Clouds are one of the largest uncertainties for climate change predictions (IPCC, 2013). They can reflect solar radiation causing cooling (albedo effect of clouds) or absorb and re-emit terrestrial radiation causing warming (greenhouse effect of clouds). While the cooling effect of clouds dominates for low-level clouds (stratus, stratocumulus), the warming effect dominates for high-level ice clouds (cirrus).
Aerosol particles scatter and absorb solar radiation and determine cloud microphysical properties by acting as cloud condensation nuclei (CCN) and ice nuclei (IN). The radiative forcing of anthropogenic (human caused) aerosol particles has the largest uncertainties of all anthropogenic forcing agents (IPCC, 2013). Especially the details of ice formation in clouds are not yet fully understood. Thus we focus our research in understanding ice formation through laboratory experiments, field measurements and modelling on various scales.