The Hidden Hydrogen Climate Impact: Leakage Risks 0.05°C Warming

Rising atmospheric hydrogen drove a global surface air temperature increase of 0.02 ± 0.006°C between 2010 and 2020. This specific metric challenges the assumption of neutrality. The study analyses global trends from 1990 to 2020, identifying a specific hydrogen climate impact derived from indirect atmospheric chemistry. Hydrogen reacts with hydroxyl radicals, the atmosphere's primary detergent. By depleting these radicals, hydrogen extends the atmospheric lifetime of methane. It further influences ozone and stratospheric water vapour. The result is a global warming potential (GWP) 11 ± 4 times that of carbon dioxide over a century.

Assessing the Hydrogen Climate Impact

This is an accounting problem with thermal consequences. Researchers constructed a comprehensive budget for the 2010–2020 decade to understand the flux.

• Sources: Averaged 69.9 Tg yr^-1. Increases were driven by methane oxidation, anthropogenic volatile organic compounds, and industrial leakage.
• Sinks: Averaged 68.4 Tg yr^-1. Soil uptake and atmospheric oxidation rose in response to higher H₂ concentrations.

Regional Disparities
Geography dictates the emission profile. The data identifies Africa and South America as the hosts of the largest total sources and sinks. Conversely, East Asia and North America lead in emissions linked specifically to fossil fuel combustion. This distribution suggests that mitigation strategies must be tailored to regional industrial profiles.

Future Implications
Modelling suggests that under future Shared Socioeconomic Pathway scenarios, the temperature impact will remain between 0.01°C and 0.05°C. The variance depends entirely on human efficiency: leakage rates and concurrent methane control. While hydrogen aids decarbonisation, the data implies that sloppy infrastructure could introduce a warming penalty. Efficiency is not just economic; it is environmental.