Elisabeth Holland, who's based at the University of the South Pacific, said the latest Intergovernmental Panel on Climate Change's (IPCC) Special Report - which she contributed to - painted another dire forecast.
The report found oceans were heating at such a rate their chemistry is being altered which, in turn, is threatening food supplies, fuelling more extreme cyclones, and posing a profound threat to people who lived in low-lying areas.
Professor Holland is at the UN climate talks in Spain, where negotiations are underway to finalise the rules of the Paris agreement, in which countries agreed to reduce emissions.
She said drastic changes were needed soon.
"Hopefully this oceans report propels us to take greater action...How that unfolds, the coming months will determine and the coming nations that have a voice in the process will determine," she said.
She hoped leaders were willing to lead by example: "Because when our leaders can lead by example, to make a difference on climate, all of the rest will follow."
*Jamie Tahana travelled to the COP25 in Madrid, Spain with the assistance of the Secretariat of the Pacific Regional Environment Programme (SPREP).