We wrote last year about the attempts of two Chinese researchers to predict earthquakes several weeks in advance using unusual cloud formations. One of the researchers, Guangmeng Guo of the Remote Sensing Center at Nanjing Normal University in Jiangsu province, eastern China, recently emailed me with an update.

He says his team has detected the same unusual clouds above Iran. They predict that there will be a magnitude 5.0 to 6.0 earthquake at the end of April in southern Iran.

According to Guo, the pressure that builds up in rocks before an earthquake causes electromagnetic disturbances which influence cloud formation overhead. The characteristic shapes can be seen in satellite pictures and act as an early warning signal of tectonic stresses.

"This method can be used to predict location and magnitude, but it is difficult to predict the date," writes Guo.

He is not alone in believing it is possible to forecast earthquakes several weeks or months before they happen (see Unknown Earth: Can we predict earthquakes and volcanic eruptions?). Friedemann Freund, a visiting astrochemist at the NASA Goddard centre, is working on a similar theory.

Plus, just last month, Italian seismologist Gioacchino Giuliani predicted the earthquake that struck l'Aquila on 6 April and killed over 200 people. Giuliani's forecasts were based on concentrations of radon gas - also thought to be related to geological stresses. He was forced to remove his findings from the internet because local authorities thought he was spreading panic.