Toi

ALOFI Liku

Hanan Airport

Tamakautoga

Avatele Village

South Pacific Ocean

Current and future climate of

> 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 r g Vanuatu 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 0 180 11 12 0 13 0 14 0 15 0 16 0 17 0 17 0 16 0 15 0 14 0 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 , 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 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) 23.5 in Figure 7 which includes the tide gauge record from the nearest tide 23

Average T 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 .

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

rapid introduction of new and more t r climate slightly differently. Scientists from 1990 500 efficient technologies. Greenhouse e n the Pacific Climate Change Science 400

gas and aerosol emissions scenarios on c Program (PCCSP) have evaluated 24 300 C

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. For further information refer to Volume 2 of Climate Change in the Pacific: Scientific Assessment and New Research, and the web-based climate projections tool – Pacific Climate Futures (available at www.pacificclimatefutures.net).

Temperatures will Changing rainfall Less frequent continue to increase patterns but more intense Projections for all emissions scenarios There is uncertainty around rainfall tropical cyclones indicate that the annual average projections for Niue as model results On a global scale, the projections air temperature and sea surface are not consistent. However, projections indicate there is likely to be a decrease temperature will increase in the suggest a general decrease in dry in the number of tropical cyclones by future in Niue (Table 1). By 2030, season rainfall and an increase in wet the end of the 21st century. But there is under a high emissions scenario, this season rainfall over the course of the likely to be an increase in the average increase in temperature is projected 21st century. Wet season increases maximum wind speed of cyclones by to be in the range of 0.3–1.1°C. are consistent with the expected between 2% and 11% and an increase intensification of the South Pacific in rainfall intensity of about 20% within Convergence Zone. Projections More very hot days 100 km of the cyclone centre. indicate little change in the frequency Increases in average temperatures of droughts throughout this century. In the Niue region, projections tend will also result in a rise in the number to show a decrease in the frequency of hot days and warm nights and More extreme of tropical cyclones by the late a decline in cooler weather. rainfall days 21st century and an increase in the Table 1: Projected annual average proportion of the more intense storms. air temperature changes for Niue Model projections show extreme rainfall for three emissions scenarios and days are likely to occur more often. three time periods. Values represent 90% of the range of the models and changes are relative to the average of the period 1980-1999.

2030 2055 2090 (°C) (°C) (°C) Low 0.2–1.0 0.5–1.5 0.7–1.9 emissions scenario Medium 0.2–1.2 0.7–1.9 1.2–2.8 emissions scenario Cliffs and reef flat at Tamakautoga. High 0.3–1.1 0.9–1.7 1.8–3.2 emissions scenario Category 5 Tropical Cyclone Heta hit Niue in January 2004 causing catastrophic damage. Satellite image originally processed by the Australian Bureau of Meteorology from the geostationary meteorological satellite GOES-9 operated by the National Oceanic and Atmospheric Administration for

Niue Department of Meterology and Climate Change Niue Department of Meterology the Japan Meteorological Agency. Damage from Tropical Cyclone Heta, January 2004.

6 Sea level will Table 2: Sea-level rise projections for Ocean acidification Niue for three emissions scenarios continue to rise and three time periods. Values will continue represent 90% of the range of the Sea level is expected to continue to Under all three emissions scenarios models and changes are relative to rise in Niue (Table 2 and Figure 7). By (low, medium and high) the acidity the average of the period 1980-1999. 2030, under a high emissions scenario, level of sea waters in the Niue region this rise in sea level is projected to be 2030 2055 2090 will continue to increase over the 21st in the range of 4-17 cm. The sea-level (cm) (cm) (cm) century, with the greatest change rise combined with natural year-to-year under the high emissions scenario. Low 5–16 10–27 17–46 changes will increase the impact of The impact of increased acidification emissions storm surges and coastal flooding. As scenario on the health of reef ecosystems is there is still much to learn, particularly likely to be compounded by other how large ice sheets such as Antarctica Medium 5–15 10 –30 19 –57 stressors including coral bleaching, emissions and Greenland contribute to sea-level storm damage and fishing pressure. scenario rise, scientists warn larger rises than currently predicted could be possible. High 4 –17 10 –30 20 – 60 emissions scenario

90 Figure 7: Observed and projected Reconstruction relative sea-level change near Niue. 80 The observed sea-level records are Satellite altimeter indicated in dark blue (relative tide- 70 Tide gauges (2) gauge observations) and light blue Projections 60 (the satellite record since 1993). The tide gauge record is from Raratonga in 50 the Cook Islands, which is the nearest tide gauge to Niue. Reconstructed 40 estimates of sea level near Niue 30 (since 1950) are shown in purple. The projections for the A1B (medium) 20 emissions scenario (representing 90% of the range of models) are shown by 10 Sea level relative to 1990 (cm) the shaded green region from 1990 0 to 2100. The dashed lines are an estimate of 90% of the range of natural −10 year-to-year variability in sea level. −20

−30 1950 2000 2050 2100 Year

7 Changes in Niue’s climate

> Temperatures have > Rainfall data since 1950 > By the end of this > Sea level near > Ocean acidification warmed and will show no clear trends. century projections Niue has risen has been increasing continue to warm Rainfall patterns are suggest decreasing and will continue in Niue’s waters. with more very hot projected to change numbers of tropical to rise throughout It will continue days in the future. over this century with cyclones but a this century. to increase and more extreme rainfall possible shift threaten coral reef days but little change towards more ecosystems. in drought frequency. intense categories.

The content of this brochure is the result of a collaborative effort between the Niue Contact the Niue Department of Department of Meteorology and Climate Change and the Pacific Climate Change Science Meteorology and Climate Change: Program – a component of the Australian Government’s International Climate Change web: http://informet.net/niuemet/ Adaptation Initiative. This information and research conducted by the Pacific Climate email: [email protected] Change Science Program builds on the findings of the 2007 IPCC Fourth Assessment Report. For more detailed information on the climate of Niue and the Pacific see: Climate phone: +683 4601 or +683 4600 Change in the Pacific: Scientific Assessment and New Research. Volume 1: Regional fax: +683 4602 Overview. Volume 2: Country Reports. Available from November 2011. © Pacific Climate Change Science www.pacificclimatechangescience.org Program partners 2011.