Abstract
Hydrogen (H(2)) will play a part in decarbonizing the global energy system(1). 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 H(2) use under future hydrogen economies(3,5). A comprehensive accounting of H(2) sources and sinks is essential for assessing changes and mitigating environmental risks. Here we analyse trends in global H(2) sources and sinks from 1990 to 2020 and construct a comprehensive budget for the decade 2010-2020. H(2) 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 H(2) production. Sinks also increased in response to rising atmospheric H(2). Estimated global H(2) 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 H(2), whereas East Asia and North America contributed the most H(2) emissions from fossil fuel combustion. We estimate that rising atmospheric H(2) 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 H(2) in future marker Shared Socioeconomic Pathway scenarios are estimated to remain within 0.01-0.05 °C, depending on H(2) usage, leakage rates and CH(4) emissions that influence photochemical H(2) production.