What is this carbon offset game and how do I play?

Enlarge Image Image Gallery Our sister site, Earth Moment, lets you shop all your favorite online retailers, and purchases carbon offsets on your behalf ? at no extra charge to you.

You've probably heard these guilt-inducing buzzwords by now: carbon footprint and carbon offset. 'What is this miraculous means by which I can reduce my personal assault on Planet Earth?' you might be thinking. 'Can I actually offset all the carbon dioxide emissions I'm responsible for?' you're saying to yourself. Well, it's actually pretty easy and affordable. Take me to your carbon offset leader!

A carbon offset is something you buy. It's a voluntary investment in an activity that leads to the reduction of Earth-warming carbon dioxide (CO2) in our atmosphere. You can choose to spend anywhere from $5 to $5 million on offsets, and the project benefitting from your donation is usually up to you.

The most popular types of carbon offsets are those that plant trees (reforestation), support activities that help us use less fossil-fueled power (energy efficiency, conservation), or invest in power systems that don't rely on our dwindling fossil fuel supplies (renewable energy). Some offset programs also invest in technologies that help prevent methane ? another potent nasty that heats up our lives ? from entering the atmosphere (methane capture).

The following organizations sell carbon offsets directly to consumers, and feature handy carbon calculators to help you determine your environmental footprint. All are certified by an independent agency that makes sure your dollars go where they should. (Learn more about the green-e certification program.)

• 
  
• Carbon Fund offers a range of pricing options to offset specific activities, such as driving or flying, or you can donate the dollar amount of your choosing. Approximately $5 offsets 1 ton of CO2. (For a frame of reference, you could prevent 1 ton of CO2 from entering the atmosphere by turning your thermostat down 2 degrees for four straight years.)
• 
  
• Native Energy invests in projects that benefit Native American communities and sustainable farmers. It costs about $12 to offset 1 ton of CO2.
• 
  
• TerraPass focuses on the CO2 created by travel. One neat feature is the ability to offset the amount emitted by your make and model of vehicle or the number of times you fly every year. It takes about $10 to offset a ton of CO2.
• 
  
• The Conservation Fund is dedicated to protecting America's landscapes and waterways. They sell reforestation carbon offsets for about $5 per ton of CO2 emitted.
•