It is hard to believe now, but when the first science pointing to the link between chlorofluorocarbon gases (CFCs) and the degradation of the Earth’s ozone layer was revealed in 1974, it was met with widespread scepticism.

That we now have behind us decades of action under the Montreal Protocol, which has reversed the growth of the hole in the ozone layer and saved millions of people around the world from developing skin cancer, is down to the dedication and single-minded vision of a small group of scientists.

Mario José Molina-Pasquel Henríquez, a Nobel Prize in Chemistry Laureate, first uncovered the link between CFCs and the ozone layer—along with Paul Crutzen and Sherwood Rowland—at a time when nobody else even dreamt there was a problem. They published their research in the journal Nature and, at a press conference held by the American Chemical Society in September 1974, took the brave and unprecedented step of calling for a complete ban on further releases of CFCs into the atmosphere—in essence challenging an industry that was raking in massive profits for corporations.

It was not until 1985 that scientists from the British Antarctic Survey found a large hole in the ozone layer over the Earth's southern hemisphere, which was expanding at the same rate as occurrences of skin cancer  in Australia and other southern hemisphere countries. The discovery vindicated Molina and his colleagues and galvanized public support for the regulation of ozone-depleting substances, which came in 1985 when 20 nations—including most of the major CFC producers—signed the Vienna Convention (now known as the Montreal Protocol).

When US President Barack Obama awarded Molina the Presidential Medal of Freedom in August 2013, he referred to him as “a visionary chemist and environmental scientist”. Without such vision, we would not have addressed one of the biggest environmental challenges of the day. Molina’s principles and belief in science, so unfairly dismissed by so many, serve as a touchstone for the environmental community today, as scientists stand by their unwavering commitment to convince the world of the need for urgent action on climate change and other pressing issues.