North Pacific Ocean M i c r o n e s i a Yap Is. Ulithi Fais Namonuito Hall Is. Ngulu Faraulep Minto Sorol Satawal Oroluk Pohnpei Elato Pulap Chuuk Is. Mokil PALIKIR Eauripik Pingelap Mortlock Is. Ngatik Kosrae Kapingamarangi Current and future climate of the Federated States of Micronesia > Federated States of Micronesia National Weather Service Office > Australian Bureau of Meteorology > Commonwealth Scientific and Industrial Research Organisation (CSIRO) Current climate of the Federated States of Micronesia In the Federated States of Micronesia there is little seasonal variation in extreme phases of the El Niño-Southern temperature, with less than 3ºF (1.5ºC) between the average hottest and Oscillation: El Niño and La Niña. There coolest months. The country has two seasons – a dry season from is also a neutral phase. In Pohnpei, El November to April and a wet season from May to October (Figure 1). Niño tends to result in drier conditions during the dry season, but higher than Rainfall in the Federated States of additional rain during the wet season. average rainfall during the wet season. Micronesia is affected by the movement The Monsoon is driven by large La Niña tends to bring above average of the Intertropical Convergence Zone. differences in temperature between the rainfall in the dry season. The West This band of heavy rainfall is caused by land and the ocean, and its seasonal Pacific Monsoon affects the western air rising over warm water where winds arrival usually brings a switch from states of Chuuk and especially Yap converge, resulting in thunderstorm very dry to very wet conditions. more than the eastern states of Pohnpei activity. It extends across the Pacific just and Kosrae. It tends to be farther east The Federated States of Micronesia’s north of the equator (Figure 2). The wet during El Niño, bringing higher rainfall, climate varies considerably from year season occurs when the Intertropical and in a more western position during to year due to the El Niño-Southern Convergence Zone strengthens and La Niña, resulting in less rainfall. The Oscillation. This is a natural climate moves north close to the Federated Intertropical Convergence Zone results pattern that occurs across the tropical States of Micronesia. The West Pacific in less rainfall during El Niño events and Pacific Ocean and affects weather Monsoon also impacts rainfall, bringing more during La Niña. around the world. There are two Maximum temperature Average temperature Minimum temperature Sea surface temperature Pohnpei, 158.22ºE, 6.97ºN Yap, 138.08ºE, 9.48ºN 35 35 20 20 95 95 500 500 90 90 400 400 30 30 15 15 85 85 80 80 300 300 25 25 10 10 75 75 200 200 70 70 Temperature (ºC) Temperature (ºC) Temperature (ºF) Temperature (ºF) 5 5 20 20 Monthly rainfall (mm) Monthly rainfall (mm) 100 65 65 100 Monthly rainfall (inches) Monthly rainfall (inches) 60 60 15 0 0 15 0 0 Jan Apr Jul Oct Jan Apr Jul Oct Figure 1: Seasonal rainfall and temperature at Pohnpei and Yap. Kolonia Harbour, Pohnpei. 2 and H represents typical positions of moving high pressure systems. typicalpositionsofmovinghighpressure and Hrepresents Warm Pool Pacific zones,thedashedovalshowsWest thebandsofrainfallconvergence the blueshadingrepresents 2: Figure extreme 110oE tropical storms occur in the Federated States of Micronesia region. stormsoccurintheFederated StatesofMicronesia tropical dry events.DuringLaNiñaeventsabove-averagenumbersof duringsevere water shortagesandfoodhaveoccurred Fires, associated withdrierconditionsandoccasionaldroughts. ElNiñoeventsare theFederatedStatesofMicronesia. affect typhoons,stormwaves,floodingandlandslidesall Droughts, weather events The average positions of the major climate features in November to April. The arrows shownearsurfacewinds, inNovembertoApril.Thearrows Theaveragepositionsofthemajorclimatefeatures 120oE M East o Timor 130oE n s Palau o I 140oE o n W Papua Ne n t a e r Fe m r w Guine 150oE derated StatesofMic t p r a o o o p l o 160 E i Solomon Islands c ro nesia a S Naur l o Va o nuatu u u 170 E Marshall Islands C t h Kiribati o Damage from high sea surge, Oneop,Chuuk. highseasurge, Damage from P n Fiji a H v Tu o c 180 valu e i f r i To c g ng Samoa e a C o 170 W Niue n o n H c 0 5001,0001,5002,000 v e e Tr r o 160 W g Z Cook Islands a e de o n c n W e e o inds 150 W Z Kilometre o n e s Johannes Berdon, National Weather Service Office 140oW 3 30oS 20oS 10oS 0o 10oN 20oN Changing climate of the Federated States of Micronesia Temperatures Pohnpei’s annual Sea level has risen have increased rainfall has decreased As ocean water warms it expands causing the sea level to rise. The Annual and seasonal maximum and Data since 1950 for Pohnpei show melting of glaciers and ice sheets minimum temperatures have increased a clear decreasing trend in annual also contribute to sea-level rise. in Pohnpei since 1952 (Figure 3). and wet season rainfall (Figure 4), Maximum temperatures have but no clear trend in the dry season. Instruments mounted on satellites and increased at a rate of 0.19ºF (0.10°C) There are no clear rainfall trends tide gauges are used to measure sea per decade. These temperature at Yap. Over this period, there has level. Satellite data indicate sea level increases are consistent with the been substantial variation in rainfall has risen in the Federated States of global pattern of warming. from year to year at both sites. Micronesia by over 0.39 inches (10 mm) per year since 1993. This is larger than the global average of 0.11-0.14 inches 27.5 El Niño La Niña 81.5 (2.8–3.6 mm) per year. This higher 81 rate of rise may be partly related to 27 80.5 natural fluctuations that take place year 80 to year or decade to decade caused 26.5 79.5 by phenomena such as the El Niño- 79 emperature (ºF) Southern Oscillation. This year-to-year T emperature (ºC) 26 T 78.5 variation in sea level can be seen in 25.5 78 Figure 6 which includes the tide gauge record since 1950 and the satellite data 77.5 Average Average 25 77 since 1993. 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 Ocean acidification Year Figure 3: Annual average temperature for Pohnpei. Light blue bars has been increasing indicate El Niño years, dark blue bars indicate La Niña years and the About one quarter of the carbon dioxide grey bars indicate neutral years. emitted from human activities each year is absorbed by the oceans. As the extra carbon dioxide reacts with sea water 7000 El Niño La Niña 270 it causes the ocean to become slightly 6000 240 more acidic. This impacts the growth 210 5000 of corals and organisms that construct 180 their skeletons from carbonate minerals. 4000 150 These species are critical to the balance 3000 120 of tropical reef ecosystems. Data Rainfall (mm) 90 show that since the 18th century the 2000 60 Rainfall (inches) level of ocean acidification has been 1000 30 slowly increasing in the Federated 0 0 State of Micronesia’s waters. 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 Year Figure 4: Annual rainfall for Pohnpei. Light blue bars indicate El Niño years, dark blue bars indicate La Niña years and the grey bars indicate neutral years. Taking temperature observations, Pohnpei Weather Service Office. 4 Future climate of the Federated States of Micronesia Climate impacts almost all aspects of life in the Federated States of Micronesia. Understanding the possible future climate of the Federated States of Micronesia 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 2090 for understanding future climate change. Intergovernmental Panel on Climate 800 Climate models are mathematical Change (IPCC) developed a series of representations of the climate system plausible scenarios based on a set of 2055 700 that require very powerful computers. assumptions about future population 600 2030 tion (ppm) a r They are based on the laws of physics changes, economic development and t 1990 500 n and include information about the technological advances. For example, e c atmosphere, ocean, land and ice. the A1B (or medium) emissions scenario 400 on C envisages global population peaking 300 There are many different global climate 2 mid-century and declining thereafter, O models and they all represent the C very rapid economic growth, and climate slightly differently. Scientists from Figure 5: Carbon dioxide (CO ) rapid introduction of new and more 2 the Pacific Climate Change Science efficient technologies. Greenhouse concentrations (parts per million, ppm) Program (PCCSP) have evaluated gas and aerosol emissions scenarios associated with three IPCC emissions 24 models from around the world are used in climate modelling to scenarios: low emissions (B1 – blue), and found that 18 best represent the provide projections that represent medium emissions (A1B – green) and climate of the western tropical Pacific a range of possible futures. high emissions (A2 – purple). The region. These 18 models have been PCCSP has analysed climate model used to develop climate projections for The climate projections for the Federated results for periods centred on 1990, the Federated States of Micronesia. States of Micronesia are based on 2030, 2055 and 2090 (shaded). three IPCC emissions scenarios: low The future climate will be determined (B1), medium (A1B) and high (A2), for by a combination of natural and human time periods around 2030, 2055 and factors. As we do not know what the 2090 (Figure 5).