Unknown to humanity, in the later decades of the last century an environmental crisis was slowly unfolding in the upper atmosphere. The existence of the ozone layer was proved by chemists in the early 20th century, but as a scientific curiosity rather than a beneficial barrier. A thin layer between the troposphere, in which we live, and the stratosphere, the ozone layer filters out about 99% of harmful ultraviolet light from the sun before it hits the Earth. Exposure to unfiltered ultraviolet light can cause skin cancers, eye damage and weakened immune systems.
What we did not know until the mid 1970s was that chlorofluorocarbons (CFCs), chemicals that had come into widespread use as refrigerant gases and aerosol propellants, were reacting unseen with the ozone layer, fatally thinning the Earth’s protective cloak.
Mario Molina, who has died of a heart attack aged 77, won the Nobel prize for chemistry in 1995, along with F Sherwood Rowland and the Dutch scientist Paul Crutzen, for their work unravelling the impact of CFCs on the ozone layer, and the stark warning they delivered to humanity. Molina and Rowland jointly published a landmark paper in the peer-review journal Nature in 1974 showing the impact of CFCs on ozone.
Read the entire obituary by Fiona Harvey at