The warming impact of hydrogen has been “overlooked” in projections of climate change, according to authors of the latest “global hydrogen budget”.
The study, published in Nature, is the most comprehensive analysis yet of the global hydrogen cycle, showing how the gas moves between the atmosphere, land and ocean.
Hydrogen has long been recognised as a clean alternative to fossil fuels and an important component of the green energy transition.
However, while hydrogen is not itself a greenhouse gas, rising emissions are “supercharging” the warming effect of methane, the authors say.
Increasing levels of atmospheric hydrogen have led to “indirect” warming of 0.02C over the past decade, the study finds.
The authors say that limiting leaks from future hydrogen fuel projects and rapidly cutting methane emissions will be key to securing benefits from hydrogen as a clean-burning alternative to oil and gas.
The international team of scientists behind the study also produce the annual “global carbon budget”, which saw its 20th edition published last month.
‘Supercharging’ methane
Hydrogen is the lightest and most abundant element in the universe. It is also an explosive gas that contains more energy per unit of weight than fossil fuels.
The gas has long been recognised as a clean alternative to fossil fuels, because it only emits water when burned.
There are many ways to produce hydrogen. It is typically generated in a carbon-intensive process that relies on fossil fuels. However, renewable energy can be used to produce “green hydrogen” with near-zero carbon emissions.
Hydrogen “indirectly” heats the atmosphere through its interactions with other gases. This warming is mainly due to interplay between hydrogen and methane – a potent greenhouse gas that is the second biggest contributor to human-caused global warming after CO2.
This interplay involves molecules in the atmosphere called hydroxyl radicals. These naturally occurring molecules are known as the atmosphere’s “detergents” because they react with certain greenhouse gases, such as methane, converting them into other compounds that do not warm the planet.
Prof Rob Jackson is a scientist at Stanford University and an author on the study. He explains that hydrogen also reacts with hydroxyl radicals, effectively “using up” these detergents and leaving less to react with methane.
This effectively “extends the lifetime” of methane in the atmosphere, Jackson tells Carbon Brief, leading to higher concentrations and greater warming.
There is also a reciprocal effect, where more methane in the atmosphere leads to more hydrogen. This occurs because methane reacts with oxygen in the atmosphere in a process called “oxidation”, which produces hydrogen.
Jackson tells Carbon Brief that interactions between hydrogen and methane have “not really been considered in climate circles”, adding:
“I think people don’t realise that the dominant source of hydrogen in the world today is methane in the atmosphere.”
Overall, the study estimates that increasing levels of hydrogen in the atmosphere led to global warming of 0.02C over 2010-20. This climate impact has been “overlooked”, the researchers say in a press release.
Jackson tells Carbon Brief that although this level of warming “looks fairly small”, it is still “comparable” to the warming caused by emissions of individual countries, such as France.
The hydrogen cycle
The global hydrogen budget brings together a range of observed data and models to quantify sources of hydrogen emissions as well as “sinks”, which absorb the gas from the atmosphere.
The authors find that hydrogen levels in the atmosphere increased from 523 parts per billion (ppb) in 1992 to 543ppb in 2020.
The graphic below shows the main sources (up arrows) and sinks (down arrows) of hydrogen over 2010-20.
As the figure shows, the largest single contributor to rising hydrogen emissions over 2010-20 is from the oxidation of human-produced methane. Methane emissions are on the rise due to human activity, such as from the fossil fuel industry, livestock and waste.
According to the study, 56% of atmospheric hydrogen over 2010-20 was caused by the oxidation of methane and non-methane volatile organic compounds (NMVOCs) reacting with oxygen to produce hydrogen.
(NMVOCs are chemicals that are released naturally from vegetation and more rapidly during wildfires. Human-produced emissions of NMVOCs – for example, from oil refineries or car tailpipes – are also on the rise, according to the study.)
The study also points to leakage from industrial hydrogen production as another driver of rising atmospheric hydrogen levels.
Jackson tells Carbon Brief that hydrogen leakage is on the rise “not because manufacturing is getting dirtier, but because we’re making more hydrogen from coal and natural gas”.
Hydrogen can also be produced as an unintentional byproduct from the combustion of fossil fuels. The study finds that these emissions of hydrogen are decreasing.
At the same time, natural sources of hydrogen emissions have not shown any increasing or decreasing trend over time, the authors say.
One of the largest natural sources of hydrogen is through “nitrogen fixing” – a chemical process in which nitrogen is converted into ammonia, which releases hydrogen as a byproduct. This process locks down nitrogen into the soil and ocean, where it is used by plants and algae to grow.
Meanwhile, hydrogen sinks have “increased in response to rising atmospheric hydrogen” over the past three decades, the study says.
Nearly three-quarters of the global hydrogen sink comes from hydrogen getting trapped in soil – for example, by microbes taking in hydrogen to use for energy, or hydrogen seeping into the soil through diffusion.
Dr Zutao Ouyang is an assistant professor at the University of Harvard and lead author on the study. He tells Carbon Brief that soil uptake is “the main mechanism removing hydrogen from the atmosphere”, but adds that it also has “the greatest uncertainty” because there is “not much long-term data” on this component of the hydrogen budget.
Mapped
Drawing on data including observational measurements and emissions inventories, the authors map the sources and sinks of hydrogen and their relative strength.
The maps below show the sources (top) and sinks (bottom) over 1990-2020, where darker colours indicate a stronger source or sink.
The largest “hotspots” for hydrogen emissions are in “south-east and east Asia”, according to the research. More widely, it says that “tropical regions” contribute about 60% of total hydrogen emissions.
The authors explain that these “hotspots” occur because the oxidation of methane and NMVOCs – processes that happen in the atmosphere and produce hydrogen as a byproduct – happen more quickly at higher temperatures.
They also find that these regions have more vegetation, which leads to higher NMVOC emissions.
For emissions related to human activity, east Asia and North America “contributed the most hydrogen emissions from fossil fuel combustion”, the study says, due to the “intensive fossil fuel use”.
Hydrogen emissions due to nitrogen fixation – when plants draw down nitrogen and release hydrogen as a byproduct – are highest in South America. The report links these emissions to the region’s “extensive cultivation” of crops such as soybeans and peanuts.
Dr Maria Sand is a senior researcher at CICERO and was not involved in the study. She tells Carbon Brief that the paper “provides a valuable and much-needed assessment of the global hydrogen budget”. She adds:
“By better constraining the sources and sinks of hydrogen, this study helps reduce the uncertainty in the climate impact [of hydrogen].”
Dr Nicola Warwick is a researcher at the National Centre for Atmospheric Science and assistant research professor at the University of Cambridge. She tells Carbon Brief that the study “provides an important update to our understanding of the atmospheric hydrogen budget by better constraining the key sources and sinks of hydrogen”.
She adds that better understanding of hydrogen uptake by soil – including how it responds to “climate-driven changes in soil moisture and temperature” – are “essential for reliably assessing the climate impacts of any future changes in hydrogen emissions”.
Study author Jackson tells Carbon Brief that he hopes the study will “prompt people to evaluate some of these emissions and sources and sinks in new ways and new places”.
Hydrogen economy
In the pursuit of net-zero, hydrogen may play an increasingly important role in the global energy system.
There are many ways to produce hydrogen gas. Most hydrogen is currently generated through a process called steam reforming, which brings together fossil gas and steam to produce hydrogen, with CO2 as a by-product.
According to the study, more than 90% of hydrogen produced today uses this “carbon-intensive” method.
However, electricity can be used to split water into hydrogen and oxygen atoms, in a process called electrolysis. If renewable energy is used, hydrogen can be produced and consumed with near-zero carbon emissions.
Hydrogen can be stored, liquified and transported via pipelines, trucks or ships. It can be used to make fertiliser, fuel vehicles, heat homes, generate electricity or drive heavy industry.
This potential hydrogen “economy” is shown in the graphic below. The illustrations, with numbered captions from one to three, show how hydrogen could be made, moved and used
The graphic below, from Carbon Brief’s explainer, illustrates the elements of a potential hydrogen economy.
Jackson tells Carbon Brief that, in his opinion, hydrogen is a “brilliant” choice to replace fossil fuels on-site, for industries such as steel manufacturing. However, he says he is “concerned” about “a hydrogen economy that distributes hydrogen around the world in millions of users”, because there is potential for lots of the gas to leak.
He adds:
“We know that methane leakage is bad. Hydrogen is a smaller molecule than methane. So wherever you have methane and hydrogen together, if methane leaks, hydrogen is likely to leak even more.”
The authors model hydrogen emissions under a range of future warming scenarios over the coming century.
They find that in “low-warming scenarios with high hydrogen usage”, methane emissions are low, limiting the formation of hydrogen via the oxidation of methane. In this instance, changes in atmospheric hydrogen levels depend strongly on leakage.
Meanwhile, in higher-warming scenarios, the authors find that hydrogen use is “relatively low”, but methane emissions remain “largely unmitigated”. In this instance, they find that the additional hydrogen formed through the oxidation of methane can outweigh hydrogen released through leaks.
Overall, the authors suggest that hydrogen could cause additional warming of 0.01-0.05C by the year 2100. Study author Zutao tells Carbon Brief that this additional warming was not included in the climate projections in the last assessment report from the Intergovernmental Panel on Climate Change.
The post Hydrogen emissions are ‘supercharging’ the warming impact of methane appeared first on Carbon Brief.
Hydrogen emissions are ‘supercharging’ the warming impact of methane
When oil and gas shipments stopped flowing through the Strait of Hormuz at the start of the Iran war, Southeast Asian nations were left reeling as the supply crunch laid bare their acute reliance on fossil fuel imports.
As prices soared, governments in the region scrambled to introduce emergency energy-saving measures – from a four-day working week to curbs on air conditioning. Thailand revived decommissioned coal plants while the Philippines, which imports nearly all of its oil, declared a “national energy emergency”.
But the crisis has also prompted renewed resolve to find a long-term solution to their vulnerability at a time when electricity demand is booming to power the region’s growing industry, cooling needs and the mushrooming of energy-hungry data centres.
At the heart of Southeast Asian nations’ response is a longstanding infrastructure project to connect the region’s power grids by 2045 and enable cross-border trading of clean electricity through a network of underground and subsea interconnectors.
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The plans will allow nations with high renewable energy generation potential to trade surplus power to their neighbours and major demand centres like Singapore, helping to integrate more renewables into the power mix and reduce reliance on fossil fuel imports.
“[It] will give us more energy security,” the Philippines’ energy secretary, Sharon Garin, told a press conference after a meeting of the Association of Southeast Asian Nations’ (ASEAN) energy ministers last week, when they discussed accelerating the delivery of the regional grid as part of measures to respond to the energy crisis.
“The Philippines is rich in solar power, Malaysia is rich in hydropower and Indonesia has geothermal: different countries have different resources. [The ASEAN Power Grid] will optimise the utilisation of renewables to the benefits of each member state,” said Garin.
But turning this decade-old political vision into a reality has been slow, held up by painstaking work to harmonise a patchwork of regulatory and legal frameworks and mobilise the private capital needed to build cross-border infrastructure.
More than $300 billion is needed to expand and modernise the region’s fragile grids to support the projected energy demand increase by 2050. This includes $27 billion required to deliver the cross-border interconnections by 2040, according to the International Energy Agency (IEA).
Every year of delay could cost the region billions of dollars in additional fuel costs and lock in new gas infrastructure for decades to come, according to analysis by global energy think-tank Ember.
The building block for energy security
With electrification high on the agenda of the COP31 climate talks in Türkiye next month, there is growing attention on the need to modernise and expand grid infrastructure to cope with growing electricity use and more renewables in the power mix.
Clean electrification and energy efficiency could deliver about a third of cumulative carbon emission reductions between 2026 and 2050, according to the International Renewable Energy Agency’s World Energy Outlook. But delivering that would require doubling annual global grid investment to $1 trillion between now and 2035.
Last month, the UN launched an initiative to accelerate investment into expanding and modernising grids in Southeast Asia and Africa.
First conceptualised in 1997, the ASEAN Power Grid has gained fresh impetus in recent years as countries turn to renewables to cut their emissions and move away from volatile fossil fuel markets.
Energy supply disruption caused by wars in Ukraine and the Middle East has strengthened the case for regional grid connections. Before this year’s conflict began, the Middle East accounted for 60% of Southeast Asia’s crude oil imports. Competition for fewer, more expensive oil and gas shipments has left Southeast Asia facing a $160 billion energy import bill this year. Based on current policies, this could rise to $400 billion by mid-century.
In the Philippines last week, energy ministers agreed on an enhanced planning framework to deliver the ASEAN Power Grid and made progress on regulatory guidelines.
Garin said ministers were considering accelerating the project’s delivery. “The first study was to connect [by] 2045 – that’s too far,” she said.
A strong business case
The economic benefits of the plan have “captured the political imagination” of leaders in the region, Robert Cooke, grids advocacy lead at the Global Renewables Alliance, told Climate Home News. “The business case is stronger than ever,” he said.
“If countries were to go about building their own separate grids, of course that would be an expensive endeavour. But the discussion around the ASEAN Power Grid includes what costs could we share in building out this grid,” added Tiza Mafira, director of the Indonesia office for the Climate Policy Initiative.
Stronger grids would help the region meet collective targets to increase the share of renewable energy in total primary energy supply from 14% to 30% and in installed power capacity from 34% to 45% by 2030.
Connecting and pooling dispersed renewable resources would also help smooth local power shortages caused by daily and seasonal variations, reducing the need for backup gas plants and battery storage.
The IEA found the ASEAN Power Grid could help unlock some of the 20 terawatts of untapped solar and wind potential across Southeast Asia – an amount around 55 times the region’s current total power capacity.
From lines on a map to shovels in the ground
Rather than building a single unified network, the ASEAN Power Grid is developing cross-border links between neighbouring countries and smaller groups of nations.
As of 2025, nine of 18 priority interconnection projects are operational – accounting for around 10 GW of capacity with an additional 13.7 GW planned by 2040.
Source: Ember
A power line channelling up to 200 MW of clean electricity generated from hydropower in Laos to Singapore via Thailand and Malaysia has emerged as a key building block for grid-to-grid trading.
Progress on technical discussions will also help provide the clarity the private sector needs to invest in bankable projects, said Cooke.
In 2025, the Asian Development Bank and the World Bank announced a dedicated funding initiative to support the project.
“The enabling pieces are emerging,” said Monalisa Dimalanta, former chair of the Philippine Energy Regulatory Commission and the National Renewable Energy Board. “But the timelines remain unclear and a 2045 vision cannot answer today’s emergency,” she said.
“A power grid… that exists only on paper will not keep the lights on.”
Singapore: the delivery test
The implications of failing to deliver the ASEAN Power Grid are most acute in Singapore.
Constrained by space, with few renewable energy resources and dependent on gas for more than 90% of its electricity mix, Singapore has emerged as a leading proponent of a regional power grid as it seeks to achieve net-zero emissions by 2050.
To meet its power needs, the city-state aims to import 6 GW of low-carbon electricity by 2035, around one-third of its energy demand – a target which it is set to miss, however.
The plans heavily rely on building interconnectors to import solar power from Indonesia across the South China Sea. Around 40% of the ASEAN Power Grid’s planned interconnections are directed towards Singapore.
Ember’s analysis found that delivering the planned interconnectors by 2035 could enable renewables to meet nearly half of Singapore’s electricity demand. Delays could drop this to only a fraction of the country’s needs, and risk locking in new gas capacity until the 2050s. Without the ASEAN Power Grid, Singapore would need to install an additional 300 MW of gas-fired power capacity to bridge the gap by 2035.
Already home to the largest data centre capacity in Southeast Asia, Singapore’s electricity demand keeps rising, driven by the boom in AI infrastructure. “At one point, [it] either has to build a new gas plant, or it has to get the interconnection to supply that demand,” Lam Pham, an Ember energy analyst and the report’s author, told Climate Home News.
A region at a crossroads
With capital increasingly available, political will is now the biggest risk standing in the way of timely execution, said Pham.
But there are other challenges too, including the lack of frameworks on transmission tariffs and how to share the benefits of clean power trading. “It’s really hard to justify projects without that,” he said.
In addition, climate-fuelled weather events, including extreme heat and tropical storms, pose major threats to the region’s grid infrastructure. Experts say stronger grid interconnection can isolate damage and build the system’s resilience.
Efforts to deliver on the ASEAN Power Grid also come as ministers stressed the “continued importance of oil and gas” for economic development and seek to secure fossil fuel supplies and stockpile oil to prepare for the next crisis.
Despite an acceleration of renewable deployment, particularly solar, coal still generates nearly half the electricity supply in ASEAN member states and dominates the power mix in Indonesia, the Philippines and Vietnam, while Singapore and Thailand rely on gas.
While these measures might help the region with the immediate crisis, “the long-term answer is more domestic renewable energy, electrification, storage, efficiency and regional power trade”, Dimalanta said.
Main image: An aerial view of the MTerra solar project in the Philippines, set to become one of the world’s largest solar-and-battery developments (Photo by Ezra Acayan