荷兰乌得勒支大学 Baxter, A. J. 和 Verschuren, D. 及其团队在研究非洲之角全新世温度-湿度关系的逆转中有新见解。相关论文发表在2023年8月9日出版的《自然》杂志上。

研究人员使用来自Chala湖(肯尼亚和坦桑尼亚)沉积物记录的有机地球化学气候替代数据，来探测过去大约 75000 年间水文气候和温度之间联系的稳定性。它们涵盖了足够宽的温度范围，以测试该时间域中气候变化的“干燥变得更干燥，潮湿变得更潮湿”典型。研究发现，在 11700 年前的全新世开始前后，在较冷的末次冰期，非洲最东部有效湿度和温度之间的正关系转变为负关系，当时大气二氧化碳浓度超过百万分之二百五十，年平均温度接近现代值。

因此，在那个时候，季风降水和大陆蒸发之间的收支平衡跨越了一个临界点，温度对蒸发的积极影响大于它对降水的积极影响。研究结果表明，在持续人为变暖的情况下，非洲之角可能会经历进一步的干旱，这突出了改进热带水文循环中动力和热力学过程模拟的必要性。

据悉，人为气候变化预计将严重影响全球水文循环，特别是在以农业为基础的经济依赖季风降雨的热带地区。在非洲之角，近几十年来更频繁的干旱条件，与预测降水量将随着气温升高而增加的气候模型形成对比。

附：英文原文

Title: Reversed Holocene temperature–moisture relationship in the Horn of Africa

Author: Baxter, A. J., Verschuren, D., Peterse, F., Miralles, D. G., Martin-Jones, C. M., Maitituerdi, A., Van der Meeren, T., Van Daele, M., Lane, C. S., Haug, G. H., Olago, D. O., Sinninghe Damst, J. S.

Issue&Volume: 2023-08-09

Abstract: Anthropogenic climate change is predicted to severely impact the global hydrological cycle, particularly in tropical regions where agriculture-based economies depend on monsoon rainfall. In the Horn of Africa, more frequent drought conditions in recent decades contrast with climate models projecting precipitation to increase with rising temperature. Here we use organic geochemical climate-proxy data from the sediment record of Lake Chala (Kenya and Tanzania) to probe the stability of the link between hydroclimate and temperature over approximately the past 75,000years, hence encompassing a sufficiently wide range of temperatures to test the ‘dry gets drier, wet gets wetter’ paradigm of anthropogenic climate change in the time domain. We show that the positive relationship between effective moisture and temperature in easternmost Africa during the cooler last glacial period shifted to negative around the onset of the Holocene 11,700 years ago, when the atmospheric carbon dioxide concentration exceeded 250 parts per million and mean annual temperature approached modern-day values. Thus, at that time, the budget between monsoonal precipitation and continental evaporation crossed a tipping point such that the positive influence of temperature on evaporation became greater than its positive influence on precipitation. Our results imply that under continued anthropogenic warming, the Horn of Africa will probably experience further drying, and they highlight the need for improved simulation of both dynamic and thermodynamic processes in the tropical hydrological cycle.

DOI: 10.1038/s41586-023-06272-5

Source: https://www.nature.com/articles/s41586-023-06272-5