Global Carbon Project Scientists Develop a Global Hydrogen Budget from Natural and Anthropogenic Sources, Including Atmospheric Oxidation of Methane and VOCs

     I will first note that global budgeting of chemical elements is notoriously difficult and often involves high margins of error. It is similar for the global budgeting of hydrogen. Some of these same scientists have developed a global methane budget previously and were responsible for helping to prove that most of the recent increases were from natural systems like wetlands, as well as anthropogenic systems, which include agriculture. Landfills, coal mines, oil facilities, natural gas facilities, biomass burning, wildfires, bioenergy facilities, and both natural and anthropogenic wetlands. In that study, they concluded that “85% of CH4 emissions growth during 2007–2020 was due to increased microbial emissions.” While natural gas facilities like pipelines, wells, and processing facilities are often seen as the major contributors, in actuality, they make up just less than 5% of total methane emissions. Oil facilities make more methane emissions, about 8.5% of total emissions. Even coal mines release more methane than natural gas facilities, about 6.9% of total emissions. These numbers come from IEA data.

     The authors point out that hydrogen is the universe’s smallest molecule and thus has a tendency to leak. Hydrogen consumes natural detergents in the atmosphere that destroy methane, which means it makes methane emissions more potent and longer-lasting. Hydrogen in the atmosphere also increases other greenhouse gases, such as ozone and stratospheric water vapor, and affects cloud formation. Atmospheric hydrogen consumes OH radicals, a crucial methane sink.

"The biggest driver of hydrogen increase in the atmosphere is the oxidation of increasing atmospheric methane," said Jackson, the Michelle and Kevin Douglas Provostial Professor at Stanford. Since 1990, the authors estimate the annual emissions from this source of hydrogen has grown by about 4 million tons, to 27 million tons per year in 2020.”

"The best way to reduce warming from hydrogen is to avoid leaks and reduce emissions of methane, which breaks down into hydrogen in the atmosphere."

     The authors note that the global surface average H2 concentration increased from 523.4 ppb in 1992 to 543.5 ppb in 2020, a 3.8% increase. As can be discerned from the graph below, the largest factor involved in the overall increase over the three decades was determined to be the increase from the oxidation of methane.

     The authors caution that these emissions need to be taken into account when evaluating the benefits of hydrogen economies. I also note that the paper’s lead author and the Chair of the Global Carbon Project, Stanford’s Rob Jackson, is regarded by many as a controversial author. I will reproduce here what I wrote about him in my post about the source of recent atmospheric methane being found to be predominantly microbial:

“The lead author of the paper, Rob Jackson of Stanford University, is also the chair of the Global Carbon Project. I have criticized his work in the past, erroneously suggesting that stray methane in some water wells in the region producing gas from the Marcellus Shale in Northeastern Pennsylvania came from the Marcellus reservoir. This was proven false by carbon isotope analysis, as the gas was identified as coming from minor gas reservoirs just below freshwater aquifers. I also criticized his recent work in targeting natural gas stoves as dangerous since his experiments showed emissions of NOx and other components in small, confined, non-ventilated conditions that did not reflect real-world conditions. Based on these and some of his other statements about fracking and methane issues, and the ability of his research to draw media attention, I have regarded him as an activist-biased scientist and tend to take his conclusions with a grain of salt.”

     One of the big changes that the paper proposes is an increase in photochemical hydrogen production in the atmosphere via methane and VOC oxidation. Increases in hydrogen production leakage were also noted. The increased estimate for H2 produced by atmospheric oxidation represents an increase of nearly 45% from previous estimates. This is a pretty big estimated increase. Thus, I think that confirmation should be sought in subsequent studies, better in my opinion, to be done by other researchers.

“H2 is produced in the atmosphere through the photolysis of formaldehyde (HCHO) (ref. 17). HCHO is produced by the oxidation of CH4 and NMVOCs by OH, with yields affected by levels of NOx gases. Previous estimates of production from CH4 oxidation range from 15 Tg yr−1 to 27 Tg yr−1 (refs. 21,23,28), but earlier studies either did not report uncertainties or disclosed much larger uncertainties (≥±8 Tg yr−1) (refs. 17,21) than ours (± 3.5 Tg yr−1). We estimate a relatively higher average rate of 26.1 ± 3.5 Tg H2 yr−1 for this source (Supplementary Table 2), primarily attributable to increasing atmospheric CH4.”

     Regionally, as can be seen below, most of the sources and half of the sinks are in tropical regions.

“…tropical regions contribute the largest share (about 60%) of the total amount of emissions and production (Fig. 3a). This result is attributable to the combination of higher temperatures in the tropics promoting CH4 and NMVOC oxidation, abundant plant biomass that leads to relatively high biogenic NMVOC emissions, and frequent tropical fires. Although the distribution of H2 sinks is more uniform across non-desert and non-frozen lands globally, tropical regions still account for the largest sink (around 50% of the global total).”

     They also note that due to a lack of mobile or portable instruments that can quantify H2 concentrations in air as can be quantified for methane with existing instruments, there is a general lack of empirical data for hydrogen emissions. They note that emissions from geologic seeps, pipeline leakage, and vegetation have yet to be fully quantified. For instance, vegetation is both a source and a sink. 

     While the paper proposes a significant potential increase in atmospheric H2's ability to increase global warming, there are still high margins of error. According to the Global Hydrogen Budget graphic, the margin of error for sources is 13.5%, and the margin of error for sinks is 26.5%. These are high margins, and further understanding is likely to adjust those numbers, perhaps significantly. Some future emissions scenarios are given in the graphic below. 

References:

 

Overlooked hydrogen emissions are heating Earth and supercharging methane, research finds. Science X staff. Phys.org. December 17, 2025. Overlooked hydrogen emissions are heating Earth and supercharging methane, research finds

The global hydrogen budget. Zutao Ouyang, Robert B. Jackson, Marielle Saunois, Josep G. Canadell, Yuanhong Zhao, Catherine Morfopoulos, Paul B. Krummel, Prabir K. Patra, Glen P. Peters, Fraser Dennison, Thomas Gasser, Alexander T. Archibald, Vivek Arora, Gabriel Baudoin, Naveen Chandra, Philippe Ciais, Steven J. Davis, Sarah Feron, Fangzhou Guo, Didier Hauglustaine, Christopher D. Jones, Matthew W. Jones, Etsushi Kato, Daniel Kennedy, …Andy Wiltshire. Nature volume 648, pages616–624 (December 17, 2025). The global hydrogen budget | Nature

Understanding methane emissions. Global Methane Tracker 2024. International Energy Agency. Understanding methane emissions – Global Methane Tracker 2024 – Analysis - IEA