The aerosol-cloud-climate conundrum

The complexity of the atmospheric aerosol and its connection with clouds and climate are illustrated with a host of examples against the background of our present limited state of understanding. A discussion of related feedbacks demonstrates the difficulties of resolving all respective research issues. The key role of aerosols and clouds in anthropogenic climate change make the high uncertainties related to them ever more painful. Nevertheless, there are suggestions to manipulate aerosols and clouds by climate engineering to counteract global warming. Before considering such remedies the aerosol-cloud-climate conundrum needs to be reduced to a level of uncertainty that is comparable to those related to anthropogenic greenhouse gases. Considering the complexity of the aerosol/cloud system the challenge will be to identify the necessary essential knowledge and differentiate that from marginal details and focus research efforts on these essentials in order to simplify the complex aerosol-cloud system without loosing indispensable features.