Up until the recent oil and commodity price crash in 2015, there has been exponential growth in global shipping and trade, and this increase means that prompt action is required to reduce vessel-sourced greenhouse gas (GHG) emissions. Future projections suggest that maritime CO2 emissions will increase substantially by between 50% and 250%. However, there is currently no international instrument holding global shipping corporations accountable for their vessels' performance in emissions reduction. This article critically assesses the current accountability practices and regulations in place for these corporations. It suggests that stakeholders in this industry need to further explore the market based mechanisms (MBMs) that can encourage and even demand that these corporations systematically disclose their vessels' emissions reduction performance in an accurate and timely manner. Developing such mechanisms is vital to assist in the reduction of GHG emissions since a comprehensive international instrument is unlikely to be implemented soon.