Corals across large parts of the Great Barrier Reef could be hit by mass bleaching for the fourth time in just seven years by the end of January, according to a forecast from a United States government agency.
Reef scientists are hoping that favourable weather, including cloud cover and rain or a cyclone, could yet cool corals and stave off the threat.
Forecasting from the Bureau of Meteorology also shows heat building over the world-heritage-listed reef in January.
The Bureau of Meteorology says there is only a slight chance of more than the average number of cyclones this current season.
Coral bleaching is a stress reaction from excess heat. The process sees corals separate from a special algae that gives them their colour and much of their nutrients.
Corals can recover from less severe bleaching, but studies suggest those that do survive are weakened.
Although 2020 was the most widespread bleaching on record, Wachenfeld said the heat levels were not as intense as previous events and so with low levels of coral mortality, the reef had been given several years to recover.
Hughes said the Noaa forecast was unusual in that it was predicting an early onset of bleaching concentrated in the north. But he said the forecast was also suggesting a rapid reduction in heat in early March which would help corals survive.
He said if northern parts of the reef did bleach again this summer, young corals that have started to grow in recent years would be at risk.
Prof Tom Bridge, an ecologist and reef scientist at the Museum of Tropical Queensland, said the Noaa forecasts did not make him any more or less worried about the prospect of bleaching as any other year.
Research last month suggested parts of the reef would be hit with temperatures high enough to kill corals five years per decade by the middle of this century if global heating was kept below 2C.
Coral reefs are considered one of the most susceptible ecosystems to the climate crisis.
The Morrison government has been asked to send a progress report to Unesco by February next year.
Unesco is yet to schedule a monitoring mission to the reef, expected in the first half of next year.
