Great Barrier Marine Park Authority chief scientist David Wachenfeld said “we are now two-thirds of the way through summer, there’s a quite reasonable accumulation of heat stress out there and the next four weeks are absolutely critical”.

“The weather that we see will very strongly influence the outcome of the reef.”

Ocean temperatures for most of the reef have been between 0.5 degrees and 1.5 degrees higher on average since the beginning of summer in most places, most of the time, he said.

While cyclones Seth and Tiffany and recent monsoonal rain did have some cooling effect, this hasn’t brought the reef back to average temperatures

There have been reports of minor coral bleaching in a range of places such as Cooktown, Townsville and Mackay that demonstrates the coral is showing early signs of stress, Dr Wachenfeld said.

“The thing that worries me when there is a severe impact to the Great Barrier Reef [is that] I always worry that people lose hope,” he said. “What the reef needs right now is the strongest possible action globally to reduce greenhouse gas emissions, with the strongest action to protect it locally.”

Last week the federal government promised to spend $1 billion on the reef over nine years, pledging new money for new technology, water management and coral seeding. Reef experts welcomed the additional funding, but said it would do nothing to save the reef from the existential threat of climate change

The Bureau of Meteorology says that December 2021 was, on average, the warmest December for the Great Barrier Reef since records began in 1900.

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Above-median rainfall is predicted for much of February at Cape York and the Great Barrier Reef, and the extent of wind, cloud and rain will influence ocean temperatures.

Associate Professor Jodie Rummer witnessed coral bleaching in 2016 when the James Cook University reef expert was working on a project on the effects of climate change on reef fish at the Lizard Island research station, off Cooktown.

The water temperature was two or three degrees higher than normal, similar to the temperatures she was simulating in the laboratory to reflect what was expected in the middle of this century.

“It was scary and disturbing,” Dr Rummer said. “I grew up with these dreams of wanting to make my contribution to science and conservation … and to see this happening before my eyes in my lifetime has been really, really upsetting.”

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The reef is an internationally significant tourist destination, which supports 64,000 jobs and contributes $6.4 billion annually to the economy. It suffered severe back-to-back bleaching that wiped out swathes of corals in 2016, 2017 and 2020.

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