If the latest climate report from the Intergovernmental Panel on Climate Change (IPCC) made anything clear, it was that much more needs to be done to reverse the impacts of climate change.
But buried in the 1,000-page document of mostly alarming reading there was one positive gem.
Our action in reducing ozone depletion is, in the short term, offsetting some of the impacts greenhouse gases are having on summer rainfall systems in the Southern Hemisphere.
What does that mean?
It's all to do with a major climate driver known as the Southern Annular Mode (SAM), a belt of strong westerly winds linked to rainfall in the Southern Hemisphere.
The SAM's position — either moving further north or south — can influence which latitudes see the impacts of storm systems and cold fronts, and can also have an influence on temperature.
Without ozone depletion and greenhouse gas emissions, its position over the southern ocean has a natural variability both north and south.
But with those things occurring, the SAM has been trending further south toward Antarctica, research has shown.
With the SAM further south, storm tracks also shift south, away from Australia — changing which areas recieve rainfall.
Australian Antarctic Division principle research scientist Andrew Klekociuk said in the last 20 years however, ozone recovery has been turning that trend around during the summer months, pushing back on the influence of greenhouse gases.
"[Ozone recovery] is starting to relax the change that we’ve seen [in the SAM]," Dr Klekociuk said.
The weakening of the pole-ward trend during the summer months was referenced in the latest IPCC report, released last month.
It's an element of the report climate science professor Julie Arblaster, from Monash University, described as a "really good news story".
"Bringing the [rainfall and storm systems] back equator-ward would certainly help return some of the rainfall patterns to their normal location."
What could this mean for rainfall?
The position of the SAM has different rainfall outcomes for different parts of the Southern Hemisphere and Australia.
Some regions, including eastern Australia, actually experience wetter conditions in summer when the wind-belt is further towards Antarctica.
That means for eastern Australia, a reversal of that trend could mean less rainfall during the summer months, according to Professor Arblaster.
Regions like western Tasmania and New Zealand, however, could see rainfall increase.
But Professor Arblaster said it was hard to say exactly what the pushback means for Australian summer rainfall, because the SAM was not the only factor influencing the weather.
"Different regions have influences from many things and not just the SAM trend," she said.
"For example, the El Nino Southern Oscillation.
"So there is a strong understanding of how the ozone hole has affected the SAM, but how much influence ozone depletion has had on Australian rainfall trends is still a question."
Impact to temperatures
When it comes to temperatures, Professor Arblaster said there was evidence international efforts to limit ozone depletion had also gone a long way in "avoiding" larger temperature rises across the globe.
"The ozone-depleting substances are really strong greenhouse gasses," she said.
"So if we had continued emitting CFCs, then a study by Goyal and co-authors found that would have led to an additional warming of 0.5 and 1 degree up to now in some regions, and additional warming after."
Short-term buffer only
Both the IPCC report, Professor Arblaster and Dr Klekociuk made one thing clear.
The buffer that ozone recovery was providing to the pole-ward shift of the SAM would not last if greenhouse gas emissions were not reduced.
The Antarctic ozone hole has recently started to show signs of recovering since The Montreal Protocol was signed in the late 1980's — an international agreement to phase out the use of ozone-depleting substances such as chlorofluorocarbons (CFCs).
It is currently on track to have recovered by the mid to late 21st Century.
