US President Donald Trump's decision to withdraw from the Paris climate accord has been described as a "crime against humanity".
Leading Hawaii climate scientist Chip Fletcher criticised Mr Trump's stance on combating global warming and said it was putting large parts of the Central Pacific state at risk, including the iconic Waikiki Beach.
He was speaking ahead of the start of the Climate Change Conference in Bonn, Germany which began on Monday.
In an interview with Sky News, the professor of geology and geophysics at the University of Hawaii's School of Ocean and Earth Sciences and Technology said: "In Hawaii we have recognised the threats and have mobilised to do something about it.
"In the United States we had made great progress up until the current administration. The current administration is doing all it can to unravel the progress of keeping our communities safe and keeping our resources sustainable.
"They are engaged in a crime against humanity."
Around a quarter of Hawaii's economy depends on tourism and the prospect of losing legendary beaches is deeply concerning to islanders, with the impact of rising sea levels and increased storm activity monitored by members of the public through an initiative called the King Tides Project.
Unusually high tides are happening more frequently and photos submitted by the public are helping scientists monitor the intensity. They say this "citizen science" is vital.
State representative Chris Lee said: "It really brings home the question about where we're going to be not ten years from now or 20 years from now, but 30 or 40 years from now.
"Because we're not talking about inches of sea level rise at that point, we're talking about feet and in some cases the loss of entire communities.
"That's something we have to address today."
State governor David Ige has defied the President by adopting much of the Paris agreement into law, but huge slices of Hawaii's beaches have already been eroded, including Waikiki.
At Kailua – where former president and Hawaii native Barack Obama spent numerous Christmas holidays – emergency repairs have taken place to rebuild a beach wiped away.
A lifeguard station has been moved fifty feet inland after its original spot ended up under water.
Loren Stack highlighted the impact of ice melting off Greenland. He said: "There is a huge amount of water coming into the ocean and it's got to affect sea level.
"You can see there are houses right on the beach, if the sea level goes up a couple of feet that's going to impact hugely everyone on the coast."
Jim Ferdinand added: "It is concerning to the point that the tourism industry may start to vaporise. And if it goes away there's nothing else in Hawaii."