Urban F E, Cole J E, Overpeck J T
Department of Geological Sciences/INSTAAR, University of Colorado, Boulder 80309, USA.
Nature. 2000 Oct 26;407(6807):989-93. doi: 10.1038/35039597.
Today, the El Niño/Southern Oscillation (ENSO) system is the primary driver of interannual variability in global climate, but its long-term behaviour is poorly understood. Instrumental observations reveal a shift in 1976 towards warmer and wetter conditions in the tropical Pacific, with widespread climatic and ecological consequences. This shift, unique over the past century, has prompted debate over the influence of increasing atmospheric concentrations of greenhouse gases on ENSO variability. Here we present a 155-year ENSO reconstruction from a central tropical Pacific coral that provides new evidence for long-term changes in the regional mean climate and its variability. A gradual transition in the early twentieth century and the abrupt change in 1976, both towards warmer and wetter conditions, co-occur with changes in variability. In the mid-late nineteenth century, cooler and drier background conditions coincided with prominent decadal variability; in the early twentieth century, shorter-period (approximately 2.9 years) variability intensified. After 1920, variability weakens and becomes focused at interannual timescales; with the shift in 1976, variability with a period of about 4 years becomes prominent. Our results suggest that variability in the tropical Pacific is linked to the region's mean climate, and that changes in both have occurred during periods of natural as well as anthropogenic climate forcing.
如今，厄尔尼诺/南方涛动（ENSO）系统是全球气候年际变化的主要驱动因素，但其长期行为却鲜为人知。仪器观测显示，1976年热带太平洋地区出现了向更温暖、更湿润状况的转变，并产生了广泛的气候和生态影响。这一转变在过去一个世纪中独一无二，引发了关于大气中温室气体浓度增加对ENSO变率影响的争论。在此，我们展示了一份来自热带太平洋中部珊瑚的155年ENSO重建记录，它为区域平均气候及其变率的长期变化提供了新证据。20世纪初的逐渐转变以及1976年的突变，均朝着更温暖、更湿润的状况发展，同时伴随着变率的变化。在19世纪中后期，较冷、较干燥的背景状况与显著的年代际变率同时出现；在20世纪初，较短周期（约2.9年）的变率加剧。1920年之后，变率减弱并集中在年际时间尺度上；随着1976年的转变，约4年周期的变率变得显著。我们的结果表明，热带太平洋的变率与该地区的平均气候相关联，并且在自然和人为气候强迫时期，两者均发生了变化。
