| Summary: | "Black carbon (BC) emissions are known to lead to negative health effects as a component of fine particulate matter (PM). BC emissions also lead to climate warming by absorbing incoming and reflected sunlight in the atmosphere and by darkening clouds, snow and ice. In contrast to the long-lived, well-mixed greenhouse gases, BC emissions remain in the atmosphere for a period of only days to weeks, meaning that their atmospheric concentrations are more variable which in turn means the location of mitigation measures can be more important for either regional health reasons or for protecting the Arctic. Organic carbon (OC), which under most conditions has a cooling effect, is always co-emitted with BC in ratios that vary with source type; both are products of incomplete combustion. Nitrogen dioxide and sulfur dioxide, also products of combustion, are often co-emitted with BC and OC and form particles that tend to have a cooling effect. Thus, the net cooling effectiveness of BC emission reductions will depend on the source type as well as the source location. The total climate impact of BC currently in the atmosphere has been estimated to be anywhere from 10% to more than 60% as large as the climate impact from carbon dioxide (CO2). One half to two thirds of the BC impact results from fossil fuels, with the remainder from biomass burning." /./
|
|---|