evidence: 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. [...] This research has been supported by Robertson Foundation, the Heising-Simons Foundation, and ClimateWorks Foundation. [...] Rahn, T., Eiler, J. M., Boering, K. A., Wennberg, P. O., McCarthy, M. C., Tyler, S., Schauffler, S., Donnelly, S., and Atlas, E.: Extreme deuterium enrichment in stratospheric hydrogen and the global atmospheric budget of H2, Nature, 424, 915–918, https://doi.org/10.1038/nature01917, 2003.