Global warming is generally blamed on the emission of greenhouse gases by human activities, chiefly the burning of hydrocarbons. But one theory blames the declining intensity of cosmic rays. As they traverse the atmosphere, they nucleate water vapour to cloud droplets, just as in a particle-detecting cloud chamber. Clouds reflect sunlight; so the lower the cosmic ray flux, the fewer clouds, the more sunlight hits the Earth, and the higher its temperature. So to counter global warming, we need more atmospheric radiation.

The nuclear industry will welcome this argument. Nuclear power not only reduces the need to burn hydrocarbons; it generates radioactive waste as well. If instead of storing the waste in careful seclusion, we released it as fine dust into the atmosphere, it would soon be wafted up to cloud altitudes. It would nucleate new clouds with splendid efficiency.

This simple proposal would arouse almost the ultimate in environmental outrage. But Daedalus reckons that conventional fuel-burning can do the job instead. It too releases particles into the atmosphere. The finest and most efficient nuclei are probably those released in annoying clouds by diesel engines, a growing segment of the automotive market. Many engineers are trying to modify the diesel engine to reduce its particulate emissions; but DREADCO engineers are modifying the fuel so as to optimize those emissions. Their aim is to reduce the size of the particles to much less than a wavelength of light. They will then be invisible, and will no longer annoy the public. They will also be ideal condensation nuclei.

The project has many hopeful clues to follow. Carbon black is made by burning fuel oil. For the finest soot particles, special alkali metal compounds are added to the oil. Fullerene chemists have their own tricks for burning fuels to very small carbon particles. So with good fortune DREADCO's clean-exhaust, high-nucleation, save-the-planet diesel fuel will soon hit the market. Ecologically aware consumers will rush to buy it. Its invisible exhaust particles, wafted aloft by atmospheric turbulence, will encourage global cloud cover and counter global warming. Sadly for cold, humid Britain, their nucleation properties will be even more effective at ground level. In dense winter traffic, the relentless nucleation of innumerable exhausts will create appalling fog on the motorways.