Global weather fluctuations called El Niño events
are likely to become more frequent by 2040, a new
study shows. El Niño – the unusual warming of surface
waters in the eastern tropical Pacific
Ocean – affects climate, ecosystems and societies
El Niño – the unusual warming of surface waters
in the eastern tropical Pacific Ocean – affects
climate, ecosystems and societies worldwide.
The study examined four possible scenarios for
future carbon emissions, and found increased risk
of El Niño events in all four.
This means El Niño events and associated climate
extremes are now more likely "regardless of any
significant mitigation actions" to reduce emissions,
the researchers warn.
Lead author Dr Jun Ying, from the Second Institute
of Oceanography, Ministry of Natural Resources in
China and the University of Exeter, said: "We know
from previous studies that, when measuring El Niño
changes in terms of rainfall shifts in the eastern
equatorial Pacific, models predict an increase in
the frequency of events.
"This study shows that those changes could happen
after the next two decades."
The study, published in Nature Climate Change, examines
the "time of emergence" of changes in the tropical
Pacific using state-of-the-art climate models.
The time of emergence is defined as when the signal
of climate change emerges from the usual background
noise of natural climate variability.
When looking at changes in El Niño rainfall patterns,
the best estimate of the time of emergence of changes
converges on 2040 in all of the four emissions scenarios
Co-author Professor Mat Collins, from the University
of Exeter and part of the Global Systems Institute,
added: "What surprised us is that changes emerge
regardless of the scenario we look at.
"Because rainfall in the tropics is associated with
the warmest sea surface temperatures (SSTs), it is
the relative changes in SST that are more important
than the absolute change.
"This leads us to the rather stark conclusion that
these changes are essentially unavoidable."
The study was carried out by Dr Ying as part of a
year-long Chinese Scholarship Council sponsored visit
to the University of Exeter.
The paper is entitled: "Emergence of Climate Change
in the Tropical Pacific."
UNIVERSITY OF EXETER
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