Current estimates of hydrogen’s climate impact are now sufficiently robust to inform policy and business decision-making, according to researchers in a new review article on the climate impacts of hydrogen emissions.  

Hydrogen is expected to be an important component of future low-carbon energy and industrial systems, particularly in sectors that are difficult to electrify, including heavy industry, long-distance transport and energy storage. As hydrogen use accelerates, understanding the climate impact of hydrogen emissions is becoming increasingly important. 

"Hydrogen can support the decarbonization of industry, transport and power, but the climate benefit depends on keeping hydrogen losses to the atmosphere as low as possible," said CICERO researcher Maria Sand, the lead author of the review. 

The review paper “Climate impacts of hydrogen emissions” was recently published in Nature Reviews Earth & Environment. The review was part of the CICERO-led HYway project funded by Horizon Europe. In addition to CICERO (Norway), Spark Climate Solutions (USA), Environmental Defense Fund (USA), LSCE-IPSL (France), University of Cambridge (UK), University of Edinburgh (UK), GFDL (USA) and University of California Irvine (USA) contributed to the review.  

Hydrogen can leak at every stage of the value chain. Additionally, hydrogen in the atmosphere arises from both natural and other anthropogenic sources. While not a greenhouse gas itself, hydrogen emitted into the atmosphere will chemically react and increase other greenhouse gases, such as methane, ozone and stratospheric water vapor, causing global warming.   

Translating these processes into policy-relevant measures of hydrogen’s climate impact requires the use of emission metrics that quantify warming over different time horizons.  

Estimates of the 100-year global warming potential of hydrogen are now converging on around 12 times that of co₂. Such metrics are now sufficiently robust to inform policy and business decision-making, according to the review. 

“Hydrogen has largely been considered environmentally benign. But as the science evolves and it is acknowledged that hydrogen has a global warming potential, including hydrogen’s climate impacts in assessments and climate accounting frameworks is key as hydrogen deployment scale up”, noted Sand.  

The review also highlights key sources of remaining scientific uncertainties that should be addressed to support the development of a sustainable hydrogen economy. Particularly, further research is needed on: 

• Improving quantification of hydrogen emissions across the value chain. 

• Better understanding of the role of the soil sink, which removes hydrogen from the atmosphere. 

• More complete representation of hydrogen chemistry in climate models.  

 Research in the HYway project is addressing key knowledge gaps highlighted in the review, particularly related to the soil sink and hydrogen chemistry. This research will contribute to more accurate assessments of hydrogen’s climate impacts and support policy and business decision-making on hydrogen use and scale-up to maximize the climate benefits of the hydrogen economy.   

The article in Nature Reviews Earth & Environment is available here.