International Aviation

Critically Insufficient4°C+
Highly insufficient< 4°C
Insufficient< 3°C
2°C Compatible< 2°C
1.5°C Paris Agreement Compatible< 1.5°C
Role model<< 1.5°C


In 2013, the ICAO Assembly set an aspirational goal of carbon neutral growth for international aviation from 2020 (ICAO, 2013a). Carbon neutral growth means that net CO2 emissions from international aviation will remain constant compared to the baseline – which is currently set at the average of emissions in 2019-2020 (paragraph 11, ICAO Assembly, 2016). Due to COVID-19, aviation emissions in 2020 will be substantially lower than anticipated. This means that, under the current rules, the baseline for carbon neutral growth would be lower than anticipated and the target stronger, assuming that the international aviation sector rebounds to pre-COVID-19 levels in the next few years. However, the International Air Transport Association (IATA) - the trade organisation for airlines – requested the ICAO Council to adjust the baseline calculation method and take 2019 emissions as the reference year (IATA, 2020a).

The ICAO Council will discuss the baseline from 8 to 26 June 2020. Member States of the European Union have indicated they will support an adjustment of the baseline rules to reflect 2019 emissions (Council of the European Union, 2020). As emissions in 2020 were expected to be higher than in 2019, this would mean that the target would be slightly more ambitious than previously anticipated, but not as ambitious as using the actual 2019-2020 average. At the time of writing this assessment, it is uncertain what decision ICAO will take, although we consider it very likely that the organisation will amend the rules. We have therefore taken a range for the baseline. Emissions in 2019 form the upper bound and average emissions in 2019 and 2020 the lower bound – assuming 2020 emissions are 60% lower than 2019 emissions (based on (IATA, 2020b; ICAO, 2020b)). We calculated 2019 emissions to be 641Mt and average 2019-2020 emissions to be 449Mt.

We rate the target of carbon neutral growth from 2020 as ‘critically insufficient’. Under our rating methodology, the upper end of the target range in 2030 alone would be rated ‘highly insufficient’. Because the international aviation sector plans to rely on emission units and alternative fuels that are unlikely to deliver sufficient real emission reductions, we downgrade the rating to ‘critically insufficient’. If average emissions in 2019 and 2020 would form the baseline, and 2020 emissions are 60% lower than in 2019, the 2030 target emission levels would fall in the ‘2˚C compatible’ range. The CAT would downgrade this rating to ‘insufficient’ for the reasons mentioned above.

Further, a significant shortcoming of ICAO’s approach is that the target of carbon neutral growth covers only CO2 and not non-CO2 emissions and respective effects – such as NOX and contrail cirrus. In its Fourth Assessment Report, the Intergovernmental Panel on Climate Change (IPCC) reported that warming effects from NOX emissions and contrails are two to four times greater than those of CO2 – even without considering the potential impact of cirrus cloud enhancement (IPCC, 2007). Researchers have estimated that aviation – domestic and international – may have contributed as much as 4.9% to global radiative forcing in 2004, whereas aviation only emitted 2-3% of global CO2 emissions that year (Owen, Lee and Lim, 2010). Efforts to reduce the climate impact from international aviation must include the full scope of climate effects and aim to bring all emissions to zero.

To be Paris-compatible, emissions from international aviation should be below 300 Mt in 2030 and decrease to zero by 2060. The carbon neutral growth goal is insufficient to reach these required emission levels.

Impact of COVID-19 on the CORSIA baseline

Under current rules, average 2019-2020 emissions determine the CORSIA baseline. However, because of the impact of COVID-19, IATA requested the ICAO Council adjust the baseline calculation method and take 2019 emissions as the reference year (IATA, 2020a).

Researchers found that if ICAO agrees to use 2019 emissions as its baseline, aircraft operators would face limited to no offsetting obligations in CORSIA’s pilot phrase. If the rules remain unchanged, COVID-19 will not substantially change the offsetting requirements that airlines face under the scheme because the lower baseline and lower future emissions cancel each other out (Schneider and Graichen, 2020).

Our results are consistent with those findings. As can be inferred from the graph, emissions from international aviation will remain below average 2019-2020 emissions until 2022 – in the fast recovery scenario - and 2024 – in the slow recovery scenario. Airlines will therefore face no to very limited offsetting obligations under CORSIA in the pilot phase (as CORSIA applies on a route-basis, it is possible that airlines will face some offsetting obligations on specific routes). On the longer term, however, offsetting obligations would be likely be larger than previously anticipated.

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