Climate modelers, rejoice: A new effort to model the atmospheric evolution of organic aerosols suggests that aerosols from diverse sources converge toward similar chemical and physical properties as they age, regardless of the original source (Science 2009, 326, 1525). A team led by Jose L. Jimenez of the University of Colorado, Boulder, and André S. H. Prévôt of Paul Scherrer Institute, in Villigen, Switzerland, uses a combination of modeling and laboratory and field measurements with aerosol mass spectrometry to show that aerosols become more oxidized, less volatile, and more hygroscopic as they age. The researchers test the model with measurements of α-pinene and its first- and second-generation oxidation products. The similar fate of aerosols from different sources suggests that models of aerosols’ effects on climate may not need to include every chemical species of aerosol to render a useful picture. “This convergence is a great advantage to climate modelers, because it reduces the amount of complexity that must be represented in models that investigate aerosol effects on climate,” Meinrat O. Andreae of Max Planck Institute for Chemistry, in Mainz, Germany, writes in an accompanying commentary.