Ice is thawing from Greenland to Antarctica and will raise sea levels by between 28 and 98 cm (11-38 inches) by 2100, threatening coasts from Bangladesh to Florida, according to a UN panel of experts.
But, in a possible window on the future, none of hundreds of impoverished residents had left four islands in the central Philippines after subsidence following a 2013 quake lowered the land by as much as 43 cms.
Many raised their homes on stilts, or mined local reefs for coral to raise floor levels after frequent floods at high tide in homes, schools and other buildings.
"Small island communities in the Philippines prefer local measures to relocation in response to sea-level rise," according to the study led by Ma Laurice Jamero at the University of Tokyo and published in the journal Nature Climate Change.
The UN's International Organization for Migration says the most often quoted estimate is that 200 million people could be forced from their homes by environmental change by 2050. Estimates range hugely from 25 million to one billion.
In the Philippines, the local government had given the islanders the option of relocating to Tubigon on the mainland, but a lack of funding meant no new homes had been built in an area also vulnerable to typhoons.
"Still, a greater problem facing the municipal government is the opposition from island residents to relocate," the study said. Many islanders wanted to keep their fishing livelihoods.
Dominic Kniveton, a professor of climate science and society at Sussex University who was not among the authors, said the findings illustrated how far people like to stay at home.
Many other studies wrongly assumed that the poor would move if offered a better place to live. "There's a lot of ingenuity (shown by people) to adapt," he told Reuters. "And people say: 'I quite like my hovel'."