Bridging the gap – the role of international shipping and aviation

Emissions from the shipping and aviation sectors have increased in the past decades (though they reduced in 2020 due to the COVID-19 pandemic) and accounted for approximately 2 GtCO2 in 2019 (International Maritime Organization [IMO] 2020; Lee et al. i n p ress). A bout t wothirds of these emissions are international, meaning they are not included in national totals reported to the United Nations Framework Convention on Climate Change (UNFCCC) and are instead added as memo items. Although international emissions are not covered under the nationally determined contributions (NDCs) of most signatories to the Paris Agreement, article 4 commits its signatories to reducing all anthropogenic greenhouse gas (GHG) emissions. No sector is exempt from this commitment. At present, the International Civil Aviation Organization (ICAO) and the International Maritime Organization (IMO) are the specialized United Nations agencies tasked with addressing international GHG emissions. Shipping and aviation both largely depend on liquid fossil fuels and have inherently long technology development and fleet turnover times, which make it difficult for the sectors to decarbonize. In addition to GHG emissions, both sectors emit other emissions that contribute to climate change, such as nitrogen oxides (NOx), water vapour, back carbon (soot) and sulphur dioxide (SO2) (Eyring et al. 2010; Eide et al. 2013; Lee et al. in press).

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