Climate creates opportunities and limitations for outdoor recreation. It is a major influence on the economic viability of some recreation enterprises. Several studies have projected shorter North American skiing seasons as a result of climate change. In a study of the implications of an effective CO2 doubling on tourism and recreation in Ontario, Canada, Wall (1988) projected that the downhill ski season in the South Georgian Bay region could be eliminated. This outcome assumed a temperature rise of 3.5-5.7�C and a 9% increase in annual precipitation levels. Some of these losses would be offset by an extended summer recreational season. Lamothe and P�riard (1988) examined the implications of a 4-5�C temperature rise throughout the downhill skiing season in Quebec. They projected a 50-70% decrease in the number of ski days in southern Quebec; ski resorts equipped with snowmaking devices probably would experience a 40-50% reduction in the number of ski days. This change in winter recreational traffic would have direct implications for road traffic (down) and requirements for snow-removal and road repair (also probably down). On the other hand, Masterton et al. (1976) have noted that low temperatures are a limiting factor on recreation activity in the northern part of the prairie provinces. The summer recreation season in many areas may be extended (Masterton et al., 1976; Staple and Wall, 1994). Warmer temperatures may offset some of the costs of sea-level rise for recreational barrier islands.
Human settlements and infrastructure are especially vulnerable to several types of extreme weather events, including droughts, intense precipitation, extreme temperature episodes, high winds, and severe storms. Hence, there could be impacts should the frequency or intensity of these extreme events increase or decrease with climate warming.
Weather-related natural disasters (wildfires, hurricanes, severe storms, ice, snow, flooding, drought, tornadoes, and other extreme weather events) are estimated to have caused damages in the United States averaging about $39 billion per year during the years 1992-96 (FEMA, 1997). Those losses included damages to structures (buildings, bridges, roads, etc.) and losses of income, property, and other indirect consequences.
As indicated in Section 8.2.3 and IPCC (1996, WG I, Section 6.5), the ability to predict changes in the frequency or intensity of extreme weather events using global and regional models has been limited by their lack of small-scale spatial and temporal resolution and uncertainties about representation of some processes.3 Historical changes in frequencies of extreme events also provide some insights on possible changes, but there is debate about which changes are significant and which are unambiguously attributable to climate warming. However, some indications of directions of change have been inferred from observations and model simulations for North America, particularly regarding increased variability of precipitation. Beyond those inferences, a number of vulnerabilities of resources to extreme events have been identified should such events increase in frequency or magnitude. Conversely, decreases in extreme events could reduce levels of damages currently experienced. Additional research is needed to better understand the sensitivity and vulnerabilities of North American human settlements and infrastructure to extreme events, including factors beyond climate that are changing those vulnerabilities.
Flooding may be a very important impact because of the large amount of property and human life potentially at risk in North America, as is evident from historical disasters. There have been relatively few studies addressing the change in risk directly because of the lack of credible climate change scenarios at the level of detail necessary to predict flooding.
The evidence for an increasing trend in warm-period rainfall intensities in the United States (discussed in Section 8.2.2) suggests the potential for a shift in the periodicity of the flood regime in North America. More frequent or more extreme flooding could cause considerable disruption of transportation and water supply systems.
Increases in heavy rainfall events (e.g., suggested changes in frequency of intense subtropical cyclones) (Lambert, 1995) and interactions with changes in snowmelt-generated runoff could increase the potential for flooding of human settlements in many water basins. Changes in snowmelt runoff may add to or subtract from rainfall events, depending on basin characteristics and climate changes for a basin. Extreme rainfall events can have widespread impacts on roads, railways, and other transportation links. As long as rainfall does not become more intense, impacts on urban roads and railways in temperate, tropical, and subtropical zones are likely to be modest.
Some areas in North America may experience changed risks of wildfire, land slippage, and severe weather events in a changed climate regime. Although this increase in risk is predicated on changes in the frequency or intensity of extreme weather events-about which there is controversy-considering these risks in the design of long-lived infrastructure may prove cost-effective in some circumstances. Human settlement infrastructure has increasingly concentrated in areas vulnerable to wildfire, such as the chaparral hillsides in California. Settlements in forested regions in many areas are vulnerable to seasonal wildfires. Areas of potentially increased fire danger include broad regions of Canada (Street, 1989; Forestry Canada, 1991) and seasonally dry Mediterranean climates like the state of California in the United States. It is possible that fuel buildup under drought conditions would decrease, decreasing fire intensities. Although generally less destructive of life than in many developing world locations, landslides triggered by periodic heavy rainfall events threaten property and infrastructure in steep lands of the western United States and Canada. Relict landslides occur in much of northern Europe and North America (Johnson and Vaughan, 1989). Although stable under present natural conditions, these landslides are reactivated by urban construction activities and are triggered by heavy rains (Caine, 1980). Lands denuded of vegetation by wildfire or urban development also are vulnerable.
Although there has been an apparent downward trend in Atlantic hurricanes in recent years (e.g., Landsea et al., 1996), not all authors agree (Karl et al., 1995b). What is certain is that the amount of property and the number of people in areas known to be vulnerable to hurricanes is large and increasing in low-lying coastal areas in much of the United States Atlantic and Gulf coasts. For example, although data on the amount or proportion of national physical assets exposed to climate hazards are not readily available, it is known that in the United States about $2 trillion in insured property value lies within 30 km of coasts exposed to Atlantic hurricanes (IRC, 1995).
Most authors have found increases in seasonal minimum temperatures in North America, but not in seasonal maximums (IPCC 1996, WG I, Chapter 3). These results would suggest reduced incidence of cold-related problems without a concomitant increase in heat-related problems. However, increases in regional cold outbreaks occurred from the late 1970s to the mid-1980s. There has been little evidence of an increase in danger from tornadoes in the region (Grazulis, 1993; Ostby, 1993).
Offshore oil and gas exploration and production would be influenced by change in extreme events. In the south, an increase in extreme storm events in the Gulf of Mexico may mean increasing fixed and floating platform engineering standards (i.e., more expensive platforms) and more frequent and longer storm interruptions. In terms of interruptions, weather-related production shutdowns result in losses to production companies in the range of $1 million dollars per day-$10,000-50,000 per facility where evacuation is necessary. The industry defers millions of dollars annually in royalties (approximately $7 million each day for offshore Gulf of Mexico facilities) paid for hydrocarbon produced from fields owned by the public.
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