Tiempo Climate Newswatch

Eliminating soot pollution from sources such as diesel engines and poorly-controlled heat sources could mean that the world has an additional eight years to limit carbon emissions, according to researchers at Princeton University in the United States. Unfortunately, most climate change mitigation scenarios used in policy contexts have focused exclusively on heat-trapping gases," commented Denise Mauzerall from Princeton's Department of Civil and Environmental Engineering. "This means those eight years aren't actually eight years we can gain by cutting soot emissions; rather, our results suggest that we need to accelerate carbon dioxide emissions [reductions] by about eight years relative to these scenarios if we don't also act to reduce soot emissions."

The components of soot, black carbon and organic carbon, have complex effects on climate. Black carbon absorbs radiation, warming the air and, as it falls on snow or ice, the earth's surface, whereas organic carbon is more reflective and tends to have a cooling effect. Both can have an additional cooling effect as they affect cloud formation. "But effects on global climate aren't the only reason to reduce soot emissions," Mauzerall said. "The public health case for reducing emissions of fine particles, including soot, is unequivocal, and aerosol pollution can have significant regional climate effects. For instance, soot pollution from India and China that is transported to the Himalayan glaciers can enhance glacier melting and hence influence water supplies in India, China and Bangladesh -potentially contributing to increased flooding in some regions in the short-term and reduced water availability in the longer term."

The Intergovernmental Panel on Climate Change (IPCC) is likely to increase its estimates of future sea-level rise in its next assessment, due 2013/14. The state of the Greenland and Antarctic ice sheets will be a major focus of the new report and experts met in Kuala Lumpur recently to start the review process.

New satellite data "are starting to show... that both the Greenland ice sheet and the Antarctic ice sheet are losing net mass, not on the margins but as an ice sheet", said Jean-Pascal van Ypersel, IPCC vice-chair. "These are new data, these are new developments and new methods, which will allow the IPCC in its developments around sea-level rises to provide numbers that will almost inevitably be higher than the last assessment."

Underground organisms hold the key to species diversity and patterns of species abundance, concludes Scott Mangan of the University of Wisconsin-Milwaukee in the United States. Seedlings of five species were planted under adults of the same species in the forest and, in a greenhouse, seedlings of each species were grown in soil collected around each of the other species. Mangan and his collaborators found that survival rates of seedlings grown in soil from the same species were closely related to how common or rare they are as adults.

"We've known for a long time that tree seedlings do not grow and survive well under their mothers or other adult trees of the same species," Mangan said. "One explanation for the maintenance of the diversity of tropical trees is that adult trees harbour pests and diseases that harm seedlings of their own species more than they do seedlings of other species," he explained. The researchers emphasise this mechanism, though important, is likely to be one of many that determine species abundance in forests.