Impact of climate variabilities on trans-oceanic flight times and emissions during strong NAO and ENSO phases

Abstract

This study investigates the impact of the North Atlantic Oscillation (NAO) and El Niño Southern Oscillation (ENSO) on trans-oceanic round-trip flight times and consequent CO2 emissions over the north Atlantic and eastern Pacific regions. For three strongest winter periods of both polarity during 1979–2016, daily mean wind data are used to compute the wind-optimal flight trajectories at cruising altitudes. Results show that intensified upper-level jet streams during the +NAO winters provide stronger headwinds for westbound flights between the eastern US and the western Europe. This causes 4.24 ∼ 9.35 min increase in an averaged total round-trip journey time during the +NAO compared to −NAO winters. In the eastern Pacific region, the jet stream is extended eastward towards the southwestern US during the +ENSO period, which lengthens the travel time for westbound flights between Hawaii and the west coast of the US. The increase in travel time of westbound flights is greater than the corresponding decrease in travel time for eastbound flights, resulting in a 5.92 ∼ 8.73 min increase of the averaged total round-trip time during the +ENSO compared to the −ENSO periods. Extrapolating these results to overall trans-oceanic air traffic suggests that aircraft will take a total of 1908 ∼ 4207 (888 ∼ 1309) extra hours during the +NAO (+ENSO) than the −NAO (–ENSO) winters over the North Atlantic (Eastern Pacific) regions, requiring 6.9 ∼ 15 (3.2 ∼ 4.7) million US gallons of extra fuel burned at a cost of 21 ∼ 45 (9.6 ∼ 14) million US dollars and 66 ∼ 144 (31 ∼ 45) million kg of extra CO2 emissions to all trans-oceanic traffic. In +ENSO and +NAO winters, the chances of a given flight having a slower round-trip flight time with more fuel burn and CO2 emissions are 2–10 times higher than in a −ENSO or −NAO winter. These results have significant implications for the planning of long-term flight routes with climate variability.