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https://doi.org/10.5194/egusphere-2022-285
https://doi.org/10.5194/egusphere-2022-285
 
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19 May 2022
19 May 2022

The Climate Impact of Hypersonic Transport

Johannes Friedrich Pletzer1,2, Didier Hauglustaine3, Yann Cohen3, Patrick Jöckel1, and Volker Grewe1,2 Johannes Friedrich Pletzer et al.
  • 1Deutsches Zentrum für Luft- und Raumfahrt, Institut für Physik der Atmosphäre, Oberpfaffenhofen, Germany
  • 2Delft University of Technology, Kluyverweg 1, 2629 HS Delft, The Netherlands
  • 3Laboratoire des Sciences du Climat et de l’Environnement, LSCE-IPSL (CEA-CNRS-UVSQ), Université Paris-Saclay, 91191 Gif-sur-Yvette, France

Abstract. Hypersonic aircraft flying at Mach 5 to 8 are a means for travelling very long distances in extremely short times and even significantly faster than supersonic transport (Mach 1.5 to 2.5). Fueled with liquid hydrogen (LH2) their emissions consist of water vapour (H2O), nitrogen oxides (NOx) and unburnt hydrogen. If LH2 is produced in a climate- and carbon neutral manner, carbon dioxide does not have to be included when calculating the climate footprint. While H2O that is emitted near the surface has a very short residence time (hours) and thereby no considerable climate impact, super- and hypersonic aviation emit at very high altitudes (15 km to 35 km), with residence times of months to several years, and therefore the emitted H2O has a substantial impact on climate via high altitude H2O changes. Since the (photo-)chemical lifetime of H2O is largely decreasing at altitudes above 30 km via the reaction with O(1D) and via photolysis, one could speculate that H2O climate impact from hypersonics flying above 30 km becomes smaller with higher cruise altitude. Here we use two state-of-the-art chemistry-climate models and a climate response model to investigate atmospheric changes and respective climate impacts due to two potential hypersonic fleets flying at 26 km and 35 km, respectively. We show for the first time that the (photo-)chemical H2O depletion at high altitudes is overcompensated by a recombination of hydroxyl radicals to H2O and an enhanced methane depletion, leading to an increase in H2O concentrations. This results in a steady increase of the H2O perturbation lifetime of up to 4.41 ± 0.20 years at 35 km. We find a 0.083 ± 0.014 % and 0.16 ± 0.015 % depletion of the ozone layer and a 43.0 ± 4.8 Tg and 94.0 ± 4.5 Tg increase in stratospheric H2O due to the two hypersonic fleets flying at 26 km and 35 km respectively. Our calculations show that the climate impact of hypersonic transport is estimated to be roughly 8–20 times larger than a subsonic reference aircraft with the same transport volume (revenue passenger kilometers) and that the main contribution stems from H2O.

Journal article(s) based on this preprint

08 Nov 2022
| Highlight paper
The climate impact of hydrogen-powered hypersonic transport
Johannes Pletzer, Didier Hauglustaine, Yann Cohen, Patrick Jöckel, and Volker Grewe
Atmos. Chem. Phys., 22, 14323–14354, https://doi.org/10.5194/acp-22-14323-2022,https://doi.org/10.5194/acp-22-14323-2022, 2022
Short summary

Johannes Friedrich Pletzer et al.

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2022-285', Anonymous Referee #1, 16 Jun 2022
  • RC2: 'Comment on egusphere-2022-285', Anonymous Referee #2, 26 Jun 2022
  • RC3: 'Comment on egusphere-2022-285', Anonymous Referee #3, 01 Jul 2022
  • AC1: 'Comment on egusphere-2022-285', Johannes Pletzer, 08 Aug 2022
    • AC2: 'Reply on AC1', Johannes Pletzer, 15 Sep 2022

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2022-285', Anonymous Referee #1, 16 Jun 2022
  • RC2: 'Comment on egusphere-2022-285', Anonymous Referee #2, 26 Jun 2022
  • RC3: 'Comment on egusphere-2022-285', Anonymous Referee #3, 01 Jul 2022
  • AC1: 'Comment on egusphere-2022-285', Johannes Pletzer, 08 Aug 2022
    • AC2: 'Reply on AC1', Johannes Pletzer, 15 Sep 2022

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision
AR by Johannes Pletzer on behalf of the Authors (09 Aug 2022)  Author's response    Author's tracked changes    Manuscript
ED: Referee Nomination & Report Request started (10 Aug 2022) by Farahnaz Khosrawi
RR by Anonymous Referee #3 (25 Aug 2022)
ED: Publish subject to minor revisions (review by editor) (25 Aug 2022) by Farahnaz Khosrawi
AR by Johannes Pletzer on behalf of the Authors (15 Sep 2022)  Author's response    Author's tracked changes    Manuscript
ED: Publish subject to technical corrections (16 Sep 2022) by Farahnaz Khosrawi
AR by Johannes Pletzer on behalf of the Authors (03 Oct 2022)  Author's response    Manuscript

Journal article(s) based on this preprint

08 Nov 2022
| Highlight paper
The climate impact of hydrogen-powered hypersonic transport
Johannes Pletzer, Didier Hauglustaine, Yann Cohen, Patrick Jöckel, and Volker Grewe
Atmos. Chem. Phys., 22, 14323–14354, https://doi.org/10.5194/acp-22-14323-2022,https://doi.org/10.5194/acp-22-14323-2022, 2022
Short summary

Johannes Friedrich Pletzer et al.

Johannes Friedrich Pletzer et al.

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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.

Emissions from conventional aircraft contribute to climate change by forming contrails and by increasing atmospheric CO2 concentrations. To fly faster and reduce the climate impact, super- or hypersonic aircraft fuelled by liquid hydrogen or natural gas are being considered. Hypersonic aircraft would fly at more than Mach 4 in the stratosphere, up to 35 km altitude, where the peak of the ozone layer resides. The paper by Pletzer et al. presents a thorough study of the chemical and radiative impacts of such high-speed aircraft using two chemistry-climate models. The study shows that hypersonic aircraft fuelled by liquid hydrogen and cruising at such altitudes would contribute to a significant global warming although they do not emit CO2. The main radiative effect comes from additional water vapour, with only a small effect from depletion of the ozone layer. Importantly, the authors discovered that although water vapour is destroyed in the stratosphere, perturbation of local photochemistry also creates water vapour. The authors estimate that the mean surface temperature change caused by a hypersonic transport fleet would be roughly 8-20 times larger than for a subsonic reference aircraft with the same transport volume. This comprehensive study provides convincing calculations for a large climatic effect of any future hydrogen-fuelled hypersonic aircraft fleet.
Short summary
Very fast aircraft can travel very long distances in extremely short times and fly at high altitudes (15 km to 35 km). These aircraft emit water vapour, nitrogen oxides and hydrogen. Water vapour emissions remain months to several years at these altitudes and have an important impact on temperature on Earth. We investigate two aircraft fleets flying at 26 km and 35 km. Ozone is depleted more and the water vapour perturbation and temperature change are larger for the aircraft flying at 35 km.