Remember that pesky ozone hole scientists discovered in the 1980s? Thanks to unprecedented global agreement to phase out chlorofluorocarbon refrigerants (CFCs) and other ozone-depleting substances, today the ozone hole has almost completely closed. Unfortunately, CFCs were replaced with hydrofluorocarbons (HFCs), which have high global warming potential and thus pose their own environmental risks.
A few years ago, Europe began replacing HFC refrigerants with hydrocarbon (HC) refrigerants, which have a much lower potential for global warming. After dithering for several years over flammability risks (freezers that burst into flame would, after all, present an entirely different set of problems), in December 2011, the U.S. finally joined Europe in approving hydrocarbon refrigerants for home use [source: EPA]. Soon, American homebuyers will be able to join European residents in replacing their HFC refrigerators with more environmentally friendly models.
Upgrading your freezer will certainly help you reduce your contribution to greenhouse gas emissions, but if you really want to get serious about reducing your carbon footprint, you'll need to go a bit further.