A、No melting has been observed in Antarctica. B、The past several winters have been unusually severe. C、Nothing unusual has happe

W: Dr. White, we recently learned that a large piece of the Larsen Ice Shelf in Western Antarctica melted in early January. Could you please tell us exactly what happened?
M: I’d be happy to. The piece that melted was over 1 000 square miles in area. More recently and quite alarming to scientists is that a 40-mile crack, some 30 feet wide in places has torn through the ice shelf.
W: I understand that the scientific community is quite concerned. What is the significance of these events?
M: Well, some scientists believe that this is a clear sign of global warming. Back in 1978, some American researchers predicted that Antarctica would show early signs of global warming due to the green house effect.
W:But couldn’t crumbling ice shelves also be a result of the unusual weather Antarctica itself has experienced lately?
M: That’s certainly possible, but you’ll have to remember that over the past thousands of years, ice shelves have been through a lot of weather changes without breaking up.
W: I think most people know that if the ice cap over Antarctica melts, the level of the oceans will rise. What sort of impact will this have?
M: Well, the ice shelves currently insulate the Antarctic continent from wind, which slows down the melting. If the winds cause even a tenth of the continent’s ice to melt, the world’s oceans could rise as much as 30 feet.
12.  What are the speakers mainly discussing?
13.  Why are the melting events of the ice important?
14.  Why doesn’t the man believe weather changes result in ice melting?
15.  What would be the likely result of the melting of the ice cap？