Sydney - Australia experienced its hottest year on record in 2013, the Bureau of Meteorology said on Friday, enduring the longest heat wave ever recorded Down Under as well as destructive bushfires."2013 was Australia's warmest year since records began in 1910," the bureau said in its annual climate statement."Mean temperatures across Australia have generally been well above average since September 2012. Long periods of warmer-than-average days have been common, with a distinct lack of cold weather."The bureau said that Australia's 2012-2013 summer was the warmest on record, and included a prolonged national heat wave which ended on 19 January 2013 - the first day since 31 December 2012 that it did not reach 45°C somewhere in the nation.Spring was also the warmest on record and winter the third warmest, meaning that overall, the annual national mean temperature was 1.2°C above average.The bureau pointed to destructive fires in the island state of Tasmania in early 2013, then later in the year, a record warm and dry winter and an early spring that culminated in "the most destructive fires in the Sydney region since at least 1968".Heat wavesThe weather authority, which last year introduced new colours on its temperature scale to cater for more extreme highs, said the Australian warming was very similar to that seen on the global scale."And the past year emphasises that the warming trend continues," it said.Professor Roger Jones, a lead author on the Intergovernmental Panel on Climate Change's Working Group II Fifth Assessment Report to be released later this year, said the findings should concern all Australians."While the increases in average temperatures may seem to be benign - heat waves are increasing faster than those averages," said Jones, a research fellow at Victoria University in Melbourne."Why heat waves are longer and hotter than anticipated is not yet clear, but they are contributing to greater fire danger and heat stress than projected by climate impact studies, affecting animals, plants and humans."University of Melbourne climate scientist David Karoly said the record high average temperature was remarkable because it did not occur in an "El Nino" year, when conditions in Australia are usually drier and warmer.He said that in climate modelling experiments it was not possible to reach such a temperature record due to natural climate variations alone."Hence, this record could not occur due to natural variability alone and is only possible due to the combination of greenhouse climate change and natural variability on Australian average temperature," he said.Ian Lowe, emeritus professor of science, technology and society at Queensland's Griffith University and president of the Australian Conservation Foundation, said the report confirmed expectations."2013 was the hottest year on record for Australia, showing that there is no rational basis for the claim that warming has slowed in recent years," he said.