In today's global economy, companies often work with literally thousands of suppliers, partners and service providers throughout the world to create and provide their products and services. They rely on these relationships to do everything from procuring raw materials to delivering finished goods. Companies used to measure the efficiency of such a complex network of interconnected relationships -- its global supply chain -- in three areas: cost, service and quality. But concerns about climate change, ranging from increasing regulation to rising consumer awareness, introduced a fourth element to the equation: carbon emissions. Driven by cheap energy, worldwide trade has more than doubled in the past decade and global GDP has grown six times, all with little regard to the impact on