Climate Processes
Our research addresses physical climate processes in the context of anthropogenic perturbations to the earth system as the underlying cause of climate change and air pollution.
Focal points of our research are aerosol and cloud physics, their interactions and their role in the climate system. Aerosols are small liquid or solid particles suspended in air of both anthropogenic and natural origin.
Figure: Biomass burning aerosols over the Amazon during the 2005 dry season with embedded cumulus clouds. (From NASA Goddard)
Atmospheric aerosols play an important role in the global climate system through direct modification of the global radiation budget, by scattering and absorption, as well as indirectly, by the modification of cloud properties.
In regions of the atmosphere with supersaturation with respect to water, suitable aerosols form cloud droplets or ice crystals. Clouds power the hydrological cycle and global atmospheric dynamics. In addition, clouds affect the global radiation balance by scattering solar radiation and trapping longwave radiation emitted from the earth’s surface and lower atmosphere. Both solar and longwave cloud radiative forcings are large compared to the anthropogenic greenhouse effect. Thus, small anthropogenic perturbations of the cloud system potentially have large radiative effects.
A particular challenge for aerosol and cloud research is that almost all relevant processes, such as formation, sinks and radiative properties of cloud droplets/crystals or aerosol particles, depend on the aerosol size-distribution, composition, and mixing state. To determine the climatic effects, the distribution of these microscopic properties has to be known on the global scale. The associated uncertainties make them a key uncertainty in the assessment of climate change - and a frontier research challenge.
