Without a chimney, the igloo could melt. 7. (c) 65 degrees It seems amazing, but these ingenious snow shelters are very comfortable inside, averaging about 65 degrees warmer than the outside air ...

Watch our film to find out how to make a crystal-frosted festive decoration in a fun science experiment to try at home.

With its focus on the ingenious craft of igloo building before it becomes too ... an elegy to a world that is melting away.