Hiu

Torres Islands Vanua Lava Banks Islands Gaua

Maéwo Espiritu Santo

Ambae Pentecost

Ambrym Malekula Épi Shepherd Islands

Éfate

PORT VILA South Pacific Ocean

Erromango

Tanna

Aneityum

Current and future climate of Vanuatu

> Vanuatu Meteorology and Geo-hazard Department > Australian Bureau of Meteorology > Commonwealth Scientific and Industrial Research Organisation (CSIRO) Vanuatu’s current climate

Across Vanuatu the annual average temperatures are between Vanuatu’s climate varies considerably 23.5–27.5°C. Changes in the temperature from season to season are from year to year due to the El Niño- strongly tied to changes in the surrounding ocean temperature. The Southern Oscillation. This is a climate country has two distinct seasons – a warm wet season from November pattern that occurs across the tropical to April and a cooler dry season from May to October (Figure 1). Pacific Ocean and affects weather around the world. There are two Rainfall in Vanuatu is affected by the systems embedded in this band of extreme phases of the El Niño-Southern South Pacific Convergence Zone. This heavy rainfall often become tropical Oscillation: El Niño and La Niña. There band of heavy rainfall is caused by air cyclones during the cyclone season. is also a neutral phase. In both Port rising over warm waters where winds Vila and Aneityum El Niño events Mountains also play a role in the converge, resulting in thunderstorm tend to bring drier conditions as well variations in rainfall across some activity. It extends across the South as a late start to the wet season and islands. During the wet season, rainfall Pacific Ocean from the Solomon Islands cooler than normal dry seasons. The is particularly high on the windward to east of the Cook Islands (Figure opposite occurs during La Niña events. (south-east) side of the mountain 2). During the wet season the South ranges of the bigger islands, and scarce Pacific Convergence Zone intensifies on the leeward (north-west) sides, and moves further south, bringing especially during the dry season. higher rainfall to Vanuatu. Low pressure

Maximum temperature Average temperature Minimum temperature Sea surface temperature 35 35 Port Vila, Vanuatu, 168.32°E, 17.74°S 400 30 300 Eton Beach, West Efate. 25 200 Temperature (ºC) Monthly rainfall (mm) 20 100 0 15 Jan Apr Jul Oct Figure 1: Seasonal rainfall and temperature at Port Vila.

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 0 180 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. Tropical 7 Tropical cyclones 11-yr moving average 6 cyclones 5 Tropical cyclones affect Vanuatu 4 between November and April. In the 41-year period between 3 1969 and 2010, 94 tropical 2 cyclones passed within 400 km

No. of tropical cyclones 1 of Port Vila, an average of two 0 to three cyclones per season (Figure 3). The number of cyclones varies widely from 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 year to year, with none in some Figure 3: Number of tropical cyclones passing within 400 km of Port Vila. seasons but up to six in others. Eleven-year moving average in purple.

3 Vanuatu’s changing climate

Temperatures Port Vila’s wet season Sea level has risen have increased rainfall has decreased As ocean water warms it expands causing the sea level to rise. The Annual maximum and minimum Data since 1950 for Port Vila show a melting of glaciers and ice sheets temperatures have increased in both decreasing trend in wet season rainfall also contributes to sea-level rise. Port Vila and Aneityum since 1950 (Figure 5). However, there are no clear (Figure 4). At Bauerfield Airport in trends in annual and dry season rainfall Instruments mounted on satellites and Port Vila, maximum temperatures at Port Vila or annual and seasonal tide gauges are used to measure sea have increased at a rate of 0.17°C rainfall at Aneityum. Over this period, level. Satellite data indicate the sea level per decade and at Aneityum the there has been substantial variation in has risen near Vanuatu by about 6 mm rate of increase has been 0.18°C rainfall from year to year at both sites. per year since 1993. This is larger than per decade. These temperature the global average of 2.8–3.6 mm per increases are consistent with the year. This higher rate of rise may be global pattern of warming. partly related to natural fluctuations that take place year to year or decade to decade caused by phenomena such as 25.5 El Niño La Niña the El Niño-Southern Oscillation. This 25 variation in sea level can be seen in Figure 7 which includes the tide gauge 24.5 record and the satellite data since 1993.

24 emperature (ºC) Ocean acidification 23.5 has been increasing

Average T 23 About one quarter of the carbon dioxide 22.5 emitted from human activities each year is absorbed by the oceans. As the extra 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 Year carbon dioxide reacts with sea water it causes the ocean to become slightly Figure 4: Annual average temperature for Bauerfield Airport, Port Vila. more acidic. This impacts the growth Light blue bars indicate El Niño years, dark blue bars indicate La Niña of corals and organisms that construct years and the grey bars indicate neutral years. their skeletons from carbonate minerals. These species are critical to the balance of tropical reef ecosystems. Data 4000 El Niño La Niña show that since the 18th century the 3500 level of ocean acidification has been 3000 slowly increasing in Vanuatu’s waters. 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 Port Vila. Light blue bars indicate El Niño years, dark blue bars indicate La Niña years and the grey bars indicate neutral years.

Eton Beach, West Efate.

4 Vanuatu’s future climate

Climate impacts almost all aspects of life in Vanuatu. Understanding the possible future climate of Vanuatu 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 very rapid economic growth, and 600 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 are used in climate modelling to 300 C models from around the world and 2 provide projections that represent O 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 Vanuatu concentrations (parts per million, ppm) develop climate projections for Vanuatu. 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 Vanuatu Meteorology and Geo-hazard Department and Geo-hazard Meteorology Vanuatu

Flooding in Teuma, Vanuatu.

5 Vanuatu’s future climate

This is a summary of climate projections for Vanuatu. 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 as model results are not On a global scale, the projections air temperature and sea surface consistent. However, projections indicate there is likely to be a decrease temperature will increase in the generally suggest a decrease in dry in the number of tropical cyclones by future in Vanuatu (Table 1). By 2030, season rainfall and an increase in the end of the 21st century. But there is under a high emissions scenario, this wet season rainfall over the course likely to be an increase in the average increase in temperature is projected of the 21st century. Increased wet maximum wind speed of cyclones by to be in the range of 0.4–1.0°C. season rainfall is expected due to the between 2% and 11% and an increase projected intensification of the South in rainfall intensity of about 20% within Pacific Convergence Zone. Drought More very hot days 100 km of the cyclone centre. projections are inconsistent for Vanuatu. Increases in average temperatures In the Vanuatu region, projections tend will also result in a rise in the number More extreme to show a decrease in the frequency of hot days and warm nights and 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 air Model projections show extreme rainfall proportion of the more intense storms. temperature changes for Vanuatu for days are likely to occur more often. three emissions scenarios and 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 0.7–2.1 emissions scenario Medium 0.3–1.1 0.8–2.0 1.3–3.1 emissions scenario

High 0.4–1.0 1.1–1.7 2.0–3.2 Department and Geo-hazard Meteorology Vanuatu emissions Damage to a house from Tropical scenario Climate data management Cyclone Gene, January 2008. training, Vanuatu Meteorology and Geo-hazard Department.

6 Sea level will Table 2: Sea-level rise projections for Ocean acidification Vanuatu 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 rise Under all three emissions scenarios models and changes are relative to in Vanuatu (Table 2 and Figure 7). By (low, medium and high) the acidity level the average of the period 1980-1999. 2030, under a high emissions scenario, of sea waters in the Vanuatu region this rise in sea level is projected to be 2030 2055 2090 will continue to increase over the 21st in the range of 3-17 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 17–47 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 5–16 8–31 20–59 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 3 –17 7–31 21– 63 emissions scenario

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

90% of the range of natural year- Sea level relative to 1990 (cm) 0 to-year variability in sea level. −10

−20

−30 1950 2000 2050 2100 Year

7 Changes in Vanuatu’s climate

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

The content of this brochure is the result of a collaborative effort between the Vanuatu Contact the Vanuatu Meteorology and Geo-hazard Department and the Pacific Climate Change Science Meteorology and Program – a component of the Australian Government’s International Climate Change Geo-hazard Department: Adaptation Initiative. This information and research conducted by the Pacific Climate web: www.meteo.gov.vu Change Science Program builds on the findings of the 2007 IPCC Fourth Assessment Report. For more detailed information on the climate of Vanuatu and the Pacific see: email: [email protected] Climate Change in the Pacific: Scientific Assessment and New Research. Volume 1: or [email protected] Regional Overview. Volume 2: Country Reports. Available from November 2011. phone: +678 24686

© Pacific Climate Change Science www.pacificclimatechangescience.org Program partners 2011.