Over recent years there have been gradual but significant changes in the weather patterns in Australia. To some extent, this type of climate change has crept up on us in Australia. The way these changing climate patterns will influence rainfall and temperature distributions in eastern Australia will be the most critical environmental outcomes to affect rural Australia probably for decades to come.
Unfortunately there is still conflicting modelling on how a changing climate and a warmer world will eventually pan out, so let's consider what we know at the moment.
Australia's climate has warmed by an average of 1.47 plus or minus 0.24 degrees since national records began in 1910. This might seem small but it is really quite significant and much of this increase has occurred in the 21st century.
Sea surface temperatures have increased by an average of 1.05 degrees since 1900. This has led to an increase in the frequency of extreme heat events over land and sea.
There has been a decline of around 15 per cent in April to October rainfall in the south west of Australia since 1970. Across the same region, May to July rainfall has seen the largest decrease, by around 19pc since 1970. There has also been a smaller decrease in southern Victoria , south east South Australia and Tasmania while in the rest of south east Australia, there has been a decrease of around 10pc in April to October rainfall since the late 1990s.
There was a decrease in streamflow at most river gauges across Australia from 1975 to 2020. This trend has been at least temporarily reversed recently. Overall, rainfall and streamflow have increased across many parts of northern Australia since the 1970s.
With an increase in temperature. there has been an increase in extreme fire weather, and a longer fire season, across large parts of the country since the 1950s. At the same time there has been a decrease in the number of tropical cyclones observed in the Australian region.
Snow depth, snow cover and number of snow days have decreased in alpine regions since the early 1960s although for reasons currently not clear this trend has decreased in recent years - perhaps only temporarily again.
Oceans around Australia are acidifying and have warmed by more than 1 degree since 1900, contributing to longer and more frequent marine heatwaves. Sea levels are rising around Australia, including more frequent extremes that are increasing the risk of inundation and damage to coastal infrastructure and communities.
This is what we know has happened. The next challenge is to determine who these changes will influence the next decade.