Most knew about the climate crisis in the 2000s, some knew in the 1980s, but very few people anywhere on the planet knew about it, with any clarity, in the early 1970s.
That's when Professor John Bockris leaned against his blackboard and began to speak.
"There's no getting out of it," he said.
He was standing in Adelaide and he was speaking about climate disaster with a kind of certainty.
"The urgency of my argument is entirely dependent on carbon dioxide. The evidence for the carbon dioxide damage … is completely definite."
The South African-born electrochemistry professor was in a lecture hall at Flinders University in 1973 and he was answering a question from the audience at an energy conference organised by the UN.
He was wearing a broad tie under a suit jacket with a wide collar. His hair — what was left of it at the age of 50 — was unkempt.
"You'd have to be a non-scientist to reject it," he said.
"If it were possible to use coal for say 100 years, we have plenty of it, and so do many countries," Professor Bockris told an ABC crew after the lecture.
"The difficulty of using coal over those long terms is that it produces carbon dioxide."
Gesturing pointedly with his left hand, he explained that humans were now producing carbon dioxide at a faster rate than it could be absorbed by plants through photosynthesis, and so it was building up in the atmosphere.
"Now, it can be shown that that does unfortunate things to our atmosphere," he said.
'The final energy source for man'
The ABC interview was one of four Professor Bockris gave to the ABC in 1973 and 1974, as he tried to alert the public to the dangers of carbon dioxide in the atmosphere.
It wasn't the first time a scientist had talked about climate change on the ABC. There had been around half a dozen mentions of the phenomenon by then.
What was extraordinary about these interviews with Professor Bockris was his confidence not only in the science, but in the solution.
"I think virtually all scientists, at least those with some knowledge of this area at all, agree that solar energy is going to be the final energy source for man," he said.
"But whether that solar energy has to be built up by the end of this century on a large scale, or whether it has to be built up 50 years later, that's the argument," he added.
At the time, solar energy was only used in Australia for hot water systems.
Photovoltaic solar panels, using the sun's energy to create electricity, were extremely expensive and were essentially only used on satellites and space probes, where there was no other option.
"I think a solar home could be built right now," Professor Bockris told the ABC in early 1974.
"Heating, cooling, refrigeration, electricity, will be collected and run from the sun.
"In the case of individual houses, we'd store the electricity, probably in batteries."
Within years, Professor Bockris would find himself at loggerheads with the Australian government, as he tried to convince it to invest heavily in solar energy research.
"What we want, clearly, is a kind of Snowy River project in solar energy research," he told the ABC in 1977.
The transport minister at the time, Peter Nixon, said Professor Bockris's proposal was not viable.
"It's just not clearly possible to find the sorts of money that Professor Bockris would like for solar energy at this time," Mr Nixon told the ABC's AM program.
"Professor Bockris is pushing his own barrow.
"I doubt the feasibility of Australia to take the lead over countries such as the United States in the area of solar energy."
John Bockris responded angrily, accusing the government of only being interested in talking to fossil fuel lobbyists, and taking a "supine attitude" to solar research.
Subsequently, significant developments were made in solar research in Australia, partially backed by grants from NASA in the US.
Providing solutions to the climate crisis before most knew it existed
While Professor Bockris's opinions on climate change and solar energy have stood the test of time, his view on another area of research now seems almost prophetic.
"Could Australia in some form export solar energy, possibly to Japan, and even to the United States?" he said in a lecture broadcast by the ABC in 1973.
"Once we have got the energy into the form of hydrogen by electrolysing brackish water, it would be possible to pipe it over very long distances for quite cheap prices."
John Bockris had a strong interest in hydrogen.
A year earlier, he had coined the term "hydrogen economy" in an academic paper, to describe the concept of transferring energy around the globe through pipes in the form of hydrogen, though he credited former Nazi engineer Franz Lawaczeck with the idea.
He was confident that Australia had a significant role to play in this new economy.
"With an area of land about 150 miles a side [58,000 square kilometres] Australia could produce sufficient energy from its sunlight to give the basic power for the whole of the United States as calculated at the year 2000," he said.
"Australia's position in the world — in the hemisphere — is just at the right position to obtain, constantly, the largest amount of solar energy.
"There are few other positions in the world, and none in developed countries, where the capability is so great."
This idea, of Australia exporting solar energy in the form of hydrogen to the rest of the world, is now the subject of significant investment by governments and private industry in Australia.
Bockris was 'prophetic', say today's climate experts
The Australia, If You're Listening podcast played a recording of John Bockris's lecture from 1973 to some of Australia's top energy advisers.
Professor Alan Finkel, former Australian chief scientist and now an energy advisor to the Commonwealth government, was shocked to hear it.
"I'm stunned and delighted to have heard that," he said.
"He saw back then, when the cost would have been inconceivable, the possibility of taking our renewable energy, converting it into electricity, converting into hydrogen and then using hydrogen as a vector to export that renewable energy around the world.
Professor Ross Garnaut, author of the Garnaut Climate Change Review, was similarly taken aback.
"I hadn't heard that before, Bockris was saying something revolutionary and sound," he said.
"It's very impressive."
Professor Graeme Pearman, a contemporary of John Bockris who corresponded with him in the early 1970s, was amazed at the foresight.
"I mean, how prophetic is that, it's fantastic," he said.
"That's a very visionary statement, and I think it probably reflects the fact that he had an extremely broad view of the world and all of the engineering capabilities that we have."
Alison Reeve, lead author of Australia's national hydrogen strategy, laughed when she heard the recording.
"That's amazing," she said.
"The thing it shows you is that there's actually very few new ideas out there — or we have ideas and then we forget them."
John Bockris wasn't entirely correct in his predictions in 1973 and 1974.
On hydrogen, he incorrectly predicted that sending gas through intercontinental pipelines would be more cost-effective than liquefying it and shipping it in specially made tankers.
Those tankers are already being used to transport liquid hydrogen around the world.
Though in 1982, he did predict that the hydrogen produced in Australia could be converted into ammonia, which is easier to transport in ships.
On solar power, he incorrectly predicted that the cost of solar power, without accounting for the cost of battery storage, would not go below $300 per kilowatt, and would remain only slightly cheaper than nuclear energy.
In fact, when adjusted for inflation, solar power is now less than half the price he predicted, and far and away cheaper than nuclear power, even when the cost of battery storage is included.
These mistakes are extremely minor in the face of the number of accurate predictions he was responsible for in the 1970s.
The rest of John Bockris's career was contentious
After moving to Texas A&M University, Professor Bockris made a number of incredible claims of breakthroughs during the 1980s and 1990s which proved less than impressive.
His "breakthroughs" in producing hydrogen directly from sunlight turned out to be based on simple scientific mistakes, though he never admitted he was wrong.
Then he became involved in research into nuclear fusion and transmutation.
He said he and two other researchers had made progress in inventing cold fusion — an entirely safe form of nuclear power generation which would save the world from fossil fuels.
He also worked with an ex-con named Joe Champion on a project which was trying to convert mercury into gold, leading colleagues and newspapers to mockingly call him an alchemist.
"He is an ambitious, egocentric, driven human being who has come a long way … by aggressive, outlandish at times, scrapping," a colleague told the Houston Press newspaper in 1994.
Another colleague, Ramesh Bhardwaj, described the descent into such ideas as shocking.
"I never thought Dr Bockris could be made a fool of."
A letter was published from 15 fellow chemistry professors demanding he resign.
Newsweek magazine began its article on the topic with the question:
"In the revered name of academic freedom, universities tolerate faculty members who are avowed communists and lifelong fascists, outspoken racists and anti-Semites, radical lesbians and rabid homophobes — but alchemists?"
Despite his ambition to win a Nobel Prize, Professor Bockris only ever won the satirical Ig Nobel Prize, in 1997.
He left Texas A&M University after being investigated and cleared three times for fraud or scientific misconduct.
In his 80s, his views became more controversial.
In 2004, eight years before his death, he published a book called The New Paradigm: A Confrontation Between Physics and the Paranormal Phenomena, which cast doubt on almost every scientific theory in existence — from evolution to the big bang to Einstein's theory of relativity.
In it, he wrote about paranormal happenings, including ones he experienced himself, such as a mysterious half-eaten ham sandwich which appeared on his bathroom floor.
On the final page of the book he writes: "I may be going a bit too far too fast."
That was probably true of his whole career.
Now, billions of dollars of investment begin to realise his dream of an Australian hydrogen industry, 49 years after he suggested one.
The number of Australian "solar homes" is approaching 4 million.
Climate change is threatening our way of life.
In 1973 and 1974, John Bockris may have been going "a bit too far too fast", but we should have followed him.
