One of the most important continent-wide issues is the effect of climate change on future water resources, particularly on extreme events-whether abundance or scarcity of water will increase in severity. A tendency toward increases in the frequency of extreme events is likely but largely unquantified. The implications of changes in the characteristics of extreme hydrological events extend beyond the water sector into agriculture, industry, settlements, coastal zones, transport, tourism, health, and insurance. Climate change is likely to lead to increased winter flows in much of Europe. In Mediterranean Europe, it is likely to increase variability in flow through the year, with summer flows reduced. In coastal areas, the risk of flooding and erosion will increase substantially. Instability of thermohaline circulation is a process whose probability of occurrence in the 21st century is low (see Chapters 3 and 19), yet potential consequences of this on the changing heat budget in Europe are very great.
Climatic observations and the scenarios presented here suggest that southern Europe will be more adversely affected than northern Europe. A shift in climate-related resources from south to north may occur in sectors such as tourism, agriculture, and forestry. In particular, the Mediterranean region appears likely to be adversely affected. Among likely adverse effects are increased variability of river flow; increased flood risk; decreased summer runoff and recharge of aquifers; and reduced reliability of public water supply, power generation, and irrigation. Increased fire hazards affecting populated regions and forests and heat stress to humans, crops, and livestock may occur. Even a change of tourist destinations is possible if the present optimal summertime climate shifts northward, and heat waves and water shortages may jeopardize the attractiveness of the present southern summer destinations.
Sustainable development (understood as relaying natural capital to future generations in a nondepleted state) has been in jeopardy in Europe from several existing pressures, mostly nonclimatic (e.g., land-use change, environmental pollution, atmospheric deposition). Yet climate change adds an important element to the threat to the environment. Sea-level rise threatens coastal habitats with a squeeze between hard defenses and rising water levels. Most (50-90%) of the alpine glaciers could disappear by the end of the 21st century, and there may be local extinctions of species that require cold habitats for their survival (e.g., subarctic and montane species). Many ecosystems will respond to climate change via migration and change; a policy challenge is how to manage these changes.
Finally, climate change impacts will be differently distributed among different regions, generations, age classes, income groups, occupations, and genders. This has important equity implications, although these implications have not been investigated in detail. For example, elderly and sick people suffer more in heat waves. There is greater vulnerability, in general, in southern than in northern Europe. Mediterranean and mountain farmers are likely to be worse off in a warmer world. This presents a challenge to existing regional policies within the EU that are aimed at leveling up less-developed areas (peripheral Europe versus core Europe). In general, the more marginal and less wealthy areas will be less able to adapt, so climate change without appropriate policies of response may lead to greater inequity.
Possible climate change impacts on key resources are sufficient to warrant early consideration by European policymakers to ensure sustainable development. In general, the adaptation potential of socioeconomic systems in much of Europe is high because of economic conditions, a stable population with the capacity to move within the region, and well-developed political, institutional, and technological support systems.
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