Economists view environmental damage as a classic “externality”—a cost that impacts society but isn’t imposed on producers or consumers. But with scientific consensus that carbon emissions threaten our climate, there’s growing political will to curb them, particularly with the global powers set to meet in Copenhagen in December. The Obama administration is pushing for a cap-and-trade system that would turn companies’ emissions into a bottom-line cost. Smart companies are working to better understand—and cut—those emissions ahead of new regulations.

The inaugural NEWSWEEK Green Rankings recognizes those efforts. For more than a year, the magazine worked with leading environmental researchers KLD Research & Analytics, Trucost, and CorporateRegister.com to rank the 500 largest U.S. companies based on their actual environmental performance, policies, and reputation.

Hewlett-Packard ranked #1 this year.  Watch their video: A look back at mankind’s innovation history and looking now at the opportunity for new solutions for the climate crisis, entrepreneurs will make a new future in the new carbon economy.