全球地表年平均温度纬向平均数据集（40Ma）

始新世时，南北纬45°之间的温度关于赤道对称，在南北半球高纬度带（纬度大于45°），温度的纬向平均随纬度的梯度不一样：在北半球，温度的梯度先较大，但在纬度大于67.5°N处，温度开始缓慢下降；在南大洋上，表面温度梯度较小，所以比北半球同纬度上的温度高，但在南极大陆上，温度随纬度而迅速降低，南极中心温度低达244K（-32℃）。

During the Eocene epoch, temperatures between 45° north and 45° south were symmetric with respect to the equator. At high latitudes of both hemispheres (latitudes greater than 45°), the zonal mean temperature gradients as a function of latitude differed. In the Northern Hemisphere, the temperature gradient was initially steeper, but began to decline slowly at latitudes above 67.5°N. Over the Southern Ocean, the sea surface temperature gradient was weaker, resulting in higher temperatures at equivalent latitudes compared to the Northern Hemisphere. Conversely, over the Antarctic continent, temperatures decreased rapidly with increasing latitude, with the central Antarctic temperature reaching as low as 244 K (-32°C).