Extended Data Fig. 1: Green hydrogen electrolysis capacity in 1.5 °C scenarios.

a-b, Institutional and corporate 1.5 °C scenarios. c-d, Integrated assessment model (IAM) scenarios. IAM scenarios from the IPCC AR6 Database⁵⁹ only include scenarios in category C1 (1.5 °C). IMP stands for illustrative mitigation pathway. IMP-LD focusses on demand, IMP-Ren on renewable energy, and IMP-SP on sustainable development. NGFS stands for Network for Greening the Financial System – a project that provides regularly updated IAM scenarios from different models⁶⁰. We exclude scenarios, which either always report zero green hydrogen, or which in any year from 2025 report a lower capacity than has already been realised in 2023. If scenarios do not report electrolysis capacity, we convert production quantities into corresponding electrolysis capacity, which implies uncertainties (see Methods). The scenarios show a very wide range, particularly in 2030, underlining the high uncertainty surrounding the green hydrogen market ramp-up. Furthermore, panels a and c show that unprecedented growth rates would be required to achieve the 1.5 °C scenarios in 2030 (apart from a few IAM scenarios that report limited use of green hydrogen in 2030). Figure 4a depicts the distribution of these two scenario groups in 2030. For the IAM scenarios, we are uncertain to what extent the different models explicitly represent the different hydrogen applications and whether hydrogen results have been vetted in detail. Therefore, in our analysis of required subsidies for 1.5 °C, we use the median of the institutional and corporate scenarios (see Supplementary Figure 11 and Supplementary Figure 13).