A multi-model assessment of the Global Warming Potential of hydrogen

With increasing global interest in molecular hydrogen to replace fossil fuels, more attention is being paid to potential leakages of hydrogen into the atmosphere and its environmental consequences. Hydrogen is not directly a greenhouse gas, but its chemical reactions change the abundances of the greenhouse gases methane, ozone, and stratospheric water vapor, as well as aerosols. Here, we use a model ensemble of five global atmospheric chemistry models to estimate the 100-year time-horizon Global Warming Potential (GWP100) of hydrogen. We estimate a hydrogen GWP100 of 11.6 +/- 2.8 (one standard deviation). The uncertainty range covers soil uptake, photochemical production of hydrogen, the lifetimes of hydrogen and methane, and the hydroxyl radical feedback on methane and hydrogen. The hydrogen-induced changes are robust across the different models. It will be important to keep hydrogen leakages at a minimum to accomplish the benefits of switching to a hydrogen economy. The 100-year Global Warming Potential of hydrogen falls in the range 11.6 +/- 2.8, according to chemistry-model estimates, through its chemical impact on methane, ozone and stratospheric water vapor. It is therefore important to avoid leakages in a hydrogen economy, to help mitigate climate change.

Automated summary

With increasing global interest in molecular hydrogen as a replacement for fossil fuels, the potential leakages of hydrogen into the atmosphere and its impact on greenhouse gases are receiving more attention. Using a model ensemble of five global atmospheric chemistry models, it is estimated that the 100-year Global Warming Potential (GWP100) of hydrogen is 11.6 +/- 2.8. The changes induced by hydrogen are consistent across different models. To fully benefit from the transition to a hydrogen economy, it is crucial to minimize hydrogen leakages.