The IOD phenomenon was first identified by climate researchers in 1999 . An average of four each positive-negative IOD events occur during each 30-year period with each event lasting around six months . However , there have been 12 positive IODs since 1980 and no negative events from 1992 until a strong negative event in late 2010 . The occurrence of consecutive positive IOD events is extremely rare with only two such events recorded , 1913 – 1914 and the three consecutive events from 2006 to 2008 which preceded the Black Saturday bushfires . Modelling suggests that consecutive positive events could be expected to occur twice over a 1,000-year period . The positive IOD in 2007 evolved together with La Niña , which is a very rare phenomenon that has happened only once in the available historical records ( in 1967 ) . A strong negative IOD developed in October 2010 , which , coupled with a strong and concurrent La Niña , caused the 2010 – 2011 Queensland floods and the 2011 Victorian floods
Black Saturday bushfires
Black Saturday bushfires
Indian Ocean Dipole