If you didn’t feel guilty about your TV habits already, here’s a new reason: a chemical used in making flat-screen televisions has been found to be a potent greenhouse gas, 17,000 times stronger than carbon dioxide. In a study published in the journal Geophysical Research Letters, atmospheric chemist Michael Prather called nitrogen trifluoride, or NF3, “the missing greenhouse gas,” and warned that the climate could suffer as the chemical is produced in ever greater amounts to meet soaring demand for LCD displays. If all of the NF3 produced in 2008 were released into the atmosphere, it would have as much warming effect as 67 million metric tons of carbon dioxide, the study found — about the same as the annual CO2 emissions of Austria. NF3 isn’t covered by the Kyoto Protocol because it was only being produced in tiny amounts in 1997 when the treaty was negotiated. Ironically, NF3 was developed as an alternative to perfluorocarbons, greenhouse gases that are governed by Kyoto.