About the temperature trend maps

Analyses available

Australian and regional temperature trend maps are available for annual and seasonal periods starting at the beginning of each decade from 1910 to 1970, through to the most recently completed year or season. Analysis periods starting after 1970 are considered too short to calculate meaningful trend values.

Trend maps are available for maximum, mean and minimum temperature grids, as well as diurnal temperature range (DTR). Mean temperatures are the simple average of the maximum and minimum temperatures, while DTR represents the difference between maximum and minimum temperature grids.

Interpreting the analyses

The trend maps are a useful way to compare how the temperature has changed in different regions of Australia over time. However, they need to be interpreted with caution. Trend values have been determined from a linear (straight line) fit to the data, but the change indicated may not have been gradual. For example, a calculated trend could be due to a relatively rapid "step" change, with the remainder of the series being fairly flat (see some of the timeseries graphs). Also, for regions and seasons in which the year-to-year changes are large, the value of the calculated trend will depend on the start and end values of the data series, potentially misrepresenting the background trend. Users are advised to keep in mind the period over which trend values have been calculated and interpret them alongside the timeseries of spatially averaged values.

In addition, the trend values calculated here using past observations should not be used to imply future rates of change. Due to the complex interactions between the natural and human drivers of climate change and variability, the climate of any location is always changing. Future rates of change will depend on how these drivers interact in future, which will not necessarily be the same as in the past.

Data used

The temperature trend maps are calculated from a homogeneous temperature dataset (known as the Australian Climate Observations Reference Network - Surface Air Temperature, or ACORN-SAT, dataset) developed for monitoring climate variability and change in Australia. The dataset employs the latest analysis techniques and takes advantage of newly digitised observational data to provide a daily temperature record over the last 100 years. This data will enable climate researchers to better understand long-term changes in monthly and seasonal climate, as well as changes in day-to-day weather.

Please note that any use of these data should be acknowledged to the Bureau of Meteorology. Apart from the purposes of study, research, criticism and review, no part of these data may be reproduced, or redistributed for any commercial purposes, or distributed to a third party for such purpose, without written permission from the Director of Meteorology.

Further information

More information about the dataset, including additional data, station details, the methods used and a peer review of the dataset can be found on the ACORN-SAT page.