With global warming such a hot topic, Charles R. Bentley, of the Geophysical and Polar Research Center at the University of Wisconsin at Madison, decided to explore the likelihood of a doomsday scenario: the melting of the West Antarctic ice sheet and the subsequent rise in sea levels worldwide -- a topic he considered likely to be of "widespread interest." That's an understatement. The discharge of the ice sheet's water into the ocean would boost sea levels by 16 to 19 feet, drowning many low-lying cities around the world. Fortunately, Dr. Bentley has found little cause for alarm. A review of evidence suggests that the sheet's three main ice-drainage systems are stable, he reports. Further, he writes, global warming -- whether due to natural causes or human activities -- is unlikely to affect ice sheets like this one anytime soon. Dr. Bentley concludes that the West Antarctic ice sheet won't collapse due to human or climatological reasons, at least not in the next century or two. Such a collapse could occur, he believes, only through natural causes. And the likelihood of that? Just about 0.1 per cent, according to Dr. Bentley.