When Hurricane Dorian smashed through the Bahamas in 2019, Selwin Hart was the Caribbean board member at the Inter-American Development Bank and saw for himself the "absolute devastation" of island communities razed to the ground by the powerful storm.

"It looked as though a bomb had landed," said the Barbadian, who now works as special adviser on climate action to the U.N. secretary-general.

Yet despite island nations being increasingly exposed to the wrath of storms made stronger by a fast-warming ocean, they are struggling to access the international funding they need to keep their people safe from the threat and from rising sea levels.