Project at a Glance

Title: Global radiative effect of particulate black carbon.

Principal Investigator / Author(s): Seinfeld, John H

Contractor: California Institute of Technology

Contract Number: 02-322

Research Program Area: Climate Change, Atmospheric Processes

Topic Areas: Modeling, Science


The primary objective of this research was to provide the ARB with state-of the-science global radiative forcing estimates for black carbon and other aerosols in conjunction/comparison with other greenhouse gases. These estimates, both at top of the atmosphere and at the surface, were obtained over 25-year intervals for 2000, 2025, 2050, 2075, 2100, based on Intergovernmental Panel on Climate Change (IPCC) estimates of emissions over the next century.

Carbon dioxide (CO2) and other greenhouse gases and black carbon (BC) particulate matter in uence global climate. With reference to potential measures to abate the effect of California emissions of greenhouse gases and particulate matter on climate, it is necessary to determine the current magnitude of that effect relative to the estimated full global impact. The present report focuses on global climatic effects of BC, and, based on an estimate of the percentage of global BC emissions attributable to California, extrapolates that effect to California emissions alone. Since black carbon particulate matter tends to mix with other particulate material in the atmosphere, the radiative effect of BC needs to be considered in conjunction with that of other aerosol species, namely, sulfate, nitrate, ammonium, and primary organic aerosol; the manner in which BC is mixed with other particulate species is quite important to its radiative impact. In the current study, we have estimated present- day BC emissions from California by scaling the recent BC inventory of Bond et al. [2004] to California on the basis of population. Based on population, California is estimated to contribute approximately 0.4% of the global mean direct radiative forcing attributable to anthropogenic BC aerosol. Assuming that BC is mixed with other aerosol species, the contribution of California emissions to top of atmosphere direct radiative forcing is currently estimated to be +0.002 W m - 2 , predicted to increase to +0.008 W m - 2 in 2100.

For questions regarding this research project, including available data and progress status, contact: Research Division staff at (916) 445-0753

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