Consumers typically choose parcel carriers based on price and transit time. Climate Counts, a non-profit group devoted to fighting climate change, wants them to add the carriers' environmental records to the equation. To that end, the group has developed a shopping guide to help consumers "support companies that take climate change seriously and avoid those that don't."

Climate Counts' shopping guide ranks 144 large companies in 17 sectors on a scale of 0 to 100 (the higher the score, the greener the company). Its "consumer shipping" scorecard includes the four largest parcel carriers: UPS (with a score of 80), DHL and its parent Deutsche Post World Net (78), the U.S. Postal Service (69), and FedEx (65). Those results, the group says, indicate that the parcel shipping industry "has begun to address its climate impact, but has far to go."

The non-profit uses 22 criteria to determine whether companies have measured their climate footprint, reduced their impact on global warming, supported progressive climate legislation, and publicly disclosed their climate-related actions.