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Many climate models failed to reproduce the eastern Pacific cooling that has been linked to slower warming in the early 20th century. Here, the authors present a feedback mechanism between the tropical Pacific and the Atlantic which contributes to this bias as it further dampens the Pacific cooling response in models.

El Niño–Southern Oscillation (ENSO) profoundly affects Australian weather, climate, ecosystems and socio-economic sectors. This Review presents the progress made in understanding ENSO teleconnections to Australian weather over the past 40 years, describing the atmospheric dynamics, complexities and impacts of this climate phenomenon.

Global mean sea surface surface temperature shows decadal fluctuations superimposed to the warming trend whose causes are still debated. Here, the authors provide a quantification of relative contributions of different drivers and conclude that both internal and externally-forced variability play a comparable role.

Unprecedented strengthening of Pacific trade winds has occurred in recent decades, while both the Indian and Atlantic Ocean surface temperatures warmed. Now a study suggests that the Atlantic Ocean warming is driving this Pacific trade wind strengthening and the warming of the Indian Ocean.

Early Eocene ENSO had stronger amplitude and longer periodicity than present, driven primarily by tectonic changes, but high atmospheric CO₂ levels offset tectonic influence on the ENSO amplitude through altered ocean-atmospheric interaction.

Simulation of observed Pacific wind trends is hampered by model limitations in representing variability or the forced response. Improved mean-state climatologies, including the recent Atlantic warming trend, should improve capture of Pacific trends.

The development and termination of El Niño events seem to be coupled with the seasonal cycle. Statistical analyses suggest that this link reflects the presence of a combination climate mode with periods of 10 and 15 months.

The Pacific trade winds have strengthened since the late 1990s, and there has been related strengthening of the atmospheric Walker circulation. Although the impacts of these changes are becoming known, their cause has not been identified. This study, using observations and models, shows that warming of the Atlantic sea surface and corresponding displacement of atmospheric pressure centres are key drivers.

Atmospheric Walker circulation results in a two-way interaction between decadal-scale sea surface temperature variability in the Atlantic and Pacific, according to pacemaker climate modelling experiments.

The South Pacific Convergence Zone is the largest rainband in the Southern Hemisphere, and its response to global warming is still undetermined. In this study a hierarchy of climate models show that the uncertainty in rainfall projections in the South Pacific Convergence Zone is the result of two competing mechanisms.

The slowdown in global average surface warming has recently been linked to sea surface cooling in the eastern Pacific Ocean. This work shows that strengthening trade winds caused a reduction in the 2012 global average surface air temperature of 0.1–0.2 °C. This may account for much of the warming hiatus and is a result of increased subsurface ocean heat uptake.

Model simulations with CO₂ forcing prescribed in discrete geographical regions reveal that polar amplification arises primarily due to local lapse-rate feedback, with ice-albedo and Planck feedbacks playing subsidiary roles.

Several mechanisms have been put forward to explain tropical Pacific decadal variability, the contributions of which are debated. This Review outlines the different drivers of tropical Pacific decadal variability, summarizing that tropical pycnocline adjustment to wind forcing and Rossby wave activity is likely the dominant mechanism, albeit with uncertainty.

The El Niño propagation asymmetry (in which sea surface temperature anomalies propagate eastwards during an extreme El Niño event) is shown to be caused by the variations in upper ocean currents in the equatorial Pacific Ocean; increased occurrences of the propagation asymmetry may be a manifestation of global greenhouse warming.

Focusing on the role of external forcing, an investigation of the causes of observed changes in the tropical Pacific surface warming pattern over recent decades discusses a possible shift in the drivers of this pattern.

Our current understanding of the spatio-temporal complexity of the El Niño–Southern Oscillation phenomenon is reviewed and a unifying framework that identifies the key factors for this complexity is proposed.

The El Niño–Southern Oscillation (ENSO) has global climatic implications, necessitating understanding of its observed and projected changes. This Review brings together knowledge of ENSO in a warming climate, revealing projected increases in ENSO magnitude, as well as ENSO-related rainfall and sea surface temperature variability.