The notion of modifying Earth's climate with sunshades or a blanket of reflective aerosols to counteract global warming - known as geoengineering - has been around for years. But climate models suggest that this would significantly reduce rainfall.

Now Christopher Doughty at the University of California, Irvine, and colleagues think they can get around that problem. Models show that geoengineering near the equator hits rainfall hardest, but focusing on latitudes between 30 and 60 degrees would produce a much smaller drop in rainfall. Planting crops bred or genetically modified to be more reflective could cool these regions by an average of 1 °C. Doughty presented the research last month at the American Geophysical Union meeting in San Francisco.

The key, Doughty says, is to deploy leaves that sport a thick layer of hairs, which reflect near-infrared wavelengths back out into space. Super-hairy strains of soya have already been bred, and these reflect 3 to 5 per cent more sunlight. Doughty calculates that this would be enough - if planted in huge amounts - to generate the cooling effect.