Maersk Line will now add the CO2 data - verified by Lloyd's Register - as one of eight performance measures in score cards that are presented to customers.
And for customers like Starbucks Coffee Company, independent verification means more transparency.
"Being a good environmental steward is important to Starbucks Coffee Company. Our global logistics providers can aid us in lowering the carbon footprint of our supply chain by improving their CO2 emission data. Quantified measurement and verification is a step in the right direction. Together, we continue to strive to better the world in which we do business," says John Bauer, director of global transportation, Starbucks Coffee Company.
Lloyd's Register also lauds the added transparency.
'Maersk Line is to be congratulated for taking the lead in promoting transparency and credibility with regard to carbon emissions,' says Madlen King, head of climate change and sustainability at Lloyd's Register.
The next challenge is to get other shipping lines to participate and thereby make independent verification an industry standard, according to Jacob Sterling, head of climate and environment in Maersk Line.
'This will enable our customers to choose shipping lines based on their environmental performance,' Sterling says, adding: 'It used to be that 'you cannot manage what you cannot measure'. That's not the case any more. We will work to develop a global industry standard for verification of shipping's CO2 emissions.'
' This effort is centred within the Clean Cargo Working Group, which consists of shipping companies and large customers in search of ways to reduce shipping's carbon foot print.
Before issuing its first-ever verification, Lloyd's Register checked whether the CO2 emissions calculated in 2009 corresponded with what auditors could find in the comprehensive vessel reporting system at Maersk Line's central offices.
The audit process also included a visit on board Maersk Clementine to check whether its logs going back over time corresponded correctly with the information in reporting system.
'If the CO2 data held by the shore office is not supported by a credible reporting system then we would not be able to verify the data and provide an assurance statement,' says Peter Catchpole from Lloyd's Register's environmental product development team.
'In this instance we also checked onboard records and reporting procedures to give greater confidence in the reported data,' he adds.
