title: Improving our fundamental understanding of the role of aerosol-cloud interactions in the climate system.
abstract: The effect of an increase in atmospheric aerosol concentrations on the distribution and radiative properties of Earth's clouds is the most uncertain component of the overall global radiative forcing from preindustrial time. General circulation models (GCMs) are the tool for predicting future climate, but the treatment of aerosols, clouds, and aerosol-cloud radiative effects carries large uncertainties that directly affect GCM predictions, such as climate sensitivity. Predictions are hampered by the large range of scales of interaction between various components that need to be captured. Observation systems (remote sensing, in situ) are increasingly being used to constrain predictions, but significant challenges exist, to some extent because of the large range of scales and the fact that the various measuring systems tend to address different scales. Fine-scale models represent clouds, aerosols, and aerosol-cloud interactions with high fidelity but do not include interactions with the larger scale and are therefore limited from a climatic point of view. We suggest strategies for improving estimates of aerosol-cloud relationships in climate models, for new remote sensing and in situ measurements, and for quantifying and reducing model uncertainty.
authors.affiliation: Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125; Division of Engineering and Applied Science, California Institute of Technology, Pasadena, CA 91125; seinfeld@caltech.edu.
authors.forename: John H
authors.initials: JH
authors.lastname: Seinfeld
authors.affiliation: Department of Atmospheric Science, University of Washington, Seattle, WA 98195;
authors.forename: Christopher
authors.initials: C
authors.lastname: Bretherton
authors.affiliation: School of Earth and Environment, University of Leeds, Leeds L32 9JT, United Kingdom;
authors.forename: Kenneth S
authors.initials: KS
authors.lastname: Carslaw
authors.affiliation: School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Manchester M13 9PL, United Kingdom;
authors.forename: Hugh
authors.initials: H
authors.lastname: Coe
authors.affiliation: Department of Atmospheric Science, Colorado State University, Fort Collins, CO 80523;
authors.forename: Paul J
authors.initials: PJ
authors.lastname: DeMott
authors.affiliation: Board on Atmospheric Science and Climate, National Academies of Sciences, Engineering, and Medicine, Washington, DC 20001;
authors.forename: Edward J
authors.initials: EJ
authors.lastname: Dunlea
authors.affiliation: Earth System Research Laboratory, National Oceanic and Atmospheric Administration, Boulder, CO 80523;
authors.forename: Graham
authors.initials: G
authors.lastname: Feingold
authors.affiliation: Atmospheric Sciences and Global Change Division, Pacific Northwest National Laboratory, Richland, WA 99352;
authors.forename: Steven
authors.initials: S
authors.lastname: Ghan
authors.affiliation: Department of Earth System Science, University of California, Irvine, CA 92697;
authors.forename: Alex B
authors.initials: AB
authors.lastname: Guenther
authors.affiliation: Sciences and Exploration Directorate, Goddard Space Flight Center, National Aeronautics and Space Administration, Greenbelt, MD 20771;
authors.forename: Ralph
authors.identifier: 0000-0002-5234-6359
authors.initials: R
authors.lastname: Kahn
authors.affiliation: Atmospheric Sciences and Global Change Division, Pacific Northwest National Laboratory, Richland, WA 99352;
authors.forename: Ian
authors.initials: I
authors.lastname: Kraucunas
authors.affiliation: Department of Atmospheric Science, Colorado State University, Fort Collins, CO 80523;
authors.forename: Sonia M
authors.identifier: 0000-0002-2561-2914
authors.initials: SM
authors.lastname: Kreidenweis
authors.affiliation: Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093; Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093;
authors.forename: Mario J
authors.initials: MJ
authors.lastname: Molina
authors.affiliation: Department of Earth and Atmospheric Science, Georgia Institute of Technology, Atlanta, GA 30332; Department of Chemical and Biological Engineering, Georgia Institute of Technology, Atlanta, GA 30332; Institute of Chemical Engineering Sciences, Foundation for Research and Technology-Hellas, Patras GR-26504, Greece; Institute for Environmental Research and Sustainable Development, National Observatory of Athens, Palea-Pendeli GR-15236, Greece;
authors.forename: Athanasios
authors.initials: A
authors.lastname: Nenes
authors.affiliation: Climate and Space Sciences and Engineering, University of Michigan, Ann Arbor, MI 48109;
authors.forename: Joyce E
authors.initials: JE
authors.lastname: Penner
authors.affiliation: Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093; Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093;
authors.forename: Kimberly A
authors.initials: KA
authors.lastname: Prather
authors.affiliation: Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093;
authors.forename: V
authors.initials: V
authors.lastname: Ramanathan
authors.affiliation: Geophysical Fluid Dynamics Laboratory, Princeton University and National Oceanic and Atmospheric Administration, Princeton, NJ 08540;
authors.forename: Venkatachalam
authors.initials: V
authors.lastname: Ramaswamy
authors.affiliation: Atmospheric Sciences and Global Change Division, Pacific Northwest National Laboratory, Richland, WA 99352;
authors.forename: Philip J
authors.initials: PJ
authors.lastname: Rasch
authors.affiliation: Department of Atmospheric Science, Colorado State University, Fort Collins, CO 80523;
authors.forename: A R
authors.initials: AR
authors.lastname: Ravishankara
authors.affiliation: Institute of Earth Sciences, The Hebrew University of Jerusalem, Jerusalem 91904, Israel;
authors.forename: Daniel
authors.initials: D
authors.lastname: Rosenfeld
authors.affiliation: Center for Climate Sciences, Jet Propulsion Laboratory, National Aeronautics and Space Administration, Pasadena, CA 91109.
authors.forename: Graeme
authors.initials: G
authors.lastname: Stephens
authors.affiliation: Department of Atmospheric Science, University of Washington, Seattle, WA 98195;
authors.forename: Robert
authors.initials: R
authors.lastname: Wood
keywords: aerosol−cloud effects; climate; general circulation models; radiative forcing; satellite observations