There is a grain of truth, but no more, in that view. The damage is most evident in Antarctica simply because the air there provides the ideal combination of icy clouds, very cold air and lots of sun to open up holes in the ozone layer. But the data reported today suggest that we who live in the world's temperate zones cannot be confident that the ozone layer above our heads is secure. Nor is the problem confined to suntans: although scientists believe that the increase in ultra-violet radiation will cause five million cases of skin cancer in the United States alone in the 21st century, the bigger question is what those rays will do to the world's plant life. Specialists now believe that ozone holes could reduce crop yields across the world by 20 per cent, and could kill off the plankton that gives life to thousands of sea species.
Environmental groups will use the Nasa findings to support demands for tougher international controls on the chemicals that harm the ozone layer. The first treaty restraining them was signed in Montreal in 1987; since then, scientists have twice come back with
evidence that the problem is worse than previously thought, and ministers have responded by bringing forward the deadlines for phasing out damaging chemicals, and cutting the emissions
of those chemicals permitted in the meantime.
They will now be under pressure to plug the two gaps that remain in existing rules. The deadline for phasing out hydrochlorofluorocarbons (HCFCs), chemicals that do less harm than old- style CFCs but still some harm, is likely to be brought forward from its present date of 2030; and use of the other ozone- damaging chemical still allowed, methyl bromide, will be subject to a deadline of its own. Sadly, the ozone holes would continue to grow for some years even
if all production ceased tomorrow, for the chemicals take time to reach the stratosphere.
The Nasa numbers have a broader lesson, however. They show that humanity has proven much more adept than anybody believed possible, even a decade ago, at altering the equilibrium of the planet; that equilibrium, in turn, has proven unexpectedly fragile. When governments are presented in future with further evidence of global environmental problems, such as the greenhouse effect, they would be wise to take a pessimistic view. Otherwise, by the time they realise the full gravity of the situation, it may be too late to do anything about it.Reuse content