One group at CERN has built a very novel cloud chamber to study the nucleation process which is responsible for cloud formation. one of there discoveries is the following:
"CLOUD has already made several important discoveries. First, the experiment has shown that the most likely nucleating vapours, sulphuric acid and ammonia, cannot account for the nucleation that is observed in the lower atmosphere. The nucleation measured in the chamber occurs at only 1/10-1/1000 of the rates observed in the lower atmosphere. It is clear from these first results from CLOUD that the treatment of aerosol formation in climate models will need to be revised substantially because all models assume that nucleation in the lower atmosphere is caused by these vapours and water alone. It is now essential to identify the additional nucleating vapours and whether their sources are mainly natural or from human activities. If the vapours have strong anthropogenic sources then there potentially exists a new climate-forcing agent from human activities. Alternatively, if the source is natural, then there is the potential for a new climate feedback that may affect the understanding of how the climate responds to radiative forcings." -Mark
