Tracking ozone: Life before the hole

Like historians raiding an archive of ancient texts, 
two atmospheric scientists are sifting through old 
satellite data, looking for a means of extending ozone 
records back in time. On the basis of ground measurements 
made in Antarctica since the 1950s, researchers believe 
the annual Antarctic ozone hole first appeared in a mild 
form during the late 1970s and then grew worse in the 1980s. 
Yet they have lacked confirming evidence from satellites 
because the principal instrument used to track ozone 
concentrations from space was first launched in 1979. 
Robert D. Boime and Stephen G. Warren of the University of 
Washington in Seattle now report that measurements from 
another type of satellite sensor may provide information 
about ozone concentrations going as far back as 1972.

The standard ozone-sensing instrument on current satellites, 
called the Total Ozone Mapping Spectrometer (TOMS), makes 
measurements by monitoring the solar ultraviolet light 
reflecting off Earth's surface. Because ozone absorbs
ultraviolet radiation, the amount bouncing off Earth reveals 
how much ozone the atmosphere holds.

But ozone also absorbs limited amounts of visible light, 
so Boime and Warren are studying whether visible-light 
measurements made by weather satellites can help track ozone 
in the atmosphere. To test their idea, the researchers 
compared the two methods, looking at the ozone hole in 1987.

Their preliminary results suggest that the two methods agree 
for that particular period. If further study shows that the 
techniques match up for other time spans, Boime and Warren 
hope to start studying data from the 1970s to recover ozone 
information for that decade.

SCIENCE NEWS, Vol. 145, No. 1, January 1, 1994