Doubts cast over aviation sector’s ability to meet Paris Agreement goals

There is a high likelihood that the aviation sector will not be able to bring down its carbon emissions in line with Paris Agreement goals, a study has found.

Aviation contributes to climate change by creating carbon dioxide (CO2) as well as non-CO2 effects such as forming nitrogen oxides, ozone and contrail cirrus clouds.

The University of Birmingham team said that assuming the industry stages a post-Covid recovery, the climate impact of restrictions placed on global air travel will only be temporary. In addition, the non-CO2 effects will continue to make a major contribution to aviation’s climate impact over the coming years.

These effects are not included in the International Civil Aviation Organisation’s (ICAO) goal of climate-neutral growth and only partly addressed in Flightpath 2050 - the European Commission’s vision for aviation.

Although Flightpath 2050 emissions goals are likely to stabilise aviation’s climate impact, and ICAO’s offsetting scheme CORSIA will surpass the climate target set to support the Paris Agreement’s 1.5 °C goal between 2025 and 2064, the researchers warn that an increasing aviation-induced global warming effect is likely despite the implementation of a range of mitigation options within the sector.

Study co-author Dr Simon Blakey said: “Technological improvements to engines and airframes and operations won’t be enough to sufficiently reduce the impact of aviation on climate change. We must explore all mitigation options in parallel - including the increased use of sustainable fuels and market-based measures in order to limit aviation’s impact on the environment.

“Accounting for sustainable fuels must include the impact of non-CO2 emissions in use as well as the CO2 emissions in fuel production. If we base all our calculations on CO2 alone, we miss the large improvements in non-CO2 emissions that these fuels can offer, particularly in reducing particulate matter emissions which contribute to an increased warming effect at cruise conditions.”

There is currently significant interest in policies, regulations and research aiming to reduce aviation’s climate impact. The researchers modelled the effect of these measures on global warming, analysing potential technical improvements and challenging assumptions of sector targets with a number of scenarios up to 2100.

Their assessment also covered several Covid-19 recovery scenarios, including changes in travel behaviour, as well as including feasible technological advancements and the availability of sustainable aviation fuels.

In order to better understand the possible implications of the pandemic on the climate impact of aviation, the researchers assessed three different pathways for the international recovery from the lock-down of nation states and the associated dramatic reduction in air travel.

They took into account a fast recovery of three years, a slow recovery of 15 years and a change in habits due to experiences during the lock-down, for example, a shift towards web conferences instead of face-to-face meetings.

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