The global hydrogen budget

Hydrogen (H₂) will play a part in decarbonizing the global energy system¹. However, hydrogen interacts with methane, ozone, and stratospheric water vapour, leading to an indirect 100-year global warming potential of 11 ± 4 (refs. ^2-5). This raises concerns about the climate consequences of increasing H₂ use under future hydrogen economies^3,5. A comprehensive accounting of H₂ sources and sinks is essential for assessing changes and mitigating environmental risks. Here we analyse trends in global H₂ sources and sinks from 1990 to 2020 and construct a comprehensive budget for the decade 2010-2020. H₂ sources increased from 1990 to 2020, primarily because of the oxidation of methane and anthropogenic non-methane volatile organic compounds, biogenic nitrogen fixation, and leakage from H₂ production. Sinks also increased in response to rising atmospheric H₂. Estimated global H₂ sources and sinks averaged 69.9 ± 9.4 Tg yr^-1 and 68.4 ± 18.1 Tg yr^-1, respectively, for 2010-2020. Regionally, Africa and South America contained the largest sources and sinks of H₂, whereas East Asia and North America contributed the most H₂ emissions from fossil fuel combustion. We estimate that rising atmospheric H₂ between 2010 and 2020 contributed to an increase in global surface air temperature (GSAT) of 0.02 ± 0.006 °C. GSAT impacts of changing atmospheric H₂ in future marker Shared Socioeconomic Pathway scenarios are estimated to remain within 0.01-0.05 °C, depending on H₂ usage, leakage rates and CH₄ emissions that influence photochemical H₂ production.