Southern Oscillation is known to influence global surface temperatures, with El Niño conditions leading to warmer temperatures and La Niña conditions leading to colder temperatures. However, a new study in Geophysical Research Letters shows that some types of El Niño do not have this effect, a finding that could explain recent decade-scale slowdowns in global warming.
The authors examine three historical temperature data sets and classify past El Niño events as traditional or central Pacific. They find that global surface temperatures were anomalously warm during traditional El Niño events but not during the central Pacific El Niño events.
They note that in the past few decades, the frequencies of the two types of El Niño events have changed, with the central Pacific type occurring more often than it had in the past, and suggest that this could explain recent decade-scale slowdowns in global warming.
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Sandra Banholzer, Simon Donner, The influence of different El Niño types on global average temperature, Geophysical Research Letters, DOI: 10.1002/2014GL059520, 2014