Comment on egusphere-2023-724

Abstract

<strong class="journal-contentHeaderColor">Abstract.</strong> Aviation emissions that are dispersed into the Earth's atmosphere affect the climate and air pollution, with significant spatiotemporal variation owing to heterogeneous aircraft activity. In this paper, we use historical flight trajectories derived from Automatic Dependent Surveillance&ndash;Broadcast (ADS-B) telemetry and reanalysis weather data for 2019&ndash;2021 to develop the Global Aviation emissions inventory based on ADS-B (GAIA). In 2019, 40.2 million flights collectively travelled 61 billion kilometres using 283 Tg of fuel, leading to CO₂, NO_X, non-volatile particulate matter (nvPM) mass and number emissions of 893 Tg, 4.49 Tg, 21.4 Gg, and 2.8&times;10²⁶, respectively. Global responses to COVID-19 led to reductions in the annual flight distance flown, CO₂, and NO_X emissions in 2020 (-43 %, -48 % and -50 %, respectively relative to 2019) and 2021 (-31 %, -41 % and -43 %, respectively) with significant regional variability. Short-haul flights with duration &lt; 3 h accounted for 83 % of all flights, yet only for 35 % of the 2019 CO₂ emissions, while long-haul flights with duration &gt; 6 h (5 % of all flights) were responsible for t43 % of CO₂ and 49 % of NO_X emissions. Globally, actual flight trajectories flown are, on average, ~5 % greater than the great-circle path between the origin-destination airport but this varies by region and flight distance. An evaluation of 8,705 unique flights between London and Singapore showed large variabilities in the flight trajectory profile, fuel consumption and emission indices. GAIA captures the spatiotemporal distribution of aviation activity and emissions and is provided for use in future studies to evaluate the negative externalities arising from global aviation.