Tiny pollutants tracked by NASA

Scientists at NASA have been engaged in the difficult task of tracking tiny aerosols and trying to gauge their impact on climate change.

The effects of greenhouse gases are relatively easy to calculate, as the gases tend to remain in the atmosphere for decades and methods for measuring them are well established.

Aerosols – tiny particles suspended in the air – are much harder to analyse as they tend to remain airborne for just a week giving researchers a much smaller window to do their work.

To add to the confusion, some play a role in cooling the atmosphere, while others add to the global warming effect of the greenhouse gases.

By altering the amount of solar energy that reaches the Earth’s surface, aerosols influence both regional and global climate.

NASA has attempted to quantify aerosols occurring naturally and emitted as manmade pollution in different areas and the results of the research have been published in the January edition of the American Geophysical Union’s Journal of Geophysical Research-Atmospheres.

The research will add to understanding of the global cooling effect of certain pollutants, and how efforts to improve air quality are having the undesired side effect of accelerating global warming.

“This study offers details on the aerosol source regions and emission source types that policy makers could target to most effectively combat climate change,” said Dorothy Koch, lead author and atmospheric scientist at NASA’s Goddard Institute for Space Studies (GISS).

The researchers used information gathered from satellites and computer modelling to estimate concentrations of common types of aerosol and then calculate the amount of light and heat they absorb and reflect in different parts of the world.

The industry and power sectors are particularly important in North America and Europe and produce large amounts of sulfur dioxide, which reflects sunlight once transformed into sulfates by favourable atmospheric conditions, while Asia has higher emissions from residential sources, which produce more carbon-containing aerosols which absorb it.

“Computer model simulations showed that black carbon in the Arctic, a potentially important driver in climate change, derives its largest portion from Southeast Asian residential sources,” said Koch.

“According to current model estimates, the residential sector appears to have a substantial potential to cause climate warming and therefore, could potentially be targeted to counter the effects of global warming.”

Black carbon – better known as soot – comes from motor vehicles and industrial pollution, in addition to outdoor fires and household burning of coal and bio-fuels.

Soot is produced by incomplete combustion, especially of diesel fuels, coal and wood. Residential soot emissions are largest in areas where cooking and heating are done with wood, field residue, animal dung and coal.

Most other particles, especially sulfates produced from the sulfur dioxide emissions of factories and power plants, are light-coloured and tend to cool the atmosphere by reflecting sunlight or making clouds more reflective.

Sam Bond

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