A recent study published in Nature (December 2025) by an international team led by researchers from Stanford University and Auburn University provides the first comprehensive global hydrogen budget from 1990–2020. It highlights how rising atmospheric hydrogen levels contribute indirectly to climate warming, posing risks for the expanding hydrogen economy during the energy transition.

Atmospheric hydrogen concentrations have increased significantly since 1990, largely due to human activities. The primary driver is the oxidation of rising methane (CH₄) emissions from sources like fossil fuels, agriculture, and landfills — this alone added about 27 million tons of hydrogen annually by 2020.

Hydrogen itself is not a direct greenhouse gas, but it indirectly warms the climate by reacting with hydroxyl radicals (OH), the atmosphere’s “detergent.” This reduces OH availability, allowing methane (a potent greenhouse gas) to persist longer. Additional effects include increased tropospheric ozone, stratospheric water vapor, and influences on aerosols/clouds.

The study estimates hydrogen’s 100-year Global Warming Potential (GWP-100) at around 11 (±4), and 20-year GWP at 37 (±18) — meaning it’s roughly 11 times more warming than CO₂ over 100 years on a per-mass basis.

Over 2010–2020, rising hydrogen levels contributed about 0.02°C to global warming, a small but non-negligible amount comparable to the cumulative emissions impact of a country like France.

Soil bacteria absorb ~70% of hydrogen emissions, acting as a major sink, but rising levels still alter atmospheric chemistry.

Hydrogen is key for decarbonizing sectors like steel, shipping, and aviation. However, leaks across the value chain (production, storage, transport, use) could exacerbate indirect warming, especially short-term.

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From Blackout- News

Hydrogen is considered the engine of the energy transition, but hydrogen emissions can worsen the climate balance. The reason is methane degradation, because additional reactions change the chemistry of the atmosphere. At the same time, leaks along production, transport and storage remain a real weak point, and soil microbes act as a sink to determine the net effect (science: 17.12.25).

How hydrogen emissions slow methane degradation
Methane escapes from gas infrastructure, livestock farming and landfills, and it has a very strong effect on temperature in the first few years. Nevertheless, it usually disappears after ten to twelve years because hydroxyl radicals break it down in a chain of reactions. Experts summarize this process as methane degradation, and they measure it by the availability of these radicals. CH4 degradation produces water and carbon dioxide, but also hydrogen as a by-product.

Zutao Ouyang of Stanford University clearly describes the bottleneck because hydrogen requires the same reaction partners. “More hydrogen means less OH in the atmosphere, which means that methane persists longer and thus warms the climate for longer,” he explains. As a result, H2 releases shift the rate of degradation and methane degradation slows down. This indirect pathway makes hydrogen emissions relevant to climate policy, even though H2 itself absorbs hardly any thermal radiation.

Why infrastructure and control determine the benefits

Ouyang and his team have taken stock of the global hydrogen cycle from 1990 to 2020, and they wanted to bring sources and sinks to a sustainable scale. Robert Jackson formulates the goal as follows: “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,” he says. For the energy transition, therefore, it is not enough to look at final consumption, but rather the energy conversion in industry and grids.

Jackson also refers to a technical fact, because H2 escapes particularly easily. “Hydrogen is the smallest molecule in the world and easily escapes from pipelines, production plants and reservoirs,” explains Jackson.

Operators can reduce leaks, but they need measurement routines, material standards and fast repairs. Leaks cost efficiency, and at the same time they exacerbate the climate effect if more hydrogen is released into the air.

Soil processes determine how much H2 remains in the air

The study attributes the growing inflows to several drivers, and it explicitly mentions human activities. “H2 sources increased from 1990 to 2020, mainly due to the oxidation of methane and other anthropogenic volatile organic compounds, biogenic nitrogen fixation, and leakage in H2 production,” the research team reports. This produces more hydrogen, and at the same time changes the reaction conditions in the atmosphere.

On the sink side, soil microbes play the main role because they use H2 as an energy source. “The world’s most important way hydrogen is removed from the atmosphere is through microbes in the soil that use H2 for their energy production,” the researchers write. These soil bacteria work over a large area, and they react directly to the concentration. In this way, they partially buffer increases, but they do not completely close the balance.

Figures show where politics and technology can start

Between 2010 and 2020, an average of 69.9 million tonnes of hydrogen per year was released into the atmosphere, and the sinks reabsorbed a large part. This balance sheet counts for the energy transition because it makes the biggest levers visible. Soil microbes removed around 50 million tonnes, and chemical reactions removed another 18.4 million tonnes. Nevertheless, a gap of about 1.55 million tons remained, so the grade continued to rise. This trend is coupled to methane sources, and hydrogen emissions thus amplify the indirect warming effect. Leaks remain controllable if operators check consistently.

“We estimate that the increase in atmospheric H2 between 2010 and 2020 contributed to an increase in global surface air temperature of 0.02 degrees Celsius,” the team said. In practice, therefore, two things count, and both can be planned: networks must remain tight, and operators must find leaks quickly. At the same time, projects need robust sinks, because soil microbes only have a sufficient effect if soils remain intact. Hydrogen emissions must therefore be reduced, and the energy transition needs dense systems and stable soils.

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The global hydrogen budget

The global hydrogen budget | Nature

Hydrogen (H₂) has received increased attention as an energy carrier to help decarbonize heavy industry and transport and to provide long-duration energy storage¹. When produced by electrolysis with renewable energy, hydrogen can, in principle, be produced and consumed with near-zero carbon emissions. As a result, many energy-system scenarios project substantial growth in H₂ production and utilization this century^1,6.

At present, hydrogen production is energy- and greenhouse gas-intensive. More than 90% of hydrogen produced today is grey hydrogen, derived mainly from steam methane reforming or coal gasification, which are both carbon-intensive¹. In anticipated net-zero scenarios, however, a shift towards cleaner, low-carbon hydrogen production is projected^1,7. This transition encompasses both green hydrogen produced through electrolysis powered by low- or zero-carbon electricity, and blue hydrogen generated by reforming fossil fuels coupled with carbon capture and storage. Ultimately, green and blue hydrogen are projected to dominate hydrogen manufacturing by 2030–2040 (ref. ⁶).

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