Changes of temperature in Sydney and in Australia

A clear warming trend of about 1K per century has been observed in Sydney, Australia (Fig 1). This apparent trend is due to a combination of regional climate change and the rapid growth of the city around the climate station. These data only do not permit a separation of the two factors. The mean temperature in entire Australia has a positive trend as well (Fig 2), although smaller (linear trend about 0.5K/century). This suggests that during the last century, in downtown Sydney, urban heating has effectively doubled the local effect of regional/global climate warming.

Fig 1. Annual mean temperatures measured at Observatory Hill in Sydney from 1859 to 1997.

Fig 2. Annual mean temperatures for all Australian stations from 1909 to 1997, expressed as a departure from the 1961-1990 average.