China’s toxic air pollution resembles nuclear winter, say scientists – ‘Now almost every farm is caught in a smog panic’
By Jonathan Kaiman
25 February 2014 Beijing (theguardian.com) – Chinese scientists have warned that the country’s toxic air pollution is now so bad that it resembles a nuclear winter, slowing photosynthesis in plants – and potentially wreaking havoc on the country’s food supply. Beijing and broad swaths of six northern provinces have spent the past week blanketed in a dense pea-soup smog that is not expected to abate until Thursday. Beijing’s concentration of PM 2.5 particles – those small enough to penetrate deep into the lungs and enter the bloodstream – hit 505 micrograms per cubic metre on Tuesday night. The World Health Organisation recommends a safe level of 25. The worsening air pollution has already exacted a significant economic toll, grounding flights, closing highways and keeping tourists at home. On Monday 11,200 people visited Beijing’s Forbidden City, about a quarter of the site’s average daily draw. He Dongxian, an associate professor at China Agricultural University’s College of Water Resources and Civil Engineering, said new research suggested that if the smog persists, Chinese agriculture will suffer conditions “somewhat similar to a nuclear winter”. She has demonstrated that air pollutants adhere to greenhouse surfaces, cutting the amount of light inside by about 50% and severely impeding photosynthesis, the process by which plants convert light into life-sustaining chemical energy. She tested the hypothesis by growing one group of chilli and tomato seeds under artificial lab light, and another under a suburban Beijing greenhouse. In the lab, the seeds sprouted in 20 days; in the greenhouse, they took more than two months. “They will be lucky to live at all,” He told the South China Morning Post newspaper. She warned that if smoggy conditions persist, the country’s agricultural production could be seriously affected. “Now almost every farm is caught in a smog panic,” she said. Early this month the Shanghai Academy of Social Sciences claimed in a report that Beijing’s pollution made the city almost “uninhabitable for human beings“. [more]
China’s toxic air pollution resembles nuclear winter, say scientists
Presumably though there is a decisive difference between this smog and a real "nuclear winter" (or volcanically caused winter). The latter are caused by aerosols that are spewed up into the stratosphere where they can hang for years blocking sunlight. the more earth-bound pollution from smokestacks, cars etc. tends to disappear almost immediately if you turn off their source. Not that that's going to happen But if you did install filters or furlough factories, the air might be clean within a week!