Worried about global warming?

The US National Academy of Sciences warns that sudden, unexpected climate change - on a scale that could cause widespread drought or plunge Earth into a deep freeze - pose a more immediate danger.

Global climate change, often seen as a process stretching over thousands of years, could in fact occur abruptly and unexpectedly -- quickly pushing up temperatures by as much as 18 degrees Fahrenheit and wreaking havoc on human society...geological evidence indicated that such rapid climate shifts had occurred frequently in the past -- moving temperatures drastically in the space of just a few decades.

See Christian Science Monitor or Yahoo / Reuters or Stanford University