Greenhouse gas emissions from international aviation have risen sharply in the last two decades. From 1990 to 2012, as global carbon dioxide emissions from fossil fuel combustion rose by 53%, CO2 emissions from international aviation fuels grew by more than 86%, to 478 million tonnes (Mt), or about 1.5% of global CO2 emissions from fossil fuel combustion.

Yet despite more than two decades of discussions about the need to reduce emissions from aviation, there is no meaningful regulation in place to do so. Progress in the regulation of international aviation emissions will require overcoming the apparent conflict between the principle of differential treatment, widely used in international environmental law, and that of equal treatment, which is a central tenet of international aviation law.

The authors find that recent developments at International Civil Aviation Organization (ICAO) and the European Union (EU) indicate that policy-makers in both venues have shifted positions, to embrace differential treatment in favour of developing countries in the regulation of international aviation emissions. This new acceptance of differentiation is based on more flexible approaches than those found in the international climate regime, following the use of contextual norms that distinguish among countries on the basis of circumstances that may change over time, as well as norms applied at the implementation level (e.g. linked to financial, technological and capacity-building assistance).

The contextual treatment approach may be better suited to accommodating both differential and equal treatment in any future regulation of international aviation emissions, as it allows for forms of differentiation that are better suited to the realities of the sector.

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