212 / 2023-09-21 22:57:26

Analysis of the impact of global warming on ENSO from the perspective of objective signals

El Niño-Southern Oscillation,Global Warming,ENSO characteristics,Objective Signals

Most studies on the relationship between global warming and El Niño-Southern Oscillation (ENSO) rely on simulation experiments, but them have yielded contradictory results and errors, which cannot guarantee the authenticity of experimental results. To address this challenge, we approached the issue from the perspective of objective ENSO and global warming signals. The effects of global warming on ENSO are not limited to the Earth surface, but are also present in the atmosphere. While objective monitoring indices exist for surface global warming and ENSO signals, objective ENSO and global warming signals in the atmosphere are difficult to obtain. To obtain high-precision ENSO and global warming signals in the atmosphere, we proposed the strategy of ICA (Independent Component Analysis) combined with a non-parametric method. With the help of this method and the ERA5 specific humidity dataset, we extracted global warming signal (Independent Component 1, IC1) and ENSO signal (Independent Component 2, IC2) in the atmosphere. The results of the objective ENSO and global warming signals suggest that the global warming signal leads the ENSO signal by approximately three months and exhibits a clear positive correlation with the ENSO signal, especially the occurrence of strong ENSO events is closely related to global warming, indicating that global warming promotes the occurrence of ENSO. Under the influence of global warming, the frequency and intensity of ENSO increase, the characteristics and complexity of ENSO atmospheric teleconnections may be altered, and there is a greater tendency for more destructive El Niño events to occur. The occurrence of ENSO has increased by 38.71% in the later warming period (Late-GW, 1959.1-2021.12) of global warming compared to the pre-warming period (Pre-GW, 1896.1-1958.12). Additionally, since the beginning of the 21st century, there have been 15 ENSO events, with a high probability of occurrence at 75%, significantly higher than the occurrence probability of ENSO events (49.2%) in the Pre-GW. Furthermore, under the influence of global warming, moderate or strong ENSO events tend to develop earlier, and extreme ENSO events not only develop earlier but also prolong their decay phase, leading to an extended lifespan of ENSO events.