Future Climates

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The future climate of the Arctic may be strongly affected by the greenhouse effect, produced by industrial greenhouse gas emissions. The Earth's greenhouse effect is produced by naturally occurring constituents of the atmosphere such as water vapor and carbon dioxide, and also increasingly by the worldwide combustion of fossil fuels. Numerous general circulation models (GCMs) have attempted to simulate the expected global warming due to the greenhouse effect. Global temperatures will continue to rise, with average global surface temperatures projected to increase between 1.4°C and 5.8°C above the 1990 levels by 2100. All the models show higher annual mean temperatures in the Arctic, compared to the rest of the Earth, and even higher temperatures in winter and spring (see Global Warming).

These modeling results are the basis of the WMO/ UNEP (World Meteorological Organization/United Nations Environment Programme) Intergovernmental Panel on Climate Change (IPCC) predictions that the Arctic will warm more than the global mean, particularly in winter. The IPCC report also predicts Arctic landmasses to warm more rapidly than the ocean, while some models show the greatest temperature increases over the Arctic Ocean. The potential future global climate impacts could be severe, including a rising sea level, more intense precipitation events in some countries and increased risks of droughts in others, and severe effects on agriculture, water resources, and human health. The environment and most human activities in the Arctic are likely to be affected adversely (see Impacts of Climate Change). Because of the growing evidence of climate change, and widespread concern about its consequences, a number of major international efforts are now under way to investigate, understand, and assess climate change and its impacts worldwide.

Gunter Weller

See also Climate Change; Climate Oscillations; High Arctic; Microclimates; Polar Desert; Precipitation and Moisture; Climate: Research Programs; Weather

Further Reading

Barry, R.G. & R.J. Chorley, Atmosphere, Weather and Climate,

New York: Holt Rinehart and Winston, 1970 CIA, Polar Regions Atlas, US Central Intelligence Agency, 1978 Intergovernmental Panel on Climate Change, Climate Change. The Scientific Assessment, edited by J.T. Houghton, G.J. Jenkins & J.J. Ephraums, Cambridge and New York: Cambridge University Press, 1990

-, Climate Change 1995. Impacts, Adaptations and

Mitigation of Climate Change: Scientific-Technical Analysis Contributions of Working Group II to the Second Assessment Report of the Intergovernmental Panel on Climate Change, edited by R.T. Watson, M.C. Zinyowera, R.H. Moss & D.J. Dokken, Cambridge and New York: Cambridge University Press, 1996

-, Climate Change 2001: Impacts, Adaptation, and

Vulnerability. Contribution of Working Group II to the Third Assessment Report of the Intergovernmental Panel on Climate Change, edited by J. McCarthy, O.F. Canziani, N.A. Leary, D.J. Dokken & K.S. White, Cambridge and New York: Cambridge University Press, 2001 Jones, P.D., "Hemispheric surface temperature variations: a reanalysis and an update to 1993." Journal of Climate, 7 (1994): 1794-1802 Jones, P.D., S.C.B. Raper, R.S. Bradley, H.F. Diaz, P.M. Kelly & T.M.L. Wigley, "Northern Hemisphere surface air temperature variations, 1851-1984." Journal of Climatology and Applied Meteorology, 25 (1986): 161-179 Weller, G., "The Weather & Climate of the Arctic." In The Arctic: Environment, People, Policy, edited by M. Nuttall & T.V. Callaghan, Amsterdam: Harwood Academic Publishers, 2000


Variations in climate occur on a global scale on time scales from seasonal to many millions of years. The Arctic affects global climate through strong feedback processes in global atmosphere and ocean circulation, and thus may have played a particular role in natural climate variations on time scales of thousands of years. The impact of recent and future climate change on the Arctic is discussed in the entry on Impacts of Climate Change. Before embarking on the subject of climate change, a few terms should be defined.

Climate is used to denote an average, mean, or integrated state of the atmosphere and the underlying land or water on time scales of seasons or longer. Climate is usually determined through observed meteorological parameters, including temperature, precipitation, pressure, humidity, wind speed and wind direction, cloudiness, and sea surface temperatures for a given place or region over a longer time span; the World Meteorological Organization (WMO) specifies that at least a 30-year record is necessary to specify the climate of a locale.

Climate variability indicates changes in climatic conditions that are solely due to natural mechanisms and are unrelated to human activities; one may distinguish between external and internal natural variability indicating changes caused by processes external or internal to the Earth's climate system. Examples for external natural variability are changes in the sun's energy output (luminosity), variation of orbital characteristics of the Earth and resulting changes in solar energy received at the land surface, and more stochastic events such as meteorite impacts, which cause gas and particle clouds to be ejected into the atmosphere. Internal variability, that is, climate variation not forced by external agents, has been observed on all time scales from weeks to centuries and even millennia. They involve the components of the global climate system, particularly the atmosphere, hydrosphere, cryosphere, and the biosphere. The geosphere exerts an indirect influence on climate variability, which may however be decisive in controlling major shifts in the climatic state of the Earth (Clark et al., 1999).

Climate change is a variation in climatic parameters that is attributed directly or indirectly to human activity. Such variations take place in addition to or despite natural climate variability observed over a given time period. Anthropogenic forcing mechanisms that contribute to climate change include the emission of greenhouse gases (i.e., carbon dioxide, methane, nitrogen dioxide, ozone, and chlorofluorocarbons or CFCs) and aerosol particles (e.g., soot), the excessive exploitation of natural resources and deforestation, increased urbanization, and land-use changes. Note that climate change can result in warming or cooling of the Earth's near-surface atmosphere and may involve a few or all of the climate variables mentioned above. While this definition of climate change is compatible with that used by the United Nations Framework Convention on Climate Change, the Intergovernmental Panel on Climate Change uses this term to denote any change in climate over time, whether due to natural variability or as a result of human activity.

Figure 1: An example for the temperature and trace gas record as derived from the Vostok ice core, East Antarctica; note the periodicity (i.e., with respect to the peak of interglacials) in both data sets and the high degree of correlation between the data.

From Vital climate graphics, the impacts of climate change, UNEP and Grid Arendal, 2000

Figure 1: An example for the temperature and trace gas record as derived from the Vostok ice core, East Antarctica; note the periodicity (i.e., with respect to the peak of interglacials) in both data sets and the high degree of correlation between the data.

From Vital climate graphics, the impacts of climate change, UNEP and Grid Arendal, 2000

Global warming is commonly used to denote the enhanced greenhouse effect and the (supposedly) general increase in mean global surface temperatures. A strengthening of the greenhouse effect is caused by enhanced atmospheric concentrations of greenhouse gases such as carbon dioxide (see Greenhouse Gas Emissions). The most recent alteration of the natural greenhouse effect has been brought about through the large-scale utilization of fossil fuels and resulting increased emission of greenhouse gases since the end of the 19th century, with the onset of the industrial revolution. Major users of fossil fuels include industry, private households, and motorized vehicles. Global warming refers primarily to increases in surface temperatures and excludes cooling effects (which may similarly result from the processes involved) as well as changes in other climatic variables.

Climate forcing can be defined as an imposed perturbation of the Earth's energy balance (National Academy of Sciences, 2001) as an underlying cause of climate variability and climate change. The term indicates neither a natural nor anthropogenic origin. An increase in the sun's luminosity constitutes a positive forcing that would result in a warmer Earth, while a large volcanic eruption and the resulting aerosols in the lower stratosphere would lead to enhanced reflections of incoming solar radiation and thus a cooler Earth. These are examples of natural forcings. Examples of anthropogenic forcings include emissions of greenhouse gases or changes in land use, for example, the conversion of forests into agricultural land.

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