Abstract
ABSTRACTThe Paris Agreement, which entered into force in 2016, sets the ambitious climate change mitigation goal of limiting the global temperature increase to below 2°C and ideally 1.5°C. This puts a severe constraint on the remaining global GHG emissions budget. While international shipping is also a contributor to anthropogenic GHG emissions, and CO2 in particular, it is not included in the Paris Agreement. This article discusses how a share of a global CO2 budget over the twenty-first century could be apportioned to international shipping, and, using a range of future trade scenarios, explores the requisite cuts to the CO2 intensity of shipping. The results demonstrate that, under a wide range of assumptions, existing short-term levers of efficiency must be urgently exploited to achieve mitigation commensurate with that required from the rest of the economy, with virtually full decarbonization of international shipping required as early as before mid-century.Key policy insightsRegulatory action is key to ensuring the international shipping sector’s long-term sustainability.For the shipping industry to deliver mitigation in line with the Paris Agreement, virtually full decarbonization needs to be achieved.In the near term, immediate and rapid exploitation of available mitigation measures is of critical importance.Any delay in the transition will increase the risk of stranded assets, or diminish the chances of meeting the Paris Agreement's temperature commitments.
Highlights
While the Paris Agreement has entered into force, international shipping emissions are notably absent from it
This article uses a range of demand scenarios from the 3rd International Maritime Organization (IMO) GHG Study (Smith, Jalkanen et al, 2015) based on the Representative Concentration Pathways (RCP), which provide a range of radiative forcing trajectories over the twenty-first century, and the complementary Shared Socio-Economic Pathways (SSP), that form a set of five contrasting narratives of future global socio-economic development (O’Neill et al, 2015)
The preceding analysis reveals the scale of reductions in CO2 intensity implied by the headline commitments of the Paris Agreement if the sector aspires to achieve the same emission reduction rates as all other sectors on average
Summary
While the Paris Agreement has entered into force, international shipping emissions are notably absent from it. For a 66% probability (as defined above, capturing only the variability within the set of climate models) of not exceeding a 2°C increase of average global surface temperature above pre-industrial levels, the cumulative CO2 emissions budget from 2017 onwards is 750 GtCO2, for a 50% probability it is 1050 GtCO2, and for a 33% probability it is 1250 GtCO2 (Table 1). Beyond the uncertainty captured by the variation between models in the ensemble, these numbers depend on the definition of global average surface temperature (e.g. using either sea surface temperature or surface air temperature over the oceans), and they are threshold exceedance budgets (TEB) rather than threshold avoidance budgets (TAB).2 They depend on assumptions about emissions of non-CO2 GHG, Collins et al (2013) show that this dependence is small across the range of RCP scenarios. Risk; and it would further constrain the remaining budget, as indicated by the large uncertainty in specifying a CO2 budget for a particular temperature rise
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