Dr. Mario Molina: Hot Atom Chemist and Atmosphere Hero

Science benefits society. But sometimes the gap between the lab and life can seem large. That’s when it helps to turn to science history and heroes like Dr. Mario Molina. A chemist by training, Dr. Molina’s research, teaching, and advocacy addressed some of the most pressing environmental problems of our age including the ozone hole, air quality, and climate change.

Mario José Molina-Pasquel Henríquez was born in 1943 in Mexico City. Growing up he idolized his Aunt Esther who was a respected chemist – especially after she helped him create a lab inside his bathroom where he could carry out experiments. By the age of 11, he had firmly decided to become a scientist. The son of a judge turned ambassador, Molina was sent to a Swiss boarding school but returned to Mexico City for his undergraduate.

At the National Autonomous University of Mexico, Mario Molina majored in chemical engineering. He then attended the University of Freiburg (Germany) where he earned his MS. After getting his masters, Molina went to Paris where he independently studied mathematics and “also had a wonderful time discussing all sorts of topics, ranging from politics, philosophy, to the arts, etc., with many good friends.” However, a few months into this “gap” year he was offered an assistant professor at his undergraduate alma mater. Here he helped set up a graduate program in chemical engineering.

In 1968 Molina moved to California to pursue his doctorate. He received a Ph.D. from UC Berkeley in 1972 for his work studying molecular dynamics using chemical lasers. Describing this time Molina says “My years at Berkeley have been some of the best of my life. I arrived there just after the era of the free-speech movement. I had the opportunity to explore many areas and to engage in exciting scientific research in an intellectually stimulating environment. It was also during this time that I had my first experience dealing with the impact of science and technology on society. I remember that I was dismayed by the fact that high-power chemical lasers were being developed elsewhere as weapons; I wanted to be involved with research that was useful to society, but not for potentially harmful purposes.”

Dr. Rowland, left, and Dr. Molina in January 1975. UC Irvine

After completing his Ph.D. Dr. Molina began a postdoc at the lab of Dr. Sherwood Rowland where he was offered a short list of potential projects. The one that he picked was investigating the long-term fate of a group of popular industrial chemicals called chlorofluorocarbons (CFCs for short). At the time CFCs were thought to be inert and harmless so the environmental applications of this work seemed limited. However, Molina loved the idea of studying a challenging molecule as well as the opportunity to dive into the new field of atmospheric chemistry.

How did Dr. Molina make this leap and start studying (and protecting) the ozone layer? By a quick decision that on the surface had little to do with this essential atmospheric shield.

The work did prove challenging! A systematic search for lower atmospheric processes that might destroy CFCs proved fruitless. Things, however, began to heat up when Molina and Rowland began investigating what happened to CFCs higher up. They found that high-altitude solar radiation destroyed CFSs. Moreover, they ascertained that the chlorine atoms produced by this decomposition quickly destroyed nearby ozone molecules. These two discoveries led them to formulate the “CFC ozone depletion theory” which warned that the release of CFCs at current levels would injure Earth’s stratospheric ozone layer.

The CFC ozone depletion theory had worldwide implications. Dr. Molina and Dr. Rowland published their findings in Nature in 1974. They also realized that need to communicate their research to a wider audience. The next few years were incredibly busy for Dr. Molina. He became a professor at UC Irvine and began setting up his own atmospheric chemistry lab. He also co-wrote a 150-page report about CFCs for the United States Atomic Energy Commission which called for a total ban on CFCs. And he spent countless hours as a science diplomat – sharing and explaining the science of CFCs to key policymakers, reporters, and the public.

Over the next decade, the CFC ozone depletion theory became widely discussed. It also came under sharp criticism, particularly by representatives of the aerosol and halocarbon industries. Molina’s research was called nonsense, rubbish, and a work of science fiction, and his advocacy was called unprofessional. However, Dr. Molina continued both with his scientific research and diplomacy. An important breakthrough came in 1985 when Molina began collaborating with Dr. Farman. The two investigated the seasonal depletion of the ozone layer over Antarctica and were able to show that this seasonal shift was largely due to chlorine-activated reactions that were augmented by the increased presence of ice.

Ozone Hole Recovery NASA, Public domain, via Wikimedia Commons

In 1987, fourteen years after Molina and others first discovered the dangers of CFCs, the international agreement known as the Montreal Protocol was signed. In it, 196 countries and the EU agreed to rapidly phase out the production of CFCs, HCFCs, and HFCs. Today the agreement is considered the most effective environmental treaty ever negotiated. CFCs are no longer used in any products (although they still are released by some older refrigerators, air conditioners, and insulation systems). Consequently, recent meteorological measurements show a 50% drop in ozone-killing materials in the atmosphere. Most importantly, signs of ozone repair indicate that by 2065 the ozone layer will recover to a pre-1980s level of health!

For their work with CFCs, Dr. Molina, Dr. Sherwood, and Dr. Crutzen were awarded the Nobel prize in chemistry in 1995. Reflecting on this Molina says “When I first chose the project to investigate the fate of chlorofluorocarbons in the atmosphere, it was simply out of scientific curiosity. I did not consider at that time the environmental consequences of what Sherry and I had set out to study. I am heartened and humbled that I was able to do something that not only contributed to our understanding of atmospheric chemistry but also had a profound impact on the global environment.”

Heartened and humbled and also energized and curious, Dr. Molina continued to explore the science of atmospheric chemistry. He taught and lead cutting-edge research at UC-Irvine, the Jet Propulsion Lab of Caltech, MIT, UC San Diego, and the Scripps Institute of Oceanography. In these labs, he not only continued to track the ozone but also began working on the issue of air quality and climate change. In 2005 he established the non-profit Centro Mario Molina para Estudios Estratégicos Sobre Energía y Medio Ambiente(Mario Molina Center for Strategic Studies in Energy and the Environment) in Mexico City where he served as director until he died in 2020. 

In addition to the Noble Prize Molina received the Presidential Medal of Freedom and 29 honorary degrees! He was an elected member of the National Academy of Sciences, the National Academy of Medicine, El Colegio Nacional de México, the Mexican Academy of Sciences, and the Mexican Academy of Engineering. He also served on the U.S. President’s Council of Advisors on Science and Technology and the Vatican’s Pontifical Academy of Sciences.

Given this long list of accomplishments and the prominent atmospheric issues that Dr. Molina researched and advocated for, it should be no surprise that he was famous. One of his mentees described the throng of people often surrounding him saying, “I had never seen a scientist treated like a rock star before.” But more importantly, she remembers his gracious, soft-spoken, and generous personality which was paired with a fervent belief in widely communicating science to implement social changes.

Interested in learning more about this incredible man whose work helped shaped international environmental policies and through this the short- and long-term well-being of humanity? You can listen to an interview with him here (49 minutes) or read a short autobiography here (5 minutes).

Title Photo: http://science.in2pic.com, CC BY-SA 3.0 https://creativecommons.org/licenses/by-sa/3.0, via Wikimedia Commons

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