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Regional climate shifts caused by gradual global cooling in the Pliocene epoch

机译：在上新世时期全球逐渐变冷引起的区域气候变化

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摘要

The Earth's climate has undergone a global transition over the past four million years, from warm conditions with global surface temperatures about 3degreesC warmer than today, smaller ice sheets and higher sea levels to the current cooler conditions. Tectonic changes and their influence on ocean heat transport have been suggested as forcing factors for that transition, including the onset of significant Northern Hemisphere glaciation similar to2.75 million years ago, but the ultimate causes for the climatic changes are still under debate. Here we compare climate records from high latitudes, subtropical regions and the tropics, indicating that the onset of large glacial/interglacial cycles did not coincide with a specific climate reorganization event at lower latitudes. The regional differences in the timing of cooling imply that global cooling was a gradual process, rather than the response to a single threshold or episodic event as previously suggested. We also find that high-latitude climate sensitivity to variations in solar heating increased gradually, culminating after cool tropical and subtropical upwelling conditions were established two million years ago. Our results suggest that mean low-latitude climate conditions can significantly influence global climate feedbacks.
机译：在过去的四百万年中，地球的气候经历了全球性的转变，从温暖的条件（全球地表温度比今天升高了3摄氏度），更小的冰盖和更高的海平面到目前的更凉爽的条件。有人认为，构造变化及其对海洋热传输的影响是这一转变的推动因素，包括类似于275万年前的北半球显着冰期的开始，但气候变化的最终原因仍在争论中。在这里，我们比较了来自高纬度，亚热带地区和热带地区的气候记录，这表明较大的冰川/冰川间周期的发生与低纬度地区的特定气候重组事件不一致。降温时间的区域差异表明，全球降温是一个渐进过程，而不是如先前所建议的对单个阈值或事件的响应。我们还发现，高纬度气候对太阳采暖变化的敏感性逐渐提高，直到两百万年前确立了凉爽的热带和亚热带上升流条件后才达到顶峰。我们的结果表明，平均低纬度气候条件会显着影响全球气候反馈。

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