Supplementary data, code, and information for ‘Long-term variability in the El Niño/Southern Oscillation and associated teleconnections’

We analyze global patterns of reconstructed surface temperature for insights into the behavior of the El Niño/Southern Oscillation (ENSO) and related climatic variability during the past three centuries. The global temperature reconstructions are based on calibrations of a large set of globally distributed proxy records, or “multiproxy” data, against the dominant patterns of surface temperature during the past century. These calibrations allow us to estimate large-scale surface temperature patterns back in time. The reconstructed eastern equatorial Pacific “Niño-3” areal-mean sea surface temperature (SST) index is used as a direct diagnostic of El Niño itself, while the global ENSO phenomenon is analyzed based on the full global temperature fields. We document low-frequency changes in the base state, amplitude of interannual variability, and extremes in El Niño, as well as in the global pattern of ENSO variability. Recent anomalous behavior in both El Niño and the global ENSO is interpreted in the context of the long-term reconstructed history and possible forcing mechanisms. The mean state of ENSO, its global patterns of influence, amplitude of interannual variability, and frequency of extreme events show considerable multidecadal and century-scale variability over the past several centuries. Many of these changes appear to be related to changes in global climate, and the histories of external forcing agents, including recent anthropogenic forcing.

本研究基于近三个世纪以来的重构地表温度全球分布格局，探究厄尔尼诺-南方涛动（El Niño/Southern Oscillation, ENSO）及其相关气候变率的演化特征。本次所用的全球温度重构数据，基于对全球广泛分布的大量代用记录（或称“多代用”数据集）与近百年地表温度主导模态的校准拟合。通过此类校准，可实现对大尺度地表温度分布格局的历史回溯估算。本研究以重构的东赤道太平洋“Niño-3”区域平均海表温度（Sea Surface Temperature, SST）指数作为厄尔尼诺事件的直接诊断指标，同时基于完整的全球温度场对全球ENSO现象展开分析。本研究刻画了厄尔尼诺事件的基准态、年际变率振幅、极端事件特征，以及ENSO变率全球分布格局的低频变化特征。针对近期厄尔尼诺与全球ENSO出现的异常行为，本研究结合长期重构历史与潜在强迫机制展开解读。在过去数个世纪中，ENSO的基准态、全球影响分布格局、年际变率振幅以及极端事件发生频率均表现出显著的年代际至世纪尺度变率。上述多数变化似乎与全球气候状态的改变以及包括近期人为强迫在内的外部强迫因子演变存在关联。