Feature article

Climate Change: the Intergovernmental Panel on Climate Change 4th Assessment Report – The South Pacific

Pene Lefale¹, Michele Hollis² and Jim Salinger³

This article highlights some of the key findings from the Small Islands chapter, released in April 2007, of Working Group II of the Intergovernmental Panel on Climate Change (IPCC), which includes material on the Pacific.

Working Group II identifies small islands, including those in the South Pacific, as one of four regions of the world likely to be especially affected by climate change. (The other three regions are the Arctic, Africa, and Asian megadeltas).

Small islands share many similar characteristics that enhance their vulnerability and reduce their resilience to climate change. These include small size, prone to natural disasters and climate extremes, limited resource base, large populations for the area they occupy (with high growth rates and densities), poorly developed infrastructure, extremely open economies, and low adaptive capacity. More details can be found at: www.ipcc.ch

Climate change already observed

• Annual and seasonal ocean surface and island air temperature increase of 0.6 –1.0°C since 1910 throughout a large part of the region southwest of the South Pacific Convergence Zone
• Significantly fewer cool days and cold nights, particularly in years after the onset of El Niño.
• Analyses of satellite and tide gauge data show a maximum rate of sea level rise in the central and eastern Pacific, spreading north and south around the subtropics of the Pacific Ocean near 90°E, mostly between 2.0–2.5 mm/ year, peaking at over 3 mm/year for the period 1950–2000.

Future climate projections

• Increased seasonal surface air temperature ranging from 0.45 to 3.11°C, relative to the baseline period of 1961–1990, by 2100.
• Projected changes in rainfall range from –14.0 to +14.6% by 2100 for the South Pacific, with more frequent heavy rainfall events.
• Projected globally averaged sea level rise at the end of the 21st century relative to 1980–1999 for the six SRES scenarios ranges from 0.19 to 0.58 mm/yr. Models indicate a geographical variation of sea level rise.
• The number of intense cyclones is likely to increase, though the total number of tropical cyclones overall may decrease on a global scale.

Future Impacts

Sea level rise

Sea level rise is likely to exacerbate inundation, storm surge, erosion, and other coastal hazards, thus threatening vital infrastructure, settlements, and facilities. Some studies suggest sea level rise could lead to possible reduction in island size, particularly in the Pacific, whilst others show a few islands are morphologically resilient and are expected to persist.

Port facilities at Suva, Fiji, and Apia, Samoa, are likely to experience overtopping, damage to wharves, and flooding of the hinterland following a 0.5 m rise in sea level combined with waves associated with a 1–in–50 year cyclone.

International airports on small islands are mostly sited on or within a few kilometres of the coast, and the main, and often only, road network runs along the coast. Under sea level rise scenarios, many of them are likely to be at serious risk.

Coral reefs, fisheries, and other marine-based resources

The impact of climate change is likely to be severe here. Fisheries make an important contribution to the GDP of many small island states. Changes in the occurrence and intensity of El Niño and La Niña events are likely to severely impact on commercial and artisanal fisheries. The following factors are very likely to affect the health of coral reefs and other marine ecosystems which sustain small island fisheries:

• increasing sea surface temperature and sea level
• increased turbidity, nutrient loading, and chemical pollution
• damage from tropical cyclones
• possible decreases in growth rates due to ocean acidifi cation

Such impacts will exacerbate non-climate change stresses on coastal systems. It is likely that these changes would in turn negatively affect the attraction of small islands as premier tourism destinations.

Pressure on water resources

There is strong evidence that under most climate change scenarios, water resources are likely to seriously compromised. Many islands in tropical regions are likely to experience increased water stress. Under all IPCC SRES scenarios, a 10% reduction in average rainfall by 2050 would lead to a 20% reduction in the size of the freshwater lens on Tarawa Atoll, Kiribati. Reduced rainfall coupled with sea level rise would compound this threat.

Human health effects

There is growing concern that climate change is likely to adversely affect human health. Many small islands are located in regions whose weather and climate are already conducive to the transmission of diseases such as malaria, dengue, filariasis, and food–water-borne diseases. Increasing temperatures and decreasing water availability are likely to increase burdens of diarrhoeal and other infectious diseases on some islands.

Economic impact

Without adaptation, by 2050, agricultural economic costs from climate change are likely to reach between 2–3% of 2002 GDP on high terrain islands (e.g., Fiji) and 17–18% of 2002 GDP on low terrain islands (e.g.,Kiribati). These figures are for mid-range climate change scenarios.

Costs & benefi ts of adaptation

Studies so far suggest that adaptation options for small island states are likely to be limited and the costs high relative to GDP. Despite this, "exploratory research" indicates prudent adaptation strategies can generate other benefits as well. For example, the use of waste-to-energy and other renewable energy systems can promote sustainable development, while strengthening resilience to climate change.

¹ Lead Author, Chapter 16: Small Islands, Working Group II, IPCC AR4. MetService of New Zealand, Wellington. Email: [email protected] ² NIWA, Wellington. Email: [email protected] ³ Lead Author, Chapter 11: Australia and New Zealand, Working Group II, IPCC AR4 NIWA, Auckland. Email: [email protected]