What do Nestle, Proctor & Gamble, Unilever, and Dell have in common? Theyve all put their suppliers on notice to provide concrete, meaningful data on their carbon footprint. Why? These companies are seeing real business value in measuring energy use and carbon emissions upstream to gain business efficiencies, reduce costs, forge closer links with supply chain partners, and make the most cost-effective reductions in their total carbon emissions. By Phil Berry