Using simple, graphic feedback The National Resource Defense Council's ambient persuasive tea cup effectively demonstrates the potential effects of global warming in an effort to make users think about the environmental consequences of over-filling the kettle.

The external surface of the cup is printed with a second layer of heat sensitive ink that is slowly revealed when hot water is poured into the cup. 

"When hot water is poured in, the sea level, which is printed on the heat-sensitive layer, gradually rises to consume the iceberg"[1].

This concept has provoked some discussion on various blogs [2]. Some of the comments are reproduced below, as they are particularly insightful in pointing out some potential "rebound effects" associated with this product;

"The idea is if they keep telling you, you might be prompted to do something about it. Same thing as a nagging wife"

"I don't mind being hit over the head with the warning of 'melting ice'.... will seeing something "new" prompt any of us to do anything? doubtful"