I remember much hotter weather as a kid. The worst heat waves in Oz were over 100 years ago. Also as areas of bush get cleared, to build more houses, those areas increase in temp, as the plants aren't absorbing the energy, and concrete etc radiation it back out.
The Suns output, the earth's variable orbit of the sun (yes, we do not follow a fixed orbit, as it wobbles and changes due to other planets gravitational pull on earth). Also the fluctuations of our magnetosphere will have far more impact on our climate then we ever will.