Editor's Introduction: The Carbon Challenge

Green may have been a catchy and colorful way to attract interest in the environment, but like most things in science and business, the concept has evolved so quickly it's no longer fully utilitarian.

Green or sustainability is now such a broad and deep subject, so multi-dimensional, that even the most aware and informed have trouble keeping up. At the same time, some still don't get it, and in that way green is a bit fuzzy.

There's nothing fuzzy about carbon, however. It's as old as the world as we know it and the core of our energy supply. In a way, we can't live without it, but we can't live on carbon alone.

That's the carbon challenge.

Our special report is meant to make sense of carbon, from science to business to government. Carbon is a controversial issue and a new profit center. It both unites us and divides us— consumers, businesses, nations.

In these pages, you'll learn how companies are making a business of carbon; whether its technology to reduce, count and track emissions or platforms to buy, sell and trade carbon; how to invest; and how the regulatory climate is being shaped. Our Carbon 101 section walks you through all of that.

You'll find a handy reference guide in our slideshow on the greenest companies, based on the Carbon Disclosure Project annual report on the carbon footprint of S&P 500 companies. This year, for the first time, its report ranks companies based on their plans and actions to reduce emissions.

You'll also find interviews, analysis and debate, as well as commentary from key players--insights and information. Have you every thought, for instance, that you might soon be buying auto insurance based on your vehicle's carbon footprint?

In the coming weeks, we'll be taking a close look at the United Nations global climate change conference in Copenhagen in December. Almost 200 world leaders were invited to attend; at this point, at least 40 intend to.

There are no borders to the carbon challenge.

© 2009 CNBC.com