An update on the Greenland Ice Shelf

Now an update on a story we first reported 15 years ago. That's when Scott Pelley went north to the Greenland Ice Shelf to witness a "Global Warning" -- the melting Arctic.

"What I'm standing on is a huge block of ice that split off from the glacier recently and dropped into the sea," Pelley reported. "It's a big iceberg at this point. This part of Greenland is melting faster than just about any other.  And to get a sense of the enormity of what's happening, consider this: The ice that is melting here is the equivalent of all of the ice in the Alps."

"And just four minutes after we cleared off this berg," Pelley said, "our ice joined in."

Since that story aired, the Greenland Ice Shelf has continued to melt and sea levels have continued to rise. The shelf has lost ice every year since 1998. Something to ponder on Earth Day this Thursday.