Agriculture in a variable climate

It is important to understand whether observed drying trends in seasonal climate are part of a long-term trend, as this might require transformational changes to the current farming systems.

Australia’s climate is characterized by large natural variability which is difficult to distinguish from long-term and more gradual trends. In some parts of Australia’s major agricultural production zones producers have experienced summer rainfall in the previous decade as largely being absent, for example in northern New South Wales.

Annual and seasonal rainfall trends are important drivers of agricultural productivity and profitability in Australian agriculture and various climatological and synoptic drivers influence rainfall patterns in Australia’s diverse climate.

Summer rainfall 1926/27 to 2021/22 in Narrabri, New South Wales. Source: Bureau of Meteorology weather data for station 053025, Narrabri (Mollee).

Change detection and trend analysis

We analyze trends in past and future climate for 24 individual locations as well as for 3 agricultural regions, the Western Australia wheat belt, coastal regions of the East Coast and the northern Murray Darling basin.

We use weather station data and gridded climate data ranging back to 1907, and projections of future rainfall changes from 30 global circulation models. We distinguish between annual, winter and summer rainfall. We use linear regression and statistical tests to identify changes and trends in the time series.

The results

We find that:

  • the Western Australia wheat belt is the only region with significant and long-term changes in summer and winter rainfall. Seasonal rainfall has increased by 0.18-0.21 mm per year in summer and has decreased by 0.42-0.43 mm per year in winter.
  • in alignment with growers’ observations, some locations in Eastern Australia experienced below average rainfall (-50 to -200 mm) in seven consecutive summers between 2011 and 2020.
  • this, however, does not constitute part of a long-term trend and our current results suggest that they are part of natural variability in seasonal rainfall.
  • the decline in winter rainfall in the Western Australia wheat belt is expected to continue as there is high agreement in climate models, while changes in rainfall in Eastern Australia are less certain.

This can assist producers in developing transformation processes and coping strategies in industries affected by changes in seasonal rainfall.

For more information

Read the research article published in Climatic Change

Explore the data using the Australian Rainfall Trend Explorer application.