Global warming potential (GWP) for hydrogen: Sensitivities, uncertainties and meta-analysis

In this study, a two-dimensional chemistry-transport model (TROPOS) has been employed to examine the sensitivity of the global warming potential (GWP) for H2 to the size of the additional emission pulse, the time-of-year in which it was added to the model, its spatial distribution and the time width of the pulse. In addition, the sensitivities of the GWP for H2 to the assumptions made in the base case concerning the surface uptake and OH oxidation sinks for H2 were examined. Quantitative descriptions of these sensitivities were then used to adjust the five literature GWP estimates and reconcile them onto a common basis using reference values for each sensitivity. By this means, the range of published GWP estimates in the five literature studies has been significantly narrowed from 3.3–12.8 to 7.1–9.3 over a 100-year time horizon. However, a consideration of the 2 – σ confidence limits of the reconciled TROPOS GWPs, showed that is likely that there was no statistically significant difference between the reconciled GWP estimates and hence the best estimate of the GWP for H2 was 8 ± 2 over a 100-year time horizon.