A group of multinational companies is embarking on a campaign to encourage their suppliers to report greenhouse-gas emissions, pressuring thousands of vendors and factories to show they are taking steps to battle climate change. At least six of the world's largest companies, including Procter & Gamble Co., Unilever, Tesco PLC and Nestlé SA, will announce today that they are banding together to press their suppliers to release data about carbon emissions and climate-change-mitigation strategies... The companies in the new group, called the Supply Chain Leadership Coalition, could eventually use the information to evaluate suppliers, setting off competition between suppliers to show their green credentials. The group, which also includes Imperial Tobacco Group PLC and Cadbury Schweppes PLC, was formed in partnership with the Carbon Disclosure Project... The announcement comes just two weeks after Wal-Mart Stores Inc. announced similar plans to begin asking suppliers for data on their energy efficiency, in partnership with the CDP... Oakhurst Dairy..., one of Wal-Mart's major milk suppliers in New England, was recently asked by the retailer to measure the carbon footprint of a case of milk. Oakhurst says it ultimately found the internal energy audit process useful.