The world's corals, including the Great Barrier Reef, can be saved but only with concerted efforts to coordinate management, recalibrate research and enact steep curbs to carbon emissions, scientists say.

In a paper published on Thursday in the journal Nature, researchers led by Terry Hughes from James Cook University argue a narrowing window remains to preserve what's left of the world's reefs that have already been altered significantly over the past three decades.

The urgency is driven in part by unprecedented bleaching from marine heatwaves that have triggered the death of about 50 per cent of the Great Barrier Reef's corals in the past two summers alone.

The impacts have come even though tropical waters have warmed by about 0.57 degrees between 1880 and 2015, well shy of the average global temperature increase of 0.88 degrees. Assuming nations fulfil their Paris climate summit pledges to keep warming to well below 2 degrees, reefs "will be able to secure a future," Professor Hughes said.