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 economies3,5. 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.