Danica Lombardozzi

replying to: Tian, J. et al. Nature https://doi.org/10.1038/s41586-026-10562-z (2026). In their Comment, Tian et al.1 argue that we overestimated tropical gross primary productivity (GPP)2. Here we address their concerns and demonstrate that the conclusions of our Article2 remain fully supported.

Abstract Hydrogen (H2) will play a part in decarbonizing the global energy system1. However, hydrogen interacts with methane, ozone, and stratospheric water vapour, leading to an indirect 100-year global warming potential of 11 ± 4 (refs. 2,3,4,5). This raises concerns about the climate consequences of increasing H2 use under future hydrogen economies3,5. A comprehensive accounting of H2 sources and sinks is essential for assessing changes and mitigating environmental risks.

Abstract Observations show an increase in the seasonal cycle amplitude of CO2 in northern latitudes over the past half century. Although multiple drivers contribute, observations and inversion models cannot quantitatively account for the factors contributing to the increased CO2 amplitude and older versions of Earth System Models (ESMs) do not simulate it.