Variability in the El Niño-Southern Oscillation Through a Glacial-Interglacial Cycle

TLDR

ENSO is the dominant source of interannual climate variability, yet its response to greenhouse warming remains uncertain. This study seeks to clarify how ENSO sensitivity to climate change has evolved over glacial–interglacial cycles. The authors reconstruct ENSO activity over the past 130,000 years using annually banded corals from Papua New Guinea, revealing its persistence even during glacial periods. They find that ENSO amplitude was weaker during past glacial and interglacial periods, but increased markedly in the 20th century, likely due to reduced dampening during cool glacial conditions and orbital forcing.

Abstract

The El Niño–Southern Oscillation (ENSO) is the most potent source of interannual climate variability. Uncertainty surrounding the impact of greenhouse warming on ENSO strength and frequency has stimulated efforts to develop a better understanding of the sensitivity of ENSO to climate change. Here we use annually banded corals from Papua New Guinea to show that ENSO has existed for the past 130,000 years, operating even during “glacial” times of substantially reduced regional and global temperature and changed solar forcing. However, we also find that during the 20th century ENSO has been strong compared with ENSO of previous cool (glacial) and warm (interglacial) times. The observed pattern of change in amplitude may be due to the combined effects of ENSO dampening during cool glacial conditions and ENSO forcing by precessional orbital variations.