Of course the range of net infrared forcing caused by changing cloud conditions (~ 100W / m2) is much greater than that caused by increasing levels of greenhouse gases (e.g. doubling pre-industrial CO2 levels will increase the net forcing by ~ 4W / m2), but the objective of this exercise was to demonstrate a relationship. (realclimate.org)
Sailors measured winds, temperatures, barometric pressure and cloud conditions as well as sea ice and animal sightings. (discovermagazine.com)
At least over the oceans, the pre-industrial cloud conditions would have been considerably different from those of today; this implies that the aerosols we have been adding to the atmosphere may have had a significant effect on global patterns of cloud formation and rain. (sciencedaily.com)