Getting a grip on soot pollution
After CO2, soot and methane are probably the biggest contributors to global warming. An interdisciplinary Norwegian research project has now concluded that efforts to reduce emissions of soot (black carbon) should focus on China rather than the Arctic.
Politicians and the media have been especially concerned about soot (also called black carbon) darkening the ice and snow of the Arctic. But soot’s worst impact on climate occurs in the atmosphere – where the warming effect of black carbon particles is thought to be four times greater than when they are deposited on ice and snow.
Important research on climate impact
The climate impact of black carbon particles first gained serious attention as part of the climate change agenda when President George W. Bush cited the phenomenon as one reason why the US did not want to adhere to the Kyoto Protocol on reducing greenhouse gas emissions.
High emissions: In China, local pollution from coal is an enormous health problem. Pictured is a coal-powered factory in Guizhou, one of China's poorest provinces. the factory burns 6,000 tonnes of coal every day. (Photo: Shutterstock)
But until recently, even less was known about the climate effects of black carbon than those of CO2 emissions. The research project “Climate effects of reducing black carbon emissions”, under the Research Council’s large-scale research programme on Climate Change and its Impacts in Norway (NORKLIMA), is generating more knowledge.
What should be done
Researchers from CICERO, the Norwegian Polar Institute, and the University of Oslo teamed up with the aim of tracing the complete life cycle of the world’s soot emissions.
Black carbon particles in the atmosphere are primarily a product of incomplete combustion of carbonaceous fuels. (Photo: Shutterstock)
The primary objective of this ambitious project has been to provide decision-makers and the public with knowledge about where to direct initial efforts toward reducing the impact of soot emissions on the climate.
The project’s researchers have studied where soot is emitted and have run various models on supercomputers to calculate soot dispersion in the atmosphere. In Svalbard and Alaska, researchers have measured the effect of black carbon particles lying atop snow. Other researchers have calculated the costs of cutting soot emissions in different parts of the world. The results were then examined within the context of what is considered politically feasible to accomplish.
Short but destructive lifetime
Atmospheric black carbon particles cause the surrounding environment to absorb excess heat which takes five to ten years to dissipate. Fortunately, black carbon actually has a very short lifetime in the atmosphere; if the world were to cut all soot emissions today, the black carbon particles would be virtually gone in two to three weeks. This contrasts sharply with current CO2 emissions, which we know will remain with us for at least 100 years to come.
Black carbon particles in the atmosphere are primarily a product of incomplete combustion of carbonaceous fuels. Examples of measures that can greatly reduce black carbon emissions include upgrading to modern wood-burning stoves and equipping coal-fired power plants and diesel vehicles with particulate filters.
Black carbon is a complex factor in climate change. As opposed to CO2, black carbon particles are not evenly dispersed throughout the earth’s atmosphere. Their short lifetime leads to great regional differences in distribution. Another significant point is that black carbon particles may also have some cooling effect on the atmosphere due to complex processes in noctilucent clouds, about which little is known.
Encouraging improvement in the north
One uplifitng finding of the Norwegian project was that the amount of black carbon on the Svalbard archipelago appears to have halved compared to 25 years ago. Samples from the Greenland Ice Sheet indicate similar developments. These findings contradict recent portrayals in the media but are consistent with the major reductions in pollution from Eastern Europe in particular.
In essence, soot particles warm the climate in two ways. The first is indirect, by darkening snow cover and hence reducing its reflectivity. The second, which is more direct and thought to have four times more impact on global climate warming than the first, is by magnifying atmospheric warming from solar radiation.
Burning coal in China
In our corner of the world, major causes of soot formation in the atmosphere are farmers burning stubble, forest fires, and the use of outdated types of wood-burning stoves. Also significant sources but probably causing less impact are industrial activities and road traffic.
Professor Terje Berntsen, (Photo: CICERO)
“Globally, if we are to implement cost-effective measures against soot emissions – beyond those already agreed upon – there are other places than here we should be focusing our efforts,” says Professor Terje Berntsen of the University of Oslo and the Center for International Climate and Environmental Research - Oslo (CICERO). “Regardless of how we analyse our findings, it is clear that the most beneficial action would be to prioritise measures against soot emissions in China and partly in India.”
Focusing on China is critical: it is the largest soot emitter by far, and emissions appear to be on the rise. Furthermore, local pollution from coal is causing enormous health problems for the country, so there is likely to be both political and social will to enact change.
Positive results can be achieved on soot emissions in China, India and the developing world by applying relatively simple technology that developed countries have been using for several decades.
- Published:
- 04.12.2009
- Last updated:
- 04.12.2009
