ACPD Atmospheric Chemistry and Physics Discussions ACPD 1680-7375 Copernicus GmbH Göttingen, Germany 10.5194/acpd-3-6093-2003 A new feedback mechanism linking forests, aerosols, and climate Kulmala M. 1 Suni T. 1 Lehtinen K. E. J. 1 Dal Maso M. 1 Boy M. 1 Reissell A. 1 2 3 Rannik Ü. 1 Aalto P. 1 Keronen P. 1 Hakola H. 2 Bäck J. 4 Hoffmann T. 5 Vesala T. 1 Hari P. 1 University of Helsinki, Department of Physical Sciences, P.O. Box 64, FIN-00014, University of Helsinki, Finland Finnish Meteorological Institute, Sahaajankatu 20 E, FIN-00880 Helsinki, Finland University of Helsinki, Department of Chemistry, P.O. Box 55, FIN-00014 University of Helsinki, Finland University of Helsinki, Department of Forest Ecology, P.O. Box 27, FIN-00014, University of Helsinki, Finland Institute of Spectrochemistry and Applied Spectroscopy, Bunsen-Kirchhoffstr. 11, D-44139 Dortmund, Germany 04 12 2003 3 6 6093 6107 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys-discuss.net/3/6093/2003/acpd-3-6093-2003.html The full text article is available as a PDF file from http://www.atmos-chem-phys-discuss.net/3/6093/2003/acpd-3-6093-2003.pdf

Among significant issues in climate change studies are the possible connections between the carbon balance of ecosystems and aerosol-cloud-climate interactions. Carbon dioxide is a greenhouse gas, whereas the net effect of atmospheric aerosols is to cool the climate. Here, we investigated the connection between forest-atmosphere carbon exchange and aerosol dynamics in the continental boundary layer by means of multiannual data sets of particle formation and growth rates, of CO<sub>2</sub> fluxes, and of monoterpene concentrations in a Scots pine forest in southern Finland. We suggest a new, interesting link and a potentially important feedback among forest ecosystem functioning, aerosols, and climate: Considering that globally increasing temperatures and CO<sub>2</sub> fertilization are likely to lead to increased photosynthesis and forest growth, an increase in forest biomass would increase emissions of non-methane biogenic volatile organic compounds and thereby enhance organic aerosol production. This feedback mechanism couples the climate effect of CO<sub>2</sub> with that of aerosols in a novel way.