Our research has shown that the forcing of weather systems from diabatic heating by the human input of aerosols is on the order of 60 times that of the forcing from the diabatic heating due to the human addition of well-mixed greenhouse gases (with the dominate gas being CO2); i.e. see
Matsui, T., and R.A. Pielke Sr., 2006: Measurement-based estimation of the spatial gradient of aerosol radiative forcing. Geophys. Res. Letts., 33, L11813, doi:10.1029/2006GL025974.
We now have a new paper that presents a quantitative methodology to assess the importance of this type of climate forcing. It is
Vukicevic, T., R. A. Pielke Sr., and A. Beltran-Przekurat, 2009: New Method For Estimating The Impact Of Heterogeneous Forcing On Atmospheric Circulations. J. Geophys. Res., doi:10.1029/2008JD010418, in press.
The abstract reads
“In this study a new method for estimating the impact of heterogeneous forcing on atmospheric circulations is discussed. This new method is similar to the commonly used model-based sensitivity studies in that the impact of forcing is diagnosed by a suitable measure of differences between atmospheric states with and without forcing, but differs in the way the atmospheric states are evaluated: by combining standard atmospheric data analysis, observationally-based estimates of the forcing, atmospheric observations and general circulation model (GCM) ensemble simulations. A new numerical technique, derived from the Ensemble Kalman Filter data assimilation approach, is used for
objective estimation of the atmospheric state not affected by the forcing. Using a tutorial example, numerical experiments were conducted varying an asymmetric thermal forcing as a proxy for the heterogeneous forcing. Results show that the method is capable of producing skilled estimates of the impact of the forcing. Strategies for application of the method with real-world data and GCMs are discussed. This new method is expected to produce more realistic estimates of the forcing impact than the standard model sensitivity approach because of the explicit use of the observationally-based estimates of atmospheric states and forcing.”
The importance of this study is that assessment groups, such as the IPCC, have a new tool with which to broaden their evaluations of the role of humans within the climate system. Climate modeling groups are urged to adopt this tool, or a similar approach, to better quantify the role of spatial variations in human climate forcings on weather and climate.