Ocean Holds Key To Future Weather Cycles
Illawarra Mercury
Saturday December 1, 2007
LA Nina may finally be back and bringing rain with it, but a researcher at the University of Wollongong is trying to determine why it's taken so long.
In the first La Nina since 1999, associate research fellow Dr Helen McGregor is curious as to whether higher temperatures over the last decade have affected the La Nina cycle.A La Nina phenomenon is a cooling over a large part of the east Pacific Ocean, while El Nino is a warming over a similar area.In Australia, La Ninas generally cause more rain on the eastern coast, and are associated with floods; El Ninos cause less rain and are associated with drought.There have been three El Ninos in the past decade, each lasting almost a year.The lack of La Nina and the predominance of El Nino, coupled with rising temperatures since the 1990s led Dr McGregor to wonder whether global warming is affecting the El Nino cycle."One of the reasons we can't be sure whether or not global warming affects El Nino is that we only have ocean temperature records for the last 100-150 years," Dr McGregor said."To get records of earlier temperatures we are using ocean corals which record temperatures in a similar way to tree rings."It is expected it will take six months to collect ocean temperature data from as far back as 6000 years ago."Once we have the data and the records, we can look at whether or not El Nino is affected directly by ocean temperatures, and if it does, Australia is in big trouble," Dr McGregor said."If global warming does cause more El Nino it could cause further droughts in Australia and northern America, floods in Peru - a lot of the world will be affected."According to Bureau of Meteorology acting climate services manager Clinton Rackich, the period since the 1990s has been the driest and hottest in history."The period we've had has seen the highest number of El Nino and lowest of La Nina on record, and that's coupled with the top five hottest years in recorded history," Mr Rackich said."The El Nino is a very complicated system and a lot of things can affect it, but if global warming does affect the El Nino-La Nina cycle it's bad news for Australia and we'll be in a bad position."Temperatures in the Illawarra from August to October were one degree hotter than the 30-year average, and three to four degrees hotter further inland.
© 2007 Illawarra Mercury