Geoscience Reference
In-Depth Information
But most westerners are unaware of these prehistoric extreme climate
events that complete the story of the region's long-term climate pattern.
h e evidence has been growing, but only recently have the clues been pieced
together to form a more accurate picture. h is topic presents an outline of
what we know about the past 20,000 years, from the peak of the last ice age
to the present. During those millennia, climate has ot en varied by extremes
in the American West. Close examination of the evidence suggests that
the benign conditions of the past century and a half have not prepared us
adequately for what could come in the region's climatic future.
h e droughts of the 1930s and 1987-92 are believed to have originated in the
Pacii c Ocean. During these periods, sea surface temperatures in the tropical
Pacii c were unusually cold, which is characteristic of the ocean-atmosphere
phenomenon known as La Niña. h e next chapter explores the connections
between the Pacii c Ocean and the American West and how extremes of
wet and dry are products of the interactions between this enormous body of
water and the atmosphere above it.
