“Black carbon” (BC) is considered to be the most important light absorbing particulate component in the atmosphere in respect of global warming. In addition to direct atmospheric impacts on global climate, BC can deposit on snow leading e.g. a reduction of snow albedo in Arctic areas. In urban areas, BC significantly affects public health.
BC sources are typically combustion processes and its main emission sources are anthropogenic, such as transportation, industry and residential combustion. Due to the importance of BC in research regarding the global warming and the potential of BC in climate protection, it has been taken into the arena of Finnish foreign policy.
Although the measurement technologies have significantly developed lately, uniform metrics does not exist for the BC emissions, concentrations and effects. No direct measurement methods exist for BC, and therefore measurement instruments are based on indirect methods, in atmospheric sciences typically on thermal and optical determination of BC concentration and in emission studies on optical and photo-acoustic methods and size distribution measurements. These issues, together with the challenges in BC instrument calibration methods, significantly complicate the policy and air quality actions related to black carbon and estimating effects of BC on global climate and human health.
The aim of the BC Footprint project is to develop a scientific basis create in-depth knowledge about BC, including measurement methods, BC emissions, ambient BC concentrations and their transformation during aging to create the BC Footprint concept that can be used for calculating the BC Footprint of a certain action or a product. Ideally BC Footprint concept should be flexible and applicable to different purposes ranging from e.g. a BC Footprint of producing a certain action (e.g. driving from point a to b) or the change in BC Footprint when e.g. the fuel is changed to a biofuel or when producing a certain product. As a part of conceptualizing BC footprint, the link from BC emissions to climate impacts that are commensurate with other established climate impact metrics (e.g. CO2 equivalents at different time horizons) should be developed. Also the health aspects of BC emissions need to be taken into account.