The Mindlin Foundation, Department of Earth and Space Sciences, Quaternary Research Center and the University Bookstore proudly present

May 16, 2001 in Kane Hall, Room 210

ABSTRACT [Quick intro ]

Recent climate events have contributed to human feast or famine, in the Dust Bowl, the Greenlandic settlements of the Vikings, and elsewhere.  Yet ice cores and other archives show that climate doesn't get much more boring than this.  Before our anomalous few millennia of climate stability with agriculture and industry, larger climate changes repeatedly affected much or all of the Earth.  Jumps that in some places were as large as 15 degrees F and twofold in precipitation occurred over decades or mere years.  We cannot fully explain these "normal" climate fluctuations.  However, some abrupt climate coolings seem to have been triggered by sudden deliveries of fresh water to the north Atlantic ocean from lakes dammed by ice-age ice sheets or from surges of those ice sheets.  Even faster warmings followed when the supply of fresh water slowed.

These studies of the past show that the climate system of ice, oceans, atmosphere, and vegetation sometimes acts as if is controlled by a light switch, ignoring small pushes and then flipping on or off from a slightly harder push.  Humans are pushing the climate system, but we don't know how hard we can push before flipping a switch, or even how many switches there are.  More than 1/3 of the ice-age ice remains on Greenland and Antarctica, but we're not yet sure how that ice will change and affect sea-level and climate switches.  Pending such knowledge, we can say that change is almost inevitable, is likely to be difficult to predict in detail, and may not be as smooth and easy to deal with as indicated by most models.

ABOUT R. B. ALLEY

The renowned glaciologist/paleoclimatologist Richard Alley, of Pennsylvania State University, worked on the Greenland Ice Sheet Project in the early 1990s and was the first to recognize the rapidity of past climate changes.

Professor Alley is the Evan Pugh Professor of Geosciences, Earth System Science Center, Pennsylvania State University.