The new estimates of the revised strategy, international shipping will exceed its current share of the world’s 1.5°C carbon budget by approximately 2032 but will not exceed the well below 2°C carbon budget if it follows the emissions reduction pathway implied by this revised strategy.
As explained, the revised strategy’s “zero date” of by or around 2050 and its focus on life-cycle emissions are both key improvements. The latter are measured in terms of CO2e100, which refers to carbon dioxide equivalent emissions based on the 100-year global warming potentials of carbon dioxide, methane, and nitrous oxide. It’s very important, IMO’s strategy to include a year by which life-cycle, well-to-wake (WTW) GHG emissions would fall to zero and that it be not later than 2050.
As International Council on Clean Transportation informed, based on the emission factors in this study and the international shipping fuel mix from the Fourth IMO GHG Study, they estimate that the ratio of WTW CO2e100 to TTW CO2 for international shipping is currently 1.21 to 1. This implies that the sector’s carbon budget is approximately 12 Gt WTW CO2e100 for 1.5°C and 21 Gt for well below 2°C.
These are associated with a 67% probability of limiting global temperature rise to these levels. With the emissions reductions expected under the initial GHG strategy, the 1.5°C budget is not exceeded until 1 year later, by 2031, and the 2°C budget is expended by 2041.
Beyond the short-term measures there are also mid-term measures being developed at the IMO that could enter into force as soon as 2027. The technical element is expected to be a GHG fuel standard (GFS) that will gradually reduce the allowable WTW CO2e intensity of marine fuels.