1Atmospheric Sciences Research Center, State University of New York at Albany, Albany, New York, USA
2Department of Atmospheric and Oceanic Sciences, University of California at Los Angeles, Los Angeles, California, USA
3Global Monitoring Division (GMD), Earth System Research Laboratory (ESRL), NOAA, Boulder, Colorado, USA
4School of Engineering and Applied Sciences, Harvard University, Boston, Massachusetts, USA
Received: 22 Aug 2011 – Discussion started: 14 Oct 2011
Abstract. New particle formation contributes significantly to the number concentration of condensation nuclei (CN) as well as cloud CN (CCN), a key factor determining aerosol indirect radiative forcing of the climate system. Using a physics-based nucleation mechanism that is consistent with a range of field observations of aerosol formation, it is shown that projected increases in global temperatures could significantly inhibit new particle, and CCN, formation rates worldwide. An analysis of CN concentrations observed at four NOAA ESRL/GMD baseline stations since the 1970s and two other sites since 1990s reveals long-term decreasing trends that are consistent in sign with, but are larger in magnitude than, the predicted temperature effects. The possible reasons for larger observed long-term CN reductions at remote sites are discussed. The combined effects of rising temperatures on aerosol nucleation rates and other chemical and microphysical processes may imply substantial decreases in future tropospheric particle abundances associated with global warming, delineating a potentially significant feedback mechanism that increases Earth's climate sensitivity to greenhouse gas emissions. Further research is needed to quantify the magnitude of such a feedback process.
Revised: 30 Jan 2012 – Accepted: 23 Feb 2012 – Published: 05 Mar 2012
Yu, F., Luo, G., Turco, R. P., Ogren, J. A., and Yantosca, R. M.: Decreasing particle number concentrations in a warming atmosphere and implications, Atmos. Chem. Phys., 12, 2399-2408, doi:10.5194/acp-12-2399-2012, 2012.