The North Pole has been frozen for 100,000 years. But according to scientists, that won't be true by the end of this century. The top of the world is melting.
There's been a debate burning for years about the causes of global warming. But the scientists you're about to meet say the debate is over. New evidence shows man is contributing to the warming of the planet, pumping out greenhouse gases that trap solar heat.
Much of this new evidence was compiled by American scientist Bob Corell, who led a study called the "Arctic Climate Impact Assessment." It's an awkward name — but consider the findings: the seas are rising, hurricanes will be more powerful, like Katrina, and polar bears may be headed toward extinction.
What does the melting arctic look like? Correspondent Scott Pelley went north to see what Bob Corell calls a "global warning."