Pacific communities face dozens of days each year battling floods caused by climate change, according to new United Nations forecasts.
Secretary-General Antonio Guterres released the "Surging Seas In A Warming World" report at the Pacific Islands Forum (PIF) Leaders Meeting in Tonga on Tuesday, using the summit as a platform for his advocacy.
"The ocean is overflowing," he said.
"I am in Tonga to issue a global SOS - Save Our Seas - on rising sea levels. A worldwide catastrophe is putting this Pacific paradise in peril."
The findings paint a dire picture for key Pacific settlements: Rarotonga, Suva, Apia, Nuku'alofa and more.
Modelling suggests each of those capitals would see floods - which currently occur five or fewer days each year - soar by the 2050s.
Rarotonga would encounter 75 flooding days in an average year. Suva would see 25, Apia 35 and Nuku'alofa 35.
Tongan communities are no stranger to the impact of flooding. Many villages were inundated in a 2022 tsunami caused by the massive eruption of undersea volcano Hunga Tonga-Hunga Ha'apai.
On Monday, Mr Guterres ventured out of Nuku'alofa to hear directly about their experiences.
In Manuka, he heard testimony from young people at a church hall, as well as cultural dancing.
Haitelenisia Angilau, from Talafo'ou, gave an impassioned address asking for a sea wall after previous promises went unfulfilled.
"It's eroded our confidence and trust in institutions, organisations and individuals, who have overpromised," she told Mr Guterres.
"This is our life. This is our livelihood ... when I got married, I brought my daughter a home (here) because there's a sense of community farm in these shows you don't find anywhere else.
"When the fisherman goes out and brings his fish he then gives it up for free to the neighbourhood.
"I dream one day I could have a grandchild who I take to the ocean like I do my daughter now and we will float along, and we will watch the changing hues of the sunset, and I can tell her about my ancestors and our forefathers and the values of this community and the beauty of our shores.
"I want to live long enough to see that."
His church hall audience was just a few dozen people, but on Tuesday he wanted leaders in advanced countries to hear his clarion call.
Mr Guterres unapologetically called out developed economies, specifically the G20 including Australia, for failing to wean off fossil fuels.
"They must keep the promises made at COP28 to triple renewables capacity, double energy efficiency and end deforestation by 2030 ... and end new coal projects and new oil and gas expansion now," he said.
Nowhere in the world is more affected than the Pacific by sea level rise, and the more savage and unpredictable storms that climate change will bring.
The average elevation of the region is under two metres above sea level.
Major industries - fishing, tourism, agriculture and more - are tied to the ocean or rely on stable climate.
Almost 90 per cent of Pacific Islanders live within five kilometres of the coast, and most infrastructure is within 500m of shorelines.
Mr Guterres also warned even a 2C rise could lead to a tipping point of the loss arctic and Antarctic ice sheets.
"That would mean condemning future generations to unstoppable sea level rise of up to 20 metres over a period of millennia," he said.
"On our current trajectory the rise in sea level would happen much more quickly: over centuries."
This science is why the Paris Agreement goals are pegged to just 1.5C of warming.
The next major Paris Agreement milestone comes in 2025 when governments are obliged to present new emissions-cutting plans, known as NDCs, at the COP28 climate change conference.
Mt Guterres also called for developed economies to improve climate financing to developed nations, to help them adapt.
