Hydrogen is an Indirect Greenhouse Gas
Here’s a paper giving details of how hydrogen, while not a greenhouse gas itself, affects the concentrations of other greenhouses gases:
(Caution: it’s a PDF, so depending on your browser settings, it may download to a directory on your computer rather than opening in a new tab on your browser.)
I think it’s probably well researched, but I’m inclined to think that the Conclusions are more accurate than the Introduction, and that the introduction may have been written by a more senior and more sceptical author, who hadn’t really been involved in the work and had read the conclusions hurriedly without actually taking in the meaning properly.
This from the Introduction:
The conclusion reached is that unless the leakage of hydrogen from any future hydrogen economy is carefully controlled, there may be little improvement in global warming from the replacement of fossil fuel based energy systems.
seems at odds with this from the Conclusions:
If a global hydrogen economy replaced the current fossil fuel-based energy system and exhibited a leakage rate of 1% then it would produce a climate impact of 0.6% of the current fossil fuel based system. If the leakage rate were 10%, then the climate impact would be 6% of the current system. Careful attention must be given to reduce to a minimum the leakage of hydrogen from the synthesis, storage and utilisation of hydrogen in a future global hydrogen economy if the full climate benefits are to be realised in comparison to fossil fuel-based energy systems.