Those that were paying attention.
Edward Teller was the first prominent modern scientist to raise the danger of climate change driven by the burning of fossil fuels. Teller worked on the hydrogen bomb during WW II. He was also director of the Lawrence Livermore National Laboratory.
At an address to the membership of the American Chemical Society in December 1957, Teller warned that the large amount of carbon-based fuel that had been burnt since the mid-19th century was increasing the concentration of carbon dioxide in the atmosphere, which would "act in the same way as a greenhouse and will raise the temperature at the surface", and that he had calculated that if the concentration of carbon dioxide in the atmosphere increased by 10% "an appreciable part of the polar ice might melt."
In 1959, at a symposium organized by the American Petroleum Institute and the Columbia Graduate School of Business for the centennial of the American oil industry, Edward Teller warned that:
"I am to talk to you about energy in the future. I will start by telling you why I believe that the energy resources of the past must be supplemented. [...] And this, strangely, is the question of contaminating the atmosphere. [...] Whenever you burn conventional fuel, you create carbon dioxide. [...] Carbon dioxide has a strange property. It transmits visible light but it absorbs the infrared radiation which is emitted from the earth. Its presence in the atmosphere causes a greenhouse effect [....] It has been calculated that a temperature rise corresponding to a 10 per cent increase in carbon dioxide will be sufficient to melt the icecap and submerge New York. All the coastal cities would be covered, and since a considerable percentage of the human race lives in coastal regions, I think that this chemical contamination is more serious than most people tend to believe."
In the years after Edward Tellers presentations, the two most active academics were Bill McKibben and James Hansen. McKibben is especially known for founding the organization 350.org and Hansen for his work at NASA and his testimony before Congress in 1988.
William Ernest "Bill" McKibben (born December 8, 1960) is an American environmentalist, author, and journalist who has written extensively on the impact of global warming. He is the Schumann Distinguished Scholar at Middlebury College and leader of the anti-carbon campaign group 350.org. He has authored a dozen books about the environment, including his first, The End of Nature (1989), about climate change.
In 2009, he led 350.org's organization of 5,200 simultaneous demonstrations in 181 countries. In 2010, McKibben and 350.org conceived the 10/10/10 Global Work Party, which convened more than 7,000 events in 188 countries, as he had told a large gathering at Warren Wilson College shortly before the event. In December 2010, 350.org coordinated a planet-scale art project, with many of the 20 works visible from satellites. In 2011 and 2012 he led the environmental campaign against the proposed Keystone XL pipeline project and spent three days in jail in Washington, D.C. Two weeks later he was inducted into the literature section of the American Academy of Arts and Sciences.
James Edward Hansen (born 29 March 1941) is an American adjunct professor directing the Program on Climate Science, Awareness and Solutions of the Earth Institute at Columbia University. He is best known for his research in climatology, his 1988 Congressional testimony on climate change that helped raise broad awareness of global warming, and his advocacy of action to avoid dangerous climate change. In recent years he has become a climate activist to mitigate the effects of global warming, on a few occasions leading to his arrest.