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UW Today

Regional cloud changes, such as those that result in less rain during monsoons in India and those that indicate a widening of the tropics, may be as important to watch as the overall amount of cloud cover, new University of Washington research indicates.

Authors of the paper, led by Ryan Eastman, a UW research scientist in atmospheric sciences, set out to examine observations collected from weather stations around the world as a way to study the distribution of clouds. The research was recently published in the American Meteorological Society’s Journal of Climate.

Among the many reasons that scientists study clouds are that cloud properties are expected to change with global warming and clouds have an impact on temperature and rainfall.

Eastman and co-author Stephen Warren, a UW professor of atmospheric sciences and of Earth and space sciences, found that from 1971 through 2009 cloud cover over land globally declined 0.4 percent per decade. That’s less of a decline than the 0.7 percent per decade that the pair found in a 2007 paper that examined data from 1971 through 1996.

Because scientists would need to examine much more data about changes in types of clouds at different altitudes at different locations in different seasons, it’s difficult to ascertain how important this change in cloud cover over land is.