Reappraising the timing and spatial pattern of the Little Ice Age in China: full-field insights from the Last Millennium Climate Reanalysis Project version 2.1

Abstract

Site-specific and regionally-composited temperature reconstructions confirmed the presence of the Little Ice Age (LIA) in certain areas of China over the last millennium. However, a country-wide view of the LIA in China is still lacking, leading to ongoing debates about whether the LIA was a coherent, nationwide cold period. This study addresses this gap by analyzing the timing and spatial pattern of the LIA across China using the Last Millennium Climate Reanalysis. Key findings include: China experienced broadly cold conditions during the last millennium, but the LIA onset was notably asynchronous, in contrast to the near-synchronous termination of the LIA across China. Peak cooling occurred at different times in various regions, e.g., the 13th century in most of southern China, the 18th century in the eastern and western parts of the Qinghai-Tibet Plateau, and the 19th century in other areas. Generally, the magnitude of peak cooling increased with latitude. EOF analysis suggests the first mode accounts for 68.53 % of the total variance in temperature variability during 1200-1900 AD and indicates spatial consistency in temperature variability during this period. Weakening solar irradiance since the late 12th century is identified as the primary driver of these variations. The second mode explains 15.05 % of the total variance and reveals a north-south dipole pattern. Teleconnection factors such as the North Atlantic Oscillation and the Atlantic Multidecadal Oscillation significantly influence this mode. However, various monsoon systems across northern and southern China may play more important roles in this mode. The third mode accounts for 5.56 % of the total variance and displays tri-pole pattern (north-center-south), largely influenced by variations in the Pacific Decadal Oscillation, volcanic eruptions, and greenhouse gases. These findings provide full-field insights into the spatiotemporal characteristics of the LIA in China and enhance our understanding of this historical climate event.