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Home , Micronesia, Mokil, Oroluk, Pacific ocean, Sorol, Trade winds

North Pacific M i c r o n e s i a Is. Fais

Namonuito Hall Is. Ngulu Faraulep Minto Sorol Elato Pulap Chuuk Is. Eauripik Pingelap Mortlock Is. Ngatik

Kapingamarangi

Current and future climate of the Federated States of

> Federated States of Micronesia Office > Australian Bureau of > 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 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 during the wet season. average rainfall during the wet season. Micronesia is affected by the movement The is driven by large La Niña tends to bring above average of the Intertropical . 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 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 (Figure 2). The wet during El Niño, bringing higher rainfall, climate varies considerably from 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 and affects weather Monsoon also impacts rainfall, bringing more during La Niña. around the world. There are two

Maximum temperature Average temperature Minimum temperature 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 N H o N 20 o Federated States of Micronesia Marshall 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 10 o W a 0 r m p Tra de W inds o o l S o New u M o t h Tu valu n S s o P o East o n a c i f i c C o n v e r g e n c e

S 10

Z o o To nga 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. extreme weather events

Droughts, , storm waves, flooding and landslides all affect the Federated States of Micronesia. El Niño events are associated with drier conditions and occasional droughts. Fires, water shortages and food shortages have occurred during severe dry events. During La Niña events above-average numbers of tropical storms occur in the Federated States of Micronesia . Johannes Berdon, National Weather Service Office National Weather Johannes Berdon, Damage from high sea surge, Oneop, Chuuk.

3 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

emperature (ºC) 26 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 T Average T 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 , 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 . 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

They are based on the laws of physics changes, economic development and t r 1990 500 and include information about the technological advances. For example, e n atmosphere, ocean, land and ice. the A1B (or medium) emissions scenario 400 on c

envisages global population peaking 300 C 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). Since individual models future holds, we need to consider a give different results, the projections range of possible future conditions, are presented as a range of values.

Climate projections training, Pohnpei Weather Service Office. Johannes Berdon, National Weather Service Office National Weather Johannes Berdon, Damage from high sea surge, Lekinioch, Chuuk.

5 Future climate of the Federated States of Micronesia

This is a summary of climate projections for the Federated States of Micronesia. 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 typhoons continue to increase patterns On a global scale, the projections indicate there is likely to be a decrease Projections for all emissions scenarios Almost all the global climate models in the number of typhoons by the indicate that the annual average project an increase in average end of the 21st century. There is also air temperature and sea surface annual and seasonal rainfall over likely to be an increase in the average temperature will increase in the future the course of the 21st century. maximum speed of typhoons by in the Federated States of Micronesia However, there is some uncertainty between 2% and 11% and an increase (Table 1). By 2030, under a high in the rainfall projections and not in rainfall intensity of about 20% within emissions scenario, this increase in all models show consistent results. 100 km of the centre. temperature is projected to be in the Droughts are projected to become range of 0.7–1.9ºF (0.4 –1.0°C) in less frequent throughout this century. The Federated States of Micronesia is in eastern Federated States of Micronesia a region where projections tend to show and 0.8–1.8ºF (0.4–1.1ºC) in western More extreme a decrease in typhoon frequency by the Federated States of Micronesia. rainfall days late 21st century, and a decrease in the proportion of the more intense storms. More very hot days Model projections show extreme rainfall days are likely to occur more often. Increases in average temperatures will also result in a rise in the number of hot days and warm nights, and a decline in cooler weather.

Table 1: Projected annual average air temperature changes for the Federated States of Micronesia (FSM) for 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 (°F) (ºC) (°F) (ºC) (°F) (ºC) Eastern FSM Low emissions 0.4–2.0 0.1–1.1 1.1– 2.9 0.6 –1.6 1.5 –4.1 0.9–2.3 scenario Medium emissions 0.5 –2.3 0.3 –1.3 1.6 –3.8 0.9–2.1 2.7– 5.9 1.5–3.3 scenario High emissions 0.7–1.9 0.4 –1.0 1.8 – 3.4 1.0 –1.8 3.9–6.3 2.2–3.4 scenario

Western FSM Low emissions 0.4–1.8 0.2–1.0 1.0–2.8 0.6 –1.6 1.4–4.0 0.8–2.2 scenario Medium emissions 0.6–2.2 0.4–1.2 1.7–3.7 0.9–2.1 2.6–5.8 1.4–3.2 scenario Kepirohi Falls, Pohnpei. High emissions 0.8–1.8 0.4–1.1 1.7–3.3 1.0–1.8 3.8–6.2 2.1–3.5 scenario

6 Sea level will Ocean acidification continue to rise will continue Sea level is expected to continue to rise Under all three emissions scenarios in the Federated States of Micronesia (low, medium and high) the acidity (Table 2 and Figure 6). By 2030, under a level of sea waters in the Federated high emissions scenario, this rise in sea States of Micronesia region will level is projected to be in the range of continue to increase over the 21st 1.2-5.9 inches (3-15 cm). The sea-level century, with the greatest change rise combined with natural year-to-year under the high emissions scenario. changes will accentuate the impact of The impact of increased acidification storm surges and coastal flooding. As 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 stressors including coral bleaching, and contribute to sea-level storm damage and pressure. rise, scientists warn larger rises than currently predicted could be possible.

Table 2: Sea-level rise projections for the Federated States of Micronesia for 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

(in) (cm) (in) (cm) (in) (cm) Service Office National Weather Johannes Berdon, Low emissions scenario 1.2–5.5 3–14 3.5–10.2 9–26 6.3–18.1 16–46 Damage to crop from salt water inundation, Lekinioch, Chuuk. Medium emissions scenario 1.2–5.9 3–15 3.5–12.6 9–32 7.5–23.6 19–60 High emissions scenario 1.2–5.9 3–15 3.9–11.8 10–30 8.3–24.4 21–62

90 35.4 Figure 6: Observed and projected Reconstruction relative sea-level change near the 80 31.5 Satellite Federated States of Micronesia. 70 Tide gauges (6) 27.6 The observed sea-level records are Projections indicated in dark blue (relative tide- 60 23.6 gauge observations) and light blue 50 (the satellite record since 1993). 19.7 Reconstructed estimates of sea 40 15.7 level near the Federated States of Micronesia (since 1950) are shown 30 11.8 in purple. The projections for the 20 7.9 A1B (medium) emissions scenario (representing 90% of the range of 10 3.9 Sea level relative to 1990 (cm) models) are shown by the shaded Sea level relative to 1990 (inches) 0 0 green region from 1990 to 2100. The dashed lines are an estimate of −10 −3.9 90% of the range of natural year- to-year variability in sea level. −20 −7.9 −30 −11.8 1950 2000 2050 2100 Year

7 Changes in the climate of the Federated States of Micronesia

> Temperatures have > Annual and wet season > By the end of this > Sea level near the > Ocean acidification warmed and will rainfall since 1952 has century projections Federated States of has been increasing in continue to warm decreased at Pohnpei suggest decreasing Micronesia has risen the Federated States with more very hot but at Yap there has been numbers of typhoons and will continue of Micronesia’s waters. days in the future. no clear change. Rainfall and a possible to rise throughout It will continue to is generally projected to shift towards less this century. increase and threaten increase over this century intense categories. ecosystems. with more extreme rainfall days and less droughts.

The content of this brochure is the result of a collaborative effort between the Contact the Federated States of Micronesia National Weather Service Offices of the Federated States of Micronesia and National Weather Service Office: the Pacific Climate Change Science Program – a component of the ’s International Climate Change Adaptation Initiative. This information web: www.prh.noaa.gov/yap and research conducted by the Pacific Climate Change Science Program builds phone: +691 350 2194 on the findings of the 2007 IPCC Fourth Assessment Report. For more detailed web: www.prh.noaa.gov/chuuk information on the climate of the Federated States of Micronesia and the Pacific see: phone: +691 330 2548 Climate Change in the Pacific: Scientific Assessment and New Research. Volume 1: Regional Overview. Volume 2: Country Reports. Available from November 2011. web: www.prh.noaa.gov/pohnpei phone: +691 320 2248 www.pacificclimatechangescience.org

© Pacific Climate Change Science Program partners 2011.