Global warming could change strength of El Nino
Via Phys.org September 11, 2013: Global warming could impact the El NiÃ±o Southern Oscillation (ENSO), altering the cycles of El NiÃ±o and La NiÃ±a events that bring extreme drought and flooding to Australia and many other Pacific-rim countries.
“Our research has showed that while the development of La NiÃ±a and El NiÃ±o events is chaotic and hard to predict, the strength of these events can change over long time spans due to changes in the global climate,” said one of the paper’s authors Dr Steven Phipps.
“For instance, we found that the ENSO cycle was much weaker 4300 years ago than it is today. This weaker cycle persisted for almost two centuries.”
The researchers determined that natural influences on the Earth’s climate, such as those caused by variations in its orbit around the sun, could affect the strength of El NiÃ±o events.
Although small, these natural influences altered seasonal trade winds across the Eastern Pacific and affected the development of El NiÃ±o events. Interestingly, the research also showed that El NiÃ±o events in the past started later in the year and were often less intense.
“We found there was a small strengthening of the regular seasonalÂ trade windsÂ in the Eastern Pacific in response to natural warming cycles in the Earth’s orbit around the sun. Remarkably this acted in a big way to stop El NiÃ±o events from forming and growing,” said lead author Dr Helen McGregor from the University of Wollongong.
“This shows us that external factors can influence the ENSO process and that it may have a sustained response to futureÂ greenhouse gasÂ changes. Currently 20th Century observations are too short to confirm whether this is occurring now.”
Importantly, these new observations can now be used inÂ climate modelsÂ to see if these past changes in ENSO processes can be reproduced.
“Currently,Â climateÂ models do not agree on how El NiÃ±o may change under future global warming scenarios,” said Dr Phipps
“With these new observations we can determine which models reproduce the most accurate response to changes in theÂ global climate. This will help us to more accurately forecast the response of ENSO under futureÂ global warmingÂ scenarios.”