Increasing frequency of extreme El Niño events due to greenhouse warming

• Published in: Nature climate change 2014-02, Vol.4 (2), p.111-116
• Main Authors: Cai, Wenju, Borlace, Simon, Lengaigne, Matthieu, van Rensch, Peter, Collins, Mat, Vecchi, Gabriel, Timmermann, Axel, Santoso, Agus, McPhaden, Michael J., Wu, Lixin, England, Matthew H., Wang, Guojian, Guilyardi, Eric, Jin, Fei-Fei
• Format: Article
• Language: English
• Subjects: 704/106/694/2786; Climate Change; Climate Change/Climate Change Impacts; Climatology. Bioclimatology. Climate change; Earth Sciences; Earth, ocean, space; Environment; Environmental Law/Policy/Ecojustice; Environmental Sciences; Exact sciences and technology; External geophysics; Geophysics; Global Changes; letter; Meteorology; Physics; Sciences of the Universe
• ISSN: 1758-678X; 1758-6798
• DOI: 10.1038/nclimate2100

Extreme El Niño events cause global disruption of weather patterns and affect ecosystems and agriculture through changes in rainfall. Model projections show that a doubling in the occurrence of such extreme episodes is caused by increased surface warming of the eastern equatorial Pacific Ocean, which results in the atmospheric conditions required for these event to occur. El Niño events are a prominent feature of climate variability with global climatic impacts. The 1997/98 episode, often referred to as ‘the climate event of the twentieth century’ 1 , 2 , and the 1982/83 extreme El Niño 3 , featured a pronounced eastward extension of the west Pacific warm pool and development of atmospheric convection, and hence a huge rainfall increase, in the usually cold and dry equatorial eastern Pacific. Such a massive reorganization of atmospheric convection, which we define as an extreme El Niño, severely disrupted global weather patterns, affecting ecosystems 4 , 5 , agriculture 6 , tropical cyclones, drought, bushfires, floods and other extreme weather events worldwide 3 , 7 , 8 , 9 . Potential future changes in such extreme El Niño occurrences could have profound socio-economic consequences. Here we present climate modelling evidence for a doubling in the occurrences in the future in response to greenhouse warming. We estimate the change by aggregating results from climate models in the Coupled Model Intercomparison Project phases 3 (CMIP3; ref.  10 ) and 5 (CMIP5; ref.  11 ) multi-model databases, and a perturbed physics ensemble 12 . The increased frequency arises from a projected surface warming over the eastern equatorial Pacific that occurs faster than in the surrounding ocean waters 13 , 14 , facilitating more occurrences of atmospheric convection in the eastern equatorial region.