qThe snow cover has decreased by about 10% since
the late 1960s.
qNorthern hemisphere spring and summer sea-ice
extent has decreased by about 10 to 15% since the 1950s.
qEl Nino phenomenon has been more frequent,
persistent, and intense since the mid-1970s.
qNo significant trends of Antarctic sea-ice extent
are apparent since
1978.
qNo systematic changes in the frequency of
tornadoes, thunder days, or hail
events are evident in the limited areas analyzed.