What sharpened his interest in the atmosphere of our own planet, he says, was his work in the 1970s modeling the environmental impact of Boeing’s proposed supersonic aircraft. In order to surpass the speed of sound, the Boeing 2707 would have flown through the thin air of the ozone layer. But the engines would have produced nitric oxide, which chemists knew destroys ozone. Prinn and other MIT researchers set up a computer simulation demonstrating the risks that a fleet of supersonic aircraft would pose to the ozone layer, which protects the planet from the sun’s ultraviolet radiation. Plans to build the fleet were eventually scrapped for a variety of reasons, but the work stayed with him. “I got interested in atmospheric chemistry on Earth,” he says.
In 1974, future Nobel laureates Sherwood Rowland and Mario Molina (who would become an MIT professor) published their seminal work describing how the inert chlorofluorocarbons (CFCs) widely used in refrigeration systems and spray cans could reach the ozone layer, where ultraviolet radiation might dislodge highly reactive chlorine molecules that could catalyze the decomposition of ozone. At the time, however, Rowland and Molina had no direct evidence that this was happening. Their work left chemists with a feeling of alarm: so little was known about the chemistry of the atmosphere, and in particular about the effects of man-made gases on it. No one knew what the life cycle of these gases might be–or whether the ozone layer was in fact breaking down. Did CFCs really persist in the atmosphere and travel into the ozone layer? How were naturally occurring, highly reactive chemicals called hydroxyl radicals interacting with the man-made emissions?
These questions spurred Prinn to launch, in 1978, a large-scale project to measure and model the chemistry of Earth’s atmosphere. AGAGE continuously monitors the emission rate and the persistence of 45 ozone-depleting and greenhouse gases, including CFCs, hydroxyl radicals, methane, and nitrous oxide. It also measures global levels of all the gases regulated under the Kyoto and Montreal Protocols (except carbon dioxide, which is monitored by a U.S. government agency). Findings from the project’s detectors at five coastal sites around the world show the regional distribution of these gases and allow researchers and governments to monitor where they originate and where they go. Results are posted online.
“Back in the 1960s, regional air pollution was the major interest in atmospheric monitoring and science; global monitoring was really the field of only a few scientists,” recalls Paul Fraser, who leads the changing-atmosphere research group at Australia’s national science agency, the Commonwealth Scientific and Industrial Research Organisation. (One of those few was Caltech’s Charles Keeling, who had begun continuous monitoring of atmospheric carbon dioxide levels in Mauna Loa, HI, in 1958.)
“Ron’s big contribution was to expand the idea that we had to look at the Earth globally, not only for CO2 but for all the gases important for climate change and ozone depletion,” says Fraser. “That was a big change of emphasis in where the exciting science was being done. His work has led to a major expansion in the effort of research agencies around the world in studying the global problem as well as maintaining regional pollution studies.”