Climate Implications of Hydrogen Deployment Considering Changes in Emissions From Direct and Indirect Forcers

Abstract Hydrogen could help to decarbonize hard‐to‐electrify end uses in future energy systems. While increased hydrogen production, transmission, distribution, and use may lead to an increase in hydrogen emissions, both greenhouse gas (GHG) and non‐GHG emissions could decline as hydrogen displaces incumbent fuels and energy carriers. The full suite of potential climate forcing changes from hydrogen deployment has not been fully examined, in part because it requires combining information from different fields. This study addresses this gap by using a well‐known integrated assessment model (the Global Change Analysis Model) to combine (1) credible hydrogen deployment scenarios that illustrate which fuels and energy carriers could be displaced by hydrogen; (2) information about emissions of hydrogen and other forcers by technology, sector, region, and time; and (3) a simple climate model capable of translating relevant emissions into changes in radiative forcing. Across all scenarios considered, when compared to a scenario without expanded hydrogen deployment, reduced forcing from lower CO 2 emissions is larger than other forcing changes by 2050 even after accounting for hydrogen and other indirect forcers. Forcing attributable to methane emissions may increase or decrease depending on how much hydrogen is produced with natural gas and how much natural gas is displaced as a fuel. Lastly, the net forcing change from changes in emissions of the indirect forcers CO, NOx, NMVOC, and H 2 , including their impact on methane's lifetime, is always small and in most cases negative at midcentury. These findings raise important questions for technology assessment regarding the treatment of indirect forcers and aerosols.