Study says targeting black carbon would cool temperatures and improve global health, farming and economy in short time.

Global warming could be slowed down if governments cleaned up what's known as black carbon from industry and cooking fires, 50 of the world's leading atmospheric scientists said on June 14.

Major air pollutants like black carbon, methane and ground level ozone mostly result from the soot and gases formed by the incomplete burning of fossil fuels, wood and biomass. These pollutants only remain in the atmosphere for a few days or weeks and are mostly seen by governments as important for health and air quality.

But the UN Environment Programme (UNEP), working with the World Meteorological Organisation, said these “short-lived climate forcers” contribute as much as 25-30 per cent to present-day climate change emissions, and if controlled would also provide dramatic health and farming benefits.

“A small number of emission reduction measures ... offer dramatic public health, agricultural, economic and environmental benefits,” said Achim Steiner, the head of the UNEP.

Black carbon affects climate by intercepting and absorbing sunlight, darkening snow and ice when deposited and helping to form clouds. It is most noticeable at the poles, on glaciers and in mountain regions — all environments which are showing the greatest impact of climate change.

Glacier melting, rainfall

The full impact of black carbon is still being assessed but it is linked to the melting of the glaciers in the Himalayas, disruption of traditional rainfall patterns in India and Africa, and low yields of maize, rice, wheat and soya bean crops in Asia and elsewhere. It is also partly generated by wood-burning stoves and dirty diesel cars.

Methane, a powerful global warming gas, is largely emitted from oil, coal and waste treatment plants, and ground-level ozone comes largely from traffic.

According to the UNEP report, launched on June 14 in Bonn at the resumed UN climate talks, ground-level ozone and black carbon together could be reducing crop yields by as much as 50m tonnes a year and be leading to 2.5m premature human deaths a year from poor outdoor air quality. A preliminary version of the report was published in February.

A team of 50 scientists convened by UNEP studied the climactic impact of the air pollutants and proposed 16 measures to address them. These included removing the dirtiest vehicles from the roads, improving cooking stoves, banning the burning of straw and farm waste, and better technology for the world's brick kilns.

The authors suggested that, if adopted, tighter controls on the pollutants could cut 0.5°C off rising temperatures. Such a reduction would help the 193 countries who agreed at the UN climate conference in Cancun last December to limit temperature rises to no more than 2°C. Temperatures have already risen by around 0.8°C since the industrial revolution, and earlier this month UN climate chief Christiana Figueres said the 2°C target was “not enough” and governments should be aiming to limit rises to 1.5°C to avoid “big, big trouble.” In six months' time the scientists hope to report on which countries could do most and how much it might cost.

“For many of the measures, especially the methane ... there are cost savings,” Johan Kuylenstierna of the Stockholm Environment Institute, told Reuters. It is possible that governments will seek an outline agreement to reduce the global emissions of the pollutants at the Rio+20 earth summit next June.

Air pollution is a serious issue in both rich and poor countries and because the benefits of cleaning it up are likely to be seen quickly, there is some hope that governments will agree to taking stronger action. In addition, most countries and regions, like Europe, already have laws and measures in place intended to reduce air pollutants. A 2009 report by the Dutch environment agency said efforts to cut carbon emissions could save millions of lives because of cleaner air. — © Guardian Newspapers Limited, 2011

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