THE capital’s “airpocalypse”, the choking smog that descended on Beijing in the winter of 2012-13, galvanised public opinion and spooked the government. The strange thing is, though, that information about air pollution—how extensive it is, how much damage it does—has long been sketchy, based mostly on satellite data or computer models. Until now.
Responding to the outcry, the government set up a national air-reporting system which now has almost 1,000 monitoring stations, pumping out hourly reports on six pollutants, including sulphur dioxide, ozone and (the main culprit) particulate matter less than 2.5 microns in diameter, or PM2.5. These are tiny particles which lodge in the lungs and cause respiratory disease. The six are the main cause of local pollution but have little to do with climate change, since they do not include carbon dioxide, the main greenhouse gas. Scientists from Berkeley Earth, a not-for-profit foundation in America, have trawled through this recent cloud of data for the four months to early August 2014, sieved out the bits that are manifestly wrong (readings where the dial seems to be stuck, for instance)...Continue reading
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