Tue 27 Jun 2017 – Although there has been recent speculation over the possibility of the United States not joining the voluntary phase of ICAO’s CORSIA carbon offsetting scheme as a result of President Trump’s decision to withdraw from the Paris climate agreement, there are other implications for global aviation emissions. Pledges made by countries under the agreement must take into account reductions in domestic aviation emissions, which are not covered by CORSIA. Globally, domestic aviation emissions make up around 38% of all aviation emissions, with the US responsible for nearly a half. According to research by Manchester Metropolitan University’s Centre for Aviation, Transport and the Environment (CATE), US domestic aviation emissions could rise by 33-50% over 2005 levels if the US does not carry out its CO2 reduction plans and so heavily impact the sector’s overall emissions.
“Aviation falls into two categories in terms of its CO2 emissions – domestic aviation, which is accounted for by the country that emits it, and international aviation, which falls to ICAO, thus Trump’s actions affect any potential reduction of US domestic aviation CO2 emissions,” explained CATE’s Professor David Lee.
As part of a wider project within CATE, the Centre’s Dr Sarah Freeman has been analysing how aviation CO2 emissions may fit into the Paris pledges.
“I realised that my previous analysis, which had assumed the US may reduce its domestic aviation emissions proportionally to other emissions as part of its Paris pledge, might be significantly affected, so needed to update my calculations,” she said.
Under a simple assumption of proportional reduction, Freeman calculated this would result in a reduction of US domestic aviation CO2 emissions of 85 million tonnes, a 50-56% reduction over business-as-usual projected emissions by 2030, based on 2005 levels.
Dr Bethan Owen, who did the complex underlying projections of aviation emissions, said: “The US currently represents 49% of global domestic aviation CO2 emissions, which is by far the largest individual contribution. This is projected to be around 33% in 2030 in a business-as-usual scenario, so if they drop out and their aviation emissions are affected in this proportional manner, it will make a large impact.”
Withdrawing from the Paris Agreement, under a simple assumption of proportional decreases, the US share of global domestic aviation CO2 emissions could be as high as 64% in 2030, say the researchers.
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