Picture: Still from El Nino animation (below). Credit: National Computational Infrastructure, ARC Centre of Excellence for Climate System Science.

As a La Niña event intensifies in the Pacific, bringing increased rain to parts of Australia and a powerful hurricane season to the Tropical Atlantic, a new book reveals the dynamics and impacts of the El Niño Southern Oscillation (ENSO), the irregular cycle that switches the Pacific Ocean between these cool La Niña and warm El Niño events.

El Niño Southern Oscillation in a Changing Climate published by Wiley for the American Geophysical Union is a comprehensive and accessible exploration of ENSO and how it is altering with human caused climate change.

“This is the first comprehensive examination of ENSO and how its dynamics and impacts may change under the influence of rising greenhouse gas concentrations in the atmosphere”, said co-editor Dr Michael McPhaden of the U.S. National Oceanic and Atmospheric Administration (NOAA).  

Ongoing ocean warming caused by climate change has amplified some ENSO impacts. For example, 2016 saw the largest global coral bleaching to date due to the 2015-16 extreme El Niño and its effect on an already warm ocean.

This animation looks beneath the ocean surface to reveal the oceanic processes that led to the 1997/98 El Niño – an event that caused billions of dollars of damage worldwide and was followed by consecutive strong La Niña events. Credit: National Computational Infrastructure, ARC Centre of Excellence for Climate System Science.

“As global climate changes because of human activities, how these changes affect ENSO has become one of the most pressing problems in Earth system science today”, said CSIRO scientist and co-editor Dr Wenju Cai.  

Along with co-editors Dr Agus Santoso of the University of New South Wales (UNSW) and Wenju Cai, Dr McPhaden brought together 98 of the world’s leading experts to write 21 chapters that comprehensively cover the latest theories, models, and observations, and explore the challenges of forecasting ENSO as the climate continues to change.

“The book was initiated in the wake of the intense El Niño of 2015-16 that left a wide swath of destruction across the globe,” said Dr Santoso.

“Whether extreme events like this may increase in the future is an issue we directly address.”

Through the course of its pages the book tracks the historical development of ideas about ENSO, explores the underlying physical processes and how it has varied over decades and now centuries thanks to advances in paleo-reconstructions. The book also reveals the latest science on how ENSO responds to external factors such as climate phenomena outside the tropical Pacific, volcanic eruptions, and anthropogenic greenhouse gas forcing. These external influences coupled with the chaotic nature of the phenomena itself are examined further in chapters that explain the barriers and potential areas of research that may help us forecast these events in advance.

Most importantly, as we look to a future affected by global warming and changes to our climate, the  book covers the extensive impacts on extreme ocean, weather, and climate events; fisheries; marine ecosystems; and the global carbon cycle.  

“The current La Niña in the tropical Pacific is one of the reasons for the high-octane Atlantic hurricane season this year,” observed Dr McPhaden. 

“Our book explains how ENSO helps influence the rise of these severe tropical storms as well as other extreme weather and climate events like droughts, floods and marine heat waves.”

ENSO’s impacts are felt far and wide across the planet, for instance on agriculture, public health, freshwater availability, power generation, and economic activity.  The book makes the case that, because it is so consequential, sustained and coordinated international efforts are needed to better observe, understand and predict ENSO and its effects on human and natural systems.

The book was written to reach a wide audience, with up-to-date content that is authoritative, compelling, and of practical value. 

“By filling a gap in the literature on the topic of ENSO in a changing climate, we expect the book to have wide appeal, particularly with students, ENSO researchers, practitioners in other fields, and policy makers,” said Dr Santoso.

“We can see the future will be different than the past and we need to be prepared”, said Dr Cai. 

“The information in this book helps us prepare for that future.”

  • Book: Michael J. McPhaden, Agus Santoso, Wenju Cai (Eds.) 2021: El Niño Southern Oscillation in a Changing Climate. 528pp. American Geophysical Union. ISBN: 978-1-119-54812-6. DOI: 10.1002/9781119548164