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IPCC Climate Change 2007 Report: Impacts, Adaptation and Vulnerability

IPCC Climate Change 2007 Report: Impacts, Adaptation and Vulnerability


The Intergovernmental Panel on Climate Change (IPCC), an arm of the United Nations, is an international committee of scientists that reports on the state of scientific knowledge on climate change. Since 1990 it has produced several major reports on climate change, the latest being its Fourth Assessment Report, Climate Change 2007. This was released in three major parts. The first was on the science of climate change, the second on the impacts of climate change and possible responses to or harms caused by it, and the third on possible ways of mitigating climate change (reducing its effects). The purpose of the IPCC's reports is to give policymakers and other interested parties an in-depth, authoritative view of the state of scientific knowledge about climate change, making possible more-informed climate-related decisions. The IPCC does not recommend specific policies, but is restricted to describing scientific knowledge and its limitations.

The second part of its Fourth Assessment Report, Climate Change 2007: Impacts, Adaptation and Vulnerability, was released in stages beginning in April 2007. It provides a comprehensive assessment of current scientific understanding of the effects of climate change on human and natural systems, the ability of these systems to adapt to climate change, and their vulnerability to its negative effects.

Historical Background and Scientific Foundations

Climate Change 2007: Impacts, Adaptation and Vulnerability was issued as part of the IPCC's Fourth Assessment Report (the other three assessment reports were issued in 1990, 1995, and 2001). The three parts of the 2007 report—Physical Science Basis; Impacts, Adaptation and Vulnerability, and Mitigation of Climate Change—are respectively devoted to describing what climate changes

are happening and are likely to happen in the future, and what is causing them; what those changes are likely to do to the world; and what we may be able to do about them. The Impacts, Adaptation and Vulnerability report describes itself as an assessment of “current scientific understanding of impacts of climate change on natural, managed, and human systems, the capacity of these systems to adapt and their vulnerability.”

Unlike the Physical Science Basis section of the Fourth Assessment Report, the Impacts, Adaptation and Vulnerability section does not delve into the past. It is concerned with the ongoing effects of climate change and is based mostly on data collected since 1970. Like the rest of the assessment, it is based entirely on scientific data found in peer-reviewed publications, that is, publications which have been subjected to criticism by the authors' fellow experts before being published in order to filter out flawed science. The Fourth Assessment Report is an effort to pool the collective knowledge and experience of the world community of scientists who are experts on climate and weather.

The Impacts, Adaptation and Vulnerability report is over 800 pages long. It offers both summary and in-depth views of the present state of scientific understanding of these aspects of climate change.

Structure of the Report

Since the report is too long for most people to read, its authors provide two summary chapters. The first is the “Summary for Policymakers,” which touches on the scientific points most relevant for governmental and other persons involved in making decisions about public policy. In democracies, this intended audience presumably includes all citizens. The second is the “Technical Summary,” which goes more deeply into the scientific support for the claims made in the “Summary for Policy makers.” The complete scientific underpinnings of the claims made in these two summary sections is found in the following 20 chapters, which are devoted to specific types of climate impacts and to the effects of climate change on particular regions of the world.

Chapters 1 and 2 describe how scientists assess observed changes in natural and managed systems as a result of climate change. Managed systems include cropland, forests, and fisheries that are not built by human beings but that are heavily influenced by human management. Chapter 3 discusses how climate change affects freshwater resources worldwide. Increased temperatures, changes in precipitation patterns, and rising sea level will all affect the availability of freshwater for drinking and irrigation. Chapter 4 delineates the effects of climate change on the properties of ecosystems, including the goods and services they supply to humans. Chapter 5 reviews the effects of climate change on food, fiber, and forest products. Chapter 6 details effects on coastal and low-lying areas. Chapter 7 reveals the effects on industry, settlement, and society. Chapter 8 presents the likely effects of climate change on human health. Chapters 9 through 16 relate the likely effects of climate change on the continents, polar regions, and small islands of the world. The last four chapters address a variety of issues dealing with the ability of human and natural systems to adapt to the stresses (and, in a smaller number of cases, the opportunities) of climate change.

Main Conclusions

The following points are highlighted in the “Summary for Policymakers” section of Climate Change 2007: Impacts, Adaptation and Vulnerability. Segments in italics are paraphrased from the original report to increase clarity.

Observational scientific evidence from all continents and most oceans shows that many natural systems are being affected by climate change, especially warming. Thereishigh confidence (at least 80% chance) that snow, ice, and frozen ground (including permafrost) are being reduced by climate change. Glacial lakes (lakes fed by melting glaciers) are becoming larger and more numerous; ground ice is melting in permafrost regions, with consequences that include more rock avalanches in mountainous areas; and Arctic predators such as polar bears are being injured by diminishing sea ice coverage and other changes. There is high confidence that meltwater runoff in glacier- and snow-fed rivers is peaking earlier in the spring and increasing overall, and very high confidence (at least 90% chance) that natural signs of spring such as egg-laying, bird migration, and the opening of leaves are happening earlier. There is also very high confidence that the ranges of many plant and animal species are moving northward or to higher (cooler) altitudes. There is high confidence that abundance of fish, algae, and plankton has changed in high-latitude (very northerly or southerly) areas, and that the ranges inhabited by these creatures have moved. Human-released carbon dioxide (CO2) dissolving in the oceans has increased their acidity, with so-far unknown affects on marine biosystems.

Data collected since 1970 show that it is likely (66– 90% chance) that human-caused (anthropogenic) global warming has altered many physical and biological systems. These data include many new observations collected since the last IPCC report, in 2001. Out of more than 29,000 sets of observations of physical and biological systems, over 89% show the predicted effects of warming. It is very unlikely (1–10% chance) that these effects are the result of natural changes in these systems. Computer models that include both anthropogenic and natural causes of climate change predict the observed changes better than models that leave out anthropogenic causes.

Although adaptation and non-climatic causes of change make some changes difficult to be sure of, there is increasing evidence that regional climate change—change on the scale of continents, regions, or ocean basins—is affecting natural and human environments. Earlier planting of spring crops at higher latitudes in the Northern Hemisphere has been documented. Heat-related deaths in Europe, some infectious diseases, and allergy-triggering pollen in the Northern Hemisphere have all increased as a result of climate change. Hunting in the Arctic and mountain sports such as skiing have been affected. Outburst floods from glacial lakes pose a higher risk to some mountainous-region communities. In the region of Africa known as the Sahel—a band of territory running across northern Africa that separates the Sahara desert in the north from the moister regions to the south—conditions have been warmer and drier, shortening the growing season. Longer dry seasons and more erratic rainfall are forcing farmers in southern Africa to change their practices.


ANTHROPOGENIC: Made by people or resulting from human activities. Usually used in the context of emissions that are produced as a result of human activities.

DESERTIFICATION: Transformation of arid or semiarid productive land into desert.

GLACIAL LAKE: Lake fed by meltwater from a glacier or glaciers.

GREENHOUSE GASES: Gases that cause Earth to retain more thermal energy by absorbing infrared light emitted by Earth's surface. The most important greenhouse gases are water vapor, carbon dioxide, methane, nitrous oxide, and various artificial chemicals such as chlorofluorocarbons. All but the latter are naturally occurring, but human activity over the last several centuries has significantly increased the amounts of carbon dioxide, methane, and nitrous oxide in Earth's atmosphere, causing global warming and global climate change.

PEER REVIEW: The standard process in science for reducing the chances that faulty or fraudulent claims will be published in scientific journals. Before publication of an article, scientists with expertise in the article's subject area review the manuscript, usually anonymously, and make criticisms that may lead to revision or rejection of the article.

PERMAFROST: Perennially frozen ground that occurs wherever the temperature remains below 32°F (0°C) for several years.

RIVER DELTA: Flat area of fine-grained sediments that forms where a river meets a larger, stiller body of water such as the ocean. Rivers carry particles in their turbulent waters that settle out (sink) when the water mixes with quieter water and slows down; these particles build the delta. Deltas are named after the Greek letter delta, which looks like a triangle. Very large deltas are termed megadeltas and are often thickly settled by human beings. Rising sea levels threaten settlements on megadeltas.

SAHEL: The transition zone in Africa between the Sahara Desert to the north and tropical forests to the south. This dry land belt stretches across Africa and is under stress from land use and climate variability.

SALINIZATION: Increase in salt content. The term is often applied to increased salt content of soils due to irrigation: salts in irrigation water tend to concentrate in surface soils as the water quickly evaporates rather than sinking down into the ground.

Information about likely future impacts of climate change is now available for a wide range of systems:

Freshwater resources. By the middle of the twenty-first century, average annual river runoff will increase by 10–40% at northerly latitudes and in some tropical areas, while decreasing by 10–30% in dry regions. Some of these tropical regions are already experiencing water shortages. Areas affected by drought will probably grow. Heavy precipitation events will increase the risk of floods.

Ecosystems. Absorption of carbon by ecosystems such as forests will probably peak before 2050 and then decline. This decline will speed climate change as more CO2 remains in the atmosphere. If global temperature increases are greater than about 3.6°F (2°C), as many as 20–30% of all plant and animal species will be at increased risk of extinction. Increasing acidity of the oceans due to dissolved CO2 will injure shell-forming marine organisms and the species that depend on them.

Food, fiber, and forest products. For temperature increases of up to 1.8–5.4°F (1–3°C), food productivity will increase slightly at mid to high latitudes. For larger temperature increases, it will decrease. Even small temperature increases will decrease food production in the dry and tropical regions of the world, making widespread hunger more likely. The global or net effect of a 1.8-5.4°F increase would probably be a slight increase in world food production. Global timber production may rise slightly with moderate global warming. Populations of wild fish (fisheries) will probably decline with continued warming.

Coastal systems and low-lying areas. Adding to development pressures, sea-level rise caused by global warming will damage coastal areas. Coastal erosion will increase because of higher water levels and increased storms. There will probably be widespread dying of coral reefs, which are sensitive to water temperature; hundreds of marine species depend on coral reefs for habitat. Coastal marshes and other wetlands will be injured by rising sea levels. Human populations on small islands and in the large, low-lying river deltas of Africa and Asia, where hundreds of millions of people live, will be exposed to greater risk of flooding. Coastal areas will adapt more easily in wealthy countries than in poor countries.

Industry, settlement, and society. Industries, settlements, and societies in coastal areas will be more vulnerable to climate change, as will communities with economies dependent on resources that can be affected by climate change and in locations where extreme weather events are already a special hazard. Poorer communities will have less ability to adapt, and are already dependent on more marginal sources of water and food.

Human health. Millions of people, especially in poorer countries, will suffer worsened health as a result of climate change. Impacts will include increased hunger, with harm to the growth and development of children and possibly increased deaths from famine; increased sickness and death due to floods, heat, and drought; increased prevalence of diarrheal disease, which is a life-threatening disease in many parts of the world that already kills five to eight million people each year; and increased heart/lung disease as a result of increased ground-level ozone. There will be fewer deaths in temperate areas because of exposure to cold, but this benefit will be greatly outweighed by the harm done to human health worldwide.

Specific predictions can now be made about the impacts likely to be suffered by the inhabitants of various regions:

Africa. Between 75 and 250 million people will find it more difficult to get sufficient water by 2020. Food production may be severely decreased in many African countries; in some countries, food production from agriculture dependent on rainfall could be cut in half by 2020. Warming of large lakes will decrease fish populations in those bodies of water, which are already pressured by overfishing.

Asia. Increased melting of glaciers in the Himalayan mountain range will increase flooding at first; later, as the glaciers disappear, river flows will drop below their present levels, decreasing the water available to human settlements. Supplies of freshwater will decrease in all parts of Asia but the north and west. Coastal areas, especially large river deltas such as the Ganges-Brahmaputra delta in Bangladesh, will be subject to greater flooding. Sickness and death due to diarrhea associated with floods and droughts, both of which make it harder to get clean water, will increase in east, south, and southeast Asia. By 2050, crop yields may have increased by up to 20% in east and southeast Asia and may have decreased by up to 30% in central and south Asia.

Australia and New Zealand. Water supplies will be less secure by 2030 in southern and eastern Australia and in parts of New Zealand. Loss of biodiversity will occur by 2020 in environments such as the Great Barrier Reef. Forestry and agricultural production will decline by 2030 over southern and eastern Australian and in parts of New Zealand. Initially, agricultural output may increase in parts of New Zealand due to a longer growing season and more rain.

Europe. Current climate change impacts have been documented in Europe since 2001, when the last IPCC Assessment Report was released. These include shrinking glaciers, longer growing seasons, heat waves, and shifting species ranges. Risks in Europe that will grow because of climate change include inland flooding, coastal flooding, and increased erosion. In mountainous areas, up to 60% of species may be lost by 2080. In southern Europe, increased heat and more drought will decrease water supplies, water for hydropower, crop productivity, and tourism; heat waves and wildfires will increase. Central and eastern Europe will see less rain, more heat waves, and lessened forest productivity. Positive short-term effects in northern Europe may include lessened heating costs and increased crop and forest yields. In the long term, negative effects such as floods and ecosystem stress are predicted to outweigh these benefits.

Latin America. By 2050, tropical forest will be replaced by savanna (grassland) in much of the eastern Amazon basin. Species extinction may be extensive throughout tropical Latin America. Crop production will decrease in drier areas due to salinization of soil and desertification. Disappearance of glaciers and shifting precipitation patterns will decrease water available for drinking, irrigation, and hydropower. Lack of money and technological resources will likely hamper efforts to adapt to climate change.

North America. Decreased snowpack in western mountain ranges will decrease water supplies. Forest fires and pests will destroy increasing areas of forest. Rain-fed agricultural output may increase by 5–20% over the next few decades. Heat waves will increase, placing the elderly especially at risk.

Polar regions. The most dramatic climate change effects yet visible anywhere in the world are in the Arctic. Shrinkage of glaciers, ice sheets, and permafrost will continue to occur and will have many negative effects on migratory birds, mammals, and predators. (In September 2007, scientists working for the U.S. Geological Survey announced that by 2050, two-thirds of the world's polar bears will probably have disappeared as a result of habitat loss from global warming.) Buildings in Arctic regions are destabilizing as the permafrost beneath them melts, and traditional indigenous ways of life (Eskimo and other) are less sustainable. There will be lower heating costs and northern seas will be more navigable as sea ice decreases.

Small islands. Small islands are particularly vulnerable to sea level rise and extreme weather events. Fish-eries, beaches, and coral reefs will all be harmed by the effects of climate change, injuring livelihoods and tourism. Storm surges, erosion, and submergence of lowlying land will threaten communities. Invasion by non-native species will occur.

Impacts can be better estimated now for a range of possible increases in global temperature.

Impacts and Issues

Like the other parts of the IPCC's Fourth Assessment Report, the report on Impacts, Adaptation and Vulnerability is an unusual and important document: the worldwide community of scientists studying climate and weather announces an agreed-upon (consensus) position. This report will be consulted during real-world decision-making by United Nations organizations and will influence the allocation of aid, development, and research dollars by scores of governments. In U.S. politics, the document's influence was apparent in April 2007 when the chair of the select House committee on climate change (Rep. Edward Markey, D-MA) cited the report and stated that legally mandated caps on greenhouse-gas emissions would be necessary. “Congress is heading toward a legislative showdown with the President [George W. Bush] on this issue,” Markey said. James L. Connaughton, top environmental adviser to President Bush, stated that the report “further underscores what the President has been saying for some time about the seriousness of this challenge,” namely climate change.

Doubters of human-caused climate change argue that the entire IPCC report is flawed by exclusion of their views. Nevertheless, governments that have long resisted acknowledging or acting on global climate change—including China, the United States, and Saudi Arabia—were among those appointing scientists to the IPCC staff and repeatedly approved all parts of the 2007 report before its release.


“At continental, regional, and ocean basin scales, numerous long-term changes in climate have been observed. These include changes in Arctic temperatures and ice, widespread changes in precipitation amounts, ocean salinity, wind patterns and aspects of extreme weather including droughts, heavy precipitation, heat waves and the intensity of tropical cyclones.”

Statement of the Intergovernmental Panel on Climate Change (IPCC) as formally approved at the 10th Session of Working Group I of the IPCC in Paris, France, during February 2007.

SOURCE: Solomon, S., et al, eds. Climate Change 2007: The Physical Science Basis: Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. New York: Cambridge University Press, 2007.

Other critics have charged that the Impacts, Adaptation and Vulnerability report was toned down for political, not scientific, reasons at the insistence of some of these governments. For example, according to the Washington Post (April 7, 2007), some scientists in the IPCC, including one of the lead authors of the Impacts, Adaptation and Vulnerability section (Patricia Lankao of the United States' National Center for Atmospheric Research), charged that parts of the impact report were altered at the insistence of Chinese and American officials to be less of a threat to business as usual. A draft paragraph of the Impacts, Adaptation and Vulnerability section originally read as follows: “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 was deleted after being challenged by U.S. officials. The Chinese government protested against the draft text stating that “there is very high confidence (i.e., at least a 90% chance) that many natural systems, on all continents and in most oceans, are being affected by regional climate changes, particularly temperature increases.” China wanted “very high confidence” reduced to “high confidence” (i.e., at least an 80% chance). The IPCC authors refused as there was no scientific ground for the change. A compromise was reached by not stating the level of confidence at all.

See Also Africa: Climate Change Impacts; Asia: Climate Change Impacts; Australia: Climate Change Impacts; Europe: Climate Change Impacts; IPCC Climate Change 2007 Report; IPCC Climate Change 2007 Report: Criticism; IPCC Climate Change 2007 Report: Mitigation of Climate Change; IPCC Climate Change 2007 Report: Physical Science Basis; North America: Climate Change Impacts; Small Islands: Climate Change Impacts; South America: Climate Change Impacts.



Parry, M. L., et al, eds. Climate Change 2007: Impacts, Adaptation and Vulnerability: Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. New York: Cambridge University Press, 2007.


Biello, David. “Conservative Climate: Consensus Document May Understate the Climate Change Problem.” Scientific American (April 2007).

Eilperin, Juliet. “U.S., China Got Climate Warnings Toned Down.” The Washington Post (April 7, 2007).

Web Sites

“Press Briefing on the Second International [sic] Panel on Climate Change.” The White House, April 6, 2002. <> (accessed October 9, 2007).

Larry Gilman

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