Following the 2009–10 El Niño, 2010 was globally the warmest year on record (averaged over both land and ocean), marginally warmer than 1998 (which immediately followed the strongest El Niño event of that century).
Sea surface temperatures north of Australia were also at record-breaking highs – October, November and December 2010 tropical sea surface temperatures north of Australia broke previous records by large margins and, in contrast to temperatures over land, ocean temperatures around Australia were the highest on record during 2010.
This contributed to the strength of the 2010–11 La Niña and its impacts on Australia. The very high sea surface temperatures contributed to an increase in evaporation and high (and at times record) humidity levels over Australia. The increase in humidity was associated with the Australian monsoon arriving earlier and being stronger than normal during the 2010–11 northern wet season. Ultimately, the increase in monsoonal activity and evaporated water added to the potential for high rainfall over northern and eastern Australia.
Sea surface temperatures around the northern coasts of Australia were also above average during the 2011–2012 La Niña event, particularly between December 2011 and February 2012, though were not at the record-breaking levels seen in 2010. This would suggest a weaker influence on Australian rainfall.
Sea surface temperature anomalies (°C) in the Australian region, for the period May 2010 to April 2011
Cool down under, warm globally
2011 was Australia's coolest year in a decade (2001–2011). Eight of the last nine years with sustained La Niña conditions recorded a cooler than normal Australian average temperature, except 2008, which was Australia's warmest year on record commencing with a La Niña.
Australian (top) and global (bottom) annual mean temperature anomalies (difference from normal) – in this instance La Niña years are defined as those where central Pacific sea surface temperature anomalies were below –1 °C for a sustained period leading into the start of the year
Global temperatures are also influenced by La Niña and El Niño events due to the exchange of heat between the atmosphere and oceans. The end of an El Niño is typically associated with higher than average global air temperatures. However, years commencing with a La Niña in place are cooler than average.
The World Meteorological Organization ranked 2011 as the equal-tenth warmest year on record. 2011 was the warmest La Niña year on record globally, considerably warmer than the most recent moderate-to-strong La Niña years (2008, 2000, and 1989).
The ten-year average for 2002–2011 was the equal-warmest ten-year period on record both for Australia and globally