Cooktown hit 40 degrees on Thursday, the first time the town has notched four consecutive days above 40, adding to the many records broken during the current hot spell that is forecast to run another week.

David Wachenfeld, chief scientist of the Great Barrier Reef Marine Park Authority, said the "amazing temperatures over land" were contributing to water temperatures running a degree above normal in the region.

"It will cause the Great Barrier Reef to get warmer, but how much warmer, how quickly and how long it will last remains to be seen," Dr Wachenfeld said.

"We’ve never seen temperatures like these in November so we don’t know what conditions like this do to the reef this early in the summer – and technically it’s not even summer."

One positive is that sea-surface temperature anomalies were not as great as during the same period prior to the 2015-16 mass coral bleaching. That season included one of the strongest El Nino events on record.

By contrast, although Pacific conditions were primed for an El Nino – an event which typically leads to fewer cyclones off northern Australia and stiller, warmer summers – such an event had yet to occur.

Also potentially reducing the risk of another mass bleaching was the prospect the 2015-16 and 2016-17 bouts had killed off the more sensitive corals, leaving hardier survivors, Dr Wachenfeld said.

In the past, corals were likely to bleach if they endured four degree-heating weeks, and start to die after eight. Such a gauge – based on the equivalent of one week of one degree of above-average conditions – is an indication of the heat stress on corals that prompt them to expel algae that provide them most of their energy and colour.

“We’re actually not expecting those thresholds that we’ve seen apply in the past to necessarily apply everywhere as strictly as they have," Dr Wachenfeld told reporters. "So predicting the future is much harder than it was a few years ago.”

Conditions have certainly been unprecedented on land, with places such as Cairns – a popular destination for visitors to the reef – smashing previous November temperature records by as much as five degrees.

The near-term outlook, according to the Bureau of Meteorology, is for those unusually warm conditions to extend for as long as another week.

While scientists may analyse the climate change fingerprints in the current heatwave, Dr Wachenfeld said the Great Barrier Reef had already warmed about 0.9 degrees over the past 200 years.

"If we continue on the global trajectory we have been on, in terms of greenhouse gas emissions, all of the world’s coral reefs are going to be in enormous trouble, and we will probably essentially lose them before the end of the century," he said.

Dr Wachenfeld declined to comment on the approvals supporting the development of the giant Galilee coal basin in central Queensland, including Thursday's announcement that the Adani Carmichael mine may soon start construction.

"It’s not the place for [the authority] to make comments on specific decisions like that, but nationally and globally we have got to embrace renewable energy, we have to move away from fossil fuels, we have to find ways to reduce ... emissions."