While not a true ice age, the term was introduced into the scientific literature by François E. Matthes in 1939...

    ).

Ice, snow, permafrost, rain, and the oceans


The SPM documents increases in wind intensity, decline of permafrost coverage, and increases of both drought and heavy precipitation events. Additionally:
  • "Mountain glacier
    Glacier
    A glacier is a large persistent body of ice that forms where the accumulation of snow exceeds its ablation over many years, often centuries. At least 0.1 km² in area and 50 m thick, but often much larger, a glacier slowly deforms and flows due to stresses induced by its weight...

    s 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
    Sea ice
    Sea ice is largely formed from seawater that freezes. Because the oceans consist of saltwater, this occurs below the freezing point of pure water, at about -1.8 °C ....

     shows no significant overall trend, consistent with a lack of warming in that region.

Hurricanes

  • There has been an increase in hurricane
    Tropical cyclone
    A tropical cyclone is a storm system characterized by a large low-pressure center and numerous thunderstorms that produce strong winds and heavy rain. Tropical cyclones strengthen when water evaporated from the ocean is released as the saturated air rises, resulting in condensation of water vapor...

     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 model
    Climate model
    Climate models use quantitative methods to simulate the interactions of the atmosphere, oceans, land surface, and ice. They are used for a variety of purposes from study of the dynamics of the climate system to projections of future climate...

    s 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."

Factors that warm or cool the planet



AR4 describes warming and cooling effects on the planet in terms of radiative forcing
Radiative forcing
In climate science, radiative forcing is generally defined as the change in net irradiance between different layers of the atmosphere. Typically, radiative forcing is quantified at the tropopause in units of watts per square meter. A positive forcing tends to warm the system, while a negative...

 — 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
Land Cover
Land cover is the physical material at the surface of the earth. Land covers include grass, asphalt, trees, bare ground, water, etc. There are two primary methods for capturing information on land cover: field survey and analysis of remotely sensed imagery....

 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 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


Climate sensitivity
Climate sensitivity
Climate sensitivity is a measure of how responsive the temperature of the climate system is to a change in the radiative forcing. It is usually expressed as the temperature change associated with a doubling of the concentration of carbon dioxide in Earth's atmosphere.The equilibrium climate...

 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


Model projections are made based on an analysis of various computer climate models running within different SRES scenarios
Special Report on Emissions Scenarios
The Special Report on Emissions Scenarios was prepared by the Intergovernmental Panel on Climate Change in 2000, based on data developed at the Earth Institute at Columbia University. The emissions scenarios described in the Report have been used to make projections of possible future climate...

. 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" 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" 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
    Ice sheet
    An ice sheet is a mass of glacier ice that covers surrounding terrain and is greater than 50,000 km² , thus also known as continental glacier...

     flow due to a lack of basis in published literature, it is estimated that sea level rise will be:
    • in a low scenario 18 to 38 cm (7 to 15 inches)
    • in a high scenario 26 to 59 cm (10 to 23 inches)
  • It is very likely that there will be an increase in frequency of warm spells, heat wave
    Heat wave
    A heat wave is a prolonged period of excessively hot weather, which may be accompanied by high humidity. There is no universal definition of a heat wave; the term is relative to the usual weather in the area...

    s and events of heavy rainfall.
  • It is likely that there will be an increase in areas affected by drought
    Drought
    A drought is an extended period of months or years when a region notes a deficiency in its water supply. Generally, this occurs when a region receives consistently below average precipitation. It can have a substantial impact on the ecosystem and agriculture of the affected region...

    s, intensity of tropical cyclone
    Tropical cyclone
    A tropical cyclone is a storm system characterized by a large low-pressure center and numerous thunderstorms that produce strong winds and heavy rain. Tropical cyclones strengthen when water evaporated from the ocean is released as the saturated air rises, resulting in condensation of water vapor...

    s (which include hurricanes and typhoons) and the occurrence of extreme high tide
    High Tide
    High Tide was a band formed in 1969 by Tony Hill , Simon House , Peter Pavli and Roger Hadden .-History:...

    s.
  • "Sea ice
    Polar ice packs
    Polar ice packs are large areas of pack ice formed from seawater in the Earth's polar regions, known as polar ice caps: the Arctic ice pack of the Arctic Ocean and the Antarctic ice pack of the Southern Ocean, fringing the Antarctic ice sheet. Polar packs significantly change their size during...

     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
Special Report on Emissions Scenarios
The Special Report on Emissions Scenarios was prepared by the Intergovernmental Panel on Climate Change in 2000, based on data developed at the Earth Institute at Columbia University. The emissions scenarios described in the Report have been used to make projections of possible future climate...

. "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


There are six families of SRES Scenarios
Special Report on Emissions Scenarios
The Special Report on Emissions Scenarios was prepared by the Intergovernmental Panel on Climate Change in 2000, based on data developed at the Earth Institute at Columbia University. The emissions scenarios described in the Report have been used to make projections of possible future climate...

, and AR4 provides projected temperature and sea level rises (excluding future rapid dynamical changes in ice flow)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

  • "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."

Reaction to WGI


In the weeks before publication of the first report, controversy broke out about the report's projections of sea-level change, which in the new report was estimated at less than previous estimates. The now-published text gives a warning that the new estimation of sea-level could be too low: "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." The mid-points of the sea level rise estimates are within ±10% of those from the TAR
Tar
Tar is modified pitch produced primarily from the wood and roots of pine by destructive distillation under pyrolysis. Production and trade in tar was a major contributor in the economies of Northern Europe and Colonial America. Its main use was in preserving wooden vessels against rot. The largest...

; but the range has narrowed.

Lord Rees
Martin Rees, Baron Rees of Ludlow
Martin John Rees, Baron Rees of Ludlow, OM, FRS is a British cosmologist and astrophysicist. He has been Astronomer Royal since 1995 and Master of Trinity College, Cambridge since 2004...

, the president of the Royal Society
Royal Society
The Royal Society of London for Improving Natural Knowledge, known simply as the Royal Society, is a learned society for science, and is possibly the oldest such society in existence. Founded in November 1660, it was granted a Royal Charter by King Charles II as the "Royal Society of London"...

, said, "This report makes it clear, more convincingly than ever before, that human actions are writ large on the changes we are seeing, and will see, to our climate. The IPCC strongly emphasises that substantial climate change is inevitable, and we will have to adapt to this. This should compel all of us - world leaders, businesses and individuals - towards action rather than the paralysis of fear. We need both to reduce our emissions of greenhouse gases and to prepare for the impacts of climate change. Those who would claim otherwise can no longer use science as a basis for their argument."

U.S. Energy Secretary Samuel Bodman told a news conference that the report was "sound science" and "As the president has said, and this report makes clear, human activity is contributing to changes in our earth's climate and that issue is no longer up for debate." Kurt Volker, Principal Deputy Assistant Secretary for European and Eurasian Affairs, said, "We support the recent IPCC report, in which U.S. scientists played a leading role."

Based on the report, 46 countries in a "Paris Call for Action" read out by French President Chirac
Chirac
Chirac may refer to:* Jacques Chirac, the President of the French Republic.* Bernadette Chirac, the wife of President Jacques Chirac** Their two daughters, Claude Chirac and Laurence...

, have called for the creation of a United Nations Environment Organization (UNEO), which is to have more power than the current United Nations Environment Programme
United Nations Environment Programme
The United Nations Environment Programme coordinates United Nations environmental activities, assisting developing countries in implementing environmentally sound policies and practices. It was founded as a result of the United Nations Conference on the Human Environment in June 1972 and has its...

 (UNEP), and is to be modelled after the more powerful World Health Organization
World Health Organization
The World Health Organization is a specialized agency of the United Nations that acts as a coordinating authority on international public health. Established on 7 April 1948, with headquarters in Geneva, Switzerland, the agency inherited the mandate and resources of its predecessor, the Health...

. The 46 countries included the European Union
European Union
The European Union is an economic and political union of 27 independent member states which are located primarily in Europe. The EU traces its origins from the European Coal and Steel Community and the European Economic Community , formed by six countries in 1958...

 nations, but notably did not include the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

, China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...

, Russia
Russia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...

, and India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...

, the top four emitters of greenhouse gases.

Working Group II (WGII): Impacts, Adaptation and Vulnerability


Working Group II's Summary for Policymakers was released on April 6, 2007. The full report was released September 18, 2007.

WGII states that "evidence from all continents and most oceans shows that many natural systems are being affected by regional climate changes, particularly temperature increases."

Observations


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


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


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

Fresh water


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


It is projected with high confidence that:
  • The resilience
    Resilience (ecology)
    In ecology, resilience is the capacity of an ecosystem to respond to a perturbation or disturbance by resisting damage and recovering quickly. Such perturbations and disturbances can include stochastic events such as fires, flooding, windstorms, insect population explosions, and human activities...

     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


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.

Coastal systems


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


US 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
National Center for Atmospheric Research
The National Center for Atmospheric Research has multiple facilities, including the I. M. Pei-designed Mesa Laboratory headquarters in Boulder, Colorado. NCAR is managed by the nonprofit University Corporation for Atmospheric Research and sponsored by the National Science Foundation...

 (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.

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.

Working Group III (WGIII): Mitigation of Climate Change


Working Group III's Summary for Policymakers (SPM) was published on 4 May 2007 at the 26th session of the IPCC. The full WG III report was published online in September, 2007.

The IPCC convened in Bangkok
Bangkok
Bangkok is the capital and largest urban area city in Thailand. It is known in Thai as Krung Thep Maha Nakhon or simply Krung Thep , meaning "city of angels." The full name of Bangkok is Krung Thep Mahanakhon Amon Rattanakosin Mahintharayutthaya Mahadilok Phop Noppharat Ratchathani Burirom...

 on April 30 to start discussions on the draft Summary, with the participation of over 400 scientists and experts from about 120 countries. At the full IPCC meeting on May 4, agreement was reached by the larger gathering of some 2,000 delegates. One of the key debates concerned a proposal to limit concentrations of greenhouse gases in the atmosphere to between 445 parts per million and 650 parts per million to avoid dangerous climate change
Avoiding Dangerous Climate Change
The related terms "avoiding dangerous climate change" and "preventing dangerous anthropogenic interference with the climate system" date to 1995 and earlier, in the Second Assesment Report of the International Panel on Climate Change and previous science it cites.In 2002, the United Nations...

, with pressure from developing countries to raise the lower limit. Despite this, the figures from the original proposal were incorporated into the Summary for Policymakers. The Summary concludes that stabilization of greenhouse gas concentrations is possible at a reasonable cost, with stabilization between 445ppm and 535ppm costing less than 3% of global GDP
Gross domestic product
Gross domestic product refers to the market value of all final goods and services produced within a country in a given period. GDP per capita is often considered an indicator of a country's standard of living....

.

The WG III report analyses mitigation options for the main sectors in the near-term, addressing also cross-sectorial matters such as synergies, co-benefits, and trade-offs. It also provides information on long-term mitigation strategies for various stabilization levels, paying special attention to implications of different short-term strategies for achieving long-term goals.

Mitigation in the short and medium term (until 2030)


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
Greenhouse gas
A greenhouse gas is a gas in an atmosphere that absorbs and emits radiation within the thermal infrared range. This process is the fundamental cause of the greenhouse effect. The primary greenhouse gases in the Earth's atmosphere are water vapor, carbon dioxide, methane, nitrous oxide, and ozone...

 emissions over the coming decades, that could offset the projected growth of global emissions or reduce emissions below current levels', taking into account financial and social costs and benefits. The technologies with the largest economic potential within this timescale are considered to be:
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
Energy supply
Energy supply is the delivery of fuels or transformed fuels to point of consumption. It potentially encompasses the extraction, transmission, generation, distribution and storage of fuels...

Improved supply and distribution efficiency; fuel switching from coal
Coal
Coal is a combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers or veins called coal beds or coal seams. The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure...

 to gas
Natural gas
Natural gas is a naturally occurring gas mixture consisting primarily of methane, typically with 0–20% higher hydrocarbons . It is found associated with other hydrocarbon fuel, in coal beds, as methane clathrates, and is an important fuel source and a major feedstock for fertilizers.Most natural...

; nuclear power
Nuclear power
Nuclear power is the use of sustained nuclear fission to generate heat and electricity. Nuclear power plants provide about 6% of the world's energy and 13–14% of the world's electricity, with the U.S., France, and Japan together accounting for about 50% of nuclear generated electricity...

; renewable heat and power
Renewable energy
Renewable energy is energy which comes from natural resources such as sunlight, wind, rain, tides, and geothermal heat, which are renewable . About 16% of global final energy consumption comes from renewables, with 10% coming from traditional biomass, which is mainly used for heating, and 3.4% from...

 (hydropower
Hydropower
Hydropower, hydraulic power, hydrokinetic power or water power is power that is derived from the force or energy of falling water, which may be harnessed for useful purposes. Since ancient times, hydropower has been used for irrigation and the operation of various mechanical devices, such as...

, solar
Solar power
Solar energy, radiant light and heat from the sun, has been harnessed by humans since ancient times using a range of ever-evolving technologies. Solar radiation, along with secondary solar-powered resources such as wind and wave power, hydroelectricity and biomass, account for most of the available...

, wind
Wind power
Wind power is the conversion of wind energy into a useful form of energy, such as using wind turbines to make electricity, windmills for mechanical power, windpumps for water pumping or drainage, or sails to propel ships....

, geothermal
Geothermal power
Geothermal energy is thermal energy generated and stored in the Earth. Thermal energy is the energy that determines the temperature of matter. Earth's geothermal energy originates from the original formation of the planet and from radioactive decay of minerals...

 and bioenergy
Biofuel
Biofuel is a type of fuel whose energy is derived from biological carbon fixation. Biofuels include fuels derived from biomass conversion, as well as solid biomass, liquid fuels and various biogases...

); combined heat and power
Cogeneration
Cogeneration is the use of a heat engine or a power station to simultaneously generate both electricity and useful heat....

; early applications of CCS
Carbon capture and storage
Carbon capture and storage , alternatively referred to as carbon capture and sequestration, is a technology to prevent large quantities of from being released into the atmosphere from the use of fossil fuel in power generation and other industries. It is often regarded as a means of mitigating...

 (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
Tidal power
Tidal power, also called tidal energy, is a form of hydropower that converts the energy of tides into useful forms of power - mainly electricity....

 and waves energy
Wave power
Wave power is the transport of energy by ocean surface waves, and the capture of that energy to do useful work — for example, electricity generation, water desalination, or the pumping of water...

, concentrating solar, and solar PV
Photovoltaics
Photovoltaics is a method of generating electrical power by converting solar radiation into direct current electricity using semiconductors that exhibit the photovoltaic effect. Photovoltaic power generation employs solar panels composed of a number of solar cells containing a photovoltaic material...

.
Transport
Transport
Transport or transportation is the movement of people, cattle, animals and goods from one location to another. Modes of transport include air, rail, road, water, cable, pipeline, and space. The field can be divided into infrastructure, vehicles, and operations...

More fuel efficient vehicles; electric vehicle
Electric vehicle
An electric vehicle , also referred to as an electric drive vehicle, uses one or more electric motors or traction motors for propulsion...

; hybrid vehicle
Hybrid vehicle
A hybrid vehicle is a vehicle that uses two or more distinct power sources to move the vehicle. The term most commonly refers to hybrid electric vehicles , which combine an internal combustion engine and one or more electric motors.-Power:...

s; cleaner diesel vehicles; biofuel
Biofuel
Biofuel is a type of fuel whose energy is derived from biological carbon fixation. Biofuels include fuels derived from biomass conversion, as well as solid biomass, liquid fuels and various biogases...

s; modal shifts from road transport
Road transport
Road transport or road transportation is transport on roads of passengers or goods. A hybrid of road transport and ship transport is the historic horse-drawn boat.-History:...

 to rail and public transport
Public transport
Public transport is a shared passenger transportation service which is available for use by the general public, as distinct from modes such as taxicab, car pooling or hired buses which are not shared by strangers without private arrangement.Public transport modes include buses, trolleybuses, trams...

 systems; non-motorised transport (cycling
Cycling
Cycling, also called bicycling or biking, is the use of bicycles for transport, recreation, or for sport. Persons engaged in cycling are cyclists or bicyclists...

, walking
Walking
Walking is one of the main gaits of locomotion among legged animals, and is typically slower than running and other gaits. Walking is defined by an 'inverted pendulum' gait in which the body vaults over the stiff limb or limbs with each step...

); land-use and transport planning
Transportation planning
Transportation planning is a field involved with the evaluation, assessment, design and siting of transportation facilities .-Models and Sustainability :...

Second generation biofuels; higher efficiency aircraft; advanced electric and hybrid vehicles with more powerful and reliable batteries
Buildings Efficient lighting and daylighting
Daylighting
Daylighting is the practice of placing windows or other openings and reflective surfaces so that during the day natural light provides effective internal lighting. Particular attention is given to daylighting while designing a building when the aim is to maximize visual comfort or to reduce energy...

; more efficient electrical appliances and heating and cooling devices; improved cook stoves, improved insulation
Building insulation
building insulation refers broadly to any object in a building used as insulation for any purpose. While the majority of insulation in buildings is for thermal purposes, the term also applies to acoustic insulation, fire insulation, and impact insulation...

; passive
Passive solar building design
In passive solar building design, windows, walls, and floors are made to collect, store, and distribute solar energy in the form of heat in the winter and reject solar heat in the summer...

 and active solar
Active solar
Active solar technologies are employed to convert solar energy into another more useful form of energy. This would normally be a conversion to heat or electrical energy. Inside a building this energy would be used for heating, cooling, or off-setting other energy use or costs. Active solar uses...

 design for heating and cooling; alternative refrigeration fluids, recovery and recycle of fluorinated gases
Integrated design of commercial buildings including technologies, such as intelligent meter
Smart meter
A smart meter is usually an electrical meter that records consumption of electric energy in intervals of an hour or less and communicates that information at least daily back to the utility for monitoring and billing purposes. Smart meters enable two-way communication between the meter and the...

s that provide feedback and control; solar PV integrated in buildings
Building integrated photovoltaics
Building-integrated photovoltaics are photovoltaic materials that are used to replace conventional building materials in parts of the building envelope such as the roof, skylights, or facades...

Industry
Industry
Industry refers to the production of an economic good or service within an economy.-Industrial sectors:There are four key industrial economic sectors: the primary sector, largely raw material extraction industries such as mining and farming; the secondary sector, involving refining, construction,...

More efficient end-use electrical equipment; heat and power recovery; material recycling
Recycling
Recycling is processing used materials into new products to prevent waste of potentially useful materials, reduce the consumption of fresh raw materials, reduce energy usage, reduce air pollution and water pollution by reducing the need for "conventional" waste disposal, and lower greenhouse...

 and substitution; control of non-CO2 gas emissions; and a wide array of process-specific technologies
Advanced energy efficiency; CCS for cement
Cement
In the most general sense of the word, a cement is a binder, a substance that sets and hardens independently, and can bind other materials together. The word "cement" traces to the Romans, who used the term opus caementicium to describe masonry resembling modern concrete that was made from crushed...

, ammonia
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...

, and iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...

 manufacture; inert electrode
Electrode
An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit...

s for aluminium manufacture
Agriculture
Agriculture
Agriculture is the cultivation of animals, plants, fungi and other life forms for food, fiber, and other products used to sustain life. Agriculture was the key implement in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that nurtured the...

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 crop
Energy crop
An energy crop is a plant grown as a low cost and low maintenance harvest used to make biofuels, or combusted for its energy content to generate electricity or heat. Energy crops are generally categorized as woody or herbaceous ....

s to replace fossil fuel
Fossil fuel
Fossil fuels are fuels formed by natural processes such as anaerobic decomposition of buried dead organisms. The age of the organisms and their resulting fossil fuels is typically millions of years, and sometimes exceeds 650 million years...

 use; improved energy efficiency
Improvements of crop yield
Crop yield
In agriculture, crop yield is not only a measure of the yield of cereal per unit area of land under cultivation, yield is also the seed generation of the plant itself...

s
Forestry
Forestry
Forestry is the interdisciplinary profession embracing the science, art, and craft of creating, managing, using, and conserving forests and associated resources in a sustainable manner to meet desired goals, needs, and values for human benefit. Forestry is practiced in plantations and natural stands...

/forest
Forest
A forest, also referred to as a wood or the woods, is an area with a high density of trees. As with cities, depending where you are in the world, what is considered a forest may vary significantly in size and have various classification according to how and what of the forest is composed...

s
Afforestation
Afforestation
Afforestation is the establishment of a forest or stand of trees in an area where there was no forest. Reforestation is the reestablishment of forest cover, either naturally or artificially...

; reforestation
Reforestation
Reforestation is the natural or intentional restocking of existing forests and woodlands that have been depleted, usually through deforestation....

; forest management
Forest management
200px|thumb|right|[[Sustainable development|Sustainable]] forest management carried out by [[Complejo Forestal y Maderero Panguipulli|Complejo Panguipulli]] has contributed to the preservation of the forested landscape around [[Neltume]], a sawmill town in Chile...

; reduced deforestation
Deforestation
Deforestation is the removal of a forest or stand of trees where the land is thereafter converted to a nonforest use. Examples of deforestation include conversion of forestland to farms, ranches, or urban use....

; 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 biosequestration
Biosequestration
Biosequestration is the capture and storage of the atmospheric greenhouse gas carbon dioxide by biological processes.This may be by increased photosynthesis ; by enhanced soil carbon trapping in agriculture; or by the use of algal bio sequestration to absorb the carbon...

. Improved remote sensing technologies for analysis of vegetation/ soil carbon sequestration potential and mapping land use change
Waste
Waste
Waste is unwanted or useless materials. In biology, waste is any of the many unwanted substances or toxins that are expelled from living organisms, metabolic waste; such as urea, sweat or feces. Litter is waste which has been disposed of improperly...

Landfill methane recovery
Biogas
Biogas typically refers to a gas produced by the biological breakdown of organic matter in the absence of oxygen. Organic waste such as dead plant and animal material, animal dung, and kitchen waste can be converted into a gaseous fuel called biogas...

; waste incineration with energy recovery
Waste-to-energy
Waste-to-energy or energy-from-waste is the process of creating energy in the form of electricity or heat from the incineration of waste source. WtE is a form of energy recovery...

; composting of organic waste; controlled waste water treatment; recycling
Recycling
Recycling is processing used materials into new products to prevent waste of potentially useful materials, reduce the consumption of fresh raw materials, reduce energy usage, reduce air pollution and water pollution by reducing the need for "conventional" waste disposal, and lower greenhouse...

 and waste minimization
Biocovers and biofilter
Biofilter
Biofiltration is a pollution control technique using living material to capture and biologically degrade process pollutants. Common uses include processing waste water, capturing harmful chemicals or silt from surface runoff, and microbiotic oxidation of contaminants in air...

s to optimize CH4 oxidation


The IPCC estimates that stabilizing atmospheric greenhouse gases at between 445-535ppm CO2 equivalent
Carbon dioxide equivalent
Carbon dioxide equivalent and Equivalent carbon dioxide are two related but distinct measures for describing how much global warming a given type and amount of greenhouse gas may cause, using the functionally equivalent amount or concentration of carbon dioxide as the reference.- Global warming...

 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%. 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
Energy security
Energy security is a term for an association between national security and the availability of natural resources for energy consumption. Access to cheap energy has become essential to the functioning of modern economies. However, the uneven distribution of energy supplies among countries has led...

, 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.

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
Energy conservation
Energy conservation refers to efforts made to reduce energy consumption. Energy conservation can be achieved through increased efficient energy use, in conjunction with decreased energy consumption and/or reduced consumption from conventional energy sources...

 improvement than in increasing energy supply.

In terms of electricity generation, the IPCC envisage that renewable energy
Renewable energy
Renewable energy is energy which comes from natural resources such as sunlight, wind, rain, tides, and geothermal heat, which are renewable . About 16% of global final energy consumption comes from renewables, with 10% coming from traditional biomass, which is mainly used for heating, and 3.4% from...

 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
Nuclear power
Nuclear power is the use of sustained nuclear fission to generate heat and electricity. Nuclear power plants provide about 6% of the world's energy and 13–14% of the world's electricity, with the U.S., France, and Japan together accounting for about 50% of nuclear generated electricity...

 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 shale
Oil shale
Oil shale, an organic-rich fine-grained sedimentary rock, contains significant amounts of kerogen from which liquid hydrocarbons called shale oil can be produced...

s, heavy oils
Heavy crude oil
Heavy crude oil or extra heavy crude oil is any type of crude oil which does not flow easily. It is referred to as "heavy" because its density or specific gravity is higher than that of light crude oil. Heavy crude oil has been defined as any liquid petroleum with an API gravity less than 20°.Extra...

, and synthetic fuel
Synthetic fuel
Synthetic fuel or synfuel is a liquid fuel obtained from coal, natural gas, oil shale, or biomass. It may also refer to fuels derived from other solids such as plastics or rubber waste. It may also refer to gaseous fuels produced in a similar way...

s from coal and gas, leading to increasing emissions, unless carbon capture and storage technologies are employed.

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.

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.

Mitigation in the long term (after 2030)


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. 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.

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. 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 and demonstration efforts and investment in new technologies during the next few decades. 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. 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.

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.

AR4 Synthesis Report


A draft version of the AR4 Synthesis Report, , "Subject to final copyedit", was published 16 November 2007.
The six topics 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 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).

Anthropogenic warming could lead to some impacts that are abrupt or irreversible


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."

Criticism



The Fourth Assessment Report has been the subject of criticism. Skeptics of anthropogenic global warming contend that their claims are not sufficiently incorporated in the report. Others regard the IPCC as too conservative in its estimates of potential harm from climate change. The report has also been criticized for inclusion of an erroneous date for the projected demise of the Himalayan glaciers.

Related to the subject of global warming in general, the IPCC Fourth Assessment Report has been discussed by various bodies such as government officials, special interest groups and scientific organizations; see the article "Politics of global warming
Politics of global warming
The politics of global warming have involved corporate lobbying, funding of special interest groups and public relations campaigns by the oil and coal industries which have affected policy decisions and legislation worldwide...

" for a thorough discussion of the politics surrounding the phenomenon, and the positions of the various parties involved.

The United Nations appointed an independent board of scientists to "review the workings of the world’s top climate science panel" which reported in September 2010; see Intergovernmental Panel on Climate Change#InterAcademy Council review.

See also



  • Avoiding Dangerous Climate Change
    Avoiding Dangerous Climate Change
    The related terms "avoiding dangerous climate change" and "preventing dangerous anthropogenic interference with the climate system" date to 1995 and earlier, in the Second Assesment Report of the International Panel on Climate Change and previous science it cites.In 2002, the United Nations...

  • Individual and political action on climate change
    Individual and political action on climate change
    Individual and political action on climate change can take many forms, most of which have the ultimate goal of limiting and/or reducing the concentration of greenhouse gases in the atmosphere, toward avoiding dangerous climate change.-Political action:...

  • Business action on climate change
    Business action on climate change
    Business action on climate change includes a range of activities relating to global warming, and to influencing political decisions on global-warming-related regulation, such as the Kyoto Protocol...

  • Energy policy
    Energy policy
    Energy policy is the manner in which a given entity has decided to address issues of energy development including energy production, distribution and consumption...

  • Energy conservation
    Energy conservation
    Energy conservation refers to efforts made to reduce energy consumption. Energy conservation can be achieved through increased efficient energy use, in conjunction with decreased energy consumption and/or reduced consumption from conventional energy sources...

  • Global climate model
    Global climate model
    A General Circulation Model is a mathematical model of the general circulation of a planetary atmosphere or ocean and based on the Navier–Stokes equations on a rotating sphere with thermodynamic terms for various energy sources . These equations are the basis for complex computer programs commonly...

  • Post–Kyoto Protocol negotiations on greenhouse gas emissions
  • Precautionary principle
    Precautionary principle
    The precautionary principle or precautionary approach states that if an action or policy has a suspected risk of causing harm to the public or to the environment, in the absence of scientific consensus that the action or policy is harmful, the burden of proof that it is not harmful falls on those...

  • Renewable Energy Sources and Climate Change Mitigation
    Renewable Energy Sources and Climate Change Mitigation
    The United Nations Intergovernmental Panel on Climate Change published a special report on Renewable Energy Sources and Climate Change Mitigation on May 9, 2011. The report evaluates the global potential for using renewable energy to mitigate climate change...

  • Special Report on Emissions Scenarios
    Special Report on Emissions Scenarios
    The Special Report on Emissions Scenarios was prepared by the Intergovernmental Panel on Climate Change in 2000, based on data developed at the Earth Institute at Columbia University. The emissions scenarios described in the Report have been used to make projections of possible future climate...

  • World energy resources and consumption
    World energy resources and consumption
    ]World energy consumption in 2010: over 5% growthEnergy markets have combined crisis recovery and strong industry dynamism. Energy consumption in the G20 soared by more than 5% in 2010, after the slight decrease of 2009. This strong increase is the result of two converging trends...


External links

  • Intergovernmental Panel on Climate Change home page
  • Ten-webpage summary of the Fourth Assessment Report SPMs by GreenFacts
    GreenFacts
    GreenFacts, formerly the GreenFacts Foundation, is an international non-profit organization founded in 2001 in Brussels, Belgium. It produces short summaries of technical scientific reports for the public...

    ; the webpages as a self-contained
  • Commentary on the Working Group I Report:
    • The Guardian Article on US political pressure on WGI Report, 27 January 2007
    • UNEP.org Press release: Evidence of Human-caused Global Warming “Unequivocal”, says IPCC, 2 February 2007
    • RealClimate
      RealClimate
      RealClimate is a commentary site on climatology. The site's contributors are a group of climate scientists whose goal is to provide a quick response to developing stories and providing the context sometimes missing in mainstream commentary. The discussion is intended to be restricted to scientific...

       blog — Commentary on Working Group I Summary for Policymakers, 2 February 2007
  • Videos:
    • From Science to Assessment: Overview of the IPCC AR4 Working Group I Report. A lecture given at Princeton University
      Princeton University
      Princeton University is a private research university located in Princeton, New Jersey, United States. The school is one of the eight universities of the Ivy League, and is one of the nine Colonial Colleges founded before the American Revolution....

       by Ronald Stouffer, Senior Research Meteorologist, Geophysical Fluid Dynamics Laboratory
      Geophysical Fluid Dynamics Laboratory
      The Geophysical Fluid Dynamics Laboratory is a laboratory in the National Oceanic and Atmospheric Administration /Office of Oceanic and Atmospheric Research . The current director is Dr. V...

       (GFDL), 11 March 2008
    • Lessons from the Climate Wars: The Future of the IPCC. A lecture given at Princeton University by Gary Yohe
      Gary Yohe
      Gary Wynn Yohe is the Woodhouse/Sysco Professor of economics at Wesleyan University, Middletown, Connecticut, and Director of the John E. Andrus Public Affairs Center at Wesleyan. He holds a PhD from Yale University....

      , Woodhouse/Sysco Professor of economics at Wesleyan University
      Wesleyan University
      Wesleyan University is a private liberal arts college founded in 1831 and located in Middletown, Connecticut. According to the Carnegie Foundation for the Advancement of Teaching, Wesleyan is the only Baccalaureate College in the nation that emphasizes undergraduate instruction in the arts and...

       and Director of the John E. Andrus Public Affairs Center at Wesleyan, 7 May 2008
    • Emissions Mitigation and Climate Stabilization. A lecture given at Princeton University by Jae Edmonds, Chief Scientist, Joint Global Change Research Institute, Pacific Northwest National Laboratory
      Pacific Northwest National Laboratory
      Pacific Northwest National Laboratory is one of the United States Department of Energy National Laboratories, managed by the Department of Energy's Office of Science. The main campus of the laboratory is in Richland, Washington....

      , 22 April 2008
    • How Would Climate Change Influence Society in the 21st Century? A lecture given at MIT by Rajendra Pachauri, 29 January 2008