A coral scientist has warned that early official optimism that the Great Barrier Reef will be spared the worst of a predicted worldwide coral bleaching event is misplaced.

The Queensland minister for the environment and the reef, Steven Miles, announced on Thursday that signs of only minor damage through the Australian summer to date had raised hopes the reef would not fall victim to its third major bleaching episode in two decades.

More than 200 surveys of the reef – which stretches 2,300km along the Queensland coast – had not detected “any significant bleaching” despite warmer than average sea temperatures, Miles said.

Miles said this was encouraging given the worst effects of heat stress on corals were predicted to soon wane in line with the El Niño weather system.

“We’re not out of the woods yet but I am crossing my fingers that we will not see any broadscale bleaching events like those that endangered the reef in 1998 and 2002 and an intense event in the southern part of the reef in 2006,” he said.

However, Terry Hughes from James Cook University’s ARC Centre of Excellence said it was “basically too early in the season for bleaching to happen”.

“[The minister] is being a little bit optimistic to say ‘so far, so good’ because it wouldn’t happen now anyway,” Hughes said.

The risk of major bleaching event would likely present when temperatures peaked “March into April” – more so in the event of heatwave and less likely by if cooling monsoons or a cyclone swept the north Queensland coast, he said.

Hughes said scientists shared Miles’ hope major bleaching would elude the reef and agreed that tourism operators should not be concerned about the bleaching.

The US government agency the National Oceanic and Atmospheric Administration in October warned of the third ever global coral bleaching event as record temperatures threatening coral from Hawaii to the Caribbean spread to the south east Pacific and the Indian Ocean.

Severe bleaching can be lethal to reef systems, triggering long-term degradation through the erosion of underlying structures generated by corals.

Hughes said the NOAA’s October prediction was a “fairly brave statement to make given it would apply to what happens the following summer in Australia, the Indian Ocean and elsewhere”.

He noted the agency had since downgraded its forecast for the Great Barrier Reef and this “hopefully” proved more accurate.

Hughes said Miles’ observation about the greater future risks to the reef amid climate change pointed to an obvious “disconnect” between conservation efforts and present government policy – specifically Australia’s abandonment of a carbon price and renewable energy targets and the Queensland government’s own support for development of one of the world’s largest proposed coal export operations in the Galilee basin.

Miles said that while news of minimal bleaching to date was “positive for the Great Barrier Reef and Queensland’s fishing and tourism industries – unfortunately predictions in a warming climate are that bleaching events, like bushfires, are likely to intensify in the future as levels of atmospheric greenhouse gases and, consequently, sea temperatures, increase”.

Indian mining conglomerate Adani this week urged the state government to press ahead with approving its Carmichael coalmine and expansion of its Abbot Point export facility to head off more legal challenges from environmental activists.

“Further delay to these job-creating projects will only incentivise activists by providing further opportunities for legal challenges in what is now a six-year long approvals process,” the Australian chief executive of Adani, Jeyakumar Janakaraj, told the Courier-Mail.

Hughes said that “building the world’s largest coal port at a time when the reef is, according to the minister, more and more likely to be affected by global warming – there’s obviously a disconnect there”.

He said Australia’s long-term conservation plan for the reef – which helped avert an “in danger” listing by Unesco last year – remained the subject of criticism by the scientific community because it was “basically a plan to deal with run off” and ignored climate change.

“The fact we could have a third [worldwide bleaching event] this summer basically demonstrates why Australia shouldn’t have taken a price off carbon or cut its renewable energy target by 30%,” Hughes said.

“Hopefully after COP21, where Australia committed to no more than a 2C temperature rise, they’ll get a bit more serious for the sake of the barrier reef and other places.”

The Great Barrier Reef marine park authority conducted the reef health surveys at 29 of the more than 3,000 individual reefs that make up the natural wonder, although these were concentrated in the warmer waters of Queensland’s far north.

Miles said low-impact coral bleaching was detected in 12 per cent of northern reef surveys and it was localised bleaching “not unusual for warm summers”.

Reef health impact surveys are scheduled for every month until April, alongside an “Eye on the Reef” citizen science program that meant there were “even more eyes out for bleaching events”, he said.