ENSO Variability and Predictability in a Warm Climate
Abstract
The response of ENSO to transient climate change has been widely studied, but its equilibrated response has received considerably less attention. Here, we investigate ENSO variability and predictability in equilibrated warm climate states by using millennial-length control and abrupt4xCO2 simulations of seven AOGCMs (LongRunMIP). We quantify ENSO variability based on the Niño3.4 index and describe predictability with contingency tables by calculating success ratios of persistence forecasts (initialized in November) for El Niño, La Niña, non-neutral, and neutral for a prediction of six months ahead. In a warmer climate, ENSO amplitude and frequency decreases in five models (up to 60% and 88%, respectively), increases in one model (21% and 90%, respectively), and shows no change in one model; ENSO predictability decreases in six models (up to 99% for El Niño, 96% for La Niña, 99% for non-neutral and 97% for neutral phase) and increases in one model (7%, 24%, 23% and 16%, respectively). For all four phases and seven models, we find higher predictive skill for stronger and more frequent events. We further discuss the influence of the Pacific mean state and the Pacific Decadal Oscillation on ENSO predictability. By considering a large enough number of ENSO events of varying degrees in LongRunMIP, our findings imply that in a future, stable, warm climate, ENSO behavior might substantially change and, if the majority of the climate models were right, be less easy to predict.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMOS018..05Z
- Keywords:
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- 3305 Climate change and variability;
- ATMOSPHERIC PROCESSES;
- 1630 Impacts of global change;
- GLOBAL CHANGE;
- 4215 Climate and interannual variability;
- OCEANOGRAPHY: GENERAL;
- 4922 El Nino;
- PALEOCEANOGRAPHY