The scientist who was branded an alarmist for exposing the fate of coral reefs

Ove Hoegh-Guldberg was just 10 years old when he first saw the Great Barrier Reef. That year, 1969, most young children around the world were inspired by NASA’s mission to land an astronaut on the moon. But for Hoegh-Guldberg, the fine gray dust on the lunar surface had nothing to do with the other world beneath the gentle waves of Queensland.

Remember the copper-banded butterflyfish and its stripes of iridescent colors whose beauty “defied logic,” as well as the “incredible” epaulette shark that uses its fins to walk on the seabed.

Today, however, reef diving carries a load of knowledge that the 10-year-old boy from Hoegh-Guldberg did not have.

“Maybe my depression is because… I feel a sense of failure,” he tells Guardian Australia in his hometown of Brisbane.

The pioneering coral scientist is watching record-breaking 2023 temperatures in oceans around the world and taking it personally.

In what is becoming a very regular event, coral reefs like the ones he has spent his entire life researching are turning white in the northern hemisphere. He is nervous about what next summer might bring to the Great Barrier Reef.

“It’s been 40 years trying to implement science to solve problems,” he says. “And with sea temperatures literally going off the rails, it’s really starting to look like we haven’t made it.”

To any objective observer, Hoegh-Guldberg’s career has been anything but a failure.

A pioneer in the scientific understanding of coral bleaching, the University of Queensland professor has written more than 400 scientific papers. His work has helped shape the world’s understanding of the risks facing the ocean’s richest ecosystems (home to a quarter of all marine species) from global warming.

Related: ‘Hope has to be a strategy’: the scientist who refused to let climate warmongers win

Hoegh-Guldberg was beginning his PhD in California in the early 1980s, when reports were beginning to emerge of coral reefs turning white over wide areas.

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Was it an illness? Was it pollution? Was it caused by excess sunlight? Were the corals reacting to a change in water salinity? “Everyone was speculating, but no one had done the experiment,” she says.

In a series of what he calls “kitchen experiments,” Hoegh-Guldberg took coral fragments and subjected them to different conditions in the laboratory.

What he and his colleagues discovered was that corals had a temperature threshold. Once these temperatures are exceeded, the corals begin to expel the tiny algae that live inside them and that give them their color and much of their nutrients.

The first time he saw major bleaching was in 1994 in Tahiti. The reef was so bright you could see the bleaching from the boat before you got in the water. Hoegh-Guldberg says locals told him that in Polynesia they had no term to describe what was happening.

Branded as an alarmist

As the 1990s drew to a close, more bleaching events were reported and their severity was increasing. In 1998, corals around the world bleached.

“So the question is: how long will it be until this becomes a problem?” says Hoegh-Guldberg. At the time, she thought the answer might be a century away.

But he took the results from the climate models and compared them to the temperature thresholds of the corals.

Instead of being a century or more old, models suggested as early as the 2020s that some reefs could bleach six or more times per decade, too high a frequency to give them time to recover.

“I thought I must have made a mistake. I didn’t believe it. I talked to the climate people who were supporting me in terms of the models. And sure enough, no matter how you look at it, there will be bleaching events every year by 2040… 2050.”

Hoegh-Guldberg wrote up the results in a paper. “Events as serious as 1998, the worst on record, will likely become commonplace within 20 years,” she wrote.

His findings were met with a storm of criticism. Some of his scientific colleagues thought he had gone too far and in conservative media he was branded an alarmist. He received threatening emails calling him a communist and saying they hoped he would die.

He felt emboldened and confident in his science, but privately it affected him.

“It’s almost like you get an ulcer because you’re always on guard,” he says. “That can build up over time and kind of get you down. I am a really very optimistic person. But it hits you a little, there’s no doubt about that.”

‘Was there anything I could have done?’

In 2022, the Great Barrier Reef experienced its sixth mass bleaching event. It was the first to take place in a supposedly colder La Niña year and the fourth in the space of six years.

“Was there anything I could have done?” he asks. “You know, I could have hit a door somewhere?”

But the idea of ​​turning to activism comes and goes quickly. He is more useful to the world, he says, like “the bald professor who comes and talks about the details.”

Hoegh-Guldberg has spoken to governments and royalty about the crisis facing the reefs (both the literal one, like that of the Prince of Monaco and now King Charles, and the figurative one, Sir David Attenborough). He has brought his expertise to climate court cases, multiple United Nations climate reports, and government committees.

What gives him reason to remain optimistic, he says, is that some reefs around the world appear to be less exposed to global warming than others, thanks to the peculiarities of ocean currents. Focusing on protecting those reefs from other impacts could allow them to hold out long enough for governments to reduce greenhouse gas emissions and temperatures to stabilize.

“If you can do that, then you start to preserve the stock,” he says.

Related: ‘What did I do wrong?’ The scientist who tried to raise the climate alarm

However, he believes that if we want to save the reefs, it will be many generations before conditions return to what he remembers as a child. “We have to think about this as multigenerational responses that we have to commit to,” he says.

As for the Great Barrier Reef, he believes the world heritage committee should have included it on a list of endangered sites, despite consecutive governments lobbying against it.

It is clear that the reef is in danger. “If it walks like a duck and sounds like a duck…” she says. “I think if you start playing with words you’re not doing the debate a good service.”

He says the Australian government is still showing a “sort of schizophrenia” by allowing new fossil fuel projects to go ahead while claiming to be taking action on climate change.

“This is a planetary emergency,” he says. “This is so crucial for humanity. We are not going to live in bubbles in the future. You know, we have to find some way to reconnect with nature as soon as possible.”

• In The Weight of the World: A Climate Scientist’s Burden, we hear how three pioneering scientists made their discoveries, the personal toll it took on them, and how, during the hottest year on record, they remain hopeful. Experience the full series here