Ocean temperatures in the Great Barrier Reef are now the hottest in at least 400 years and are an “existential threat” to the planet’s unique natural wonder, according to new scientific research.

Scientists analysed long-lived corals in and around the reef that keep a record of temperature hidden in their skeleton and matched them to modern observations. The research, published in the journal Nature, used climate models to find the extreme temperatures of recent decades could not have happened without the extra greenhouse gases in the atmosphere caused mostly by burning fossil fuels.

The “existential threat” to the reef from the climate crisis was “now realised”, the scientists wrote, and without ambitious and rapid cuts to greenhouse gas emissions “we will likely be witness to the demise of one of the Earth’s natural wonders.”

The research comes two weeks after the World Heritage committee decided not to place the reef, which covers an area larger than Italy, on its list of sites “in danger”, saying it would consider the question again in 2026.

Before the bleaching, the institute said surveys showed coral cover in the north and central parts of the reef was the highest since monitoring began in the early 1980s.

For the new study, scientists built a record of temperatures for the peak three-month January to March period for heat for all years from 1618 onwards. The study found 2024 was the hottest in at least 407 years and 1.73C hotter than the average for years before 1900.

Figure 3 from Henley et al., 2024

Dr Benjamin Henley, lead author of the research at the University of Melbourne, said: “I was shocked when I saw that data point pop out. We had to recheck it several times. It’s shocking too to realise that, right at the point, it was the warmest January to March the Coral Sea had experienced in at least 400 years.”

To read the full Guardian article click here

To read the paper in Nature click here