In terms of the "global warming problem", at least. The population of Australia is a rounding error. (7,050M global population - 23M Australians = still over 7B people; Australia is about 3/10th of 1%). The entire population is less than the city of Shanghai, or Karachi, or Beijing... The top 20 cities in the world have 10 X as many people of the Australian continent.
Good on them that they are voting not to piss in the wind. Specifically,
this wind.
Even if humans can significantly affect the rate of change of global warming, taxing the most advanced economies is not going to help as much as doing [insert magic policy here] to change the course of the emerging economies which are going down the path that the 1st world traveled half a century ago.