Tuvalu faces challenges to its natural environment which will be exacerbated by climate change: Coastal erosion,
saltwater intrusion and increasing vector and water borne diseases due to sea level rise.
Climate systems that affect Tuvalu Tuvalu participates in the operations of the
Secretariat of the Pacific Regional Environment Programme (SPREP). The climate of the Pacific region at the equator is influenced by a number of factors; the science of which is the subject of continuing research. The SPREP described the climate of Tuvalu as being: conditions. Blue=temperature below average; red=temperature above average The sea level in Tuvalu varies as a consequence of a wide range of atmospheric and oceanographic influences. The 2011 report of the
Pacific Climate Change Science Program published by the Australian Government, describes a strong zonal (east‑to-west) sea-level slope along the equator, with sea level west of the International Date Line (180° longitude) being about a half metre higher than found in the eastern equatorial Pacific and South American coastal regions. The trade winds that push surface water westward create this zonal tilting of sea level on the equator. Below the equator a higher sea level can also be found about 20° to 40° south (Tuvalu is spread out from 6° to 10° south). The
Pacific Climate Change Science Program Report (2011) describes the year-by-year volatility in the sea-level as resulting from the
El Niño–Southern Oscillation (ENSO): The
Pacific (inter-)decadal oscillation is a climate switch phenomenon that results in changes from periods of La Niña to periods of El Niño. This has an effect on sea levels as El Niño events can actually result in sea levels falling by 20 - 30 centimeters as compared to the sea level during a La Niña events. For example, in 2000 there was a switch from periods of downward pressure of El Niño on sea levels to an upward pressure of La Niña on sea levels, which upward pressure causes more frequent and higher high tide levels. The
Perigean spring tide (often called a
king tide) can result in seawater flooding low-lying areas of the islands of Tuvalu.
Temperature and weather changes atoll showing the storm dunes, the highest point on the atoll. A report in 2011 concluded in relation to Tuvalu that over the course of the 21st century: • Surface air temperature and sea‑surface temperature are projected to continue to increase (very high confidence). • Annual and seasonal mean rainfall is projected to increase (high confidence). • The intensity and frequency of days of extreme heat are projected to increase (very high confidence). • The intensity and frequency of days of extreme rainfall are projected to increase (high confidence). • The incidence of drought is projected to decrease (moderate confidence). • Tropical cyclone numbers are projected to decline in the south-east Pacific Ocean basin (0–40ºS, 170ºE–130ºW) (moderate confidence).
Sea level rise ,
Fongafale,
Funafuti atoll Sea level observation to collect data for the purpose of the
Permanent Service for Mean Sea Level (PSMSL) has been made at two locations within the Funafuti lagoon. In 1978 a tide gauge was installed at
Funafuti by the
University of Hawaii. The two records were synthesised into a single data source by averaging the difference between the two records over the period during which both gauges operated simultaneously. The analysis of years of sea level data identified the effect of the four
El Niño events that took place during that period, including a very severe one in 1997/98 that generated a significant sea level drop in the Tuvalu sea level data. The usual positive (rising) sea level trends were changed to negative values (falling) for several months due to the effect of the El Niño event. There is an inverted barometric pressure effect on sea level during a severe El Niño event due to the high
air pressure in the western Pacific. which gives Tuvalu the second-lowest maximum elevation of any country (after the
Maldives). However, the highest elevations are typically in narrow storm dunes on the ocean side of the islands which are prone to over topping in
tropical cyclones, such as occurred with
Cyclone Bebe. In March 2015 the storm surge created by
Cyclone Pam resulted in waves of breaking over the reef of the outer islands caused damage to houses, crops and infrastructure. On
Nui the sources of fresh water were destroyed or contaminated. Tuvalu is also affected by
perigean spring tide events (often called a
king tide), which raise the sea level higher than a normal
high tide. The highest peak tide recorded by the
Tuvalu Meteorological Service was on 24 February 2006 and again on 19 February 2015. As a result of historical sea level rise, the
king tide events lead to flooding of low-lying areas, which is compounded when sea levels are further raised by
La Niña effects or local storms and waves. The atolls have shown resilience to gradual sea-level rise, with atolls and reef islands being able to grow under current climate conditions by generating sufficient sand and broken coral that accumulates and gets dumped on the islands during cyclones. There remains the risk that the dynamic response of atolls and reef islands does not result in stable islands as
tropical cyclones can strip the low-lying islands of their vegetation and soil.
Tepuka Vili Vili islet of
Funafuti atoll was devastated by
Cyclone Meli in 1979, with all its vegetation and most of its sand swept away during the cyclone.
Vasafua islet, part of the
Funafuti Conservation Area, was severely damaged by
Cyclone Pam in 2015. The coconut palms were washed away, leaving the islet as a sand bar. The effect of Cyclone Pam, which did not pass directly over the islands, shows that Tuvaluans are exposed to storm surges causing damage to their houses and crops, and also the risk of water born disease as a consequence of contamination of the water supplies. Between 1971 and 2014, during a period of global warming, Tuvalu islands overall have increased in size, according to
aerial photography and
satellite imagery documented in a study from the
University of Auckland. Over those four decades, there was a net increase in land area in Tuvalu of 73.5 ha (2.9%). These changes in land area vary across the nation's various atolls and islands, where land gains were observed in eight of nine atolls and 74% of islands, while land losses were observed in one atoll and 27% of islands. The sea level at the
Funafuti tide gauge has risen at 3.9 mm per year, which is approximately twice the global average. This may be because gradual sea-level rise allows for coral
polyp activity to raise the atolls with the sea level. However, if the increase in sea level occurs at faster rate as compared to coral growth, or if
polyp activity is damaged by
ocean acidification, then the resilience of the atolls and reef islands is less certain. Prime Minister
Enele Sopoaga has responded to the University of Auckland study with assertions that Tuvalu is not expanding and has gained no additional habitable land. Tuvaluans point to observable changes that have occurred to that show there have been changes to sea levels. Those observable changes include sea water bubbling up through the porous coral rock to form pools on each high tide and flooding of low-lying areas including the airport on a regular basis during
spring tides and
king tides. Several causes of coastal flooding in Tuvalu have been identified, including: "
sand mining, paving of surface areas, and manipulation of coastlines in addition to high seas caused by meteorological and climatological forces."
Ecosystems Ocean acidification was projected to continue in 2011 (with very high confidence). The degree of aquifer salinization depends on the specific
topographic characteristics and the
hydrologic controls in the sub-surface of the atoll. About half of Fongafale islet is reclaimed swamp that contains porous, highly permeable coral blocks that allow the tidal forcing of salt water. Increases in the sea level will exacerbate the aquifer salinization as the result of increases in
tidal forcing. The reefs at Funafuti have suffered damage, with 80 per cent of the coral having been bleached as a consequence of the increase of the ocean temperatures and acidification from increased levels of carbon dioxide. The coral bleaching, which includes
staghorn corals, is attributed to the increase in water temperature that occurred during the
El Niños that occurred from 1998 to 2000 and from 2000 to 2001. Researchers from Japan have investigated rebuilding the
coral reefs through introduction of
foraminifera. The atolls have shown resilience to gradual sea-level rise, with atolls and reef islands being able to grow under current climate conditions by generating sufficient sand and coral debris that accumulates and gets dumped on the islands during cyclones. Gradual sea-level rise also allows for coral
polyp activity to increase the reefs. However, if the increase in sea level occurs at faster rate as compared to coral growth, or if polyp activity is damaged by
ocean acidification, then the resilience of the atolls and reef islands is less certain. == Impacts on people ==