[The Regional Impacts of Climate Change Executive Summary of Chapter 8: North America]
BEIJING -- In the most forceful warning yet on the threat of global warming, an international panel of hundreds of scientists issued a report today predicting brutal droughts, floods and violent storms across the planet over the next century because air pollution is causing surface temperatures to rise faster than anticipated.
The report, approved unanimously at a U.N. conference in Shanghai and described as the most comprehensive study on the subject to date, says that Earth's average temperature could rise by as much as 10.4 degrees over the next 100 years -- the most rapid change in 10 millennia and more than 60 percent higher than the same group predicted less than six years ago.
If new scientific models are accurate, rising temperatures will melt polar ice caps and raise sea levels by as much as 34 inches, causing floods that could displace tens of millions of people in low-lying areas -- such as China's Pearl River Delta, much of Bangladesh and the most densely populated area of Egypt. Droughts will parch farmlands and aggravate world hunger. Storms triggered by such climatic extremes as El Niño will become more frequent. Diseases such as malaria and dengue fever will spread.
"The scientific consensus presented in this comprehensive report about human-induced climate change should sound alarm bells in every national capital and in every local community," said Klaus Topfler, head of the U.N. Environment Program. "We should start preparing ourselves."
The report was drafted by the Intergovernmental Panel on Climate Change, a group of hundreds of scientists established by the United Nations in 1988 to assess warming. The Shanghai survey relies on complex new computer simulations based on weather records from the last 150 years, as well as data collected from ice corings, coral and tree rings -- all of which can provide information on climate going back millions of years.
The results of the new models persuaded the panel to declare unequivocally for the first time that mankind is responsible for global warming rather than changes brought by the sun or other natural factors. "We see changes in climate, we believe we humans are involved, and we're projecting future climate changes much more significant over the next 100 years than the last 100 years," said Robert T. Watson, an American scientist who is chairman of the panel.
The report cited "new and stronger evidence that most of the observed warming of the last 50 years is attributable to human activities," primarily the burning of oil, gasoline and coal, which produces carbon dioxide and other gases that trap heat in Earth's atmosphere.
Carbon dioxide levels have increased by 31 percent over the past 250 years, reaching a concentration unseen on the planet in 420,000 years and perhaps as far back as 20 million years, the report said. In 1995, by contrast, the panel reported only a "discernible human influence" on global warming.
At that time, the group predicted a temperature rise of no more than 6.3 degrees by 2100.
The panel raised that prediction by more than 4 degrees in part because successful efforts to reduce the air pollutant sulfur dioxide, a common element of smog, have had the unintended effect of reducing particles in the air that help deflect the sun's rays, the report said.
The global warming issue has proved highly contentious among environmental scientists, with many respected figures arguing that Earth undergoes periodic climatic changes with or without contributions from mankind.
Fred Singer, professor emeritus of environmental sciences at the University of Virginia and former director of the U.S. Weather Satellite Service, called the new report "a political statement" based on theoretical models that does not conform to existing scientific data from thermometers at weather stations, Earth-circling satellites and high-altitude balloons. Almost all instrumental data, he said, show no warming trend in the past 60 years, and he called data that do "suspect."
But David Easterling, principal scientist at the Commerce Department's National Climate Data Center, noted that reductions in airborne sulfates, which act to cool temperatures, are expected this century because of such factors as the burning of cleaner coal. He called the "physics pretty well established."
The new calculations add urgency to international treaty talks on curbing greenhouse gas emissions that collapsed in November as participants disagreed over how to cut such emissions under a commitment made by industrialized countries in 1997. Negotiations have been complicated by a U.S.-led effort to soften the impact of required cuts by adjusting for the amount of carbon dioxide that is absorbed by each nation's forests and farmlands. New climate talks are scheduled in Germany in May.
"Only a few countries, such as Britain and Germany, are on track to meet their targets," said Watson, who is the chief science adviser to the World Bank. "The United States is way off meeting its targets."
The United States is the largest producer of greenhouse gases, accounting for a quarter of the world total. China ranks second, but its per capita amount is relatively low.
The Working Group I report includes observations of the current changes and trends in the climate system, a reconstruction of past changes and trends, an understanding of the processes involved in those changes, and the incorporation of this knowledge into models that can attribute the causes of changes and that can provide simulation of natural and human-induced future changes in the climate system.
The Working Group II report on impacts, adaptation and vulnerability will be finalized in Geneva from 14 – 16 February. The Working Group III report on the mitigation of climate change will be finalized in Accra from 28 February to 3 March. All three reports will be accepted by the full IPCC Plenary when it meets in Nairobi from 4- 6 April.
Within the North American region (defined for the purposes of this report as the portion of continental North America south of the Arctic Circle and north of the U.S.-Mexico border), vulnerability to climate change varies significantly from sector to sector and from subregion to subregion. Recognition of this variability or subregional “texture” is important in understanding the potential effects of climate change on North America and in formulating viable response strategies.
The characteristics of the subregions and sectors of North America suggest that neither the impacts of climate change nor the response options will be uniform. This assessment suggests that there will be differences in the impacts of climate change across the region and within particular sectors. In fact, simply considering the relative climate sensitivity of different sectors or systems within a particular subregion (i.e., climate-sensitive, climate-insensitive, or climate-limited) would suggest differentiated impacts. This diversity also is reflected in the available response options. Sectors and subregions will need to adopt response options to alleviate negative impacts or take advantage of opportunities that not only address the impacts but are tailored to the needs and characteristics of that subregion.
Comprising most of Canada and the contiguous United States, this large area is diverse in terms of its geological, ecological, climatic, and socioeconomic structures. Temperature extremes range from well below -40°C in northern latitudes during the winter months to greater than +40°C in southern latitudes during the summer. The regional atmospheric circulation is governed mainly by upper-level westerly winds and subtropical weather systems, with tropical storms occasionally impacting on the Gulf of Mexico and Atlantic coasts during summer and autumn. The Great Plains (including the Canadian Prairies) and southeastern U.S. experience more severe weather—in the form of thunderstorms, tornadoes, and hail—than any other region of the world.
Our current understanding of the potential impacts of climate change is limited by critical uncertainties. One important uncertainty relates to the inadequacy of regional-scale climate projections relative to the spatial scales of variability in North American natural and human systems. This uncertainty is compounded further by the uncertainties inherent in ecological, economic, and social models—which thereby further limit our ability to identify the full extent of impacts or prescriptive adaptation measures. Given these uncertainties, particularly the inability to forecast futures, conclusions about regional impacts are not yet reliable and are limited to the sensitivity and vulnerability of physical, biological, and socioeconomic systems to climate change and climate variability.
Within most natural and human systems in North America, current climate—including its variability—frequently is a limiting factor. Climate, however, is only one of many factors that determine the overall condition of these systems. For example, projected population changes in North America and associated changes in land use and air and water quality will continue to put pressure on natural ecosystems (e.g., rangelands, wetlands, and coastal ecosystems). Projected changes in climate should be seen as an additional factor that can influence the health and existence of these ecosystems. In some cases, changes in climate will provide adaptive opportunities or could alleviate the pressure of multiple stresses; in other cases, climate change could hasten or broaden negative impacts, leading to reduced function or elimination of ecosystems.
Virtually all sectors within North America are vulnerable to climate change to some degree in some subregions. Although many sectors and regions are sensitive to climate change, the technological capability to adapt to climate change is readily available, for the most part. If appropriate adaptation strategies are identified and implemented in a timely fashion, the overall vulnerability of the region may be reduced. However, uncertainties exist about the feasibility of implementation and efficacy of technological adaptation.
Even when current adaptive capability has been factored in, long-lived natural forest ecosystems in the east and interior west; water resources in the southern plains; agriculture in the southeast and southern plains; human health in areas currently experiencing diminished urban air quality; northern ecosystems and habitats; estuarine beaches in developed areas; and low-latitude cold-water fisheries will remain among the most vulnerable sectors and regions. West coast coniferous forests; some western rangelands; energy costs for heating in the northern latitudes; salting and snow clearance costs; open-water season in northern channels and ports; and agriculture in the northern latitudes, the interior west, and west coast may benefit from opportunities associated with warmer temperatures or potentially from carbon dioxide (CO2) fertilization.
The availability of better information on the potential impacts of climate change and the interaction of these impacts with other important factors that influence the health and productivity of natural and human systems is critical to providing the lead time necessary to take full advantage of opportunities for minimizing or adapting to impacts, as well as for allowing adequate opportunity for the development of the necessary institutional and financial capacity to manage change.
Key Impacts to Physical, Biological, and Socioeconomic Systems
Ecosystems: Nonforest Terrestrial (Section
8.3.1).
The composition and geographic distribution of many ecosystems will shift as
individual species respond to changes in climate. There will likely be
reductions in biological diversity and in the goods and services that nonforest
terrestrial ecosystems provide to society.
Increased temperatures could reduce sub-arctic (i.e., tundra and taiga/tundra) ecosystems. Loss of migratory wildfowl and mammal breeding and forage habitats may occur within the taiga/tundra, which is projected to nearly disappear from mainland areas. This ecozone currently is the home of the majority of the Inuit population. It also provides the major breeding and nesting grounds for a variety of migratory birds and the major summer range and calving grounds for Canada’s largest caribou herd, as well as habitat for a number of ecologically significant plant and animal species critical to the subsistence lifestyles of the indigenous peoples. Current biogeographic model projections suggest that tundra and taiga/tundra ecosystems may be reduced by as much as two-thirds of their present size, reducing the regional storage of carbon in the higher latitudes of North America—which may shift the tundra region from a net sink to a net source of CO2 for the tundra region.
The relatively certain northward shift of the southern boundary of permafrost areas (projected to be about 500 km by the middle of the 21st century) will impact ecosystems, infrastructure, and wildlife in the altered areas through terrain slumping, increased sediment loadings to rivers and lakes, and dramatically altered hydrology; affected peatlands could become sources rather than sinks for atmospheric carbon. Projections suggest that peatlands may disappear from south of 60°N in the Mackenzie Basin; patchy arctic wetlands currently supported by surface flow also may not persist.
Elevated CO2 concentrations may alter the nitrogen cycle, drought survival mechanisms (e.g., the rate of depletion of soil water by grasses), and fire frequency—potentially decreasing forage quality and impacting forage production on rangelands. Increases in CO2 and changes in regional climate could exacerbate the existing problem of loss of production on western rangelands related to woody and noxious plant invasions by accelerating the invasion of woody C3 plants (many crop and tree species) into mostly C4 (tropical grasses, many weed species ) grasslands. Mechanisms include changes in water-use efficiency (WUE), the nitrogen cycle (increase in carbon-to-nitrogen ratio and concentrations of unpalatable and toxic substances), drought survival mechanisms, and fire frequency. Growth and reproduction of individual animals could decrease as CO2 concentrations rise, without dietary supplementation. However, the data are ambiguous, and production may increase in some grassland ecosystems. Uncertainty exists in our ability to predict ecosystem or individual species responses to elevated CO2 and global warming at either the regional or global scale.
Arid lands may increase. Current biogeographical model simulations indicate up to a 200% increase in leaf area index in the desert southWest region of North America and a northern migration and expansion of arid-land species into the Great Basin region of North America. Although uncertainty exists in predictions of regional climate changes and simulations of ecosystem responses to elevated CO2 and global warming, long-term change in ecosystem structure and function is suggested.
Landslides and debris flows in unstable Rocky Mountain areas and possibly elsewhere could become more common as winter wet precipitation increases, permafrost degrades, and/or glaciers retreat. Water quality would be affected by increased sediment loads. Fish and wildlife habitat, as well as roads and other artificial structures, could be at increased risk.
page source: http://www.grida.no/climate/ipcc/regional/173.htm 23jan01
Authors: Robert T. Watson (co-chair of IPCC Working Group II until September 1997, at which time he assumed the overall chairmanship of the IPCC. He also is Director of the Environment Department of the World Bank. Before taking up his current responsibilities, he was Associate Director for Environment in the Office of Science and Technology Policy, Executive Office of the President of the United States of America. He previously held the positions of Director of the Science Division and Chief Scientist for the Office of Mission to Planet Earth at NASA. He served as Chair of the Science and Technical Advisory Panel to the Global Environmental Facility), Marufu C. Zinyowera (co-chair of IPCC Working Group II until September 1997. He has been Director of the Zimbabwe Meteorological Services since 1984, and has represented Zimbabwe in many meteorological and environmental fora) and Richard H. Moss (Head of the IPCC Working Group II Technical Support Unit since 1993. Prior to this, he was Deputy Director of the Human Dimensions of Global Environmental Change Programme at the International Geosphere-Biosphere Programme in Stockholm, Sweden. He also served on the faculty of Princeton University, United States).
Edited by: Robert T. Watson (The World Bank), Marufu C. Zinyowera (Zimbabwe Meteorological Services), Richard H. Moss (Battelle Pacific Northwest National Laboratory), David J. Dokken (Project Administrator)
paper index: http://www.grida.no/climate/ipcc/regional/index.htm
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