Cover Image

Not for Sale



View/Hide Left Panel

directly off the North Atlantic, uncontaminated by recent urban pollution.

This unexpected discovery prompted Lovelock to do further studies. Accordingly, he asked the British government for a modest sum of money to place his apparatus on board a ship traveling from England to Antarctica. His request was rejected; one reviewer commented that even if such a measurement succeeded, he could not imagine a more useless bit of knowledge than finding the atmospheric concentration of CFC-11.

But Lovelock persisted. Using his own money, he put his experiment aboard the research vessel Shackleton in 1971. Two years later the British researcher reported that his shipboard apparatus had detected CFC-11 in every one of the more than 50 air samples collected in the North and South Atlantic. Lovelock correctly concluded that the gas was carried by large-scale wind motions. He also stated that CFCs were not hazardous to the environment, a conclusion soon to be proven wrong.

Ozone Loss: The Chemical Culprits

In 1972, the life of atmospheric scientist F. Sherwood Rowland took a critical turn when he heard a lecture describing Lovelock's work. Like other researchers at the time, Rowland had no inkling that CFCs could harm the environment, but the injection into the atmosphere of large quantities of previously unknown compounds piqued his interest. What would be the ultimate fate of these compounds? Rowland, joined by Mario Molina, a colleague at the University of California, Irvine, decided to find out.

The scientists showed that CFCs remained undisturbed in the lower atmosphere for decades. Invulnerable to visible sunlight, nearly insoluble in water, and resistant to oxidation, CFCs display an impressive durability in the atmosphere's lower depths. But at altitudes above 18 miles, with 99 percent of all air molecules lying beneath them, CFCs show their vulnerability. At this height, the harsh, high-energy ultraviolet radiation from the sun impinges directly on the CFC molecules, breaking them apart into chlorine atoms and residual fragments.

If Rowland and Molina had ended their CFC study with these findings, no one other than atmospheric scientists would ever have heard about it. However, scientific completeness required that the researchers explore not only the fate of the CFCs, but also of the highly reactive atomic and molecular fragments generated by the ultraviolet radiation.

In examining these fragments, Rowland and Molina were aided by prior basic research on chemical

74

Sherwood Rowland and Mario Molina discover that CFCs can destroy ozone the stratosphere.

1976

The National Academy of Sciences releases its report verifying the Rowland-Molina finding.

1976

The Food and Drug Administration and the Environmental Protection Agency announce a phase-out of CFCs in aerosols.

1978

CFCs used in aerosols are banned in the United States.

1984

A British research group led by Joseph Farman detects a 40 percent ozone loss over Antarctica during spring in the southern hemisphere.

1985

NASA satellite data confirm the existence of the ozone hole over the Antarctic.

1987

The Montreal Protocol is signed, calling for eventual worldwide CFC reduction by 50 percent.

1988

The United States ratifies the Montreal Protocol in a unanimous vote.

1988

Scientists present preliminary findings of a hole in the ozone layer over the Arctic.

1996

Complete ban on industrial production of CFCs goes into effect.

1995

F. Sherwood Rowland, Mario Molina, and Paul Crutzen awarded the Nobel prize for their work in atmospheric chemistry.



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement