Recent Arctic Climate Trends Observed from Space and the Cloud-Radiation Feedback

There is evidence that Arctic temperatures have been increasing and sea ice thickness and extent have been decreasing over the last few decades. However, it is not clear how clouds are responding to, and modulating, these changes. Here we examine trends in satellite-derived cloud, surface, and radiation properties in the Arctic for 1982-1999. Results show that the Arctic has warmed and become cloudier in spring and summer, but has cooled and become less cloudy in winter. The surface albedo has decreased in autumn as a result of a longer melt period and later freeze-up. The radiative interaction between clouds, surface temperature, and surface albedo, the cloud-radiation feedback, is such that there is no significant trend in net radiation during winter, spring, summer, or fall, even though there are trends in cloud and surface properties. It appears that during the sunlit part of the year the decreases in sea ice extent and albedo that result from surface warming modulate the increasing cloud cooling effect, resulting in little or no change in the surface radiation budget. Additionally, the cooling effect of clouds may be damping the increase in surface temperature to some degree; i.e., if cloud amount were not increasing then the surface temperature might be increasing at an even greater rate than what was found here and in other studies.