Some of the world's biggest shippers and charterers are now emphasizing their contribution to the climate in relation to the summit in Paris these coming weeks. 26 companies, including Cargill, BHP Billiton and Rio Tinto, are all using the tool GHG Emissions Rating, which enables them to measure ships' efficiency. In this way the companies can lower their fuel expenses while also contributing to the efforts to cut CO2 emissions, reports risk management group RightShip, which developed the tool.