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Mediterranean

-35.6 to +55.1

-52.6 to +38.3

-61.0 to +6.2

Caribbean

-14.2 to+13.7

-36.3 to +34.2

-49.3 to +28.9

Indian Ocean

-5.4 to +6.0

-6.9 to +12.4

-9.8 to +14.7

Northern Pacific

-6.3 to +9.1

-19.2 to +21.3

-2.7 to +25.8

Southern Pacific

-3. 9 to +3.4

-8.23 to +6.7

-14.0 to+14.6

163.1.2 Sea levels

Sea-level changes are of special significance, not only for the low-lying atoll islands but for many high islands where settlements, infrastructure and facilities are concentrated in the coastal zone. Projected globally averaged sea-level rise at the end of the 21st century (2090 to 2099), relative to 1980 to 1999 for the six SRES scenarios, ranges from 0.19 to 0.58 m (Meehl et al., 2007). In all SRES scenarios, the average rate of sea-level rise during the 21st century very probably exceeds the 1961 to 2003 average rate (1.8 ± 0.5 mm/yr). Climate models also indicate a geographical variation of sea-level rise due to nonuniform distribution of temperature and salinity and changes in ocean circulation. Furthermore, regional variations and local differences depend on several factors, including non-climate-related factors such as island tectonic setting and postglacial isostatic adjustment. While Morner et al. (2004) suggest that the increased risk of flooding during the 21st century for the Maldives has been overstated, Woodworth (2005) concludes that a rise in sea level of approximately 50 cm during the 21st century remains the most reliable scenario to employ in future studies of the Maldives.

163.13 Extreme events

Global warming from anthropogenic forcing suggests increased convective activity but there is a possible trade-off between localised versus organised convection (IPCC, 2001). While increases in SSTs favour more and stronger tropical cyclones, increased isolated convection stabilises the tropical troposphere and this, in turn, suppresses organised convection, making conditions less favourable for vigorous tropical cyclones to develop. Thus, the IPCC (2001) noted that changes in atmospheric stability and circulation may produce offsetting tendencies.

Recent analyses (e.g., Brazdil et al., 2002; Mason, 2004) since the TAR confirm these findings. Climate modelling with improved resolutions has demonstrated the capability to diagnose the probability of occurrence of short-term extreme events under global warming (Meehl et al., 2007). Vassie et al. (2004) suggest that scientists engaged in climate change impact studies should also consider possible changes in swell direction and incidence and their potential impacts on the coasts of small islands. With an increasing number of people living close to the coast, deep ocean swell generation, and its potential modifications as a consequence of climate change, is clearly an issue that needs attention, alongside the more intensively studied topics of changes in mean sea level and storm surges.

Although there is as yet no convincing evidence in the observed record of changes in tropical cyclone behaviour, a synthesis of the recent model results indicates that, for the future warmer climate, tropical cyclones will show increased peak wind speed and increased mean and peak precipitation intensities. The number of intense cyclones is likely to increase, although the total number may decrease on a global scale (Meehl et al., 2007). It is likely that maximum tropical cyclone wind intensities could increase, by 5 to 10% by around 2050 (Walsh, 2004). Under this scenario, peak precipitation rates are likely to increase by 25% as a result of increases in maximum tropical cyclone wind intensities, which in turn cause higher storm surges. Although it is exceptionally unlikely that there will be significant changes in regions of formation, the rate of formation is very likely to change in some regions. Changes in tropical cyclone tracks are closely associated with ENSO and other local climate conditions. These suggest a strong possibility of higher risks of more persistent and devastating tropical cyclones in a warmer world.

Mid-latitude islands, such as islands in the Gulf of St. Lawrence and off the coast of Newfoundland (St. Pierre et Miquelon), are exposed to impacts from tropical, post-tropical, and extra-tropical storms that can produce storm-surge flooding, large waves, coastal erosion, and (in some winter storms) direct sea ice damage to infrastructure and property. Possible increases in storm intensity, rising sea levels, and changes in ice duration and concentration, are projected to increase the severity of negative impacts progressively, particularly by mid-century (Forbes et al., 2004). In the Queen Charlotte Islands (Haida Gwaii) off the Canadian Pacific coast, winter storm damage is exacerbated by large sea-level anomalies resulting from ENSO variability (Walker and Barrie, 2006).

16.3.2 Other relevant conditions

Populations on many small islands have long developed and maintained unique lifestyles, adapted to their natural environment. Traditional knowledge, practices and cultures, where they are still practised, are strongly based on community support networks and, in many islands, a subsistence economy is still predominant (Berkes and Jolly, 2001; Fox, 2003; Sutherland et al., 2005). Societal changes such as population growth, increased cash economy, migration of people to urban centres and coastal areas, growth of major cities, increasing dependency on imported goods which create waste management problems, and development of modern industries such as tourism have changed traditional lifestyles in many small islands. Trade liberalisation also has major implications for the economic and social well-being of the people of small islands. For example, the phasing out of the Lomé Convention and the implementation of the Cotonou Agreement will be important. The end of the Lomé Convention means that the prices the EU pays for certain agricultural commodities, such as sugar, will decline. Such countries as Fiji, Jamaica and Mauritius may experience significant contractions in GDP as a result of declining sugar prices (Milner et al., 2004). In Fiji, for example, where 25% of the workforce is in the sugar sector, the replacement of the Lomé Convention with the terms of the Cotonou Agreement is likely to result in significant unemployment and deeper impoverishment of many of the 23,000 smallholder farmers, many of whom already live below the poverty line (Prasad, 2003). Such declines in the agricultural sector, resulting from trade liberalisation, heighten social vulnerability to climate change. These changes, together with the gradual disintegration of traditional communities, will continue to weaken traditional human support networks, with additional feedback effects of social breakdown and loss of traditional values, social cohesion, dignity and confidence, which have been a major component of the resilience of local communities in Pacific islands.

16.4 Key future impacts and vulnerabilities

The special characteristics of small islands, as described in Section 16.2.1, make them prone to a large range of potential impacts from climate change, some of which are already being experienced. Examples of that range, thematically and geographically, are shown in Box 16.1. Further details on sectors that are especially vulnerable in small islands are expanded upon below.

16.4.1 Water resources

Owing to factors of limited size, availability, and geology and topography, water resources in small islands are extremely vulnerable to changes and variations in climate, especially in rainfall (IPCC, 2001). In most regions of small islands, projected future changes in seasonal and annual precipitation are uncertain, although in a few instances precipitation is likely to

Box 16.1. Range of future impacts and vulnerabilities in small islands

Numbers in bold relate to the regions defined on the map

Numbers in bold relate to the regions defined on the map

Region* and system at risk

Scenario and reference

Changed parameters

Impacts and vulnerability

1. Iceland and isolated Arctic islands of Svalbard and the Faroe Islands: Marine ecosystem and plant species

SRES A1 and B2 ACIA (2005)

Projected rise in temperature

• The imbalance of species loss and replacement leads to an initial loss in diversity. Northward expansion of dwarf-shrub and tree-dominated vegetation into areas rich in rare endemic species results in their loss.

• Large reduction in, or even a complete collapse of, the Icelandic capelin stock leads to considerable negative impacts on most commercial fish stocks, whales, and seabirds.

2. High-latitude islands (Faroe Islands): Plant species

Scenario I / II: temperature increase / decrease by 2°C. Fosaa et al. (2004)

Changes in soil temperature, snow cover and growing degree days

• Scenario 1: Species most affected by warming are restricted to the uppermost parts of mountains. For other species, the effect will mainly be upward migration.

• Scenario II: Species affected by cooling are those at lower altitudes.

3. Sub-Antarctic Marion Islands: Ecosystem

Own scenarios Smith (2002)

Projected changes in temperature and precipitation

• Changes will directly affect the indigenous biota. An even greater threat is that a warmer climate will increase the ease with which the islands can be invaded by alien species.

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