Many, if not most, major companies are doing something to cut their greenhouse gas emissions—reducing their use of electricity perhaps, or starting a recycling program. But cutting-edge businesses are rising to another level—taking more ambitious and sophisticated steps to address the rise in global temperatures caused by climate change. Concerned about an array of issues, from the excessive use of water at suppliers' plants and potential risks posed by government regulation to an increasing investor focus on climate change, companies are venturing beyond the tried-and-true. They're trying new strategies that range from producing a trailblazing sustainability report to helping farmers participate in carbon offset exchanges or changing the firm's very business model. "These companies recognize the serious business risks to the long-term sustainability of the company," says John Jarrett, director of research at GovernanceMetrics International. "With world resources becoming increasingly limited, they see the imperative of addressing issues that previously weren't even on the radar screen." Here's what five such companies are doing.(NRG's Steve Corneli, left)

NRG: It's All About Diversity

NRG wasn't always focused on clean and renewable energy. But 20 years after it was spun off from Northern States Power in Minnesota, the $9 billion, Princeton, N.J.-based independent power producer's business model has an unusual emphasis on diverse sources of energy, ranging from coal and natural gas to solar and wind.