A simple model of global aerosol indirect effects
Article first published online: 28 JUN 2013
©2013. American Geophysical Union. All Rights Reserved.
Journal of Geophysical Research: Atmospheres
Volume 118, Issue 12, pages 6688–6707, 27 June 2013
How to Cite
2013), A simple model of global aerosol indirect effects, J. Geophys. Res. Atmos., 118, 6688–6707, doi:10.1002/jgrd.50567., , , , , , , , and (
- Issue published online: 23 JUL 2013
- Article first published online: 28 JUN 2013
- Accepted manuscript online: 10 JUN 2013 03:46PM EST
- Manuscript Accepted: 6 JUN 2013
- Manuscript Revised: 10 MAY 2013
- Manuscript Received: 21 FEB 2013
 Most estimates of the global mean indirect effect of anthropogenic aerosol on the Earth's energy balance are from simulations by global models of the aerosol lifecycle coupled with global models of clouds and the hydrologic cycle. Extremely simple models have been developed for integrated assessment models, but lack the flexibility to distinguish between primary and secondary sources of aerosol. Here a simple but more physically based model expresses the aerosol indirect effect (AIE) using analytic representations of cloud and aerosol distributions and processes. Although the simple model is able to produce estimates of AIEs that are comparable to those from some global aerosol models using the same global mean aerosol properties, the estimates by the simple model are sensitive to preindustrial cloud condensation nuclei concentration, preindustrial accumulation mode radius, width of the accumulation mode, size of primary particles, cloud thickness, primary and secondary anthropogenic emissions, the fraction of the secondary anthropogenic emissions that accumulates on the coarse mode, the fraction of the secondary mass that forms new particles, and the sensitivity of liquid water path to droplet number concentration. Estimates of present-day AIEs as low as −5 W m−2 and as high as −0.3 W m−2 are obtained for plausible sets of parameter values. Estimates are surprisingly linear in emissions. The estimates depend on parameter values in ways that are consistent with results from detailed global aerosol-climate simulation models, which adds to understanding of the dependence on AIE uncertainty on uncertainty in parameter values.