In 1972, F. Sherwood Rowland, chair of the chemistry department at UC Irvine, attended a lecture.
Nothing inherently unusual about that, of course. But that particular lecture would set thoughts in motion in Rowland’s mind that would prove of planetary significance and ultimately result in his being awarded the Nobel Prize for Chemistry.
The man giving the lecture, maverick British professor James Lovelock, would later achieve fame for his development of the Gaia hypothesis. But on this occasion, he was discussing the electron-capture detector, a device of his own invention, and how he had used it to find the presence in the atmosphere of chlorofluorocarbons, chemicals used in consumer and industrial products such as coolants in refrigerators and air conditioners and propellants in aerosols. Lovelock suggested the chemicals were harmless, but Rowland was less certain.
Rowland knew that CFCs were highly stable. Indeed, he and his postgraduate student Mario Molina soon determined that CFCs stayed in the atmosphere for years, steadily working their way up to the stratosphere. There, finally, they were split apart by ultraviolet radiation from the Sun. When that happened, the reaction released chlorine atoms, which attached themselves to molecules of stratospheric ozone, which comprises three oxygen atoms. The chlorine would strip away the third oxygen atom to form chlorine monoxide; but, because that compound is unstable, the chlorine would soon be free again to attack more ozone.
In this way, Rowland and Molina determined, one chlorine atom could chew up 100,000 ozone molecules during its journey — a matter of great import, as straospheric ozone forms an important shield to protect Earth from the same UV radiation that breaks CFCs apart. The cycle then becomes a vicious feedback loop.
Rowland and Molina published their findings in the journal Nature in June 1974, and initial response was, by the standards of such things, relatively swift. In 1978, the US unilaterally phased out CFCs in aerosols. But other countries did not, and the use of CFCs in refrigerators, air conditioners, and even styrofoam containers, continued. The chemical industry fought back and challenged the science; a trade journal even questioned whether Rowland was a KGB agent, bent on destroying capitalism.
And then, in 1985, Nature published another paper, by a team of scientists from the British Antarctic Survey, who had recorded enormous losses in straospheric ozone above the southern continent over the course of just a few years – what became known as the ozone ‘hole.’
Why Antarctica, of all places? The reason was simple: the extreme cold above the Antarctic leads to the formation of wispy polar stratospheric clouds, which provide a platform for the chemical processes that break apart CFCs; the return of sunlight in the Antarctic spring melts the clouds, frees the trapped chlorine and kick-starts the process of ozone destruction.
In 1987, the Montreal Protocol phased out CFC compounds, although such is the persistence of CFCs that a full recovery in the ozone layer above the Antarctic is not expected until the middle of this century.
But because the ‘weather layer’ in the Arctic has been trapping more heat, the Arctic stratosphere has become significantly cooler, leading in recent years to an Arctic ozone hole.
In 1995, Rowland, Molina and Dutch scientist Paul Crutzen were awarded the Nobel Prize for their work.
Rowland died on March 10 at his home in California, from complications from Parkinson’s disease. He was 84.
“We really sort of stumbled onto a problem of global proportions. His impact and his legacy are extraordinary,” Molina said. “He was a superb scientist, and he worked with a very important problem affecting society. He was always persevered and kept his values, he always did it with honesty and with all the qualities a scientist should have.”
“We have lost our finest friend and mentor,” said Kenneth Janda, physical sciences dean at UC Irvine. “He saved the world from a major catastrophe: never wavering in his commitment to science, truth and humanity, and did so with integrity and grace.”
IMAGE: False-color view of total ozone over the Antarctic pole in September 2006, during one of the largest recorded ozone holes. The purple and blue colors are where there is the least ozone, and the yellows and reds are where there is more ozone.
VIDEO: A NASA-led study found that Earth’s protective ozone layer above the Arctic thinned to the lowest levels ever observed in early 2011. (NASA/JPL)
