Sydney - Australia experienced its hottest winter on record this year amid a long-term warming trend largely attributed to climate change, the weather bureau said on Friday.Maximum daytime temperatures were 1.9 degrees Celsius (3.4 Fahrenheit) above the long-term national average of 21.8 during the June-August season, the Bureau of Meteorology said.Winter rainfall was the ninth-lowest on record, and lowest since 2002, the bureau added. National records started in 1910 for temperatures and 1900 for rainfall."You have a long-term warming trend which is largely attributed to changing levels of greenhouse gases," the bureau's senior climatologist Blair Trewin told AFP.He added that 19 of Australia's last 20 winters had seasonal maximum temperatures averaging above the long-term national average."On top of that, to get an individual extreme year like this one, you also need the more general weather pattern to be favourable to warm conditions as well, as this year was."The record temperatures occurred despite the absence of the island continent's most important large-scale climate drivers - the El Nino weather phenomenon and the Indian Ocean Dipole.El Nino occurs when trade winds that circulate over waters in the tropical Pacific start to weaken and sea surface temperatures rise.The Indian Ocean Dipole system is defined by the difference in sea surface temperature between western and eastern areas of the ocean.Australia has warmed by approximately 1.0 Celsius since 1910, according to a report last year by the weather bureau and national science body CSIRO.More recently, over 200 weather records were broken during the last summer, with intense heatwaves, bushfires and flooding plaguing the December 2016-February 2017 season.The warmer and drier winter weather has seen New South Wales state's Rural Fire Service bring forward its bushfire danger period, which usually starts in October, by a month in some areas.Bushfires are common in Australia's arid summers although climate change has pushed up land and sea temperatures and led to more extremely hot days and severe fire seasons.On Friday, a Hercules C-130 dubbed 'Thor', capable of dropping 15 000 litres of water, returned from the United States to Sydney ahead of the bushfire season.