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A plasma physicist in California has come up with a grandiose plan to
repair the damage wrought by CFCs on the ozone layer. Alfred Wong, from
the University of California at Los Angeles, would like to hoist giant electronic
‘curtains’ into the stratosphere to carry out the renovation work. But his
ideas have met with scepticism from atmospheric scientists.

Wong’s strategy, outlined in last week’s Physical Review Letters, is
straightforward. Highly reactive chlorine atoms, released from CFCs by ultraviolet
light, are the culprits that destroy ozone. Wong suggests converting these
into ions, which do not destroy ozone, by supplying negative electric charge
to the stratosphere. The ions could then be harvested.

Wong has demonstrated the technique in his laboratory, using an aluminium
chamber filled with ozone and oxygen. When he and his colleagues added CFCs
to the chamber, ozone concentrations plummeted. But when they supplied a
negative electric charge, the ozone concentration returned to normal. A
series of computer simulations of stratosphere chemistry also suggested
the scheme would work, says Wong.

To apply his ideas to the real world, Wong envisions raising platforms
carrying large electronic ‘curtains’ to the stratosphere, using helium balloons.
One curtain would supply negative electric charge and another would capture
the chloride ions. Alternatively, the chloride ions could be ejected into
outer space, using radio waves tuned to a frequency that resonates with
the ions, causing them to accelerate.

Wong’s ideas caused heated exchanges at a geosciences meeting in San
Francisco last autumn. Now the plan has been published, atmospheric chemists
are no less sceptical.

‘I give Dr Wong credit for submitting the paper to a refereed journal
– that’s the responsible way to air these ideas,’ says Ralph Cicerone of
the University of California at Irvine, who has himself considered heroic
ways to fix the ozone hole. ‘But it appears he’s giving people the idea
that there’s more than just a lab experiment here.’

The sceptics feel the vast scale of the stratosphere, and the estimated
3.6 million tonnes of chlorine that would need to be collected, render the
plan unworkable. ‘Anyone who proposes a technological fix for the ozone
hole owes it to everybody to do an energy balance calculation,’ says Adrian
Tuck, head of the meteorological chemistry programme at the National Oceanic
and Atmospheric Administration in Boulder, Colorado. He calculates that
repairing the ozone hole Wong’s way would need 30 times the energy-generating
capacity of the US.

Wong’s laboratory experiment is too simple, the critics argue. Chlorine
atoms are hungry for electrons, but other atmospheric chemicals which were
not present in Wong’s chamber are hungrier still. ‘You can put a charge
on a chlorine atom but that doesn’t mean it’s going to stay there,’ says
NOAA research physicist David Fahey.

Wong says these practical problems can be overcome. Solar power would
provide the energy, he says, and if the chloride ions were collected rapidly,
other chemicals would not have the chance to pull the electrons away again.
He is also studying the effects of a wider range of atmospheric chemicals
in laboratory tests.

But Wong’s scheme might even exacerbate matters, says Carl Howard, a
NOAA chemist specialising in atmospheric ion chemistry. Most of the chlorine
in the atmosphere is not in its ozone-destroying form, but is bound up in
other molecules such as hydrogen chloride. Ionising the stratosphere would
liberate this chlorine, leading to more ozone destruction.

While scientists remain sceptical, they do not necessarily object to
thinking about the issues Wong has raised. ‘A lot of these ideas are well-meaning,
and not without use as thought experiments,’ says Fahey. And you never
know, says Robert Hudson of the University of Maryland at College Park:
‘One day, one of these ideas might even work.’