evidence: The third challenge is how hydrogen's warming impacts are calculated and reported. Beyond the general uncertainties associated with estimating the direct and indirect radiative effects of any atmospheric constituent, the way in which scientists typically report the radiative potency of a climate forcer (such as via radiative efficiency or radiative forcing) can be inaccessible to and lack context for climate policy and business decision makers. Therefore, decades ago, scientists began developing simplified metrics for comparing the warming impacts among different greenhouse gases, with the potency of CO2 typically being used as the baseline for the comparison given its status as the most concerning human-emitted climate forcer. The most well-known and widely used metric has consistently been the global warming potential (GWP) with a 100-year time horizon, and this metric is even baked into policies, international agreements, and greenhouse gas reporting requirements. The GWP metric calculates the relative warming effect over a specified time interval from a pulse of emissions of a climate forcer compared to an equal pulse in mass of CO2. [...] This amount of warming (∼0.1 ∘C) is also equal to the amount of warming projected in 2100 from carbon dioxide emissions from international shipping and aviation combined in the absence of climate action (Ivanovich et al., 2019). However, if leakage does not exceed 1 %, the temperature response could be an order of magnitude smaller.