It may have been six months ago, but dazzling and vibrant sunsets and sunrises observed across Australia in recent weeks have been linked to the long-lasting impacts of a volcanic eruption in January.
According to scientists, they could continue for another year.
In Albany, on the south-coast of WA, photographer Ilona Diessner said she had noticed lots of vivid oranges in the sunsets and sunrises lately.
That compared to more purple and pink hues last year.
"I've noticed that the sunrises are as colourful as the sunsets, which I didn't see much of last year," she said.
On January 15 this year, undersea volcano Hunga Tonga-Hunga Ha'apai erupted in a massive explosion thought to be one of the world's largest in recent decades.
Analysis from NASA showed it burst through the troposphere, the stratosphere and even into the third layer of the atmosphere — the mesosphere, reaching 58 kilometres at its highest point.
University of Melbourne atmospheric chemist Robyn Schofield said the "big and energetic" eruption had pumped particles such as ash, sulphates and water vapour into the stratosphere.
"It injected a lot of material into the stratosphere, and that's almost certainly contributing to what we're seeing right now," she said.
"Particles in the atmosphere, on the whole, provide a surface to scatter and it's the scattering of light that causes our beautiful sunsets and sunrises.
"So what happens is the troposphere is all in shadow and about 20 to 25 minutes after sunset, most of the light is scattering off the stratosphere and down into our eyes."
She said there was currently estimated to be about three times more aerosols in the stratosphere than normal.
Three decades since last mega eruption
Professor Schofield said the reason Australia was still seeing the impacts six months later was partly due to the size of the volcano.
"It has been close to 30 years now since we have had such a big volcanic eruption," she said.
"So really, the last time we had enough materials equivalent to what we're seeing at the moment, was Mount Pinatubo."
The ongoing vivid sunsets and sunrises were also due to the time it took for the air to circulate, gradually moving southward toward Antarctica.
"We have fast winds in the stratosphere, and it takes about 12 days for an injection of material to circumnavigate the globe," she said.
"But it also needs to move slowly toward the poles and come out.
"And that overturning circulation, which will remove material from the stratosphere, will take between three and five years."
However, she said the dramatic sunset colours would likely not last as long, becoming less noticeable as the material thinned out, likening it to dropping a food colouring into water.
"So it is mixed around quickly because of the strong easterly winds, and then it's moving down toward the poles," she said.
"You've got a larger volume that it's mixing across, so you will dilute the concentration."
Greenhouse effect studied
Professor Schofield said researchers were also keeping a close eye on the broader impacts of the materials produced by the eruption.
The underwater volcano pushed a large amount of water vapour into the stratosphere, rather than sulphate.
"So we're really just watching what the large amount of water vapour will mean," she said.
"Because water vapour will have an influence on ozone, water vapour is a strong greenhouse gas.
"And when we have a lot of sulphate aerosols, that certainty means we see a cooling at the surface, but the prediction is we will actually see a warming from this."
