Climate change is particularly threatening for the long-term habitability of the island country of Tuvalu, which has a land area of only and an average elevation of less than above sea level, with the highest point of Niulakita being about above sea level. Potential threats to the country due to climate change include rising sea levels, increasingly severe tropical cyclones, high temperatures, and drought. King tides can combine with storm surges and the rising sea level to inundate the low lying atolls.
Tuvalu is widely considered one of the first countries likely to be significantly impacted by rising sea levels due to global climate change. According to some estimates, the highest tides could regularly flood 50% of the land area of national capital Funafuti by the mid-21st century, and 95% by 2100. The rising saltwater table could also destroy deep rooted food crops such as coconut, pulaka, and taro before they're overtaken by actual flooding. Meanwhile, one 2018 study from the University of Auckland suggested that Tuvalu may remain habitable over the next century, finding that the country's islands have even grown in area overall in recent decades, though the authors stressed that "Climate change remains one of the single greatest environmental threats to the livelihood and well-being of the peoples of the Pacific" and that "Sea-level rise and climatic change threaten the existence of atoll nations".
The Human Rights Measurement Initiative finds that the climate crisis has worsened human rights conditions in Tuvalu greatly (5.4 out of 6). Human rights experts provided that the climate crisis has impacted food, water, and housing security as well as forced migration.
The installed photovoltaic production capacity in Funafuti in 2020 was 735 kW compared to 1800 kW of diesel (16% penetration).
The South Pacific Applied Geoscience Commission (SOPAC) suggests that, while Tuvalu is vulnerable to climate change, environmental problems such as population growth and poor coastal management also affect sustainable development. SOPAC ranks the country as extremely vulnerable using the Environmental Vulnerability Index.
Greenhouse gas emissions
On 27 November 2015 the Government of Tuvalu announced its intended nationally determined contributions (INDCs) in relation to the reduction of greenhouse gases (GHGs) under provisions of the United Nations Framework Convention on Climate Change (UNFCCC):
Impacts on the natural environment
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:
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
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
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 University of Hawai'i Sea Level Center (UHSLC) operated a tide gauge from November 1979 until December 2001. Since June 1993 the National Tidal Centre of the Australian Bureau of Meteorology has operated an Aquatrak acoustic gauge. This was done due to the uncertainty as to the accuracy of the data from the tide gauge. The Aquatrak acoustic gauge was installed by the Australian National Tidal Facility (NTF) as part of the AusAID-sponsored South Pacific Sea Level and Climate Monitoring Project.
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 from Funafuti, identified that the sea level rise rate was 5.9 mm per year (in the years to September 2008) and the sea level in the Funafuti area rose approximately 9.14 cm during that period of time.
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.
The highest elevation is above sea level on Niulakita, 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.Bureau of Meteorology (1975) Tropical Cyclones in the Northern Australian Regions 1971-1972 Australian Government Publishing Service 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. In the future, sea level rise may threaten to submerge the nation entirely as it is estimated that a sea level rise of in the next 100 years could make Tuvalu uninhabitable.Hunter, J. A. (2002). Note on Relative Sea Level Change at Funafuti, Tuvalu . Retrieved 13 May 2006.
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.Supplementary note 2 in 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 investigation of groundwater dynamics of Fongafale Islet, Funafuti, show that tidal forcing results in salt water contamination of the surficial aquifer during spring tides. 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.