A triple whammy of accelerating sea level rise, ocean warming and acidification is imperilling Pacific Islands, which face growing threats to their socioeconomic viability and indeed their very existence because of climate change.
- Climate change threatens the future of Pacific islands
- Sea level rise accelerates and is above global average
- Ocean heating and acidification harm ecosystems and livelihoods
- Early warnings are integral part of climate change adaptation and disaster risk reduction
The World Meteorological Organization (WMO) State of the Climate in the South-West Pacific 2023 report details how sea level rise in the region is above the global average. Sea surface temperatures have risen three times faster than the global average since 1980. During that time marine heatwaves have approximately doubled in frequency since 1980 and are more intense and are lasting longer.
The report was released by United Nations Secretary-General António Guterres and WMO Secretary-General Celeste Saulo at the Pacific Islands Forum in Tonga. It was accompanied by a special briefing document on Surging Seas in a Warming World, described by Mr Guterres as "an SOS on sea level rise."
"A worldwide catastrophe is putting this Pacific paradise in peril," said Mr Guterres." Global average sea levels are rising at an unprecedented rate. The ocean is overflowing."
"The reason is clear: greenhouse gases - overwhelmingly generated by burning fossil fuels - are cooking our planet. And the sea is taking the heat - literally."
Despite accounting for just 0.02 per cent of global emissions - the Pacific islands are uniquely exposed. Their average elevation is just one to two meters above sea level; 90 percent of the population live within 5 kilometres of the coast and half the infrastructure is within 500 metres of the sea, said Mr Guterres.
But the problem is global, he said.
"Surging seas are coming for us all - together with the devastation of fishing, tourism, and the Blue Economy. Across the world, around a billion people live in coastal areas threatened by our swelling ocean. Yet even though some sea level rise is inevitable, its scale, pace, and impact are not. That depends on our decisions," said Mr Guterres, reiterating his urgent calls for drastic cuts in greenhouse gas emissions and increasing in climate adaptation.
The 53rd Pacific Island Forum Leaders Meeting's host nation, the Kingdom of Tonga, is on the frontline of climate change and is exposed to hazards such as tropical cyclones and flooding. It also suffered a massive volcanic eruption which unleashed a basin-wide tsunami in January 2022 and caused a massive injection of water vapour into the Earth's atmosphere, impacting the global climate.
"Climate change has become a global crisis and is the defining challenge that humanity currently faces. Communities, economies and ecosystems throughout the South-West Pacific region are significantly affected by its cascading impacts. It is increasingly evident that we are fast running out of time to turn the tide," said WMO Secretary-General Celeste Saulo.
"The ocean has taken up more than 90 percent of the excess heat trapped by greenhouse gases and is undergoing changes which will be irreversible for centuries to come. Human activities have weakened the capacity of the ocean to sustain and protect us and - through sea level rise - are transforming a lifelong friend into a growing threat," she said. "Already we are seeing more coastal flooding, shoreline retreat, saltwater contamination of freshwater supplies and displacement of communities."
"WMO welcomes the Weather Ready Pacific Programme as part of the international Early Warnings for All initiative. Furthermore, the domino effects of the eruption of the Hunga Tonga-Hunga Ha'apai volcano highlight the need for multi-hazard early warnings against inter-connected and cascading risks," she said.
Early warning systems facilitate proactive measures such as evacuation plans, resource allocation and infrastructure reinforcement. Even though they are a lifeline, they are available in only one third of Small Island Developing States globally, she said.
The State of the Climate in the South-West Pacific 2023 report was prepared in cooperation with National Meteorological and Hydrological Services, the United Nations Economic and Social Commission for Asia and the Pacific (ESCAP) and other United Nations agencies and international partners. It also looks at climate drivers in 2023 - including the last El Niño event - temperature, precipitation and extreme events like tropical cyclones, drought and extreme heat in the region.
Overall, 34 reported hydrometeorological hazard events in 2023 - most of them storm or flood related - led to over 200 fatalities and impacted more than 25 million people in the region.
Severe Tropical Cyclones Kevin and Judy were notable for making landfall on the island nation of Vanuatu within 48 hours of each other in March. Cyclone Lola, which made landfall in Vanuatu on 24 October, prompted the Government of Vanuatu to declare a six-month state of emergency in the affected provinces.
Tropical Cyclone Gabrielle brought significant rainfall, causing major impacts to the eastern North Island of New Zealand.in February 2023.
Elsewhere in the region, Typhoon Doksuri brought heavy rainfall and flooding to the Philippines in July 2023, claiming at least 45 lives and displacing almost 313 000 people.
Celeste Saulo will present a deeper dive into all aspects of the report at a three-day Forum convened by WMO and the Association of Southeast Asian Nations (ASEAN) Specialized Meteorological Centre (ASMC) in Singapore on 5 September 2024. The report will inform discussions at the event, entitled Towards a Weather-Ready and Climate Resilient ASEAN).
Sea level rise
In much of the western tropical Pacific, sea level has risen approximately 10-15 cm (4-6 in), close to or nearly twice the global rate measured since 1993. In the central tropical Pacific, sea level has risen approximately 5-10 cm (2-4 in), according to the State of the Climate in the South-West Pacific 2023 Report.
In annual terms, the mean rate of sea-level rise between January 1993 and May 2023 is about 4.52 mm per year in the ocean around and east of the Maritime Continent and about 4.13 mm per year in the ocean around New Zealand.
Sea level trend from 1993-2023 captured from sea level gridded data.
Climate Change Service (C3S) Climate Data Store (CDS). DOI: 10.24381/cds.4c328c78
This compares with average global mean sea level rise of about 3.4 mm per year during that period.
Rising sea levels have resulted in dramatic increases in the frequency of coastal flooding since 1980.
According to the Pacific Islands Climate Change Monitor 2021, notable increases include
Guam from 2 to 22 times a year; Penrhyn, Cook Islands from 5 to 43 times a year; Majuro, Republic of the Marshall Islands from 2 to 20 times a year; Papeete, French Polynesia from 5 to 34 times a year; and Pago Pago, American Samoa from 0 to 102 times a year.
Global mean sea level will continue to rise over the 21st century in response to continued warming of the climate system, and this rise will continue for centuries to millennia due to continuing deep ocean heat uptake and mass loss from ice sheets.
Sea Surface Temperature
Over 1981-2023, nearly the entire South-West Pacific region shows ocean surface warming, reaching rates of more than 0.4°C per decade north-east of New Zealand and south of Australia. This is about three times faster than the global surface ocean warming rate (global mean sea surface temperature has increased over recent decades at a rate of about 0.15°C per decade)
Marine heatwaves
Marine heatwaves have become more intense and have approximately doubled in frequency since 1980.
From the 1980s to 2000s the average duration of marine heatwaves in much of the Pacific region was within the five to 16-day range. However, this has increased markedly since 2010, with most of the Pacific now suffering heatwaves of eight to 20 days - or even longer.
Linear trends in SST (°C per decade) over the period 1982-2022
Copernicus
The most prominent and persistent marine heatwave in 2023 occurred in a large area around New Zealand. This heatwave was categorized as extreme and lasted approximately six months, according to the WMO report.
Even under moderate climate warming scenarios, marine heatwaves will become more frequent and last longer in the coming years, according to the Intergovernmental Panel on Climate Change (IPCC).
The increasing intensity of marine heatwaves has far-reaching implications, from adverse impacts on fish stocks and coral reef resilience, to toxic algae blooms and species distinction for most severe and persistent extremes. This has a major impact on ecosystems, economies, and livelihoods in the Pacific.
In 2023, mass bleaching of coral reefs occurred throughout the tropics, including in
Australia's Great Barrier Reef and large areas of the South Pacific (including Fiji, Vanuatu, Tuvalu, Kiribati, the Samoas and French Polynesia), according to the US National Oceanic and Atmospheric Administration's Coral Reef Watch.
Ocean Heat Content: Most of the South-West Pacific region has experienced upper ocean (0-700m) warming since 1993. Warming is particularly strong, with rates exceeding two to three times the global average in the Solomon Sea and east of the Solomon Islands; in the Arafura, Banda and Timor Seas; east of the Philippines; along the southern coast of Indonesia and in the Tasman Sea, according to the WMO report.
In addition to climate change, upper ocean warming in the region is strongly affected by natural variability, for instance El Niño/La Niña, whereby large amounts of heat are redistributed from the surface down to deeper layers of the ocean.
Ocean acidification: The ocean absorbs an estimated 25 per cent of carbon dioxide emissions. As a result, ocean acidification has increased globally over the past four decades. Measurements collected from Station ALOHA in Hawaii show a more than 12 per cent increase in acidity over the period 1988-2020.
Significant declines in surface ocean chlorophyll and estimated phytoplankton size since 1998 are detectable across major portions of the Pacific Islands region. This has major implications for the marine food chain.