The period of the late Miocene Tortonian （11.61~7.25 Ma） was warmer and wetter than today， with atmospheric partial pressure of carbon dioxide （pCO₂） near the preindustrial level. Greenhouse climate under low pCO₂ was rare throughout the Cenozoic and understanding its mechanisms will help to better forecast the future climate. We summarized two hypotheses to elucidate this mechanism. One is the late Miocene climate-pCO₂ "decoupling hypothesis" based on geological records， and the other is "synergistic effects hypothesis" based on climate modeling. Geological records indicate that the late Miocene climate may not have been affected by pCO₂， that is， climate and pCO₂ were decoupled. Climate modeling results indicate that different vegetation and tectonic conditions in the late Miocene may have contributed to the global temperature increase. However， realistically， it is difficult to fully simulate the amplitude and pattern of the late Miocene warmth. Future work should focus on reconstructing pCO₂ records with high accuracy and resolution. Vegetation， clouds， water vapor feedback， and soil properties may be the dominant factors contributing to the late Miocene greenhouse climate， which should also be considered in future simulation work.