Defining possible future socio-economic conditions is a key to understanding future vulnerabilities to climatic change and assessing the capacity to adapt in the face of new risks and opportunities. A range of tools, including scenarios and storylines, has been used to develop characterisations of the future (Chapter 2). While specific characterisations have been developed for vulnerability and adaptation studies in certain climate-sensitive sectors (for example, Arnell et al., 2004; Nicholls, 2004), few characterisations have been developed that relate specifically to climate impacts as they could affect industry, settlement and society. Where such characterisations have been done (e.g., NACC, 2000; London Climate Change Partnership, 2004; Raskin et al., 2005), they have common roots in the perspectives embedded in the IPCC Special Report on Emissions Scenarios (SRES; Nakicenovic and Swart, 2000; see also Chapter 2, Section 2.4.6). Drivers in the SRES scenarios - population, economic growth, technology and governance - are all highly relevant for the development of industry, settlement and society.
A key future condition, for instance, is human population and its distribution. According to the latest United Nations projections (i.e., post-SRES), even as the rate of population growth continues to decline, the world's total population will rise substantially. The total is expected to reach between 8.7 and 9.3 billion in 2030 (UN, 2004). More than half these people live in urban centres, and practically all live in settlements, many depending on industry, services and infrastructures for jobs, well-being and mobility. Most population growth will take place in cities, largely in urban areas of developing countries, especially from Asia and Africa (Table 7.1). Some mega-cities will grow very substantially, but the major population growth will take place in medium cities of 1 to 5 million people and in small cities of under 500,000 people, which still represent half of the world population (Table 7.1, see also UN-Habitat, 2003).
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