Hanuabada village, Port Moresby Chapter 11 Papua New Guinea The contributions of Kasis Inape from the Papua New Guinea National Weather Service and Maino Virobo from the Department of Environment and Conservation are gratefully acknowledged 169 Introduction This chapter provides a brief Oscillation) are analysed and These projections are presented description of Papua New Guinea, discussed. Observed trends and along with confidence levels based on its past and present climate as well analysis of air temperature, rainfall, expert judgement by Pacific Climate as projections for the future. The extreme events (including tropical Change Science Program (PCCSP) climate observation network and the cyclones), sea-surface temperature, scientists. The chapter concludes availability of atmospheric and oceanic ocean acidification, mean and with a summary table of projections data records are outlined. The annual extreme sea levels are presented. (Table 11.4). Important background mean climate, seasonal cycles and Projections for air and sea-surface information, including an explanation the influences of large-scale climate temperature, rainfall, sea level, ocean of methods and models, is provided features such as the West Pacific acidification and extreme events in Chapter 1. For definitions of other Monsoon and patterns of climate for the 21st century are provided. terms refer to the Glossary. variability (e.g. the El Niño-Southern 11.1 Climate Summary 11.1.1 Current Climate • Annual and seasonal rainfall • The incidence of drought trends for Port Moresby for the is projected to decrease • Sites in Papua New Guinea have period 1950–2009 and Kavieng (moderate confidence). very weak seasonal variations for the period 1957–2009 are not • Tropical cyclone numbers are in temperature. Sea-surface statistically significant. projected to decline in the temperatures have a strong • The sea-level rise near Papua south-west Pacific Ocean influence on average monthly New Guinea measured by satellite basin (0–40ºS, 130ºE –170ºE) air temperatures. altimeters since 1993 is about (moderate confidence). • The south of Papua New Guinea 7 mm per year. • Ocean acidification is projected to has a wet season from November • On average, Port Moresby continue (very high confidence). to April and a dry season from experiences six tropical cyclones May to October, while further • Mean sea-level rise is projected to per decade, with most occurring north rainfall is more consistent continue (very high confidence). between November and April. throughout the year. • Rainfall in Papua New Guinea is influenced by the West Pacific 11.1.2 Future Climate Monsoon. High year-to-year Over the course of the 21st century: variability in rainfall is mostly • Surface air temperature and due to the impact of the sea-surface temperature are El Niño-Southern Oscillation. projected to continue to increase • Warming trends are evident in (very high confidence). both annual and seasonal mean • Annual and seasonal mean air temperatures at Port Moresby rainfall is projected to increase for the period 1950–2009. These (high confidence). trends are considerably stronger in minimum air temperatures • The intensity and frequency of days when compared to maximum of extreme heat are projected to air temperatures. increase (very high confidence). • The intensity and frequency of days of extreme rainfall are projected to increase (high confidence). 170 Climate Change in the Pacific: Scientific Assessment and New Research Volume| 2: Country Reports 11.2 Country Description Papua New Guinea consists of the Dense rainforests can also be found Eighty-five percent of the population eastern half of New Guinea Island in the lowland and coastal areas as live a subsistence lifestyle in rural and about 700 offshore islands well as the very large wetland areas areas. These people depend on between the equator and 12°S, surrounding the Sepik and Fly Rivers. traditional agriculture and fishing and 140°E–160°E. At 462 243 km2, The highest peak is Mount Wilhelm at for their livelihoods. Mining and oil Papua New Guinea is the largest of 4697 m (Papua New Guinea Country production are the main sources the 15 PCCSP Partner Countries. Statistics, SOPAC, 2010). of revenue for Papua New Guinea, The country’s geography is diverse accounting for 60% of export earnings The population of Papua New and, in places, extremely rugged. and 20% of government revenue. Guinea is approximately 6 744 955, A spine of mountains, the New Agricultural crops are still a major with 40% living in the highlands and Guinea Highlands, runs the length of source of revenue, in particular copra 18% in urban areas. The capital, New Guinea Island, which is mostly (Papua New Guinea is the biggest Port Moresby, is located in the covered with tropical rainforest. producer in the South Pacific), coffee, south-east and has a population of palm oil and cocoa. Export of forestry approximately 500 000. products, once among the country’s main sources of revenue, has declined in recent years. Figure 11.1: Papua New Guinea Chapter 11: Papua New Guinea 171 11.3 Data Availability There are currently 39 operational There are a number of sea-level of local vertical land motion in future meteorological stations in Papua records available for the Papua New years. Both satellite (from 1993) and in New Guinea. Multiple observations Guinea region. The best appear to situ sea-level data (1950–2009; termed within a 24-hour period are taken at be Port Moresby II (1984–1994), reconstructed sea level; Volume 1, 18 stations: four synoptic stations in Rabaul (1966–1997), Lombrum Section 2.2.2.2) are available on a Momase, two in the Highlands, six (1994– present), Lae (1984–2000), global 1° x 1° grid. in the Southern region and six in the Anewa Bay (1968–1977), Kavieng Long-term locally-monitored New Guinea Islands. In addition there (1984–1998), Madang (1984–1998), sea-surface temperature data are are three single observation climate Goods Island (1989–present) and unavailable for Papua New Guinea, stations and 18 single observation Thursday Island III (1983–2002). so large-scale gridded sea-surface rainfall stations. The primary climate A global positioning system instrument temperature datasets have been used station is located in Port Moresby to estimate vertical land motion was (HadISST, HadSST2, ERSST and (Figure 11.1). Rainfall data for Port deployed at Manus Island in 2002 and Kaplan Extended SST V2; Volume 1, Moresby are available from 1890, will provide valuable direct estimates Table 2.3). largely complete from 1905. Air temperature data are available from 1939. Madang, Wewak, Misima, Kavieng and Momote have more than 50 years of rainfall data. Climate records for Port Moresby from 1950 and Kavieng (an island to the north-east) from 1957 (air temperature from 1962) have been used. Both records are homogeneous and more than 95% complete. Training in Pacific Climate Futures, Port Moresby 172 Climate Change in the Pacific: Scientific Assessment and New Research Volume| 2: Country Reports 11.4 Seasonal Cycles Sites in Papua New Guinea have However, these seasons are only Guinea are affected by the Intertropical very weak seasonal variations in clearly different in Port Moresby, Convergence Zone and to a lesser temperature (Figure 11.2). Port where about 78% of the yearly extent the South Pacific Convergence Moresby is further south than Kavieng, average rainfall comes in the wet Zone. They lie in the West Pacific so its seasonal temperature cycle is season. The West Pacific Monsoon Warm Pool, so experience convective stronger with about 2.5ºC between is responsible for most of the rainfall rain throughout the year. As a result, the warmest month (November) in Port Moresby and during the dry Kavieng’s average annual rainfall and the coolest (July). Sea-surface season Port Moresby is exposed to (3150 mm) is much higher than Port temperatures have a strong influence dry south-easterly winds. In Kavieng Moresby’s (1190 mm). on average monthly air temperatures. rainfall is more consistent year-round although the peak in rainfall The seasonal cycles of monthly-mean corresponds to the monsoon season rainfall (Figure 11.2) show a wet from December to April. Kavieng and season from November to April and other sites in the north of Papua New a dry season from May to October. Figure 11.2: Mean annual cycle of rainfall (grey bars) and daily maximum, minimum and mean air temperatures at Port Moresby (left) and Kavieng (right), and local sea-surface temperatures derived from the HadISST dataset (Volume 1, Table 2.3). Chapter 11: Papua New Guinea 173 11.5 Climate Variability Year-to-year variability in rainfall is high Table 11.1: Correlation coefficients between indices of key large-scale patterns of in Papua New Guinea. At both Port climate variability and minimum and maximum temperatures (Tmin and Tmax) and Moresby and Kavieng the wettest rainfall at Port Moresby. Only correlation coefficients that are statistically significant at years receive up to three times the the 95% level are shown. rainfall of the driest years (Figure 11.4). The El Niño-Southern Oscillation Dry season Wet season (ENSO) drives much of this variability. Climate feature/index (May-October) (November-April) Generally, El Niño years are drier Tmin Tmax Rain Tmin Tmax Rain than average while La Niña years are ENSO Niño3.4 -0.66 -0.43 0.42 0.59 -0.51 wetter than average. Table 11.1 shows Southern Oscillation Index 0.65 -0.61 -0.28 -0.52 0.49 that at Port Moresby, the dry season Interdecadal Pacific Oscillation Index in El Niño years tends to be cooler ENSO Modoki Index -0.34 -0.43 0.30 -0.29 than normal and warmer in La Niña Number of years of data 67 66 99 69 67 107 years, while the wet season is cooler than normal in El Niño years.