The hole in the ozone layer above Antarctica could be ‘fixed’ by injecting
50 000 tonnes of ethane or propane into the stratosphere, say three Americans.
Ralph Cicerone and Scott Elliott of the University of California at
Irvine and Richard Turco of the University of California at Los Angeles
propose removing active chlorine from the stratosphere by reacting it with
simple hydrocarbons (alkanes) to produce hydrogen chloride. The gases would
be released at altitudes of between 15 and 20 kilometres above Antarctica
each spring. In this week’s issue of Science, the researchers suggest that
this will remove chlorine from the chain of reactions which destroys ozone.
Cicerone and his colleagues carried out computer simulations of the
effect of adding alkanes to the stratosphere at the key time in the southern
spring. They found that all their computer models showed less depletion
of ozone when the concentration of hydrocarbons was set at 3.6 parts per
billion. But the technique is not foolproof. In some simulations a smaller
amount of gas – just 1.8 parts per billion of hydrocarbon – actually increased
the loss of ozone.
As well as recognising the practical difficulties of spreading the hydrocarbons
evenly through 20 million cubic kilometres of the stratosphere, the researchers
admit that their calculations are ‘sensitive to many assumptions’ and that
‘serious uncertainties remain’. They also point out that: ‘Before any actual
injection experiment is undertaken there are many scientific, technical,
legal and ethical questions to be faced, not the least of which is the issue
of unintended side effects.’
Cicerone and his colleagues say that although their scheme is not practicable
today, it holds out the hope that future generations, armed with a better
understanding of the mechanism of ozone depletion, may be able to repair
some of the damage we are doing.