Anthropogenic forcing has impacted precipitation variability in the North China Monsoon Marginal Region

The Asian Summer Monsoon (ASM) is a crucial driver of precipitation, sustaining ecological balance and socio-economic development in North China. However, the extent to which climate change has influenced this monsoonal system, leading to detectable and attributable modifications in precipitation regimes, remains unclear. Here, we present a robust annual precipitation reconstruction spanning 1770-2020, derived from tree-ring stable oxygen isotope data and a simple linear regression model in the North China Monsoon Marginal Region (NCMMR). Reconstructed precipitation and independent hydroclimatic records reveal a pronounced drying trend across the NCMMR since the 1950s. Multiple linear regression (MLR) modelling, water vapor transport analyses using ensemble means from the Community Earth System Model-Last Millennium Ensemble, and correlation analysis indicate that precipitation variability in the NCMMR is modulated by the Indian Ocean Dipole, El Niño-Southern Oscillation, Atlantic Multidecadal Oscillation, and Interdecadal Pacific Oscillation. Nevertheless, fingerprint analysis suggests that the observed precipitation decline since the 1950s is strongly associated with greenhouse gas concentrations, albeit partially offset by the effects of anthropogenic aerosol emissions and internal variability. The impact of greenhouse gas forcing on precipitation variability is expected to intensify in the coming decades.

亚洲夏季风（Asian Summer Monsoon, ASM）是降水的关键驱动因子，维系着中国华北地区的生态平衡与社会经济发展。然而，气候变化对这一季风系统的影响程度，以及其引发的降水格局可检测、可归因的改变，目前仍不明确。本研究基于中国华北季风边缘区（North China Monsoon Marginal Region, NCMMR）的树木年轮稳定氧同位素数据与简单线性回归模型，构建了覆盖1770-2020年的稳健年际降水重建序列。重建降水序列与独立水文气候记录均显示，自1950年代以来，华北季风边缘区出现了显著的干旱化趋势。多元线性回归（Multiple Linear Regression, MLR）建模、基于社区地球系统模型-过去千年集合模拟（Community Earth System Model-Last Millennium Ensemble）集合平均结果的水汽输送分析，以及相关分析均表明，华北季风边缘区的降水变率受印度洋偶极子、厄尔尼诺-南方涛动、大西洋多年代际振荡以及太平洋年代际振荡调控。然而，指纹检测分析显示，1950年代以来观测到的降水减少与温室气体浓度密切相关，尽管人为气溶胶排放与系统内部变率的影响部分抵消了这一效应。未来数十年内，温室气体强迫对降水变率的影响预计将进一步加剧。