Abstract

Hydrogen forms an important part of the UK’s plan to reach Net Zero by 2050, with potential to be used in heating, transport and power generation. A switch from fossil fuel to hydrogen has potential benefits for both climate and air quality, resulting from reductions in emissions of CO2 and other species co-emitted with CO2 including CH4 , CO and NOx (depending on whether H2 is combusted). However, there are also potential disbenefits arising from H2 leakage occurring during its production, transport and storage. Increases in H2 emissions could lead to an increase in the lifetime of methane, an important greenhouse gas, and changes in stratospheric composition that could influence stratospheric ozone recovery. The possible impact of H2 leakage and estimated changes to CH4 , CO and NOx emissions in a global hydrogen economy is explored using a combination of box modelling and simulations using a chemistry-climate model. We also derive a new GWP for H2, which is first to include the impact of changes in stratospheric composition.