Although the climate of the Pacific region will undergo will have on the El Niño-Southern Oscillation (ENSO) weather phenomenon, accordingto an international science review by the World Climate Research Program’s Climate Variability and Predictability Pacific Panel, published online 23 May in Nature Geoscience.

The paper’s lead author is Dr. Mat Collins from the Met Office Hadley Centre in the UK.

The Panel convened in Australia at the Greenhouse 2009 climate change conference to consider new research that could build an understanding of changes in the behaviour of ENSO. ENSO is a naturally occurring phenomenon causing climate variability that originates in the tropical Pacific region and influences ecosystems, agriculture, freshwater supplies, hurricanes and other severe weather events worldwide.

There is an increasing body of evidence pointing to significant changes in Pacific Ocean climate as a consequence of global warming. What we are attempting to clarify is how those changes will enhance or moderate ENSO and, in Australia’s case, deliver stronger or weaker El Niño events which would have vastly different implications.

—Dr. Wenju Cai, CSIRO

The report concludes that rising global temperatures will bring change to the Pacific region in several ways:

  • tropical easterly trade winds are expected to weaken;
  • surface ocean temperatures are expected to warm fastest near the equator; and
  • the thin water layer separating the ocean’s upper surface layer from its calm deep water below (the thermocline) is expected to become narrower and less deep.

The authors suggest further research directions and coordination efforts that would continue to improve science’s understanding of, and ability to accurately model ENSO, and enable researchers to predict the level of ENSO activity in the short-term (10 to 30 years).

Year-to-year ENSO variability is controlled by a delicate balance of amplifying and damping feedbacks, and one or more of the physical processes that are responsible for determining the characteristics of ENSO will probably be modified by climate change. Therefore, despite considerable progress in our understanding of the impact of climate change on many of the processes that contribute to El Niño variability, it is not yet possible to say whether ENSO activity will be enhanced or damped, or if the frequency of events will change.

—Collins et al.


  • Mat Collins, Soon-Il An, Wenju Cai, Alexandre Ganachaud, Eric Guilyardi, Fei-Fei Jin, Markus Jochum, Matthieu Lengaigne, Scott Power, Axel Timmermann, Gabe Vecchi & Andrew Wittenberg (2010) The impact of global warming on the tropical Pacific Ocean and El Niño. Nature Geoscience doi: 10.1038/ngeo868