The author of today’s post, Sheryl Canter, is an Online Writer and Editorial Manager at Environmental Defense.

Total greenhouse gas emissions from cars and trucks is a function of three factors: amount of driving, fuel economy, and carbon emissions per gallon of fuel (the "three-legged stool [PDF]"). The news media tend to focus on the latter two factors, but how much people drive has a huge impact.

A new report published by the Urban Land Institute says that greenhouse gas emissions cannot be reduced sufficiently by making vehicles more efficient, because growth in driving cancels out improved fuel economy. People also must drive less. And the report’s solution is not just better public transportation.

The way to reduce driving sufficiently, the authors say, is to shift development patterns to favor compact, mixed-land-use neighborhoods where you can walk to school and the grocery store. If you live in a car-dependent area, moving to a walkable area will do more to fight global warming than buying a fuel-efficient hybrid car.

This idea is already being put into action in some areas. New York City is expecting one million more people by the year 2030, and is using rezoning to direct development towards areas with strong transit access.

Environmental Defense helped California’s San Joaquin Valley, which is notorious for bad air quality, implement a similar strategy. The Air Pollution Control Board adopted an incentive program [PDF] that gives developers two choices: reduce the environmental impact by creating sidewalks, bike paths, and nearby schools and commercial districts, or pay a fee for any excess pollution.

Living in a walkable neighborhood has other advantages. Recently released figures from the New York City Department of Health show that New Yorkers tend to live longer than most people in the country — an odd finding considering the lack of fresh air and other hazards. The city’s Commissioner of Public Health thinks it’s because New York is a walking city.

By Erica Rowell, Environmental Defense Writer, Editor, ProducerCFL and incandescent bulbs side by side

Quality was spotty in the 70s, but this is a new millennium

Apple computers. Punk. Compact fluorescent light bulbs (CFLs). What do they have in common? They were introduced in the 1970s and are now back in style.

CFLs have improved dramatically from their inauspicious beginnings. They took a while to come on, flickered as they lit and gave off an unpleasant green hue. That was then. CFLs not performing well today is a myth—as fictitious as the urban legend that says Mikey from the Life cereal ad died from noshing on Pop Rocks. He's alive. CFLs rock.

Brighter, whiter, faster

Thanks to improved technology, CFLs are now like familiar old-fashioned incandescent bulbs (ICs) in just about every way. CFLs can be as bright, come on as quickly and provide warm white, eye-pleasing hues. They can even be dimmable and used in 3-way sockets. If you haven't tried a new-fangled CFL, go on, "Try it—you'll like it."

Plus, as their prices have come down and energy rates have ticked up, the savings keep improving. CFLs slash global warming pollution, too.

How CFLs save money and global warming pollution

Turning on a light taps electricity from your local utility. About half our electricity comes from coal-burning power plants and another 20 percent comes from from natural gas, so powering things on generally means spewing lots of heat-trapping pollution. These greenhouse gases drive climate change. So using less electricity means less global warming pollution—and lower electricity bills.

How much savings CFLs rack up

Crunching the numbers is eye-opening. Let's compare a 25-watt CFL costing $3 (a good average price) to a 60-cent, 75-watt IC.

Now, let's turn on both our 10,000-hour CFL and our 750-hour IC bulb at 12:01 a.m. on January 1 and keep them running 24/7 for a year. On December 31, our CFL has racked up extraordinary savings in cash and pollution.

What to look for in energy-saving bulbs

To replace a 75-watt bulb look for a CFL with these specs:

• 20 to 25 watts. CFLs use roughly a quarter of the energy to produce the same light.
• 1200 lumens. This minimum level of brightness provides what you're used to.
• Warm white (or 2700-2850 degrees Kelvin). This color temperature mimics an incandescent light.
• Energy Star symbol. This label indicates high-standards and ensures that the CFLs' claims (brightness, longevity, power used, etc.) are real.
• Get more CFL tips

Time to switch to CFLs and save

Bottom line: CFLs save you money and cut heat-trapping pollution. How much of each depends on things like your electricity rate, the energy mix your utility uses, and which CFLs you buy. (See our chart for info on other bulbs.)

Check out the Environmental Defense CFL guide to get started and see which CFLs are right for your needs. And then turn on your new Mac, crank up the Ramones, and dim your new dimmable CFL.