Who won the prize, and why is it important?

The prize was shared equally between three winners: Paul J. Crutzen, F. Sherwood Rowland and Mario J. Molina. Their field of expertise was atmospheric chemistry, specifically their discoveries about the ozone layer.

Crutzen, 61, was born in Amsterdam. His school years were disrupted by the Wehrmacht invasion of the Netherlands, but he was able to advance through his education and went to Stockholm University to work as a computer programmer. He studied meteorology, learning about the carbon cycle, cloud physics and acid rain.

In the 1970s he moved to researching stratospheric ozone, a field which had not been explored much before.

Molina spent his childhood in Mexico City, then had his higher education in Europe. In 1968 he began graduate studies into physical chemistry at the University of California. He completed a PhD in 1972 and began to work under Rowland studying CFCs. Chlorofluorocarbons are inert chemicals which at the time were released in a lot of industrial gases. Molina and Rowland developed the “CFC-ozone depletion theory”.

Rowland, 68, was born to an academic family in Delaware. He skipped some academic years and had his final year of university before this eighteenth birthday. In 1973 he started work on atmospheric chemistry, following discoveries by Jim Lovelock. He worked with Molina on the ozone layer, which by 1974 had become a major issue of public concern.

The ozone layer is a section of the Earth’s atmosphere which contains the largest quantities of Ozone gas (O3). It is between 15km and 50km from the surface. Were this layer absent, plant and animal life could not evolve on Earth. Ozone absorbs the ultraviolet radiation from the sun, so that most of it does not reach ground level.

Research by the prize winners revealed that the layer was being damaged by emissions of man-made chlorofluorocarbons into the atmosphere. CFCs were at the time used widely in industry, having been chosen because their inertness and non-toxicity were thought to have made them environmentally harmless. In fact, as it was later realised, CFCs were rising to a similar height as the ozone layer then being blasted by ultraviolet radiation – which split up the molecules, releasing chlorine gas atoms.

In 1970 Crutzen had shown that nitrogen oxide and nitrogen dioxide (formed by the decay of N2O) can also cause a catalytic reaction with O3. This effect accelerates the ozone layer’s deterioration. Combined with that of Harold Johnston, Crutzen’s work sparked fears that the rise of supersonic air travel would destroy the ozone layer, because the aeroplanes would fly at altitudes of around 20km (ie. Within the layer) and release nitrogen oxides among their waste gases.

In 1974, Rowland and Molina showed that CFCs in spray cans also damaged the atmosphere. There were restrictions placed upon their use until 1985, when a hole in the ozone layer was discovered over the south pole. In 1987 the United Nations introduced protocols to protect the ozone layer and by 1996 the offending gases were entirely outlawed. The 1995 prize rewards the contributions of Molina, Crutzen and “Sherry” to our understanding of the ozone layer, without which there might by now have been permanent damage done.