"We have never seen temperatures like this in November so we don't know what conditions are happening to these reefs in the early summer – and technically this is not even summer."
One positive is that the sea surface temperature anomalies were not as good as during the same period before 2015-16 mass coral bleaching. That season was one of the strongest El Nino events recorded.
On the contrary, even though the Pacific conditions were initiated for El Nino – an event that usually causes fewer cyclones from northern Australia and warmer and warmer summers – such events have not yet occurred.
Also potentially reducing the risk of other mass bleaching is the prospect of the 2015-16 and 2016-17 attacks that have killed more sensitive corals, leaving more violent victims, said Dr Wachenfeld.
In the past, corals tended to turn white if they lasted for four weeks warming up, and began to die after eight years. Such a gauge – which is based on the equivalent of one week of a degree above the average – is an indication of the heat pressure on the reef that encourages them to expel algae which gives them most of their energy and color.
"We actually do not expect the threshold we have applied in the past to always apply everywhere as much as they have," Wachenfeld told reporters. "So predicting the future is far more difficult than a few years ago."
Conditions must have been unprecedented on land, with places such as Cairns – a popular destination for visitors to melt coral – a record November temperature of five degrees.
The short-term view, according to the Bureau of Meteorology, is for unusually warm conditions to extend for another week.
Link to climate change
While scientists can analyze fingerprints of climate change in the current heat wave, Dr. Wachenfeld said the Great Barrier Reef has warmed about 0.9 degrees over the past 200 years.
"If we continue on the global trajectory we are aiming for, in terms of greenhouse gas emissions, all the world's coral reefs will be in big trouble, and we might lose them before the end of the century," he said.
Dr Wachenfeld declined to comment on the agreement supporting the development of the giant Galilee coal basin in central Queensland, including the announcement Thursday that the Adani Carmichael mine could begin construction immediately.
"Not the place [the authority] to make comments about specific decisions like that, but nationally and globally we must embrace renewable energy, we must stay away from fossil fuels, we must find ways to reduce … emissions. "
Peter Hannam is the Environmental Editor at The Sydney Morning Herald. He covers broad environmental issues ranging from climate change to renewable energy to Fairfax Media.