Fig. 1. Tangled hydrogen (H2) and methane (CH4) budgets.
Sketch of H2 and CH4 tropospheric budgets and their interconnections: (1) the competition for OH; (2) the production of H2 from CH4 oxidation; (3) the potential emissions [minimum-maximum] due to a more hydrogen-based energy system. Flux estimates (Tg/year) are from refs. 11,18. Arrows are scaled with mass flux intensity, CH4 scale being 10 times narrower than H2 scale. On a per-mole basis, H2 consumes only around 3 times less OH than CH4. ppq = part per quadrillon (10−15). a top-down estimate including also minor atmospheric sinks (<10%). b range obtained as a difference between total and fossil fuel emissions18.