Ontong Java Atoll Shortland Islands Choiseul South Pacific Ocean Vella Lavella Kolombangara Santa Isabel Ranongga New N Georgia e Sikaiana Atoll w G Rendova Vangunu eo rg ia Malaita Is Russell Islands lan ds HONIARA Guadalcanal Solomon Sea Ugi I. Makira Ndeni Utupua Rennell Vanikoro Is. Current and future climate of the Solomon Islands > Solomon Islands Meteorological Service > Australian Bureau of Meteorology > Commonwealth Scientific and Industrial Research Organisation (CSIRO) Current climate of the Solomon Islands Temperatures in the Solomon Islands are relatively constant throughout the occurs across the tropical Pacific Ocean year with only very small changes from season to season. Across the Solomon and affects weather around the world. Islands temperatures are strongly tied to changes in the surrounding ocean There are two extreme phases of the temperature. The country has two distinct seasons – a wet season from El Niño-Southern Oscillation: El Niño November to April and a dry season from May to October (Figure 1). and La Niña. There is also a neutral phase. El Niño events bring warmer, Honiara has a very marked wet season thunderstorm activity. The South Pacific drier wet season conditions, while when on average almost 70% of the Convergence Zone extends across the La Niña events usually bring cooler, yearly total rain falls. In the dry season Pacific Ocean from the Solomon Islands wetter wet seasons. The impact is (May to October) on average about to the Cook Islands. The Intertropical stronger in Santa Cruz than in Honiara. 100 mm falls per month compared to Convergence Zone extends across upwards of 300 mm in wet season the Pacific just north of the equator months. Further to the east, Santa (Figure 2). The West Pacific Monsoon extreme Cruz receives more constant rainfall also influences rainfall in the Solomon weather events during the year, averaging between Islands. The monsoon is driven by Tropical cyclones result in 280 mm and 420 mm per month. large differences in temperature flooding and wind damage in between the land and the ocean, and Rainfall in the Solomon Islands is the Solomon Islands. There its arrival usually brings a switch from affected by the movement of the have been severe floods on very dry to very wet conditions. South Pacific Convergence Zone and Guadalcanal, Malaita, Makira the Intertropical Convergence Zone. The climate of the Solomon Islands and Santa Isabel in recent These bands of heavy rainfall are varies considerably from year to year years with a number of lives caused by air rising over warm water due to the El Niño-Southern Oscillation. lost, and severe damage to where winds converge, resulting in This is a natural climate pattern that agriculture and infrastructure. Maximum temperature Average temperature Minimum temperature Sea surface temperature 35 35 35 500 Honiara, Solomon Islands, 159.97ºE, 9.42ºS 500 Santa Cruz, Solomon Islands, 165.80°E, 10.70°S 400 400 30 30 300 300 25 25 200 200 Temperature (ºC) Temperature (ºC) Monthly rainfall (mm) Monthly rainfall (mm) 20 20 100 100 0 0 15 15 Jan Apr Jul Oct Jan Apr Jul Oct Figure 1: Seasonal rainfall and temperature at Honiara and Santa Cruz. 2 N H o N 20 o Federated States of Micronesia Palau Marshall Islands o n e I n t e r t r o p i c a l C o n v e r g e n c e Z Kiribati 10 o W a Nauru 0 r m p Tra de W inds o o l S o Papua New Guinea u M o t h Tu valu n Solomon Islands S s o P o East Timor o n a c i f i c C o n v e Samoa r g Vanuatu Fiji e n Niue c e S 10 Z o o To nga Cook Islands n e S 20 H o 0 500 1,000 1,500 2,000 30 Kilometres o E E E E E E E W W W W o o o o o o o o o o o 0 0 0 0 0 0 0 0 0 0 0 180 11 12 13 14 15 16 17 17 16 15 14 Figure 2: The average positions of the major climate features in November to April. The arrows show near surface winds, the blue shading represents the bands of rainfall convergence zones, the dashed oval shows the West Pacific Warm Pool and H represents typical positions of moving high pressure systems. 6 Tropical Tropical cyclones 11-yr moving average 5 cyclones 4 Tropical cyclones affect the Solomon Islands between 3 November and April. In the 2 41-year period between 1969 and 2010, 41 tropical cyclones 1 passed within 400 km of Number of tropical cyclones 0 Honiara, an average of one cyclone per season (Figure 3). 1969/701971/72 1973/74 1975/76 1977/78 1979/80 1981/82 1983/84 1985/86 1987/88 1989/90 1991/92 1993/94 1995/96 1997/98 1999/00 2001/02 2003/04 2005/06 2007/08 2009/10 The number of cyclones varies widely from year to year, with Figure 3: Number of tropical cyclones passing within 400 km of Honiara. none in some seasons but up Eleven-year moving average in purple. to five in others. Over the period 1969–2010, cyclones occured more frequently in El Niño years. 3 Changing climate of the Solomon Islands Temperatures No rainfall change Instruments mounted on satellites and tide gauges are used to measure sea have increased Data for Honiara since 1950 level. Satellite data indicate the sea level show no clear trends in annual or has risen near the Solomon Islands Annual maximum and minimum seasonal rainfall. Over this period, by about 8 mm per year since 1993. temperatures have increased in Honiara there has been substantial variation This is larger than the global average since 1951 (Figure 4). Maximum in rainfall from year to year. of 2.8–3.6 mm per year. This higher temperatures have increased at a rate of rate of rise may be partly related to 0.15°C per decade since 1951. These natural fluctuations that take place year temperature increases are consistent Sea level has risen to year or decade to decade caused with the global pattern of warming. As ocean water warms it expands by phenomena such as the El Niño- causing the sea level to rise. The Southern Oscillation. This variation in melting of glaciers and ice sheets sea level can be seen in Figure 7 which also contributes to sea-level rise. includes the tide gauge record since 28.5 El Niño La Niña 1974 and satellite data since 1993. 28 Ocean acidification 27.5 has been increasing 27 emperature (ºC) T About one quarter of the carbon dioxide 26.5 emitted from human activities each year is absorbed by the oceans. As the 26 Average extra carbon dioxide reacts with sea 25.5 water it causes the ocean to become slightly more acidic. This impacts 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 the growth of corals and organisms Year that construct their skeletons from Figure 4: Annual average temperature for Honiara. Light blue bars indicate carbonate minerals. These species are El Niño years, dark blue bars indicate La Niña years and the grey bars critical to the balance of tropical reef indicate neutral years. ecosystems. Data show that since the 18th century the level of ocean 4000 El Niño La Niña acidification has been slowly increasing 3500 in the Solomon Islands’ waters. 3000 2500 2000 Rainfall (mm) 1500 1000 500 0 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 Year Figure 5: Annual rainfall for Honiara. Light blue bars indicate El Niño years, dark blue bars indicate La Niña years and the grey bars indicate neutral years. Coastal village of Lilisiana, Malaita Province. 4 Future climate of the Solomon Islands Climate impacts almost all aspects of life in the Solomon Islands. Understanding the possible future climate of the Solomon Islands is important so people and the government can plan for changes. How do scientists develop climate projections? Global climate models are the best tools or scenarios, in climate models. The for understanding future climate change. Intergovernmental Panel on Climate Climate models are mathematical Change (IPCC) developed a series of representations of the climate system plausible scenarios based on a set of that require very powerful computers. assumptions about future population They are based on the laws of physics changes, economic development and 2090 and include information about the technological advances. For example, 800 atmosphere, ocean, land and ice. the A1B (or medium) emissions scenario envisages global population peaking 2055 700 There are many different global climate 600 mid-century and declining thereafter, 2030 tion (ppm) models and they all represent the a r very rapid economic growth, and t climate slightly differently. Scientists 1990 500 n rapid introduction of new and more e from the Pacific Climate Change 400 c efficient technologies. Greenhouse on Science Program (PCCSP) have C 300 gas and aerosol emissions scenarios 2 evaluated 24 models from around O are used in climate modelling to the world and found that 18 best C provide projections that represent represent the climate of the western Figure 6: Carbon dioxide (CO ) a range of possible futures. 2 tropical Pacific region. These 18 models concentrations (parts per million, ppm) have been used to develop climate The climate projections for the associated with three IPCC emissions projections for the Solomon Islands. Solomon Islands are based on three scenarios: low emissions (B1 – blue), IPCC emissions scenarios: low (B1), medium emissions (A1B – green) and The future climate will be determined medium (A1B) and high (A2), for time high emissions (A2 – purple).