Hydrogen is often hailed as a clean, alternative energy source capable of powering industries, homes, and infrastructure while helping decarbonize the global energy system. But a new study suggests the path to a hydrogen-powered future may be more complicated than expected.

 

Scientists caution that hydrogen (H₂), while not a greenhouse gas itself, interacts with methane, ozone, and water vapor in the atmosphere in ways that can indirectly warm the planet—potentially negating its environmental benefits.

 

A study co-led by Auburn University researcher Zutao Ouyang and published today in Nature stresses that a climate-safe “hydrogen economy” will require deeper scientific understanding of the global hydrogen cycle.

 

“This indirect warming raises concerns about the climate consequences of potential hydrogen leakage, and highlights that the climate benefits of a future hydrogen economy will depend on minimizing leakage through the hydrogen value chain and reducing natural gas (methane) emissions,” said Ouyang, assistant professor of ecosystem modeling in Auburn’s College of Forestry, Wildlife and Environment.

 

Unlike carbon dioxide or methane, hydrogen does not trap heat on its own. But in interactions with other atmospheric gases, it heats the atmosphere roughly 11 times faster than CO₂ over the first 100 years, and about 37 times faster during the first 20 years after release.

 

To study the potential impacts, Ouyang teamed up with the Global Carbon Project to develop the first comprehensive global accounting of hydrogen sources and sinks, revealing how hydrogen leaks and human methane emissions influence the atmosphere.

 

“The team collected direct measurements of hydrogen in the atmosphere, along with the most comprehensive ever data collection and modeling to estimate the major sources and sinks of hydrogen and produce a first-of-its-kind global picture,” said Pep Canadell, executive director of the Global Carbon Project and chief research scientist at CSIRO Environment, Australia.

 

The study, titled The Global Hydrogen Budget, was co-led by Ouyang and Rob Jackson, a Stanford University professor and chair of the Global Carbon Project, with contributions from researchers across 30 institutions in France, Australia, China, Japan, the UK, Norway, and Austria.

 

The researchers found that since hydrogen production ramped up 30 years ago, atmospheric hydrogen has risen about 70% from preindustrial levels through 2003, stabilized briefly, and then began increasing again around 2010. Much of this increase comes from leakage in hydrogen production—but also from the oxidation of methane emissions, a less well-known source.

 

“Methane (CH₄) emissions — especially from fossil fuel extraction, distribution and use — have an important, but often under-appreciated, influence on atmospheric hydrogen,” the study notes. 

 

“Methane and hydrogen share the same pathway by which they are cleaned (oxidized) in the atmosphere, and because methane oxidation itself produces hydrogen, this creates feedback that can raise atmospheric hydrogen concentrations when methane emissions increase; further competing for the detergent that cleans the atmosphere from methane.”

 

“The largest source of hydrogen in the world is the oxidation of methane in our atmosphere,” Jackson said. “But methane and hydrogen also compete for atmospheric cleansing detergents. This competition extends methane's lifecycle in the presence of hydrogen, thereby increasing indirect climate warming. More hydrogen means more methane, and more methane means more hydrogen.”

 

Although current climate effects remain relatively small, researchers warn these complex interactions could undermine hydrogen’s climate benefits.

 

“By quantifying the previously unaccounted warming feedback between hydrogen and methane that are missing in current climate projections, we hope to improve future climate scenarios and support decision-makers in minimizing both economic losses and climate risks associated with hydrogen leakage,” Ouyang said.