China's pollution seen from space

Scientists said on Friday they had mapped ground-level air pollution in China from space for the first time, a feat that should help the fight against a notorious health hazard. French and Belgian atmospheric scientists used an infrared sensor aboard a European MetOp weather satellite to map plumes of particles and carbon dioxide, sulphur dioxide and ammonia over the north China plain, blanketing Beijing, Tianjin and Hebei province in January 2013. The experts were surprised to find the technology works, but discovered the success also depends on two conditions, France's National Centre for Space Research (CNRS) said. There have to be "stable" weather conditions, so pollution accumulates at ground level. There also has to be a big temperature difference between air at ground level and higher layers of the atmosphere for the warm emissions of pollution to stand out, it said. Satellites could be a useful tool for monitoring the extent of pollution clouds and predicting their movement, according to the study published in the Geophysical Review Letters, helping authorities advise residents in time.