Europe constitutes the western part of the Eurasian continent. Its eastern boundary is formed by the Ural Mountains, the Ural River, and part of the Caspian Sea. The proximity of the relatively warm Gulf Stream and typical atmospheric circulation contribute to the large spatial and temporal variability of the region's temperature and precipitation. South of the main Alpine divide, the climate is of the Mediterranean type.
Ecosystems: Natural ecosystems generally are fragmented, disturbed, and confined to poor soils. This situation makes them more sensitive to climate change. Mediterranean and boreal grasslands may shift in response to changes in the amount and the seasonal distribution of precipitation. The northern boundaries of forests in Fennoscandia and northern Russia would likely expand into tundra regions, reducing the extent of tundra, mires, and permafrost areas. Survival of some species and forest types may be endangered by the projected movement of climate zones at rates faster than migration speeds. High-elevation ecosystems and species are particularly vulnerable because they have nowhere to migrate. An increase in temperature, accompanied by decreases in soil moisture, would lead to a substantial reduction in peat formation in Fennoscandian and northern Russian peatlands. Thawing of the permafrost layer would lead to lowered water tables in some areas and would flood thaw lakes in others, altering current wetland ecosystem types. Although the diversity of freshwater species may increase in a warmer climate, particularly in middle and high latitudes, there may be an initial reduction in species diversity in cool temperate and boreal regions. Ecosystems in southern Europe would be threatened mainly by reduced precipitation and subsequent increases in water scarcity.
Hydrology and Water Resources: Most of Europe experienced temperature increases this century larger than the global average, and enhanced precipitation in the northern half and decreases in the southern half of the region. Projections of future climate, not taking into account the effect of aerosols, indicate that precipitation in high latitudes of Europe may increase, with mixed results for other parts of Europe. The current uncertainties about future precipitation are mainly exacerbated by the effects of aerosols.
Water supply may be affected by possible increases in floods in northern and northWest Europe and by droughts in southern portions of the continent. Many floodplains in western Europe already are overpopulated, which hampers effective additional flood protection. Pollution is a major problem for many rivers; a warmer climate could lead to reduced water quality, particularly if accompanied by reduced runoff. Warmer summers would lead to increased water demand, although increased demand for irrigation would be at least partly offset for many crops by increased water-use efficiency associated with CO2 fertilization.
Expected changes in snow and ice will have profound impacts on European streams and rivers. Up to 95% of Alpine glacier mass could disappear by 2100, with subsequent consequences for the water flow regime-affecting, for example, summer water supply, shipping, and hydropower. Also, in some areas, winter tourism would be negatively affected.
Water management is partly determined by legislation and cooperation among government entities, within countries and internationally; altered water supply and demand would call for a reconsideration of existing legal and cooperative arrangements.
Food and Fiber Production: Risks of frost would be reduced in a warmer climate, allowing winter cereals and other winter crops to expand to areas such as southern Fennoscandia and western Russia. Potential yields of winter crops are expected to increase, especially in central and southern Europe, assuming that neither precipitation nor irrigation are limiting and that water-use efficiency increases with the ambient atmospheric concentration of CO2. Increasing spring temperatures would extend suitable zones for most summer crops. Summer crop yield increases are possible in central and eastern Europe, though decreases are possible in western Europe. Decreases in precipitation in southern Europe would reduce crop yields and make irrigation an even larger competitor to domestic and industrial water use. Along with potential crop yields, farmer adaptation, agricultural policy, and world markets are important factors in the economic impact of climate change on the agricultural sector.
Coastal Systems: Coastal zones are ecologically and economically important. Settlement and economic activity have reduced the resilience and adaptability of coastal systems to climate variability and change, as well as to sea-level rise. Some coastal areas already are beneath mean sea level, and many others are vulnerable to storm surges. Areas most at risk include the Dutch, German, Ukrainian, and Russian coastlines; some Mediterranean deltas; and Baltic coastal zones. Storm surges, changes in precipitation, and changes in wind speed and direction add to the concern of coastal planners. In general, major economic and social impacts can be contained with relatively low investment. This is not true, however, for a number of low-lying urban areas vulnerable to storm surges, nor for ecosystems-particularly coastal wetlands-which may be even further damaged by protective measures.
Human Settlements: Supply and demand for cooling water will change. Energy demand may increase in summer (cooling) and decrease in winter (heating), and peak energy demand will shift. Infrastructure, buildings, and cities designed for cooler climates will have to be adjusted to warming, particularly heat waves, to maintain current functions. In areas where precipitation increases or intensifies, there are additional risks from landslides and river floods.
Human Health: Heat-related deaths would increase under global warming and may be exacerbated by worsening air quality in cities; there would be a reduction in cold-related deaths. Vector-borne diseases would expand. Health care measures could significantly reduce such impacts.
Conclusions: Even though capabilities for adaptation in managed systems in many places in Europe are relatively well established, significant impacts of climate change still should be anticipated. Major effects are likely to be felt through changes in the frequency of extreme events and precipitation, causing more droughts in some areas and more river floods elsewhere. Effects will be felt primarily in agriculture and other water-dependent activities. Boreal forest and permafrost areas are projected to undergo major change. Ecosystems are especially vulnerable due to the projected rate of climate change and because migration is hampered.
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