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Solomons - Climate

Solomon Islands climate is tropical, though temperatures are rarely extreme due to cooling winds blowing off the surrounding seas. Temperature is the least varied of climate parameters with daytime temperatures fluctuating between 25oC to 32oC. The rainy season occurs between November to April and the dry season from June to October during the year. Most islands have a mean annual rainfall of 3,000 to 5,500 mm with two-peak rainfalls during the year. The highest rainfall recorded in Solomon Islands is an annual average of 8,304 mm at 430 m above sea level at Koloula on Guadalcanal. Daily rainfall of over 250 mm is normal. High rainfall intensity events occur during tropical storms and often result in flooding of most river systems. The highest recorded rainfall of 281mm over a 12 hour period was recorded in 2009 resulting in destructive flooding and loss of lives. More recently the highest recorded daily rainfall of 318mm was recorded in April 2014 causing widespread flooding and damage to property, infrastructure and loss of 23 lives along the Mataniko River, Central Honiara. Rainfall trends vary across the country and are influenced by geographic differences.

Solomon Islands has been working actively on climate change adaptation for 20 years, and with the development of pioneering tools and methodologies that are regarded as best practices regionally and internationally, has made and continues to make a considerable contribution to the global and regional adaptation planning and management process and pool of knowledge on building climate resilience. This contribution is made in the face of severe constraints and challenges confronted by Solomon Islands as a small island developing States (SIDS) and Least Developed Country (LDC). For Solomon Islands, as with other small islands developing States and Least Developed Countries, where climate change threatens the very existence of the people and the nation, adaptation is not an option – but rather a matter of survival.

Current climate, projected climate change and related assumptions The interannual climate of Solomon Islands is basically driven by natural drivers such as the Inter-Tropical Convergence Zone (ITCZ), the South Pacific Convergence Zone (SPCZ), the West Monsoon and the El Nino Southern Oscillation (ENSO). The wet season is generally driven by the ITCZ and the West Monsoon resulting in strong north-westerly winds and seas affecting mostly the northern part of the country. Associated heavy and long rainfall periods usually influence agriculture activities in the northern parts of the country during this time. The SPCZ typically drives the weather and the climate of the southern part of Solomon Islands during the dry season where strong southeast trades brings onshore heavy rainfall that disturbs agricultural activities as well.

During an El Nino ocean surface waters over the western Pacific (including Solomon Islands) are usually cooler than normal and warmer than normal from central to eastern of the Pacific. Hence, in most cases, prolonged dry periods could escalate from meteorological drought to agricultural drought in the western Pacific. Solomon Islands experiences drought conditions during El Nino events such as that occurring in 1997 causing water shortages on many islands. The divergence results in nutrient rich waters rising to the ocean surface in the eastern Pacific causing outbreaks in plankton growth which is followed by tuna stocks.

During a La Nina event the opposite seems to happen, where waters over the western Pacific (including Solomon Islands) are warmer than normal hence causing more cloud formation resulting in prolonged and high rainfall periods. Cyclones and high rainfall events are associated with the La Nina periods in the western Pacific. The future of ENSO events is still not clear but it is expected that it will continue to be an important driver of Pacific Islands climate into the future.

Observed temperature data by the Solomon Islands Meteorological Services show that annual surface temperature for the western, central and eastern regions of Solomon Islands have increased during the last 30 to 50 years. The range of increase in mean air temperature for most provinces is between 0.14oC and 0.17oC/decade.

A study carried out by the Pacific Climate Change Scientific Programme (PCCSP) under Australian Government showed that for three emission scenarios (low, medium and high) using 18 Global Circulation Models the temperature in the Solomon islands will increase by 0.2oC (low) in 2030 to 3.3 oC (high) in 2090. The sea surface temperature (SST) is projected to increase in the next 30 -70 years in Solomon Islands.

Rainfall data analysed to date show that annual rainfall in the three regions (western, eastern and western Solomon Islands) is mostly varied due to the geography of the different islands, their relative position with each other, the direction and duration of prevailing winds and drivers of climate in the Pacific. However, it can be clearly seen that there were sharp declines around mid-1990s for all the three regions. These declines correlated with the severe El Nino event between 1997 and 1998 that affected most parts of the country. The general trends however show that in the central region there was a decrease in rainfall and a slight increase for the western and eastern regions in the past 30-50 years.

Tropical cyclones pose a serious threat to the people, economy and environment and result in flooding and wind damage in the Solomon Islands. There have been severe floods on Guadalcanal, Malaita, Makira and Santa Isabel in recent years with a number of lives lost, and severe damage to agriculture and Infrastructure. In 2002 the remote island of Tikopia was hit by a Category 5 cyclone Zoe.

In the Solomon Islands’ region, projections tend to show a decrease in the frequency of tropical cyclones by the late 21st century and an increase in the proportion of the more intense storms. As per Pacific Climate Change Science Program (Australian Government), by the end of this century projections suggest decreasing numbers of tropical cyclones but a possible shift towards more intense categories.

Solomon Islands is highly vulnerable to droughts, extreme rainfall, floods, king tides and sea level rise. Droughts are usually associated with the El Nino phenomenon. The 1997/98 El Nino caused severe drought conditions in many parts of the country and one of the major prolonged droughts occurred in the eastern part of the country in the Temotu province in 2004 causing food and water shortages. Another major problem associated with extremely high rainfall or prolonged rainfall is the big decline in the yields of sweet potato, the main staple crop in rural areas, due to increased vegetative growth and decline in the growth of tuber. Flooding can also occur as a result of a combination of factors, including king tides, areas associated with low atmospheric pressure, and rising sea levels. In 2008 king tides struck northern Choiseul, Ontong Java and other parts of the country. These came in the form of high swells never before experienced in the islands. The tides caused more coastal erosion, considerable damage to coral reefs, coastal inundation, pollution of water sources and damage to coastal infrastructures.

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Page last modified: 30-11-2021 13:07:02 ZULU