Bounding Global Aerosol Radiative Forcing of Climate Change

An assessment of Aerosol Radiative Forcing by Nicolas Bellouin, Johannes Quaas and thirty additional co-authors appeared in AGU Advancing Earth and Space Science, Reviews of Geophysics. The assessment is an outcome of a process initiated by Prof Bjorn Stevens in the framework of the WCRP Grand Challenge Program on Clouds, Circulation and Climate Sensitivity which he co-leads with Dr Sandrine Bony, LMD/CNRS, Paris, France. In addition to Bjorn Stevens, co-authors from the Max Planck Institute for Meteorology (MPI-M) are Stefan Kinne, Stefanie Fiedler, and Maria Rugenstein. The assessment, the most comprehensive of its kind ever performed, follows the distinct trail of different lines of evidence, as left by aerosol studies published over the past 40 years, to quantify how particulate matter (aerosols) resulting from human activity powers global climate change.

From: Bellouin, N., et al. (2020) Bounding aerosol radiative forcing of climate change. Reviews of Geophysics, 58: https://doi.org/10.1029/2019RG000660

Bellouin, Quaas and their co-authors conclude that the aerosol effective radiative forcing is likely between -0.6 and -1.6 W/m2. This estimate is consistent with the previous assessment by the Intergovernmental Panel on Climate Change (IPCC), in its fifth assessment report, but is more clearly and quantitatively reasoned. Given the breadth of expertise involved in the assessment, it is expected to be a cornerstone of the forthcoming sixth assessment report. It differs from past assessments in its ability to identify which lines of evidence most importantly constrain the estimates of the forcing. In a further break from past assessments it more strongly discounts the possibility that absorption, by carbonaceous aerosols, substantially offsets the effective radiative forcing. This results in a more negative upper bound. The primary effect of aerosol perturbations on cloud optical properties is shown to be relatively well constrained, although secondary effects are not necessarily small, and remain uncertain, in some cases even in sign. The study encourages the more systematic application of top-down approaches (which try to reconcile past emissions with past temperature changes) to test the plausibility of aerosol forcings near the stronger (more negative) range of the assessed range.

 

Original publication

Bellouin, N., Quaas, J., Gryspeerdt, E., Kinne, S., Stier, P., Watson-Parris, D., Boucher, O., Carslaw, K., Christensen, M., Daniau, A.-L., Dufresne, J.-L., Feingold, G., Fiedler, S., Forster, P., Gettelman, A., Haywood, J., Malavelle, F., Lohmann, U., Mauritsen, T., McCoy, D., Myhre, G., Mülmenstädt, J., Neubauer, D., Possner, A., Rugenstein, M., Sato, Y., Schulz, M., Schwartz, S., Sourdeval, O., Storelvmo, T., Toll, V., Winker, D. & Stevens, B.(2020) Bounding aerosol radiative forcing of climate change. Reviews of Geophysics, 58: https://doi.org/10.1029/2019RG000660.

 

More information

WCRP Grand Challenge Program: https://www.wcrp-climate.org/component/content/article/61-gc-clouds-circulation?catid=30&Itemid=267

 

Contact

Prof Dr Bjorn Stevens
Max Planck Institute for Meteorology
Phone: +49 (0)40 41173 422 (Assistant Angela Gruber)
Email: bjorn.stevens@we dont want spammpimet.mpg.de