Nothing like a stark data visualization to impress upon you just how bad pollution has gotten in Beijing. Here you can see the levels of sulfur in the air over the past several years in three similarly-sized regions of the world: on the far left is the U.S. midwest, the middle is eastern Europe, and the right is the Beijing region. Areas shaded red have the highest sulfur emissions. Created by researchers at the University of Maryland, Baltimore County, these images are a stark reminder that economic development is often accompanied by environmental degradation.

The New York Times' Dot Earth blog asked one of the researchers, Simon Carn, to interpret the satellite photos. Carn said:

The images clearly show the high SO2 emissions from sources in northeast China. China is the world's largest SO2 emitter, mostly due to the burning of high-sulfur coal in its many coal-fired power plants, which lack the technology used in many other countries to remove sulfur from smoke stack emissions. The eastern Europe image shows a few SO2 ‘hot spots' in Romania, Bulgaria, Greece and Turkey - these are probably also power plants or metal smelters. The hot spot in Sicily is the active volcano Mt Etna - volcanoes are probably the second largest source of SO2 after anthropogenic emissions.

The main region of elevated SO2 in the USA image is the Ohio Valley and SW Pennsylvania, where there is a high concentration of coal-fired power plants (shown as diamond symbols on the image).

The significance of SO2 (apart from as a component of acid rain) is that it is a precursor of sulfate aerosol (sulfuric acid droplets), which is the main ingredient of the haze often seen in polluted regions. Sulfate aerosol is a health hazard, limits visibility, degrades buildings, reflects solar radiation (cooling the climate) and also impacts cloud properties (increasing their lifetime and reducing rainfall).

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No word on how the Chinese cloud-seeding techniques to prevent rain during the Olympics are affecting any of this.

What Will Cure China's Sulfurous Skies? [Dot Earth]