Methane and black carbon cuts won't buy us time

摘要

The Guardian reports that the global warming effect of black carbon, or soot, has been greatly exaggerated due to mistaken assumptions about the atmospheric altitude at which its particles are concentrated, according to a study by Norwegian resarchers. "Uncertainty surrounds the exact influence of black carbon on global warming, partly because of the difficulties involved in estimating how much of it is there is. Soot particles are also enigmatic substances, with warming and cooling properties that depend on the atmospheric conditions they encounter as they drift upwards. In the upper troposphere at tropical and middle latitudes, they have the potential to absorb and emit heat and solar radiation. But if they do not rise that far, they may stabilise lower-lying clouds that block the sunlight, so reducing temperatures. Global warming efforts should focus on CO2, not soot particles known as black carbon", says the Norwegian team.