Ozone Alert
A large part of the controversy over the British-French Concorde arises from concern about the big jets' effect on the ozone layer, which protects life on earth from lethal doses of ultraviolet light. Laboratory tests and chemical theory have shown that the nitrogen oxides given off by jet engines destroy ozone. Do nitrogen oxides have the same effect in the stratosphere? A Dutch meteorologist working at Boulder, Colo., reports there is now evidence that the answer is yes.
Paul Crutzen and associates at the National Oceanic and Atmospheric Administration (NOAA) and the National Center for Atmospheric Research (NCAR) have long theorized that the sun occasionally produces the same effect that SST foes charge would result from large-scale use of Concordes. As he explains it, high-energy protons from solar flares, or eruptions on the surface of the sun, are hurled through space to the earth. At lower latitudes, most of the protons are deflected by the earth's magnetic field. But near the poles, where the lines of the field bend toward the earth, the protons slam into molecules in the upper atmosphere and cause a shower of electrons. These, in turn, crash into nitrogen molecules, ionizing them and allowing them to combine with oxygen. As a result, nitric oxide (NO) and nitrogen dioxide (NO2) are formed; both react readily with ozone molecules and cause their destruction.
Last summer, Crutzen declared that a large solar flare in 1972 must have doubled the amount of nitrogen oxides in the stratosphere at an altitude of about 25 miles over the polar regions, and thus depleted the ozone over these areas by an amount he calculated at 20%. There was a way of checking his theory. A Nimbus satellite, in orbit at the time, had been measuring the amount of ultraviolet light reflected from the earth's atmosphere. Because ozone absorbs ultraviolet, any decrease in ozone would result in an increase in the ultraviolet "seen" by the satellite. Sure enough, after months of analyzing data from the Nimbus, two NASA scientists, Donald Heath and Arlin Krueger, determined that the solar flare had depleted the ozone in that region by about 16%.
These results show the need for further research into the effects of technology on the ozone layer. Large solar flares occur infrequently, allowing the ozone layer time to be replenished by natural processes. But man's assaults on the ozone shield, in the form of SST flights, aerosol sprays and other chemicals, are continuous and could permanently deplete the layer.
A different study by Crutzen and three other scientists emphasizes the importance of the ozone layer. Researchers have been able to correlate the disappearance of certain species of animals and plants with periods when the earth's magnetic field was reversing. At some point during the reversal, the field virtually disappears, allowing solar particles that are normally deflected by the magnetic field to strike the earth. Some scientists have suggested that during these periods high-energy cosmic rays and particles from solar flares may have killed off entire species and caused extensive mutations in others.
In a paper published in Nature, G.C. Reid and I.S.A. Isaksen of NOAA, T.E. Holzer of NCAR and Crutzen suggest that the solar particles may not directly wreak their havoc on life during magnetic field reversals. Instead, unobstructed by the field, they may deplete the ozone layer by as much as 50% by creating nitrogen oxides, letting in lethal doses of ultraviolet light.
That could explain the sudden disappearance throughout the earth's history of many animal and plant species, from the single-celled, ocean-dwelling radiolaria to the dinosaurs. Thus, Crutzen and his colleagues note, a long-term threat to the ozone layer from any source may well be a threat to the species that now inhabit the earth--including man.
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