Container shipping is the most efficient and most environmentally sound method of transport : for every ton of cargo transported by ship, only 10 grams of CO2 per km are produced. This number is 2 times less than rail, 5 times less than road and 50 times less by air. CMA CGM carbon efficiency (the emission of CO2 per twenty equivalent unit per kilometre) has continuously improved, reaching 73 grams for global fleet in 2012.