As António Guterres concludes his tenure as United Nations Secretary General in September 2026, he offers a final, unflinching reckoning with humanity's response to the climate crisis he made the moral center of his leadership. For years he pressed governments and corporations toward urgency, framing global warming not as one concern among many but as the thread running through every other instability the world faces. His departure arrives at a hinge moment — one where the choices of the coming years will echo across decades — and his parting words carry the particular gravity of a witness who