Drivers of the Earth’s interhemispheric temperature gradient through the Phanerozoic Eon

The interhemispheric temperature gradient (ITG) is a pivotal factor in shaping Earth’s climatic spatial patterns, modulating the position of tropical rain belts and global atmospheric circulation. Based on an ensemble of Phanerozoic climate model simulations, this study reveals that the long-term evolution of the ITG at tectonic time scales is primarily governed by hemispheric asymmetry in continental configuration. Fixed-CO 2 sensitivity experiments demonstrate that paleogeographic evolution alone can drive 5°C–8°C of ITG variability, predominantly by governing interhemispheric energy partitioning through its control on surface albedo and thermal inertia. In contrast, variations in atmospheric CO 2 concentration exert a modulating and amplifying influence on the background state, with their effects becoming particularly pronounced when coupled with specific continental configurations. Energy budget decomposition further identifies the difference in surface downwelling longwave radiation as the dominant energetic component of ITG variation, with shortwave radiation absorption and sensible and latent heat fluxes providing integrated modulation. This work elucidates the prevailing mechanisms and energetic pathways that govern ITG evolution on geological time scales, thereby providing mechanistic insights and modeling evidence to facilitate comprehension of the long-term development of spatial heterogeneity in the global climate system. 南北半球温度梯度 (ITG) 通过调控热带雨带位置与全球大气环流, 是塑造地球气候空间格局的关键因素.本研究基于多套显生宙气候模拟数据揭示, ITG在构造时间尺度上的长期演变主要受控于海陆分布的半球性不对称.固定CO₂的敏感性试验表明, 仅古地理演变即可驱动5–8°C的ITG变化, 其通过调控地表反照率与热惯性主导半球间能量分配;而大气CO₂浓度的变化则扮演背景依赖性的调制与放大角色, 其效应在与特定海陆分布耦合时尤为显著.能量收支分解进一步表明, 地表向下长波辐射差异是ITG变化的主导能量项, 短波辐射吸收及感热,潜热通量起综合调制作用.本研究从地质时间尺度厘清了ITG演变的主导机制与能量学路径, 为理解全球气候系统空间分异的长期演化提供了机制性见解与模拟证据.