Our planet has warmed by 1 degree Fahrenheit since the beginning of the century, but for reasons that aren’t entirely clear, the Antarctic Peninsula--the stretch of land that reaches up toward South America--has warmed 4.5 degrees in just the past 50 years. In 1995 the warming made itself felt in a dramatic way, as this satellite image illustrates. The image shows, at the lower center, a thousand-square-mile iceberg that calved off the huge Larsen Ice Shelf sometime in January or February. At around the same time, a large chunk of the ice shelf just north of the berg disintegrated into much smaller pieces. What’s more, so did two smaller ice shelves elsewhere on the peninsula. The Antarctic gives off large icebergs maybe every three or four years, says glaciologist David Vaughan of the British Antarctic Survey. The big story for us is that three ice shelves-- which had been thought fairly permanent features--disintegrated. Such rapid disintegration has never been observed before, and it suggests the ice shelves were weakened by warm temperatures. By late in the year the giant iceberg had drifted a few hundred miles to the north; Vaughan said it could survive for as long as several years.