Your graph shows average temperature is calculated from 1961-1990.The link states that they are working on the premise that it may have deliberately been started. There is no proof that it was started, and we have to wait and see. However, most fires are started by persons being dummies to throw their cigarette butts etc that then starts the fires. But fires are then brought under control irrespective with how they are started, and within a certain window of time. These Australians fires are unprecedented in the manner in which they have spread and the bone dry and very hot temperatures. They have spread at an alarming rate with no respite from the weather. There is absolutely zero proof that it is not due to the Climate Change, as it has been announced that these are the worst bush fires ever recorded and at this time of the year.
Australia broke its all-time temperature record twice in December. An average maximum of 40.9C was recorded on 17 December, broken a day later by 41.9C, both beating 2013's record of 40.3C.
By the end of the month every state had measured temperatures above 40C - including Tasmania, which is usually much cooler than the mainland.
https://www.youtube.com/watch?v=J28cnAcPGXA
That is the definition of cherry picking data.