The timing of ice ages over the past ∼2,600 thousand years (kyr) follows pacing by cyclical changes in three aspects of Earth's orbit that influence the solar energy received as a function of latitude and season. Explaining the large magnitude of the climate changes is challenging, particularly so across the period of time from ∼1,250 to 750 ka—the Mid-Pleistocene Transition or MPT. The average repeat time of ice age cycles changed from an earlier 41-kyr rhythm to longer and more intense glaciations at a spacing of about 100 kyr. Explaining this change is very difficult because there was no corresponding change in the orbital pacing that would trigger a change in timing. While the first generation of hypotheses looked largely to changes in the behavior of Northern Hemisphere ice sheets, more recent work integrates ice behavior with new data capturing the evolution of other important aspects of past climate. A full explanation is still lacking, but attention increasingly focuses on the ocean carbon cycle and atmospheric CO2levels as the crucial agents involved in the MPT. ▪ The pattern of climate changes connected to the ice ages of the past few million years changed radically between about 1,250 and 750 thousand years ago, a time known as the Mid-Pleistocene Transition or MPT. ▪ While the glacial cycles were ultimately triggered by cyclical changes in Earth's orbit, the changes across the MPT came from changes in the Earth system itself, most likely in the form of a change in the carbon cycle. ▪ The dramatic change in many essential aspects of climate—ice volume, temperature, rainfall on land, and many others—in the absence of an external change suggests how important feedbacks are to the climate system.

中文翻译：

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中更新世气候转变

过去大约 2,600,000 年 (kyr) 的冰河时代的时间遵循地球轨道三个方面的周期性变化，这些变化影响着作为纬度和季节函数接收的太阳能。解释大规模的气候变化具有挑战性，特别是在大约 1,250 到 750 ka 的时期（中更新世过渡期或 MPT）。冰期周期的平均重复时间从早期的 41 kyr 节奏转变为间隔约 100 kyr 的更长、更强烈的冰川作用。解释这种变化非常困难，因为轨道节奏没有相应的变化来触发时间的变化。虽然第一代假设主要着眼于北半球冰盖行为的变化，但最近的工作将冰行为与捕捉过去气候其他重要方面演变的新数据结合起来。仍然缺乏完整的解释，但人们的注意力越来越集中在海洋碳循环和大气二氧化碳上2水平作为参与 MPT 的关键因素。 ▪ 与过去几百万年的冰河时代相关的气候变化模式在大约 1,250 至 75 万年前发生了根本性的变化，这一时期被称为中更新世过渡期 (MPT)。 ▪ 虽然冰川循环最终是由地球轨道的周期性变化引发的，但MPT 的变化来自地球系统本身的变化，最有可能以碳循环变化的形式出现。 ▪ 在没有外部变化的情况下，气候的许多基本方面（冰量、温度、陆地降雨量等）发生的巨大变化表明反馈对于气候系统有多么重要。