Sensitivity of climate effects of hydrogen to leakage size, location, and chemical background

The use of hydrogen as an energy carrier and reactant in metal production can reduce carbon dioxide emissions by replacing fossil fuel usage. When hydrogen is used, some hydrogen will leak during production, storage, transport, and end use. Via OH-induced reactions in the atmosphere, the hydrogen will enhance methane, ozone, and stratospheric water vapour in the atmosphere and hence will increase the radiation imbalance. A recent multi-model study found the global warming potential over a 100-year time horizon (GWP100) for hydrogen to be 11.6±2.8 (1 standard deviation). Here, we use a chemistry transport model to investigate the sensitivity of GWP100 to the magnitude and the location of the hydrogen emission and the chemical composition of the background atmosphere. We show that the hydrogen GWP100 is independent of the size of the emission perturbation; is not dependent on where emissions occur, except for sites far from soil sink active areas; and is not very different for possible future chemical compositions of the atmosphere. The methane GWP100 increases by up to 3.4 for different future atmospheric compositions compared to the present day. Overall, the changes in the hydrogen GWP100 are within 1 standard deviation of the multi-model GWP100, except for emission perturbations at two distant sites not relevant for a future hydrogen economy. Therefore, when assessing emissions at different locations or for a future with a different atmospheric composition compared to the present day, it is not necessary to adjust the multi-model GWP values.