2013 confirmed as Australia's hottest year on record

Australia smashed its previous annual heat record in 2013, with a summer heatwave and spring hot spell among the outstanding periods of unusual warmth.

The Bureau of Meteorology on Friday confirmed that last year was the hottest nationwide in more than a century of standardised records, with mean temperatures 1.2 degrees above the 1961-90 average.

The 12 months easily eclipsed the previous annual record set in 2005, when mean temperatures were 1.03 degrees above average.

Every state and the Northern Territory recorded at least their fourth warmest year by mean temperatures, underscoring the breadth of 2013's unusual heat. 

By maximums, all but Victoria and Tasmania recorded their hottest years, with nationwide maximums a full 1.45 degrees above the long-term average, shattering the previous record anomaly of 1.21 degrees set in 2002.

Among the cities, Sydney posted daily maximums averaging 23.7 degrees in 2013, well above the previous high in more than 150 years of records, of 23.4 degrees set in both 2004 and 2005, said Blair Trewin, a senior climatologist at the Bureau of Meteorology. 

Australia's heat in 2013: no region below average. Souce: BoM

Minimum temperatures were the third-highest, at 15.1 degrees, a shade below the 15.2 degrees set in 2007 and 2009.

Melbourne posted its third hottest year, also based on records going back to the 1850s, with maximums averaging 21.5 degrees, shy of 2007's record of 21.8 degrees. The city's minimums averaged 12.2 degrees, second only to 2007's 12.5 degrees.

'Unprecedented year'

David Karoly, a climate scientist at the University of Melbourne, said 2013 was "an unprecedented year" for Australia not least because it came in a period without an El Nino weather pattern over the Pacific. The so-called El Nino-Southern Oscillation - which typically warms up eastern Australia in particular - remained in neutral through the year, and continues to do so.

‘‘These record high temperatures for Australia in 2013 cannot be explained by natural variability alone," Professor Karoly said. "This event could not have happened without increasing greenhouse gases, without climate change."

A heatwave in early January, when the national average maximum temperatures reached 40.3 degrees on January 7, set the country up for a hot year. January was Australia's hottest month on record and December 2012-February 2013 was the hottest summer.

This January has also started with a blast of heat over inland regions, with Moomba in South Australia recording 49.3 degrees on Thursday, while Birdsville in Queenland clocked up 48.6 degrees.

Neutral conditions

Unusually warm waters around Australia helped keep temperatures well above average in 2013, while many parts of the country recorded their mildest winters on record.Climate experts say another intense El Nino year, such as in 1998, could challenge even 2013's newly set temperature highs.Australia's warmth during 2013 extended into spring, with September setting records as the most exceptionally hot month on record. Average maximum temperatures were 3.41 degrees above the long-run average, with South Australia's 5.39 degrees above the norm – a record for any state or territory in any month.

The heat was accompanied by early season bushfires, particularly around Sydney in October, and extensive drought across much of Queensland.

Rainfall nationally averaged 428 millimetres, about 37 millimetres below average, for the year.

Capitals, states, world

Aside from Sydney and Melbourne, most other state capitals also had notably hot years.

Canberra and Hobart posted their second warmest years. Perth had its third-warmest year by maximum temperatures, while Darwin and Adelaide had their third-equal warmest. Brisbane, in the midst of a very warm period to start 2014, lagged in 2013 with only its ninth warmest year.

Among the states, NSW had its warmest year, with maximums 1.76 degrees above the long-term average, beating the 1.63 degree anomaly set in 2002, said the bureau's Dr Trewin. By mean temperature, the state was the second warmest on record, behind 2009.

For Victoria, maximum temperatures were 1.3 degrees above normal, placing it third-warmest on records behind the 1.42 degree anomaly set in 2007. Both mean and minimums were also third-highest for the state.

South Australia was exceptional in a remarkable year, with the state setting its highest maximum, mean and minimum temperatures, the bureau said.

Globally, 2013 was the sixth hottest year in records dating back to 1880. No year since 1985 has recorded a below-average global mean temperature reading, and nine of the 10 warmest years have occurred in the past 12 years, the Bureau of Meteorology said.

The bureau also noted that only one year in the last decade was cooler than average, when a strong La Nina weather pattern over the Pacific kept temperatures low in 2011. The average for each of the rolling 10-year periods from 1995-2004 to 2004-2013 have been among the top 10 records, it said.

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