AUSTRALIA had an unusually cool and rainy year in 2011, the trend of rising temperatures damped down by the La Nina effect, which brought cyclones and floods to northern Australia.
Sydney was also hit by heavy rainfall but it remained relatively hot and 2011 was the 19th consecutive year in which the city's temperatures were higher than the long-term average.
The Bureau of Meteorology's national climate statement, released yesterday, says Australia as a whole had a cooler year than average, mainly due to rain and cloud cover caused by La Nina.
Worldwide, 2011 was the equal tenth-hottest year since instrumental records began in 1850 and the hottest La Nina year on record, the World Meteorological Organisation said.
A La Nina event takes place when cool ocean temperatures in the Pacific Ocean are sustained for a few months, causing rain and severe weather over Australia, Indonesia and Papua New Guinea.
In Sydney, the average temperature across the year was 22.6, 0.9 degrees above average, based on continual records kept at Sydney's Observatory Hill since 1858.
''We had particularly warm temperatures at the start of the year,'' said a Bureau of Meteorology climatologist, Acacia Pepler. ''There were five consecutive nights above 24 degrees in February, which has never been recorded before in Sydney.''
The soaking-wet November meant that 1369 millimetres fell in Sydney in 2011, well above the average of 1137 millimetres, while last December was the coldest since 1960.
Despite the cool ending to 2011, Ms Pepler said the Sydney weather conditions were in line with the projections from climate change models.
''We've been expecting temperatures to warm and this is within those projections,'' she said. ''What we are seeing in Sydney is definitely consistent with global-warming impacts.''
Water temperatures in the Indian Ocean suggest more warm but rainy weather is likely for Sydney in January, February and March.
''Based on other years that have had these results, there is a 60 per cent chance of having above-normal rainfall in this seasonal outlook,'' Ms Pepler said.
The World Meteorological Organisation, in its most recent update on global temperatures in 2011, said the 13 warmest years on record have occurred in the 15 years since 1997.
''Global temperatures in 2011 are currently the tenth-highest on record and are higher than any previous year with a La Nina event, which has a relative cooling influence,'' the organisation said in a statement.
''The extent of Arctic sea ice in 2011 was the second-lowest on record and its volume was the lowest.''
The most recent temperature maps produced by the US National Climatic Data Centre show that most of the Earth's surface was about half a degree warmer than the average temperatures between 1961 and 1990 - a period currently used as the global measuring stick.
They show that northern Australia, the Pacific north-west, parts of south-east Asia and a small zone in central Asia were the only land areas that had cooler than average temperatures in 2011.
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