Published by the American Geophysical Union as part of the Geophysical
Monograph Series, Volume 126.
Until a few decades ago, scientists generally believed that significant
large-scale past global and regional climate changes occurred at a
gradual pace within a time scale of many centuries or millennia. A
secondary assumption followed: climate change was scarcely perceptible
during a human lifetime. Recent paleoclimatic studies, however, have
proven otherwise: that global climate can change extremely rapidly. In
fact, there is good evidence that in the past at least regional mean
annual temperatures changed by several degrees Celsius on a time scale
of several centuries to several decades.