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Clouds of Discontent

The ABC is an annual environmental catastrophe, affecting hundreds of millions

Pollution forecast
A permanent smog hides the Great Wall, and has replaced it as the only human-made object visible from the Moon

Every year a giant brown cloud of pollution grows and moves across South-East Asia. In this cloud are smoke from deforestation, but also huge quantities of SO2 and NO2 from the burning of fossil fuels.

These chemicals lead to the formation of sulphuric and nitric acid in clouds, which do not respect national boundaries. The acid rain they produce can fall far from the source of the pollution, and cause major damage to ecosystems, water resources, agriculture and infrastructure. The economic costs are far from insignificant.

There is a long-established link between poor pollution control and economic and environmental impacts. But what are developed and developing nations doing in their struggle to reduce this perennial, transboundary problem?

An environmental catastrophe occurs every year during the dry season, affecting hundreds of millions in the Asian/Indian region. Along with serious human health impacts, the Atmospheric Brown Cloud exacerbates and complicates the effects of climate change, and is a cause of both direct and indirect forcing of the radiation budget.

Previously known as the Asian Brown Cloud, technically it is a haze, consisting of fine particles and dust, rather than liquid water drops like normal clouds. However, these particles can form the nuclei of droplets. Related phenomena exist in many other parts of the world: the North American haze (now extending as far as Europe), the North and Eastern European aerosol haze, the biomass burning aerosol hazes in the Africa and the Amazon regions, and a Saharan dust plume extending over the tropical Atlantic.

The Atmospheric Brown Cloud appears as a brown smear from space. It consists of a mixture of anthropogenic pollutants such as sulphate, nitrate, VOCs, black carbon, dust and fly ash, as well as naturally occurring aerosols, such as sea salt and mineral dust. In the South-East Asia - India region, three-quarters of the annual cloud is due to biomass and fossil fuel burning.

In India, during the dry winter monsoon period, which is at least January to March, but may extend by a month either side, the lack of rain results in a peak accumulation of the cloud. The effects of the cloud are many, and tend to manifest according to prevailing conditions in each region. It is causing a change in rainfall patterns. The Asian monsoon is known to have been delayed by as much as a month by the cloud. The Indian monsoon is seriously weakened, and China experiences drought in the north, and flooding in the south, as a result of the cloud.

Australia accuses the cloud of pushing the thermal equator further south, causing tropical storms and increased rainfall across northern Australia.

China smog
China's cities are now swathed in permanent man-made clouds

The cloud also has an impact on global warming, with aerosols and ozone both reflecting sunlight and trapping infrared radiation from the ground. The black carbon settles on glaciers and snow in the Hindu Kush Himalayas, causing them to absorb solar energy, and to lose their reflective qualities. The resulting melting causes both flooding and water shortages right across the region, including the Ganges catchment. The gases in the clouds form acid rain, and the increase in terrestrial ozone results in decreased crop yields and human health issues.

Article by Andrew Bone, Wednesday, 14th September 2016