Atmospheric H₂ variability over the past 1,100 years

Area of Science:

• Atmospheric Chemistry
• Paleoclimatology
• Green Energy Transition

Background:

• Anthropogenic hydrogen (H2) emissions are projected to increase with green energy adoption.
• Atmospheric H2, while not directly radiative, influences climate by altering methane, ozone, and water vapor concentrations.
• Long-term atmospheric records are crucial for understanding H2 biogeochemistry and climate impacts, but instrumental records are limited.

Purpose of the Study:

• To reconstruct a millennium-long record of atmospheric H2 using ice cores.
• To investigate historical H2 emissions and their relationship with climate change.
• To assess the sensitivity of H2 biogeochemistry to climate variations.

Main Methods:

• Analysis of atmospheric hydrogen (H2) concentrations from a Greenland ice core.
• Reconstruction of H2 levels spanning the past 1000 years.
• Comparison of H2 trends with historical climate events like the Little Ice Age.

Main Results:

• A 70-111% rise in atmospheric H2 from pre-industrial to modern times was observed.
• This increase correlates with rising fossil fuel emissions and H2 precursors.
• A 4-25% decrease in H2 levels during the Little Ice Age suggests climate sensitivity.

Conclusions:

• Ice core H2 records provide valuable long-term data on emissions and biogeochemical cycles.
• Atmospheric H2 levels have significantly increased due to anthropogenic activities.
• The sensitivity of H2 sources and sinks to climate warming warrants consideration in future climate projections.