The Hiatus in Global Warming and Interactions between the El Niño and the Pacific Decadal Oscillation: Comparing Observations and Modeling Results

Knut Seip,Hui Wang

doi:10.3390/cli6030072

Abstract

Ocean oscillations interact across large regions and these interactions may explain cycles in global temperature anomaly, including hiatus periods. Here, we examine ocean interaction measures and compare results from model simulations to observations for El Niño and the Pacific decadal oscillation (PDO). We use the global climate model of the Met Office Hadley Centre. A relatively novel method for identifying running leading-agging LL-relations show that the observed El Niño generally leads the observed PDO and this pattern is strengthened in the simulations. However, LL-pattern in both observations and models shows that there are three periods, around 1910–1920, around 1960 and around 2000 where El Niño lags PDO, or the leading signature is weak. These periods correspond to hiatus periods in global warming. The power spectral density analysis, (PSD), identifies various ocean cycle lengths in El Niño and PDO, but the LL-algorithm picks out common cycles of 7–8 and 24 years that shows leading-lagging relations between them.

Highlights

To study the effects of global warming on the global climate system, global circulation models are frequently used
The material consists of two parts: the time series for ocean current proxies and the “regime shifts”
We examine two variables that are closely related to the climate variability of the Pacific Ocean and/or global warming, and examine the interactions between these two variables

Summary

Introduction

To study the effects of global warming on the global climate system, global circulation models are frequently used. An overview of the models used in global warming studies can be found in Wang et al [1]. The model produces time series of ocean variables that describe climate models in the oceans, like the Niño index and the Pacific decadal oscillation, (PDO). Between pairs of movements there will be “bridges” that make one movement impact another. The “bridges” may be facilitated by surface or subsurface water flows, or by interactions with the atmosphere. In the ocean movement time series there will be patterns that reflect the impact of one movement on the other. Movements of ocean water appear to produce cycles in global warming, and of particular interest are the hiatus periods and the temperature “regime shifts”

Methods

Results

Discussion

Conclusion