Hydrogen can be used to produce water. Its image is that of clean fuel. The engineers who will operate our future energy systems are being warned.

The UK government launched its hydrogen strategy in 2021, providing a plan to get a hydrogen economy up and running in the next 15 years.

The first problem for engineers is that burning hydrogen isn't the only way to make water. The pollution from burning fossil fuels could continue.

Hydrogen leak is the second problem. The global warming potential of hydrogen is 11 times greater than that of carbon dioxide.

Hydrogen does not have an effect on climate. Other pollutants are affected by it.

Methane, the second most important global warming gas, would stay in our air for longer and have more impact because of increased hydrogen in our air.

The amount of ozone in our atmosphere could be changed by more hydrogen. Climate-warming gas is the third most important. Ozone is harmful to our health and attacks plants.

Increased hydrogen would change the amount of water in the atmosphere and affect the weather.

Our home boilers and the start up and shut down of the turbine are likely to cause hydrogen leaks. It is possible that hydrogen will leak from pipe networks where it will be mixed with fossil methane to make hydrogen-powered villages and towns.

The co-author of Air Quality and Climate Change: the basics said that hydrogen could be used in a low-carbon economy.

Methane emissions from the gas distribution network are underestimated. With time, they are getting worse.

The gas industry in the UK has no idea what the natural gas leak rate is, so why do we expect it to be different? It's possible that hydrogen could be problematic.

It is clear from the government's reports that burning hydrogen instead of fossil fuels will be climate beneficial but, regardless of how hydrogen is made, maximising the climate benefits will require hydrogen leaking.