From 1963 to 1991 very few studies of CCN were conducted and published since there were no commercially available instruments and large scale climate change had yet to be definitively linked to aerosols and clouds.

When the first report of the Intergovernment Panel on Climate Change (IPCC) was published identifying aerosols and clouds as significant yet highly uncertain factors in climate change, the number of publications with CCN measurements rose significantly.

Nucleation is VERY dependent on the composition, mass and surface characteristics of the nucleus.

Little known about dust, organic and black carbon, bioaerosols and effects of aging, photochemistry and cloud processing