Geoscience Reference
In-Depth Information
ultraviolet energy from the sun, protecting the biosphere below from dam-
aging wavelengths of light.
9
In the late 1960s and early 1970s, concerns over ozone depletion revolved
around the potential for water vapor and oxides of nitrogen from high-
elevation supersonic transport flights to accelerate natural stratospheric
ozone destruction. These concerns did not die with the end of the Ameri-
can SST program, however. As Paul Crutzen, Harold Johnston, and others
studied the effects of stratospheric NO
x
on ozone in the mid-1970s, they
realized that other substances that seemed stable in the troposphere might
undergo chemical changes as they interacted with radiation and ozone in
the stratosphere.
10
In 1974, Sherwood Rowland and Mario Molina published a ground-
breaking paper that investigated the role of halogenated hydrocarbons
(also known as halocarbons) in the destruction of stratospheric ozone.
11
The paper, which earned the two chemists the 1995 Nobel Prize in chem-
istry, addressed two specific chlorofluoromethanes (CF
2
CL
2
and CFCL
2
)
commonly used as refrigerants and as propellants in aerosol spray cans.
Molina and Rowland also suggested that chlorofluorocarbons (CFCs)and
other halocarbons, like those in the widely used DuPont refrigerant Freon,
might also catalyze the destruction of stratospheric ozone.
12
Scientists
working in conjunction with the U.N. Environment Programme and the
World Meteorological Organization soon created projections of CFC and
halocarbon usage, from which they then attempted to extrapolate future
ozone depletion.
13
By the time the
Global 2000 Report to the President
laid
these issues out for policymakers in 1980, it was clear that halocarbons and
CFCs presented a potentially significant danger to stratospheric ozone
and, by association, to both the human and nonhuman denizens of the
earth.
As an environmental issue, ozone depletion bridged the gap between
regional air pollution, which was subject to existing legal and political
frameworks, and global CO
2
-induced warming. Ozone depletion and
global warming shared two important attributes that distinguished them
politically from acid rain. First, though
Global 2000
expressed concern
over the expanding geographical reach of SO
2
and NO
x
, the two gases'
environmental and public health impacts directly affected the geographi-
cally discrete places where either the gas settled and people breathed it
in or the chemicals fell as precipitation. CO
2
and stratospheric ozone, by
