Hydrogen study warns of a small climate problem

Hydrogen has long been promoted as a potential answer to the climate crisis. However, a study published on Wednesday warned that it may also contribute, albeit modestly, to the problem.

Supporters hope hydrogen can eventually be produced and used at scale in transport and heavy industry. As its use emits only water vapour, it is seen as a clean replacement for fossil fuels.

Hydrogen emissions and global warming

Research published in the journal Nature found that hydrogen has contributed to rising temperatures by allowing methane, a powerful greenhouse gas, to remain in the atmosphere for longer.

Between 1990 and 2020, hydrogen emissions increased and added a fraction of a degree - 0.02 °C - to the nearly 1.5 °C rise in average temperatures recorded since the pre-industrial era, according to the research.

"We need a deeper understanding of the global hydrogen cycle and its links to global warming to support a climate-safe and sustainable hydrogen economy," said Rob Jackson, a Stanford University scientist and the paper's senior author.

The study was carried out by the Global Carbon Project, an international consortium of scientists. It concluded that human activity is responsible for most of the growth in hydrogen emissions.

Researchers said the increase is associated with rising methane emissions from fossil fuels, livestock and landfill sites.

How hydrogen extends methane's effect

The two molecules are closely linked: methane generates hydrogen as it breaks down in the atmosphere.

Hydrogen is not itself a pollutant, but it contributes indirectly to warming because it absorbs natural detergents that would otherwise destroy methane. Methane is a potent greenhouse gas with a shorter atmospheric lifetime than carbon dioxide.

"More hydrogen means fewer detergents in the atmosphere, causing methane to persist longer and, therefore, warm the climate longer," said the study's lead author, Zutao Ouyang, an assistant professor of ecosystem modelling at Auburn University in Alabama.

Hydrogen's interaction with these natural detergents also influences cloud formation and leads to greenhouse gases including ozone and stratospheric water vapour.

Hydrogen production and leakage

Since 1990, other sources of atmospheric hydrogen have included leaks from industrial hydrogen production.

Hydrogen may be made through electrolysis, which uses an electric current to separate water into hydrogen and oxygen.

At present, though, most hydrogen is made from natural gas or coal through energy-intensive methods that release substantial quantities of carbon dioxide.

The aim is instead to produce "green" hydrogen at scale with renewable energy, but this remains costly and the industry has encountered considerable obstacles.

© Agence France-Presse