The most powerful of feedbacks in the Arctic is sea ice and snow cover, said Miller, the lead author on a paper about past "Arctic amplification" in the journal Quaternary Science Reviews.

We'll wrap him in tissue paper, put him in a little box, then have a nice burial ceremony in the back yard. After that, we'll go out for an ice cream soda, and then get you a new pet.

On any summer day thousands of visitors stroll through Rushmore, many licking ice-cream cones wrapped in paper American flags.