From time to time some boffin, somewhere in the world, experiences a flash of genius, and suggests an "instant fix" for our climatic ills. He - and almost always it seems to be a he - proposes some technique which, if successful, would allow us to continue to produce greenhouse gases as at present but enable us to repair, by artificial means, whatever damage they might cause. And an attractive thought it is, undoing the effects of decades of environmental change with just a little tinkering. But life, love and climatology are never simple.
One suggested ploy has been to add iron salts artificially to vast areas of the surface water of the oceans. This, the theory goes, would stimulate the growth of phytoplankton, for which this mineral, normally scarce in ocean waters, is essential; the algae would then absorb huge quantities of CO2 from the atmosphere by photosynthesis, to be carried down to the ocean floor for permanent storage when the phytoplankton died. Indeed an experiment along these lines, involving some 13,000 sq km of the Pacifi c, is planned for next year, during which it is hoped that millions of tonnes of CO2 will be absorbed in just a week or two.
Prima facie, it is not a bad idea. Carbon dioxide is harmless in the oceans; the sea already holds something like 38,000 billion tonnes of dissolved carbon, more than 65 times the amount contained in the atmosphere. The world's oceans have from time immemorial absorbed much of the additional CO2 produced by human activities, and the few extra billion tonnes produced by, say, a power station would be just, almost literally, a drop in the ocean.
But mainstream scientists have serious concerns about the plan. For one thing, some tests have shown that although the addition of iron does indeed lead to an explosive growth of algae, the extra algae are quickly gobbled up by microscopic animal life in the vicinity; the latter thrive, but they are of no help in preventing global warming. Moreover, the plankton bloom reduces oxygen levels in the water, encouraging the growth of bacteria that produce other greenhouse gases like methane and nitrous oxide, thereby counteracting the whole objective of the exercise.
The greatest fears, however, concern the dangers of tampering with a delicate ecosystem in a manner which may change the way the system works, with unknown and possibly very undesirable results. And in any event, the mainstream scientists say, seeding the oceans with a giant influx of iron for a century or more would remove from the atmosphere only a mere 15 per cent of the carbon dioxide created by human activity.