The frequency of extreme weather events has increased steadily over the 20th century. The number of weather-related disasters during the 1990s was four times that of the 1950s, and cost 14 times as much in economic losses. One in five Canadians was directly affected by a weather disaster between 1996 and 2000.

These trends confirm the predictions of computer models: as the atmosphere warms, the climate will not only become hotter but much more unstable.