New research indicates that the levels of molecular hydrogen in the atmosphere have surged due to human activity. The research analyzed air samples trapped in drilled cores of Antarctica's ice, revealing that atmospheric hydrogen had increased by 70% over the 20th century.
While recent air pollution laws have aimed to curb fossil fuel emissions, hydrogen emissions have continued to rise with no signs of slowing down, possibly due to leakage. Molecular hydrogen is a natural component of the atmosphere and a byproduct of fossil fuel combustion, especially from automobile exhaust and biomass burning.
Although hydrogen does not trap heat in the atmosphere alone, it can indirectly impact the distribution of methane and ozone, the two most important greenhouse gases after carbon dioxide. The sources and sinks of atmospheric hydrogen are rarely studied, and there is no good estimate of how much humans have emitted since industrial times.
The news is not good. It turns out that we may have been significantly underestimating our hydrogen emissions, and some tailpipe emissions have been mitigated in recent years using catalytic converters, which ideally would have seen hydrogen emissions decrease or even plateau. However, hydrogen levels have continued to rise in the atmosphere almost uninterrupted.
Prior research has also shown a consistent rise in hydrogen between 2000 and 2015, distinct from trends in other forms of exhaust pollution. Regarding human-caused emissions, hydrogen emissions are mostly thought to come from automobile exhaust, but hydrogen leakage from industrial processes is rarely considered. Researchers estimate that a 10% leakage rate between 1985 and 2005 would account for roughly half the rise in recent hydrogen emissions.
If green hydrogen processes, which split hydrogen from water to create carbon-free power, are scaled up, they could also result in substantial leakage. This is not a new worry, as it is a concern that scientists have pointed out for years. If hydrogen leaks from industrialized hydrogen gas plants, experts are troubled it could increase the lifetime of methane in our atmosphere, a greenhouse gas 20 times more potent than carbon dioxide.
However, researchers estimate that even with a small percentage of leaks, a global hydrogen economy would likely have far lower climate impacts than our existing fossil fuel-based energy system.