July 25, 2017
The CSIRO says the frequency of extreme El Niño events is likely to increase for 100 years even when global mean temperature is stabilised at 1.5°C above pre-industrial levels.
Research published this week in the journal “Nature Climate Change” by an international team shows that if warming is halted at the aspirational 1.5°C target stated in the Paris Agreement, the frequency of extreme El Niño events could continue to increase due to a continuation of faster warming in the eastern equatorial Pacific.
CSIRO researcher and lead author Dr Guojian Wang said the growing risk of extreme El Niño events did not stabilise in a stabilised climate.
“Currently the risk of extreme El Niño events is around five events per 100 years,” Dr Wang said.
“This doubles to approximately 10 events per 100 years by 2050, when our modelled emissions scenario reaches a peak of 1.5°C warming.
“After this, as faster warming in the eastern equatorial Pacific persists, the risk of extreme El Niño continues upwards to about 14 events per 100 years by 2150.
“This result is unexpected and shows that future generations will experience greater climate risks associated with extreme El Niño events than seen at 1.5°C warming.”
The research was based on five climate models that predict future scenarios past 2100.
The models were run using the Intergovernmental Panel on Climate Change’s lowest emissions scenario which requires negative emissions late in the century.
Director of the Centre for Southern Hemisphere Oceans Research and report co-author Dr Wenju Cai said the research continued important work on the impacts of climate change on the El Niño-Southern Oscillation which is a significant driver of global climate.
“The most severe previous extreme El Niño events occurred in 1982-83, 1997-98 and 2015-16, years associated with worldwide climate extremes,” Dr Cai said.
“Extreme El Niño events occur when the usual El Niño Pacific rainfall centre is pushed eastward toward South America, sometimes up to 16,000 kilometres, causing massive changes in the climate. The further east the centre moves, the more extreme the El Niño.
“This pulls rainfall away from Australia bringing conditions that have commonly resulted in intense droughts across the nation. During such events, other countries like India, Ecuador, and China have experienced extreme events with serious socio-economic consequences.”
The research indicated that under a scenario of climate stabilisation (ie. 1.5°C warming) there would be little or no change to La Niña events, which can increase Australian rainfall.
