Some impacts of climate change are expected to be beneficial in some locations with a few degrees of warming (e.g., increased agricultural productivity in some regions, less need for space heating, opening of the Northwest Passage for shipping and resource exploitation).
|The first version of this article was drawn from Climate Change: Science Highlights by Jane Leggett, Congressional Research Service, February 23, 2009.|
Risks of abrupt, perhaps unidentified climate changes in aspects of the environment, with accompanying dislocations, are expected to increase as global average temperature increases, and could push natural and socioeconomic systems past key thresholds. An example that recently occurred is the rapid and widespread infestation of beetles in western North America. Such changes could precipitate major reorganization of ecosystems, and under some circumstances, stresses on nearby or dependent human systems.
Impacts on water resources are expected to be among the most serious due to climate change, combined with rising demand and management issues in many regions. Earlier melting of snowpack and ice in some regions (e.g., the Andes, the U.S. West) and loss of ice and snow would reduce water supply to settlements that now depend on the snowmelt, and change the seasonality of water supply. Snowfall in some regions is expected to increase, however, with greater atmospheric moisture.
One U.S. Climate Change Program (CCSP) assessment examined the implications of projected sea level rise, with emphasis on the U.S. mid-Atlantic region. It concluded:
Today, rising sea levels are submerging low-lying lands, eroding beaches, converting wetlands to open water, exacerbating coastal flooding, and increasing the salinity of estuaries and freshwater aquifers. Other impacts of climate change, coastal development, and natural coastal processes also contribute to these impacts. In undeveloped or less developed coastal areas where human influence is minimal, ecosystems and geological systems can sometimes shift upward and landward with the rising water levels. Coastal development, including buildings, roads, and other infrastructure, are less mobile and more vulnerable. Vulnerability to an accelerating rate of sea-level rise is compounded by the high population density along the coast, the possibility of other effects of climate change, and the susceptibility of coastal regions to storms and environmental stressors, such as drought or invasive species.
Agriculture in many regions, especially in the tropics, may experience losses of productivity, especially where higher temperatures coincide with increased dryness and limits on irrigation. The general shift upward in growing season temperatures could raise typical temperatures to or above those considered extreme today. Agriculture may also confront challenges from invasive species, including pests. One 2008 study examined four key pests of maize in the United States with climate change. It projected increased winter survival and expanded ranges of all four pests, especially of the corn earworm, which may be resistant to insecticides. The authors concluded that even with pest management adaptations, the effects of climate change could increase seed and insecticide costs, decrease yields and alter crop yield variability.
In 2008, a number of studies highlighted risks to human health with climate change, and at least one study found potential benefits of reduced cold weather mortality. Raised risks and adaptation costs could be associated with increased diarrhoeal disease, renal disease, heat stress, malaria, cholera, malnutrition, and respiratory and other health effects associated with elevated ozone and particulate air pollution due to higher temperatures, among other concerns.
Effects on, and concerns about, mental health have been raised by several studies, especially associated with projected increases in extreme weather events.
One 2008 study found potential for higher temperatures to result in lower ratios of male to female births and reduced male longevity in humans, at least in Nordic countries.
As the degree and distribution of climate changes continue, ranges of species are likely to change. Climate change is highly likely to create substantial changes in ecological systems and services in some locations, and may lead to ecological surprises. The disappearance of some types of climate also raises risks of extinctions of species, especially those with narrow geographic or climatic distributions, and where existing communities disintegrate. One study projected that, under the highest Intergovernmental Panel on Climate Change (IPCC) emissions scenario, 12% to 39% of the Earth’s land areas may experience novel climates (i.e., climate conditions not existing now) while 10% to 48% of land areas’ climates may disappear by 2100 AD. In the lowest IPCC climate change scenarios, 4% to 20% of land areas gain novel climates and 4% to 20% see existing climates disappear.
Because climate change will occur with different magnitudes and characteristics in different regions, resulting dislocations and disparities across locations are expected to increase pressure on international aid and migration, with possible implications for political stability and security.
Impacts may be alleviated with investments in adaptation. Adaptation as a strategy, however, is thought to be more challenging and potentially less effective the more widespread, uncertain and severe the climate changes.
- ^See CCSP, Coastal Sensitivity to Sea-Level Rise: A Focus on the Mid-Atlantic Region. A report by the U.S. Climate Change Science Program and the Subcommittee on Global Change Research. [James G. Titus (Coordinating Lead Author), K. Eric Anderson, Donald R. Cahoon, Dean B. Gesch, Stephen K. Gill, Benjamin T. Gutierrez, E. Robert Thieler, and S. Jeffress Williams (Lead Authors)], U.S. Environmental Protection Agency, Washington D.C., USA. (2009).
- ^See, for example, CCSP, Thresholds of Climate Change in Ecosystems. A report by the U.S. Climate Change Science Program and the Subcommittee on Global Change Research. [Fagre D.B., Charles C.W., Allen C.D., Birkeland C., Chapin F.S. III, Groffman P.M., Guntenspergen G.R., Knapp A.K., McGuire A.D., Mulholland P.J., Peters D.P.C., Roby D.D., and Sugihara G.] (2009) U.S. Geological Survey, Department of the Interior, Washington D.C., USA.
- ^CRS Report R40203, Mountain Pine Beetles and Forest Destruction: Effects, Responses, and Relationship to Climate Change, by Ross W. Gorte.
- ^CCSP, Coastal Sensitivity to Sea-Level Rise: A Focus on the Mid-Atlantic Region. A report by the U.S. Climate Change Science Program and the Subcommittee on Global Change Research. [James G. Titus (Coordinating Lead Author), K. Eric Anderson, Donald R. Cahoon, Dean B. Gesch, Stephen K. Gill, Benjamin T. Gutierrez, E. Robert Thieler, and S. Jeffress Williams (Lead Authors)], U.S. Environmental Protection Agency, Washington D.C., USA. (2009).
- ^David. S. Battisti and Rosamond L. Naylor, “Historical Warnings of Future Food Insecurity with Unprecedented Seasonal Heat,” Science 323, no. 5911 (January 9, 2009): 240-244.
- ^Noah S. Diffenbaugh et al., “Global warming presents new challenges for maize pest management”, Environ. Res. Lett. 3 (October-December 2008
- ^A. Analitis et al., “Effects of Cold Weather on Mortality: Results From 15 European Cities Within the PHEWE Project,” Am. J. Epidemiol. (October 24, 2008)
^CCSP, Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems. A Report by the U.S. Climate Change Science Program and the Subcommittee on Global Change Research. [Gamble, J.L. (ed.), K.L. Ebi, F.G. Sussman, T.J. Wilbanks, (Authors)]. U.S. Environmental Protection Agency, Washington, DC, USA (2008);
Bernard Doyon, Diane Bélanger, and Pierre Gosselin, “The potential impact of climate change on annual and seasonal mortality for three cities in Québec, Canada,” International Journal of Health Geographics 7 (2008);
Kristie L Ebi, “Adaptation costs for climate change-related cases of diarrhoeal disease, malnutrition, and malaria in 2030,” Globalization and Health 4 (2008);
Michael Emch et al., “Seasonality of cholera from 1974 to 2005: a review of global patterns,” International Journal of Health Geographics 7 (2008): 31;
Paola Michelozzi et al., “http://ajrccm.atsjournals.org/cgi/content/short/200802-217OCv1 High Temperature and Hospitalizations for Cardiovascular and Respiratory Causes in 12 European Cities],” Am. J. Respir. Crit. Care Med. (December 5, 2008)
Paul Reiter, “Global warming and malaria: knowing the horse before hitching the cart,” Malaria Journal 7, no. Suppl 1 (2008).
^Jessica G Fritze et al., “http://www.ijmhs.com/content/2/1/13 Hope, despair and transformation: Climate change and the promotion of mental health and wellbeing,” International Journal of Mental Health Systems 2 (2008);
Alana Hansen et al., “http://www.ehponline.org/docs/2008/11339/abstract.html The Effect of Heat Waves on Mental Health in a Temperate Australian City],” Environmental Health Perspectives 116, no. 10 (October 2008).
- ^Ralph Catalano, Tim Bruckner, and Kirk R. Smith, “Ambient temperature predicts sex ratios and male longevity,” Proceedings of the National Academy of Sciences (February 4, 2008).
- ^John W. Williams, Stephen T. Jackson, and John E. Kutzbach, “Projected distributions of novel and disappearing climates by 2100 AD,” Proceedings of the National Academy of Sciences of the United States of America 104, no. 14 (April 3, 2007).
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