Roasting a similar-size bird—that is, putting it in an electric oven at 350 degrees for 3½ hours—would use about six kilowatt-hours. To generate this much electricity, your average power plant emits about 7.8 pounds of carbon dioxide, making the old-school oven-roasted turkey the clear winner.
During this stressful holiday season it's helpful to remember, however, that these are fairly minor differences. To compensate for the fried turkey's 17 extra pounds of carbon dioxide, you'd need to drive just 19 fewer miles. If you really want to scrimp on CO2, just tell your in-laws you're staying home this Christmas for the sake of the earth.