Atmospheric History of H2 Over the Past Century Reconstructed From South Pole Firn Air

Molecular hydrogen (H2) is an abundant and reactive constituent of Earth's atmosphere, with links to climate and air quality. Anthropogenic emissions of H2 are expected to rise as the use of H2 as an energy source increases. Documenting past variations in atmospheric H2 will help to validate cu...

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Bibliographic Details
Published in:Geophysical research letters 2020-07, Vol.47 (14), p.n/a
Main Authors: Patterson, J. D., Aydin, M., Crotwell, A. M., Petron, G., Severinghaus, J. P., Saltzman, E. S.
Format: Article
Language:English
Subjects:
20th century
Air pollution
Air pollution measurements
Air quality
Anthropogenic factors
Atmosphere
Atmospheric methane
Biogeochemistry
Burning
Climate
Earth atmosphere
Emission measurements
Emissions
Firn
Fossil fuels
Fuel combustion
Human influences
Hydrogen
Natural gas
Oxidation
Photochemical reactions
Photochemicals
Photochemistry
South Pole
Trace gases
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Summary:Molecular hydrogen (H2) is an abundant and reactive constituent of Earth's atmosphere, with links to climate and air quality. Anthropogenic emissions of H2 are expected to rise as the use of H2 as an energy source increases. Documenting past variations in atmospheric H2 will help to validate current understanding of the global H2 budget. The modern instrumental record begins in the 1980s; there is little information about atmospheric H2 prior to that time. Here, we use firn air measurements from a 2001 South Pole campaign to reconstruct atmospheric H2 levels over the 20th century. Inversion of the measurements indicates that H2 over South Pole has increased from 350–540 ppb from 1910–2000. A biogeochemical box model indicates that the atmospheric burden of H2 increased by 37% over that time. The rise in H2 is consistent with increasing H2 emissions from fossil fuel combustion and increasing atmospheric production from methane oxidation. Plain Language Summary Hydrogen (H2) is an atmospheric trace gas with both natural and anthropogenic sources. In the atmosphere, photochemical reactions of H2 can contribute to air pollution and influence climate. Future use of hydrogen as a possible replacement for fossil fuels will likely lead to increased emissions and atmospheric levels. Here we use measurements of hydrogen in South Pole firn air to reconstruct atmospheric hydrogen levels over the 20th century. We find that atmospheric H2 increased by about 40% over that time. This increase is consistent with estimates of emissions of hydrogen and hydrogen precursors from fossil fuel burning. Key Points South Pole firn air was used to reconstruct atmospheric levels of H2 during the 20th century H2 levels at South Pole increased from 340 to 540 ppb from 1910 to 2000 The increase in atmospheric H2 is consistent with increasing anthropogenic emissions and methane oxidation
ISSN:0094-8276
1944-8007
DOI:10.1029/2020GL087787