United Nations Secretary-General Antonio Guterres has issued a climate SOS to the world to “save our seas.”

The UN and the World Meteorological Organisation (WMO) issued reports on worsening sea level rises on Monday, accelerated by a warming Earth and melting ice sheets and glaciers.

The reports highlight how the Southwestern Pacific is not only hurt by rising oceans but by other climate change effects of ocean acidification and marine heat waves.

Mr Guterres made his climate plea from Tonga’s capital Nuku’alofa on Tuesday at a meeting of the Pacific Islands Forum, whose member countries are among those most imperiled by climate change.

Next month the United Nations General Assembly holds a special session to discuss rising seas.

“This is a crazy situation,” Mr Guterres said.

“Rising seas are a crisis entirely of humanity’s making. A crisis that will soon swell to an almost unimaginable scale, with no lifeboat to take us back to safety.”

“A worldwide catastrophe is putting this Pacific paradise in peril,” he said.

“The ocean is overflowing.”

A report commissioned by his office found that sea level lapping against Nuku’alofa had risen 21 centimetres between 1990 and 2020, twice the global average of 10 centimetres. Apia in Samoa, has seen 31 centimetres of rising seas, while Suva-B in Fiji has had 29 centimetres.

“This puts Pacific Island nations in grave danger,” Mr Guterres said, adding about 90% of the region’s people live within three miles of the rising oceans.

Since 1980, coastal flooding in Guam has jumped from twice a year to 22 times a year and from five times a year to 43 times a year in the Cook Islands.

In Pago Pago, American Samoa, coastal flooding went from zero to 102 times a year, according to the WMO State of the Climate in the South-West Pacific 2023 report.

“Because of sea level rise, the ocean is transforming from being a lifelong friend into a growing threat,” said Celeste Saulo, secretary-general of the World Meteorological Organisation.

Sea levels are rising faster in the western tropical Pacific because of where the melting ice from western Antarctica heads, warmer waters and ocean currents, UN officials said.

Mr Guterres said he can see changes since the last time he was in the region in May 2019.

While he met in Nuku’alofa on Tuesday with Pacific nations on the environment at their leaders’ annual summit, a hundred local high school students and activists from across the Pacific marched for climate justice a few blocks away.

Globally, sea level rise has been accelerating, the UN report said, echoing peer-reviewed studies. The rate is now the fastest it has been in 3,000 years, Mr Guterres said.

Between 1901 and 1971, the global average sea rise was 1.3 centimetres a decade, according to the UN report. Between 1971 and 2006 it jumped to 1.9 centimetres per decade, and then between 2006 and 2018, it was up to 3.7 centimetres a decade.

In the last decade, seas have risen 4.8 centimetres.

The UN report highlighted cities in the richest 20 nations, which account for 80% of the heat-trapping gases, where rising seas are lapping at large population centres.

Cities where sea level rise in the past 30 years has been at least 50% higher than the global average include London, Shanghai, Perth, Atlantic City, Boston and Miami.

New Orleans topped the list with 26 centimetres of sea level rise between 1990 and 2020 while UN officials highlighted the flooding in New York City during 2012’s Superstorm Sandy as worsened by rising seas.

Mr Guterres is amping up his rhetoric on what he calls “climate chaos” and urged richer nations to step up efforts to reduce carbon emissions, end fossil fuel use and help poorer nations.

He said he expects Pacific island nations to “speak loud and clear” in the next General Assembly, and because they contribute so little to climate change, “they have a moral authority to ask those that are creating accelerating the sea level rise to reverse these trends.”