Findings in leading scientific journal that globe has breached key warming milestone challenged by climate science experts

Between 30 metres and 90 metres below the surface of the Caribbean Sea, an ancient sponge species that grows a hard skeleton has been quietly recording changes in the ocean temperature for hundreds of years.

Now those sponges are at the centre of a bold and controversial claim made in a leading scientific journal that, since the start of the Industrial Revolution, the planet may have already warmed by 1.7C – half a degree more than estimates used by the United Nation’s climate panel.

Several leading scientists urged caution, saying the research had “over-reached” and questioned whether such a bold claim could be made based on one sponge species from a single location.

But Prof Malcolm McCulloch of the University of Western Australia, who led the research published in the journal Nature Climate Change, said the results were robust.