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The energy sector is diverse, but a few generalizations can be made. Many components of conventional energy supply systems that involve fossil and nuclear energy-including onshore extraction (with exceptions), land transportation of fuels, conversion, and end-use (except for space conditioning)-are largely independent of climate. However, exploration and well servicing offshore and in tundra and boreal regions, particularly in wet springs in boggy areas, are dependent on the climate regime; if climate conditions change (wetter or drier), the duration of the servicing/exploration season could change, with economic impacts in those sectors. Water transportation, activities in the arctic and mountainous areas, cooling systems for thermal power generation, and energy demand for space conditioning also may be affected to some degree by changes in climate, positively or negatively. Many renewable energy sources-such as hydropower, solar, wind, and biomass-are strongly affected by climate in positive or negative ways. Only large-scale hydropower and some biomass currently make a large contribution to the North American energy supply. However, this sector may become more dependent on renewable energy in the future, and hence more vulnerable to climate change, especially if greenhouse gas controls constrain the use of fossil fuels and current barriers to nuclear growth continue.
Thermal electric generating plants and nuclear energy plants are susceptible to hydrological and water resource constraints that affect their cooling water supply. Power plant output may be restricted because of reduced water availability or thermal pollution of rivers with a reduced flow of water. Events such as these have occurred during droughts in several parts of the world, including the United States (Energy Economist, 1988). Under more extreme temperature conditions, some nuclear plants might shut down to comply with safety regulations (Miller et al., 1992). Future power plants are less likely to depend on once-through cooling and may be designed to deal with anticipated shortages of cooling water supplies.
Hydroelectricity, which provides 20% of the region's electricity (and is the primary energy source in some areas of North America, such as the Pacific NorthWest and Quebec), depends on the quantity and seasonal distribution of precipitation. Greater annual precipitation overall in the North American region is projected, with the greatest increases in winter and spring. For the north, this likely will mean greater snowfall to be added to the spring runoff, which would put greater demand on reservoirs to even out electricity supply. For southern hydroelectric facilities, climate projections suggest greater seasonal variation-unfortunately not coincidental with anticipated increased demand for summer air conditioning. Some areas (particularly the southWest of the continent) may experience lower rainfalls in the summer and fall, which, along with increased demand for air-conditioning, would exacerbate peak power requirements. However, GCMs are less reliable in simulating regional precipitation than temperature, and these predictions currently are not sufficiently reliable as a basis for hydroelectric and water resource planning.
Local energy distribution will not be affected, but long-distance transmission lines and pipelines may be subject to land disturbances, particularly in the western mountains where increased precipitation may induce slope instability. In the north, the permafrost, which normally provides a solid base for construction and transportation, is expected to degrade or thaw faster in some areas, producing stress on structures that may have been designed for a permafrost regime. Projected changes include not only melting but also decreases in the strength properties of the permafrost and increases in frost heaving. The vulnerability of pipelines as a result of projected changes in underlying permafrost (Nixon et al., 1990) are expected to be particularly acute in discontinuous permafrost areas and in the southern reaches of continuous permafrost. As a result, modifications or repairs to pipelines may be necessary, and some concerns have been raised regarding the potential of increased risk of environmental contamination.
Small-hydropower-usually located in nondammed streams-may provide more power in periods of peak runoff. Solar energy is highly dependent on cloud cover, which may increase with the expected intensification of the hydrological cycle; the exception might be the south-central area of North America, where increased insolation is expected (and where it would coincide with increased electricity demand for space cooling). The wind-not yet a significant contributor to North America's energy supply-is a highly variable source. Biofuels, currently primarily wood waste and grains, provide about 4% of the region's primary energy supply; changes in the availability of these fuels are possible as a result of projected changes to forest growth and productivity (see Section 8.3.2) and projected changes in the availability (absolutely and regionally) of grains, mainly corn for ethanol (see Section 8.3.4.1). However, future growth in biofuels is likely to involve dedicated energy farms utilizing short-rotation, highly managed crops.
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