In 2015 and with global emissions rising at unprecedented rates one clear certainty is that the future will be very different from the past. Whether the world continues to follow a trajectory of greenhouse gas emissions exceeding those in RCP8.5, the highest in the IPCC’s suite of scenarios and associated with an expected temperature increase of between and 3°C and 5°C, or whether we begin a programme of stringent mitigation, is a decision for the international community. These two paths lead to very different futures, each radically different from the past. This paper reflects on and analyses the role of the global shipping industry as an important player in both these potential futures.The Kyoto Protocol has called on the International Maritime Organisation (IMO) to “... [control greenhouse gas emissions from shipping]”. In 2009, the then secretary general of the IMO concluded that “our collective way of life has become unsustainable” and stressed “the need to make some tough decisions ... and ... to start putting life ahead of lifestyle”. In contrast, the baseline suite of six shipping emissions scenarios in the 2nd IMO GHG Study (2009) has CO2 emissions between 2007 and 2050 rise by a factor of between 2.2 and 3.1. Similarly, the 3rd IMO GHG Study (2014) presents a suite of sixteen scenarios, with rises of up to 3.5 times those estimated for 2012.It is important to that the updated emissions estimates in the 3rd IMO GHG Study (2014) demonstrate a fall in CO2 over the period 2007 to 2012. It argues that much of this emission reduction was due to slow steaming in response to a global economic downturn. Recent emissions reductions may, therefore, represent ‘latent CO2’, that could be realised once the economic situation changes and vessels revert to pre-crisis speeds.The paper contrasts the different emissions pathways for the shipping sector, placing them in the quantitative context of global emissions scenarios and associated temperature responses. It concludes that steering a mitigation course has never been more critical, nor the choice more stark.