Key future impacts and vulnerabilities

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The ability to project how climate change may affect industry, settlement and society is limited by uncertainties about climate change itself at a relatively fine-grained geographical and sectoral scale and also by uncertainties about trends in human systems over the next century regardless of climate change (Chapter 2). In some cases, uncertainties about socio-economic factors such as technological and institutional change over many decades undermine the feasibility of comparing future prospects involving considerable climate change with prospects involving relatively little climate change. Typically, therefore, research often focuses on vulnerabilities to impacts of climate change (defined as the degree to which a system, subsystem or system component is likely to experience harm due to exposure to a perturbation or source of stress (Turner et al., 2003a; also see Clark et al., 2000) rather than on projections of impacts of change on evolving socioeconomic systems, especially in the longer run.

Furthermore, climate change will not often be a primary factor in changes for industry, settlement and society. Instead, it will have an impact by modifying other more significant aspects of ongoing socio-economic changes. This may have either an exacerbating or an ameliorating effect in influencing overall vulnerabilities to multi-causal change. It is especially difficult to associate levels of climate-change impacts or their costs with a specified number of degrees of mean global warming or with a particular time horizon such as 2050 or 2080, when so many of the main drivers of impacts and costs are not directly climate-related, even though they may be climate-associated, and when impacts are often highly localised. Some projections have been made for particular sectors or areas and they are cited in appropriate sections below; but in general they should be considered with caution, especially for longer-range futures.

7.4.1 General effects

Certain kinds of effects follow from particular manifestations of climate change, wherever those phenomena occur. For example, increased precipitation in already well-watered areas can increase concerns about drainage and water-logging

(Parkinson and Mark, 2005), while reduced precipitation in areas already subject to water shortages could lead to infrastructure crises. Sea-level rise will affect land uses and physical infrastructures in coastal areas. Changes in conditions can affect requirements for public health services (Chapter 8), water supplies (Chapter 3) and energy services (such as space heating and cooling). Effects can either be cumulative (additive), as in losses of property, or systematic (affecting underlying processes), as in damages to institutions or systems of production (Turner et al., 1990). Even very gradual changes can be associated with thresholds at which the resilience of human systems switches from adequate to inadequate, such as water-supply infrastructures faced with shrinking water availability. Parry et al. (2001), for instance, estimate that many tens of millions of the world's population are at risk of hunger due to climate change, and billions are at risk of water shortages.

Besides gradual changes in climate, human systems are affected by a change in the magnitude, frequency and/or intensity of storms and other extreme weather events, as well as changes in their location. In fact, some assessments suggest that many impact issues are more directly associated with climatic extremes than with averages (NACC, 2000). Of some concern is the possibility of abrupt climate changes (Chapter 19), which could be associated with locally or regionally catastrophic impacts if they were to occur.

Although localities differ, interactions between climate change and human systems are often substantively different for relatively developed, industrialised countries versus less developed countries and regions. In many cases, it appears that possible negative impacts of climate change pose risks of higher total monetary damages in industrialised areas (i.e., currency valuations of property damages) but higher total human damages in less-developed areas (i.e., losses of life and dislocations of population) - although such events as Hurricane Katrina show that there are exceptions (Section 7.4.2.5) for developed countries, and monetary damages in developing countries may represent a larger share of their GDP.

Not all implications of possible climate change are negative. For instance, along with possible carbon fertilisation effects and a longer growing season (Chapter 5), many mid- and upper-latitude areas see quality-of-life benefits from winter warming, and some areas welcome changes in precipitation patterns, although such changes could have other social consequences. The greater proportion of the research literature, however, is related to possible adverse impacts. Climate impact concerns include environmental quality (e.g., more ozone, water-logging or salinisation), linkage systems (e.g., threats to water and power supplies), societal infrastructures (e.g., changed energy/water/health requirements, disruptive severe weather events, reductions in resources for other social needs and maintaining sustainable livelihoods, environmental migration (Box 7.2), placing blame for adverse effects, changes in local ecologies that undermine a sense of place), physical infrastructures (e.g., flooding, storm damage, changes in the rate of deterioration of materials, changed requirements for water or energy supply), and economic infrastructures and comparative advantages (e.g., costs and/or risks increased, markets or competitors affected).

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