Impact of California’s air pollution laws on black carbon and their implications for direct radiative forcing
We examine the temporal and the spatial trends in the concentrations of black carbon (BC) - recorded by the IMPROVE monitoring network for the past 20 years - in California. Annual average BC concentrations in California have decreased by about 50% from 0.46 11g m-3 in 1989 to 0.24 11 gm-3 in 2008 compared to the corresponding reductions in diesel BC emissions (also about 50%) from a peak of 0.013 Tg Yr -1 in 1990 to 0.006 Tg Tr -1 by 2008. We attribute the observed negative trends to the reduction in vehicular emissions due to stringent statewide regulations. Our conclusion that the reduction in diesel emissions is a primary cause of the observed BC reduction is also substantiated by a significant decrease in the ratio of BC to non-BC aerosols. The absorption efficiency of aerosols at visible wavelengths - determined from the observed scattering coefficient and the observed BC - also decreased by about 50% leading to a model-inferred negative direct radiative forcing (a cooling effect) of -1.4 w m-2 (±60%) over California.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- California Environmental Protection Agency - Air Resources Board
- DOE Contract Number:
- AC02-06CH11357
- OSTI ID:
- 1396191
- Journal Information:
- Atmospheric Environment (1994), Vol. 45, Issue 5; ISSN 1352-2310
- Publisher:
- Elsevier
- Country of Publication:
- United States
- Language:
- English
Similar Records
Response to comments on “Impact of California’s air pollution laws on black carbon and their implications for direct radiative forcing” by R. Bahadur et al.
Black Carbon Concentrations and Diesel Vehicle Emission FactorsDerived from Coefficient of Haze Measurements in California:1967-2003