Ninigo Group Admiralty Islands Mussau Is. South Pacific Ocean New Hanover N Tabar Is. Bismark Sea e w I Lihir Group re Bismarck l a n Archipelago d Rabaul Karkar Witu Islands Long Island B o Buka Is. Mount u Umboi Is. g Hagen a i n i Arawa a n

INDONESIA t r i v N e w B i l l e Huon Gulf Solomon Sea Gulf of Papua Kiriwina Islands SOLOMON Woodlark Is. ISLANDS PORT d’Entrecasteaux Is. MORESBY L o A r u c h i s i p i a Coral Sea e d Conflict l a e g Group o Tagula

Current and future climate of

> Papua New Guinea National Weather Service > Australian Bureau of Meteorology > Commonwealth Scientific and Industrial Research Organisation (CSIRO) Papua New Guinea’s current climate

The temperature of the ocean surrounding Papua New Guinea has a strong Papua New Guinea’s climate varies influence on average monthly air temperatures. Changes in the temperature considerably from year to year due from season to season are small but more marked around than to the El Niño-Southern Oscillation. further to the north. This is a natural climate pattern that occurs across the tropical Pacific Papua New Guinea has a wet season to very wet conditions. In the north of Ocean and affects weather around the from November to April and a dry the country rainfall is more consistent world. There are two extreme phases season from May to October (Figure 1), year-round, although the peak in rainfall of the El Niño-Southern Oscillation: but these seasons are only noticeably corresponds to the monsoon season. El Niño and La Niña. There is also a different in Port Moresby, where about neutral phase. Generally in Papua New Rainfall in the north of Papua New 78% of the yearly average rainfall Guinea El Niño years are usually drier Guinea is also affected by the comes in the wet season. Due to their than normal while La Niña events are Intertropical Convergence Zone and, location in the West Pacific Warm Pool, usually wetter. La Niña-associated to a lesser extent, the South Pacific islands in the north of Papua New prolonged rainfall has led to flooding Convergence Zone. These bands Guinea experience rain throughout the and landslides, whilst El Niño- of heavy rainfall are caused by air year. As a result, Kavieng’s average associated droughts have also taken rising over warm water where winds annual rainfall (3150 mm) is much their toll on Papua New Guinea. During converge, resulting in thunderstorm higher than Port Moresby’s (1190 mm). El Niño events the monsoon season activity. The South Pacific Convergence also starts later. The dry season at Port Most of the rainfall in Port Moresby Zone extends across the South Moresby is cooler than normal in El comes from the West Pacific Monsoon. Pacific Ocean from the Solomon Niño years and warmer than normal in Large differences in temperature Islands to east of the Cook Islands, La Niña years, while the wet season between the land and the ocean drive whilst the Intertropical Convergence tends to be warmer and drier than the monsoon, and its seasonal arrival Zone lies across the Pacific just normal during an El Niño event. usually brings a switch from very dry north of the equator (Figure 2).

Maximum temperature Average temperature Minimum temperature Sea surface temperature 35 35 35 400 Port Moresby, 147.22ºE, 9.38ºS 400 Kavieng, 150.82°E, 2.57°S 30 30 300 300 25 25 200 200 Temperature (ºC) Temperature (ºC) Monthly rainfall (mm) 20 20 100 Monthly rainfall (mm) 100 0 15 15 0 Jan Apr Jul Oct Jan Apr Jul Oct

Figure 1: Seasonal rainfall and temperature at Port Moresby and Kavieng.

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 2.5 Tropical cyclones 11-yr moving average cyclones 2 Tropical cyclones affect southern 1.5 Papua New Guinea between November and April. In the 1 41-year period between 1969 and 2010, 23 tropical cyclones 0.5

No. of tropical cyclones passed within 400 km of Port 0 Moresby, an average of less than one cyclone per season (Figure 3). Over this 1969–2010 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 period, cyclones occurred more Figure 3: Number of tropical cyclones passing within 400 km of Port Moresby. frequently in neutral phases of Eleven-year moving average in purple. the El Niño-Southern Oscillation.

3 Papua New Guinea’s changing climate

Temperatures Port Moresby’s Sea level has risen have increased rainfall unchanged As ocean water warms it expands causing the sea level to rise. The Annual maximum and minimum Data since 1950 show no clear trends melting of glaciers and ice sheets temperatures have increased in in annual or seasonal rainfall at Port also contributes to sea-level rise. Port Moresby since 1950 (Figure 4). Moresby (Figure 5). However, at Maximum temperatures have increased Kavieng there has been a decrease in Instruments mounted on satellites and at a rate of 0.11°C per decade wet season rainfall. Over this period, tide gauges are used to measure sea since 1950. These temperature there has been substantial variation in level. Satellite data indicate the sea increases are consistent with the rainfall from year to year at both sites. level has risen near Papua New Guinea global pattern of warming. by about 7 mm per year since 1993. This is larger than the global average 29 El Niño La Niña of 2.8–3.6 mm per year. This higher 28.5 rate of rise may be partly related to 28 natural fluctuations that take place year 27.5 to year or decade to decade caused 27 by phenomena such as the El Niño- emperature (ºC) 26.5 Southern Oscillation. This variation in 26 sea level can be seen in Figure 7 which 25.5 includes the tide gauge records since Average T 25 1966 and the satellite data since 1993. 24.5 Ocean acidification 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 Year has been increasing Figure 4: Annual average temperature for Port Moresby. Light blue bars About one quarter of the carbon dioxide indicate El Niño years, dark blue bars indicate La Niña years and the emitted from human activities each grey bars indicate neutral years. year is absorbed by the oceans. As the extra carbon dioxide reacts with sea 2000 El Niño La Niña water it causes the ocean to become 1800 slightly more acidic. This impacts 1600 the growth of corals and organisms 1400 that construct their skeletons from 1200 carbonate minerals. These species are 1000 critical to the balance of tropical reef

Rainfall (mm) 800 ecosystems. Data show that since 600 the 18th century the level of ocean 400 200 acidification has been slowly increasing 0 in Papua New Guinea’s waters. 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 Year Figure 5: Annual rainfall for Port Moresby. Light blue bars indicate El Niño years, dark blue bars indicate La Niña years and the grey bars indicate neutral years.

4 Papua New Guinea’s future climate

Climate impacts almost all aspects of life in Papua New Guinea. Understanding the possible future climate of Papua New Guinea 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 and include information about the technological advances. For example, 2090 atmosphere, ocean, land and ice. the A1B (or medium) emissions scenario 800 envisages global population peaking There are many different global climate mid-century and declining thereafter, 2055 700 models and they all represent the 600 very rapid economic growth, and 2030 tion (ppm)

climate slightly differently. Scientists a

rapid introduction of new and more t r from the Pacific Climate Change 1990 500 efficient technologies. Greenhouse e n Science Program (PCCSP) have 400

gas and aerosol emissions scenarios on c evaluated 24 models from around 300 C

are used in climate modelling to 2

the world and found that 18 best O provide projections that represent represent the climate of the western C a range of possible futures. tropical Pacific region. These 18 models Figure 6: Carbon dioxide (CO2) have been used to develop climate The climate projections for Papua concentrations (parts per million, ppm) projections for Papua New Guinea. New Guinea are based on three associated with three IPCC emissions IPCC emissions scenarios: low (B1), scenarios: low emissions (B1 – blue), The future climate will be determined medium (A1B) and high (A2), for time medium emissions (A1B – green) and by a combination of natural and human periods 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).

Above: Taking weather observations, Papua New Guinea Weather Service. Left: A coastal village near Port Moresby completely destroyed by Tropical Cyclone Justin in 1992. Papua New Guinea National Weather Service Papua New Guinea National Weather

5 Papua New Guinea’s future climate

This is a summary of climate projections for Papua New Guinea. 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 Average annual and seasonal rainfall tropical cyclones indicate that the annual average is projected to increase over the On a global scale, the projections air temperature and sea surface course of the 21st century. Projected indicate there is likely to be a temperature will increase in the future in increases are consistent with the decrease in the number of tropical Papua New Guinea (Table 1). By 2030, expected intensification of the West cyclones by the end of the 21st under a high emissions scenario, this Pacific Monsoon and the Intertropical century. But there is also likely to be increase in temperature is projected Convergence Zone. However, there an increase in the average maximum to be in the range of 0.4–1.0°C. is some uncertainty in the rainfall wind speed of cyclones by between projections and not all models show 2% and 11% and an increase in consistent results. Drought projections More very hot days rainfall intensity of about 20% within are inconsistent for Papua New Guinea. Increases in average temperature 100 km of the cyclone centre. will also result in a rise in the number of hot days and warm nights and More extreme In the Papua New Guinea region, a decline in cooler weather. rainfall days projections tend to show a decrease in the frequency of tropical Table 1: Annual average air Model projections show extreme rainfall cyclones by the late 21st century temperature projections for Papua days are likely to occur more often. and an increase in the proportion New Guinea for three emissions of the more intense storms. 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 0.3–1.1 0.6–1.6 1.0–2.2 emissions scenario Medium 0.4–1.2 1.0–2.0 1.6–3.2 emissions scenario High 0.4–1.0 1.1–1.9 2.2–3.4 emissions scenario

Rouna Falls, Sogeri Road, Port Moresby.

Weather balloon launch, Papua New Guinea National Weather Service.

6 Sea level will Table 2: Sea-level rise projections for Ocean acidification Papua New Guinea for three emissions continue to rise scenarios and three time periods. will continue Values represent 90% of the range of Sea level is expected to continue to Under all three emissions scenarios the models and changes are relative to rise in Papua New Guinea (Table 2 (low, medium and high) the acidity level the average of the period 1980-1999. and Figure 7). By 2030, under a high of sea waters in the Papua New Guinea emissions scenario, this rise in sea 2030 2055 2090 region will continue to increase over the level is projected to be in the range of (cm) (cm) (cm) 21st century, with the greatest change 4-15 cm. The sea-level rise combined under the high emissions scenario. Low 4–14 10–26 17– 46 with natural year-to-year changes will The impact of increased acidification emissions increase the impact of storm surges scenario on the health of reef ecosystems is and coastal flooding. As there is still likely to be compounded by other much to learn, particularly how large Medium 5–14 9–30 20–58 stressors including coral bleaching, emissions ice sheets such as Antarctica and storm damage and fishing pressure. scenario Greenland contribute to sea-level rise, scientists warn larger rises than High 4–15 10 – 29 22–60 currently predicted could be possible. emissions scenario

90 Figure 7: Observed and projected relative sea-level change near Papua 80 Reconstruction New Guinea. The observed sea-level Satellite altimeter records are indicated in dark blue 70 Tide gauges (9) (relative tide-gauge observations) and 60 Projections light blue (the satellite record since 1993). Reconstructed estimates of sea 50 level Papua New Guinea (since 1950) are shown in purple. The projections 40 for the A1B (medium) emissions 30 scenario (representing 90% of the range of models) are shown by the 20 shaded green region from 1990 to 2100. The dashed lines are an estimate 10 of 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 Papua New Guinea’s climate

> Temperatures have > Rainfall shows no clear > By the end of this > Sea level near Papua > Ocean acidification warmed and will trend since 1950 at Port century projections New Guinea has risen has been increasing in continue to warm Moresby but a decrease suggest decreasing and will continue Papua New Guinea’s with more very hot in wet season rainfall numbers of tropical to rise throughout waters. It will continue days in the future. at Kavieng. Rainfall is cyclones but a this century. to increase and threaten generally projected to possible shift coral reef ecosystems. increase 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 Papua New Contact the Papua New Guinea Guinea National Weather Service and the Pacific Climate Change Science Program – a National Weather Service: component of the Australian Government’s International Climate Change Adaptation phone: + 675 325 2557 Initiative. This information and research conducted by the Pacific Climate Change Science Program builds on the findings of the 2007 IPCC Fourth Assessment Report. For more detailed information on the climate of Papua New Guinea and the Pacific see: Climate Change in the Pacific: Scientific Assessment and New Research. Volume 1: Regional Overview. Volume 2: Country Reports. Available from November 2011. © Pacific Climate Change Science www.pacificclimatechangescience.org Program partners 2011.