THE spell of cooler than expected weather in the south-eastern states in late winter and early spring is likely to come to an end soon with north-west winds dragging down warmer air from the heat engine over the north-west of the continent. Temperatures close to 40 degrees have already been recorded in this region.
In addition, the Southern Ocean fronts have weakened a fair bit recently and with the potential for warmer weather along with less influence from the “winter westerlies” will increase the chance of a little thundery weather with coming changes and associated trough lines over the next few weeks.
Nevertheless, there has been little change in the long term prognosis of a developing El Nino which might be fairly weak but which also has the potential to last well into 2019.
So apart from the occasional one off event, it is likely that rainfall in the majority of the next four to six months will be slightly down on normal although it is likely to be variable in places with more rain expected than in the previous six months in central and northern parts of the state.
The very term outlook is unclear because we are entering a period that has no comparison in recorded human history.
Carbon dioxide is an important heat-trapping (greenhouse) gas, which is released through human activities such as deforestation and burning fossil fuels, as well as natural processes such as respiration and volcanic eruptions.
Last month its concentration in the atmosphere reached a record 408 parts per million, as measured at Mauna Loa Observatory, high up in the Hawaiian islands.
By reconstructing carbon dioxide levels during the past 40,000 years from ice cores, we know there has been no periods when levels exceeded 300 parts per million.
There is uncertainty what effects this will have on moisture distribution and therefore on long term rainfall patterns in Australia, but it will result in the continued trend of warmer conditions with higher evaporation levels which we will need to cope with and plan for.