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Transportation is one of the biggest culprits in human production of carbon dioxide—the source of about one-fifth of global-warming emissions worldwide. In the United States, two-thirds of the oil consumed goes toward powering vehicles, according to the U.S. Department of Energy. Passenger cars alone are responsible for 25 percent of the greenhouse gases we produce.
In the future, advanced technologies—fuel cells, hybrid vehicles, biofuels—will help to substantially reduce our reliance on fossil fuels and in turn decrease our carbon emissions. There's plenty you can do in the short term as well, and we don't expect you to rush out and buy a Toyota Prius, either (though if you do, you get major extra credit).
According to the Natural Resources Defense Council, today's passenger cars average just 24 miles per gallon, the lowest level since 1980. In the early 20th century, by comparison, Ford's Model T got 28.5 miles per gallon. For each gallon of gas your car burns, it releases about 19 pounds of carbon dioxide. So, if you could tweak your ride to eke out just three extra miles per gallon, you'd save about 1,000 pounds of CO2 emissions a year, based on an average mileage of 12,000 a year. Then there's air travel: It costs 100 gallons of fuel per passenger to go coast to coast. We won't debate that some flights are necessary, and we're not against vacations. But does that describe all your air travel? Some suggestions for reducing the miles you log in the car and on the plane:
• Keep your tires properly inflated by checking them regularly when you fill up at the gas station. Environmental Defense notes that 32 million U.S. vehicles ride on at least two under-inflated tires, wasting 500 million gallons of gas each year.
• Drive 65 miles per hour instead of 75. This increases fuel efficiency by 15 percent, thereby reducing emissions. And speeding tickets.
• It seems almost too obvious to point out, but idling cars get zero miles per gallon. According to the Department of Energy, no more than 30 seconds of idling is needed to warm up a car, even on cold winter days.
• Cutting your driving by a few miles each day stops tons of CO2 from entering the air each year. Could you walk or bike to do that nearby errand? Could you carpool or commute by mass transit—even just one day a week?
• On relatively short trips—Boston to New York, for example—could you take the train instead of flying?
• OK, so it's a long way and you have to fly. Consider buying carbon offset credits from a company such as TerraPass or Native Energy. You calculate your annual carbon emissions for flying and then buy a credit to help offset the pollution. The money funds renewable energy projects like wind farms. (Read this Slate piece for more details and analysis.) You can buy offsets for your car's emissions, too. Though some critics contend that you can't buy your way green, we say buying carbon offsets is better than doing nothing.