Department of Geosciences, University of Arizona, Tucson, AZ, USA.
Climate and Global Dynamics Laboratory, National Center for Atmospheric Research, Boulder, CO, USA.
Nature. 2021 Nov;599(7884):239-244. doi: 10.1038/s41586-021-03984-4. Epub 2021 Nov 10.
Climate changes across the past 24,000 years provide key insights into Earth system responses to external forcing. Climate model simulations and proxy data have independently allowed for study of this crucial interval; however, they have at times yielded disparate conclusions. Here, we leverage both types of information using paleoclimate data assimilation to produce the first proxy-constrained, full-field reanalysis of surface temperature change spanning the Last Glacial Maximum to present at 200-year resolution. We demonstrate that temperature variability across the past 24 thousand years was linked to two primary climatic mechanisms: radiative forcing from ice sheets and greenhouse gases; and a superposition of changes in the ocean overturning circulation and seasonal insolation. In contrast with previous proxy-based reconstructions our results show that global mean temperature has slightly but steadily warmed, by ~0.5 °C, since the early Holocene (around 9 thousand years ago). When compared with recent temperature changes, our reanalysis indicates that both the rate and magnitude of modern warming are unusual relative to the changes of the past 24 thousand years.
过去 24000 年的气候变化为了解地球系统对外部强迫的响应提供了关键的见解。气候模型模拟和代理数据已经独立地允许对这一关键时期进行研究；然而，它们有时会得出不同的结论。在这里，我们利用这两种类型的信息，使用古气候数据同化来制作第一个代理约束的、全领域的再分析，跨越末次冰盛期到现在，分辨率为 200 年。我们证明，过去 24000 年来的温度变化与两个主要的气候机制有关：冰盖和温室气体的辐射强迫；以及海洋翻转环流和季节性太阳辐射变化的叠加。与以前基于代理的重建相比，我们的结果表明，自全新世早期（约 9000 年前）以来，全球平均温度已经略微但稳定地变暖了约 0.5°C。与最近的温度变化相比，我们的再分析表明，现代变暖的速度和幅度与过去 24000 年的变化相比是不寻常的。
