CR2 Policy Brief: Hydrogen’s Impacts on the Climate System

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Rodrigo Seguel, Charlie Opazo y Lucas Castillo, researchers CR2

Editor: José Barraza, CR2 Science Communicator

  • Hydrogen causes methane, a greenhouse gas (GHG), to persist longer in the atmosphere, thereby contributing to enhanced global warming.
  • The chemical transformation of hydrogen generates increased quantities of ozone, another GHG significant to climate change.
  • Hydrogen degradation also produces water vapor in the lower stratosphere, resulting in surface-level warming.

Molecular hydrogen (H2) possesses high energy content compared to fossil fuels and can be utilized in modified internal combustion engines or through fuel cells (Staffell et al., 2019).(Staffell et al., 2019). H2 is obtained through electrolysis, a process where water molecules are split using electricity to produce hydrogen and oxygen gas..

Since 2020, interest in H₂ has increased significantly, particularly because its industrial production through electrolysis can be powered by renewable energy sources (Pétron et al., 2024). In northern Chile, this would primarily rely on solar panels, while in the south, wind turbines would be the main source. Thus, hydrogen emerges as a significant alternative for achieving national decarbonization and facilitating the global energy transition toward low-carbon consumption.

It should be noted that no known energy generation process is entirely environmentally benign. In the case of molecular hydrogen, the primary environmental impact from production, transport, and storage is associated with leaks, venting, and purging, with atmospheric emissions estimated to range between 1% and 12% (Patterson et al., 2021). Given that the hydrogen market is nascent in Chile, anticipating its impacts on the climate system is crucial to ensure its benefits outweigh potential negative effects.

Current State of Knowledge

Atmospheric molecular hydrogen can originate from both natural and anthropogenic sources. It can be produced through photochemical formation from methane and biogenic volatile organic compounds [1] biomass burning, and fossil fuel combustion, respectively (Paulot et al., 2024). The primary hydrogen sinks are microbial activity in soils and photochemical reactions involving the primary atmospheric cleaning agent (technically known as the hydroxyl radical). The atmospheric residence time of molecular hydrogen has been estimated at two years (Novelli et al., 2009).

Hydrogen is considered an indirect greenhouse gas with high global warming potential. The emission of 1 kg of hydrogen into the atmosphere will produce global warming equivalent to 11.6 kg of carbon dioxide (CO2) over a 100-year period (Sand et al., 2023). This climate system impact can be explained through three mechanisms:

  1. Molecular hydrogen and methane (the second most potent greenhouse gas) compete for the same atmospheric removal agent. Therefore, increased hydrogen abundance leads to longer atmospheric residence time for methane, resulting in enhanced global warming.
  2. The chemical destruction of hydrogen produces a highly reactive agent (technically known as the hydroperoxyl radical), whose subsequent reactions increase tropospheric ozone formation (the third most important greenhouse gas for climate change). This process is particularly significant in atmospheres with elevated nitric oxide levels, such as those found in South American megacities.
  3. Finally, molecular hydrogen degradation also produces water, whose impact in the troposphere is considered negligible. However, small changes in stratospheric water vapor, characterized by extreme dryness, affect atmospheric circulation patterns, resulting in surface-level warming.

Recent estimates indicate that atmospheric hydrogen abundance has increased by 70% compared to preindustrial levels due to anthropogenic activities (Patterson et al., 2021). Global observations also show hydrogen increases during the 2010-2019 period (Paulot et al., 2024). Furthermore, Figure 1 demonstrates an upward trend for hydrogen in remote areas of Chile (Rapa Nui) and Argentina (Ushuaia).

Figure 1. Molecular hydrogen trend in remote regions of the South Pacific (left) and Patagonia (right) based on monthly averages. In Rapa Nui and Ushuaia, an annual increase of approximately 2 nmol mol-1 is observed, representing a total accumulated increase of 18 nmol mol-1 over a decade. Measurements conducted by NOAA’s Global Monitoring Laboratory (USA).

Scientific and Technological Challenges

These findings initially suggest a potential underestimation of hydrogen emissions and the difficulties in estimating its global balance. They also highlight the scientific and technological challenges of this promising alternative to fossil fuels, whose climate benefits will depend on emission rates established as targets by industry, regulatory agencies, and society.

Recommendations
    1. Promote the development of new measurement technologies in the country to establish baselines and detect molecular hydrogen leaks.
    2. Anticipate hydrogen emission mitigation strategies throughout the entire value chain.
    3. Develop adaptation plans emphasizing molecular hydrogen’s feedback mechanisms with other gases and the geographical (physical) particularities of areas where new infrastructure will be located.
    4. Reduce information gaps related to global hydrogen balance and its indirect effects on the climate system to project the real impact associated with its mass adoption.
    5. Reduce emissions of methane, volatile organic compounds, and nitrogen oxides to maximize the benefits of hydrogen use.
    6. Improve hydrogen monitoring coverage in remote locations to decouple the upward trend from local impacts.
References

Novelli, P. C., Crotwell, A. M., & Hall, B. D. (2009). Application of gas chromatography with a pulsed discharge helium ionization detector for measurements of molecular hydrogen in the atmosphere. Environ Sci Technol, 43, https://doi.org/10.1021/es803180g.

Patterson, J. D., Aydin, M., Crotwell, A. M., Pétron, G., Severinghaus, J. P., Krummel, P. B., Langenfelds, R. L., & Saltzman, E. S. (2021). H2 in Antarctic firn air: Atmospheric reconstructions and implications for anthropogenic emissions. Proc Natl Acad Sci U S A, 118, https://doi.org/10.1073/pnas.2103335118.

Paulot, F., Pétron, G., Crotwell, A. M., & Bertagni, M. B. (2024). Reanalysis of NOAA H2 observations: implications for the H2 budget. Atmos. Chem. Phys., 24, 4217–4229, https://doi.org/10.5194/acp-24-4217-2024.

Pétron, G. B., Crotwell, A. M., Mund, J., Crotwell, M., Mefford, T., Thoning, K., Hall, B. D., Kitzis, D. R., Madronich, M., Moglia, E., Neff, D., Wolter, S., Jordan, A., Krummel, P., Langenfelds, R., and Patterson, J. D. (2024). Atmospheric H2 observations from the NOAA Global Cooperative Air Sampling Network, Atmos. Meas. Tech. Discuss. [preprint], https://doi.org/10.5194/amt-2024-4, in review.

Sand, M., Skeie, R. B., Sandstad, M., Krishnan, S., Myhre, G., Bryant, H., Derwent, R., Hauglustaine, D., Paulot, F., Prather, M., & Stevenson, D. (2023) A multi-model assessment of the Global Warming Potential of hydrogen. Commun Earth Environ, 4, https://doi.org/10.1038/s43247-023-00857-8.

Staffell, I., Scamman, D., Velazquez Abad, A., Balcombe, P., Dodds, P. E., Ekins, P., Shah, N., & Ward, K. R. (2019). The role of hydrogen and fuel cells in the global energy system, https://doi.org/10.1039/c8ee01157e

Notas

[1] Reacciones químicas en la atmósfera que incluyen absorción de radiación solar.