Future global temperature impact of global aviation in ICAO scenarios

We model the global temperature change due to global aviation based on the recently developed International Civil Aviation Organization (ICAO) Long Term Aspirational Goal (LTAG) emissions scenarios. ICAO has produced four different “scenarios”, including a baseline scenario with frozen technology and three “integrated scenarios” with varying levels of in-sector CO2 reductions from technology and operational improvements and including different fuel mixes. Aviation activity leads to a mix of long-lived CO2 effects and several short-lived effects. Our analysis includes CO2, contrails/cirrus, NOx, water vapor, and black carbon. The non-CO2 emissions and activity are developed in this study to be consistent with each of the ICAO CO2 scenarios.

We combine these fuel and emission data with recent knowledge on radiative forcing, including uncertainties. By using the simple climate model CICERO-SCM, we model the change in global temperature until 2100 given the different scenarios. We will show how scenario range, uncertainty in RF, effect of background conditions, and uncertainties in other parameter choices impact the temperature calculations. For NOx, we include scenarios that account for the effect of background NOx emissions. We also compile CO2 emission aviation scenarios available in the literature from the past decade and compare these with ICAO’s.

Our results confirm the temperature impact of the aviation sector estimated by other studies, but also show large uncertainties. When accounting for the impact of aviation NOx being dependent on the background conditions, we find a large variation in global temperature change based on what SSP is used as background. While NOx emissions from aviation will likely grow according to the ICAO scenarios, global emissions of NOx are declining in the SSPs, making this issue important to study further. With a growing share of SAF and LH2 in the fuel mix, we also observe a large range in temperature impact accounting for the literature range on contrail formation for different types of fuels.

Our overarching study shows that better understanding is needed to more robustly estimate the climate impact of aviation, including estimating RF of non-CO2 and in going from aviation activity to RF from contrails for different types of fuels.