Global warming is making the oceans sicker than ever before, spreading disease among animals and humans and threatening food security across the planet, a major scientific report said on Monday.

The findings, based on peer-reviewed research, were compiled by 80 scientists from 12 countries, experts said at the International Union for Conservation of Nature (IUCN) World Conservation Congress in Hawaii.

"We all know that the oceans sustain this planet. We all know that the oceans provide every second breath we take," IUCN Director General Inger Andersen told reporters at the meeting, which has drawn 9,000 leaders and environmentalists to Honolulu.

"And yet we are making the oceans sick."

The report, "Explaining Ocean Warming," is the "most comprehensive, most systematic study we have ever undertaken on the consequence of this warming on the ocean," one of the lead authors, Dan Laffoley, said.

The world's waters have absorbed more than 93 per cent of the enhanced heating from climate change since the 1970s, curbing the heat felt on land but drastically altering the rhythm of life in the ocean, he said.

"The ocean has been shielding us and the consequences of this are absolutely massive," said Laffoley, marine vice chair of the World Commission on Protected Areas at IUCN.

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