Assumptions about future trends for coastal systems and lowlying areas

This section builds on Chapter 2 and Section 6.2 to develop relevant environmental, socio-economic, and climate change scenarios for coastal areas through the 21st century. The IPCC Special Report on Emissions Scenarios (SRES; Nakicenovic and Swart, 2000) provides one suitable framework (Arnell et al., 2004; Chapter 2, Section 2.4).

6.3.1 Environmental and socio-economic trends

In the SRES, four families of socio-economic scenarios (A1, A2, B1 and B2) represent different world futures in two distinct dimensions: a focus on economic versus environmental concerns, and global versus regional development patterns. In all four cases, global gross domestic product (GDP) increases substantially and there is economic convergence at differing rates. Global population also increases to 2050 but, in the A1/B1 futures, the population subsequently declines, while in A2/B2 it continues to grow throughout the 21st century (see Chapter 2, Box 2.2). Relevant trends for coastal areas under the SRES scenarios are described in Table 6.1.

National coastal socio-economic scenarios have also been developed for policy analysis, including links to appropriate climate change scenarios. Examples include the UK Foresight Flood and Coastal Defence analysis (Evans et al., 2004a,b; Thorne et al., 2006), and the US National Assessment (NAST, 2000), while model-based methods have been applied to socio-economic futures in the Ebro delta, Spain (Otter, 2000; Otter et al., 2001). However, socio-economic scenarios of coastal areas are underdeveloped relative to climate and sea-level scenarios.

6.3.2 Climate and sea-level scenarios

In terms of climate change, the SRES scenarios in Section 6.3.1 translate into six greenhouse-gas emission 'marker' scenarios: one each for the A2, B1 and B2 worlds, and three scenarios for the A1 world - A1T (non-fossil fuel sources), A1B (balanced fuel sources) and A1FI (fossil-intensive fuel sources) (Nakicenovic and Swart, 2000). B1 produces the lowest emissions and A1FI produces the highest emissions (see Chapter 2).

Table 6.2 summarises the range of potential drivers of climate change impacts in coastal areas, including the results from Meehl et al. (2007) and Christensen et al. (2007). In most cases

1A clade of algae is a group of closely related, but nevertheless different, types.

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