Finds that from 1980 - 2010:

• Areas covered by extreme cold air in cold seasons decreased significantly in the northern hemisphere; observed trend was negative but not statistically significant in the southern hemisphere
• Areas covered by warm air during summer seasons increased significantly in both hemispheres
• The northern hemisphere is tending toward increasingly warmer and more humid summers: "overall, more warm air, larger ridges, and warmer air"
• During the warm season, the global area covered by precipitable water values equal to or greater than 60mm is increasing
• The significant changes in weather are "occurring in the tails of the distribution"