The predominant view attributes climate change to altered atmospheric radiative properties caused by greenhouse gases and aerosols. This paper proposes an additional thermodynamic framework, emphasizing the role of meridional (horizontal) energy transport between the tropics and poles. Because the greenhouse effect is strong in humid tropics and weak in dry polar regions, changes in poleward energy flux necessarily affect Earth’s total energy balance. Increased transport cools the planet; reduced transport warms it. Observations of late-1990s Arctic winter warming, unaccounted for by radiative models, align with this mechanism. Paleoclimate data further show stable tropical temperatures but large polar changes, implying that global climate depends mainly on the tropical–polar temperature gradient. This model also explains the strong effects of small Milanković orbital variations, suggesting that horizontal energy redistribution, rather than radiative forcing alone, governs the planet’s long-term climate dynamics.
