Decreases in elemental carbon and fine particle mass in the United States 1Chemical Sciences Division, Earth System Research Laboratory, National Oceanic and Atmospheric Administration, Boulder, CO 80305, USA
19 May 2011
2Division of Atmospheric Sciences, Desert Research Institute, Reno Nevada, 89512, USA
3School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, 02138, USA
4Cooperative Institute for Research in the Atmosphere, Colorado State University, Fort Collins, CO 80523, USA
5Air Resources Laboratory, National Oceanic and Atmospheric Administration, Las Vegas, NV 89119, USA
6National Park Service, Colorado State University, Foothills Campus, Fort Collins, Colorado 80523, USA
7Crocker Nuclear Laboratory, University of California Davis, Davis, CA 95616, USA
Received: 30 December 2010 – Published in Atmos. Chem. Phys. Discuss.: 20 January 2011 Abstract. Observations at national parks and other remote sites show that average
elemental carbon and fine particle mass concentrations in the United States
both decreased by over 25 % between 1990 and 2004. Percentage decreases in
elemental carbon were much larger in winter than in summer. These data
suggest that emissions controls have been effective in reducing particulate
concentrations not only in polluted areas but also across the United States.
Despite the reduction in elemental carbon, the simultaneous decrease in
non-absorbing particles implies that the overall radiative forcing from
these changes was toward warming. The use of a 2005 instead of 1990 as a
baseline for climate-relevant emissions from the United States would imply a
significantly lower baseline for aerosol emissions. The use of older data
will overestimate the possibility for future reductions in warming due to
black carbon controls.
Revised: 04 May 2011 – Accepted: 13 May 2011 – Published: 19 May 2011
Citation: Murphy, D. M., Chow, J. C., Leibensperger, E. M., Malm, W. C., Pitchford, M., Schichtel, B. A., Watson, J. G., and White, W. H.: Decreases in elemental carbon and fine particle mass in the United States, Atmos. Chem. Phys., 11, 4679-4686, doi:10.5194/acp-11-4679-2011, 2011.