Abstract Anthropogenic emissions of hydrogen (H2) are expected to rise if H2 energy technology is widely implemented as part of the green energy transition1,2. Although atmospheric H2 is not radiatively active, it warms the Earth’s climate through chemical effects on methane, ozone and water vapour1,2,3,4,5,6. Predicting the atmospheric response to anthropogenic perturbations is challenging, in part because of the limited duration of the modern instrumental record7.