Holocene dust storm data from Lake Gonghai, northern China.

Asian dust storms have long been a major environmental concern in China, affecting the lives of about one billion people. However, it is unclear whether the mechanisms responsible for Asian dust storms during the Holocene varied on different timescales, and thus it is unclear whether there was a shift from a natural forcing to an anthropogenic forcing of dust storms. We reconstructed a high-resolution Holocene record of dust storms from the sediments of an undisturbed alpine lake on the Chinese Loess Plateau. We found that Asian dust storm activity generally increased during the Holocene, with the largest fluctuations occurring during the past 2000 years. The increase in dust storm activity was in contrast to the decrease in East Asian winter monsoon (EAWM) intensity during the Holocene, indicating that the EAWM played a limited role in modulating dust storms. By contrast, the increase in dust storms corresponded to a decrease in East Asian summer monsoon (EASM) precipitation. This demonstrates that EASM precipitation was the dominant control of dust storm activity on a millennial timescale, because decreased EASM precipitation expanded the desert area and thus increased the dust storm activity. The increasing intensity of human activity in the region since the Bronze Age resulted in an acceleration of dust storm activity against the background of decreased EASM precipitation. As human disturbance continued to intensify, beginning at least at ~2 cal ka BP, increased dust storms were closely linked to increasing human populations in the dust source regions, and there is a strong temporal coherence between increased dust storms and higher EASM precipitation. This was completely different from when natural processes dominated, when fewer dust storms occurred during periods of a strengthened EASM. Therefore, there was a shift from a natural forcing to an anthropogenic forcing of dust storms on a multi-decadal to centennial timescale, and was a mode in which “human activity overtook the EASM as the dominant control of the Earth surface system”.

亚洲沙尘暴长期以来都是中国首要的环境忧患，影响了约10亿民众的生产生活。然而，目前学界尚未明确全新世（Holocene）期间驱动亚洲沙尘暴的机制是否在不同时间尺度上存在分化，因此也无法确认沙尘暴的驱动因子是否已从自然强迫转向人类活动强迫。本研究基于中国黄土高原上一处未受干扰的高山湖泊的沉积物，重建了一套高分辨率的全新世沙尘暴活动记录。研究结果显示，全新世时期亚洲沙尘暴活动整体呈增强趋势，其中过去2000年的波动幅度最为显著。沙尘暴活动的增强与全新世期间东亚冬季风（East Asian winter monsoon, EAWM）强度的衰减形成显著反向对应关系，这表明东亚冬季风对沙尘暴活动的调控作用较为有限。与之形成鲜明对比的是，沙尘暴活动的增强恰好对应东亚夏季风（East Asian summer monsoon, EASM）降水的减少。这一结果证明，在千年时间尺度上，东亚夏季风降水是调控沙尘暴活动的主导因子：东亚夏季风降水减少会导致沙漠面积扩张，进而推高沙尘暴活动强度。自青铜时代（Bronze Age）以来，该区域人类活动强度持续提升，在东亚夏季风降水减少的背景下进一步加速了沙尘暴活动的增强态势。至少从距今约2 cal ka BP开始，随着人类干扰程度不断加剧，沙尘暴活动的增强与沙尘源区的人口增长呈现紧密关联，且沙尘暴活动增强与东亚夏季风降水升高之间存在显著的时间一致性。这与自然过程主导的时期完全相悖：在自然主导阶段，东亚夏季风增强时沙尘暴活动反而会减弱。因此，在数十年至百年的时间尺度上，沙尘暴的驱动因子确实已从自然强迫转变为人类活动强迫，形成了“人类活动取代东亚夏季风成为地球表层系统主导调控因素”的演化模式。