I always hear people telling me that the melting of the polar ice caps will cause the oceans to rise.  This is false.  In order to float, an iceberg displaces a volume of water which weighs the same as the iceberg.  When an ice cube melts in your glass of water does it overflow?  No.  The melting of ice caps and the rising ocean levels are both results of the heating planet, however.  Water is the most dense at 4 degrees Celsius.  When the water temperature exceeds 4 degrees, it becomes less dense and expands, thus causing the water levels to rise.  While this fact does not make global warming any less frightening, it will allow you to shut up the whiny yuppie-hippie at Whole Foods.