If car shopping, get to know the just-released MPG ratings. Use gas-sipping driving strategies when behind the wheel.

Before you fall in love, check the MPG rating.

RODALE NEWS, EMMAUS, PA—On Black Friday, malls seem to have a magnetic quality, sucking people in from all directions to shop. But, to a lesser extent, so do places that house big-ticket items, including dealerships with new cars and trucks. If you find yourself perusing a vehicle showroom in search of one of those end-of-the-year deals, make sure you pay attention to the car's miles per gallon (MPG) rating—the ratings are now more accurate than ever. You'll spend less on gas, and create fewer emissions that contribute to a warmer planet.

THE DETAILS: In 2008 the U.S. Environmental Protection Agency (EPA) adjusted the MPG rating system to reflect more real-life driving conditions: faster accelerating, use of air-conditioning, and driving when it's colder outside. Right now the importance of those ratings may be greater than ever. Earlier this month, an environmental health report from Worldwatch Institute and the United Nations Foundation cited global warming as the biggest health threat humans face in the 21st Century. From a surge in infectious diseases such as malaria, to mass migration and unprecedented food and clean-water shortages, the consequences of not lowering the level of greenhouse gases in the atmosphere will dramatically alter the world we live in, the report author concludes. "More than ever before, there's a crystal-clear moral imperative that we're now faced with," says Samuel Myers, MD, professor of medicine at Harvard Medical School and research associate at Harvard University Center for the Environment. "It's our energy use and consumption practices in the wealthy world that are putting hundreds of millions of people in the poor, developing countries in harm's way. There's no way around it. It's not debatable."

And a significant chunk of that consumption comes in the form of planes, trains, and automobiles. Transportation accounts for nearly 30 percent of total greenhouse-gas emissions in this country, accounting for nearly half of the net increase in total U.S. emissions since 1990, according to the EPA.

WHAT IT MEANS: Last spring, President Barack Obama announced tougher fuel-economy standards that will require automakers to hit a minimum of 33.5 MPG by model year 2016. But a steady flow of peer-reviewed, scientific data from climate researchers from all over the world suggests we don't have any time to waste in cutting greenhouse-gas emissions. Currently, carbon dioxide registers at about 390 parts per million (ppm) in the atmosphere. "The world starts to look pretty scary when you go above 400 ppm," says Dr. Myers.

Complicating matters, The New York Times last weekend reported that a group of world leaders, including President Obama, said there's not sufficient time to hash out a legally binding, global climate deal by the time the United Nations Climate Change Conference talks start in Copenhagen in just three weeks. Politicians may be puttering around, but that doesn't mean you can't help put the brakes on global warming through better driving techniques and more fuel-efficient vehicles.

Here's how you can get your own improved MPG rating when you're behind the wheel.

• Pass gas-guzzlers by. Or course, it's best to walk or take public transportation whenever you can. But if you're looking for a new car, be sure to check out the most fuel-efficient models so your time behind the wheel will have less impact on global climate. Here are some of the 2010 fuel-economy leaders from the newly released 2010 Annual Fuel Economy Guide, released by the EPA and the U.S. Department of Energy. (MPG: City/Highway)

Two-Seater Cars
Smart ForTwo, automatic, 33/41
Mazda MX-5, manual, 22/28

Minicompact Cars
Mini Cooper, manual, 28/37
Mini Cooper Convertible, automatic, 25/33
Mini Cooper, automatic, 25/33