Hikutavake Mutalau Toi Namukulu Tuapa Makefu Lakepa ALOFI Liku Hanan Airport Tamakautoga Avatele Vaiea Hakupu Village South Pacific Ocean Current and future climate of Niue > Niue Department of Meteorology and Climate Change > Australian Bureau of Meteorology > Commonwealth Scientific and Industrial Research Organisation (CSIRO) Niue’s current climate The annual average temperature on Niue is around 24°C. Changes in the the tropical Pacific Ocean and affects temperature from season to season are relatively small (4°C difference weather around the world. There are between the warmest and coolest months) and strongly tied to changes two extreme phases of the El Niño- in the surrounding ocean temperature. The country has two distinct seasons – Southern Oscillation: El Niño and La a warm wet season from November to April and a cooler dry season from Niña. There is also a neutral phase. May to October (Figure 1). El Niño events tend to bring drier than normal conditions to Niue, Niue’s wet season is affected by Niue’s climate is also influenced by particularly in the wet season. They the movement of the South Pacific sub-tropical high pressure systems also bring cooler conditions during Convergence Zone. This band of heavy and the trade winds, which blow the dry season. La Niña events rainfall is caused by air rising over mainly from the south-east. usually bring wetter conditions. The warm water where winds converge, Niue’s climate varies considerably drier conditions in El Niño years are resulting in thunderstorm activity. It from year to year due to the El Niño- often caused by the South Pacific extends across the South Pacific Southern Oscillation. This is a natural Convergence Zone moving away to the Ocean from the Solomon Islands climate pattern that occurs across north-east. In La Niña years the South to the Cook Islands (Figure 2). Pacific Convergence Zone moves south-east, bringing more rainfall. Maximum temperature Average temperature Annual rainfall in the wettest years Minimum temperature Sea surface temperature can be almost four times the rainfall 35 300 in the driest years. Severe droughts Hanan Airport, Niue, 169.93ºW, 19.08ºS have occurred in Niue, most recently in 1983, 1991 and 1998. 250 30 200 25 150 Temperature (ºC) Monthly rainfall (mm) 100 20 0 05 15 Jan Apr Jul Oct Figure 1: Seasonal rainfall and temperature at Hanan Airport. Coast at Limu Pools. 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 Niue between November and April. 3 In the 41-year period between 2 1969 and 2010, 63 tropical cyclones passed within 400 km 1 No. of tropical cyclones of Alofi, an average of one to two 0 cyclones per season. Over this period cyclones occurred more frequently in El Niño years. Niue’s 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 economy suffered significantly Figure 3: Number of tropical cyclones passing within 400 km of Alofi. from high winds, storm surge Eleven-year moving average in purple. and intense rainfall associated with Tropical Cyclone Heta on 4 January 2004. In all, it caused over NZ$37.7 million damage, three times Niue’s annual Gross Domestic Product. 3 Niue’s changing climate Temperatures Annual rainfall Sea level has risen have increased unchanged As ocean water warms it expands causing the sea level to rise. The Annual and seasonal maximum and Data for Hanan Airport since 1950 melting of glaciers and ice sheets minimum temperatures at Hanan Airport show no clear trends in annual or also contribute to sea-level rise. have increased since 1950 (Figure 4). seasonal rainfall (Figure 5). Over this Maximum temperatures have increased period, there has been substantial Instruments mounted on satellites and at a rate of 0.15°C per decade. These variation in rainfall from year to year. tide gauges are used to measure sea temperature increases are consistent level. Satellite data indicate the sea level with the global pattern of warming. has risen near Niue by about 5 mm per year since 1993. This is larger than the global average of 2.8–3.6 mm per 25.5 El Niño La Niña year. This higher rate of rise may be partly related to natural fluctuations that 25 take place year to year or decade to 24.5 decade caused by phenomena such as the El Niño-Southern Oscillation. 24 This variation in sea level can be seen emperature (ºC) T 23.5 in Figure 7 which includes the tide gauge record from the nearest tide 23 Average gauge to Niue (Raratonga in the Cook 22.5 Islands) and satellite data since 1993. 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 Ocean acidification Year Figure 4: Annual average temperature for Hanan Airport. Light blue bars has been increasing indicate El Niño years, dark blue bars indicate La Niña years and the grey About one quarter of the carbon dioxide bars indicate neutral years. emitted from human activities each year is absorbed by the oceans. As the extra carbon dioxide reacts with sea water 3500 El Niño La Niña it causes the ocean to become slightly 3000 more acidic. This impacts the growth of corals and organisms that construct 2500 their skeletons from carbonate minerals. 2000 These species are critical to the balance 1500 of tropical reef ecosystems. Data Rainfall (mm) show that since the 18th century the 1000 level of ocean acidification has been 500 slowly increasing in Niue’s waters. 0 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 Year Figure 5: Annual rainfall for Hanan Airport. Light blue bars indicate El Niño years, dark blue bars indicate La Niña years and the grey bars indicate neutral years. Reef flat at Tamakautoga. 4 Niue’s future climate Climate impacts almost all aspects of life in Niue. Understanding the possible future climate of Niue is important so people and the government can plan for changes. How do scientists develop climate projections? Global climate models are the best tools Intergovernmental Panel on Climate for understanding future climate change. Change (IPCC) developed a series of Climate models are mathematical plausible scenarios based on a set of representations of the climate system assumptions about future population that require very powerful computers. changes, economic development and They are based on the laws of physics technological advances. For example, 2090 and include information about the the A1B (or medium) emissions scenario 800 atmosphere, ocean, land and ice. envisages global population peaking mid-century and declining thereafter, 2055 700 There are many different global climate 600 very rapid economic growth, and 2030 tion (ppm) models and they all represent the a r rapid introduction of new and more t climate slightly differently. Scientists from 1990 500 n efficient technologies. Greenhouse e the Pacific Climate Change Science 400 c gas and aerosol emissions scenarios on Program (PCCSP) have evaluated 24 C 300 are used in climate modelling to 2 models from around the world and O provide projections that represent found that 18 best represent the climate C a range of possible futures. of the western tropical Pacific region. Figure 6: Carbon dioxide (CO2) These 18 models have been used to The climate projections for Niue concentrations (parts per million, ppm) develop climate projections for Niue. are based on three IPCC emissions associated with three IPCC emissions scenarios: low (B1), medium (A1B) scenarios: low emissions (B1 – blue), The future climate will be determined and high (A2), for time periods medium emissions (A1B – green) and by a combination of natural and human around 2030, 2055 and 2090 high emissions (A2 – purple). The factors. As we do not know what the (Figure 6). Since individual models PCCSP has analysed climate model future holds, we need to consider a give different results, the projections results for periods centred on 1990, range of possible future conditions, are presented as a range of values. 2030, 2055 and 2090 (shaded). or scenarios, in climate models. The House damaged by Tropical Cyclone Heta, January 2004. Cliffs and reef flat near Alofi. 5 Niue’s future climate This is a summary of climate projections for Niue.