Australia continues to heat up. Days of extreme heat continue to become more frequent, wildfire weather continues to rise, and sea levels continue to rise.
- Domestic and global temperatures continue to rise despite the COVID-induced decline in emissions
- Australia’s climate has now warmed by around 1.5 degrees Celsius since national records began in 1910
- There have been heavy rains in the southeast this year, but long-term trends towards a drying rainy season in South Australia remain
The latest biannual State of the Climate report, released jointly by the Bureau of Meteorology and the CSIRO, showed that even the global pandemic with a downturn in industry and transportation has not been enough to stymie relentless warming.
Blair Trewin, a senior research scientist at the Bureau of Meteorology, said COVID has had an impact on greenhouse gas emissions.
“Globally, at its peak, emissions were down about 6 percent. In Australia, about 5 percent,” he said.
Sadly, post-COVID global emissions have returned to near or above pre-COVID levels.
But according to Dr. Trewin, Australia is bucking the trend, with levels slightly up but still “significantly lower than 2019”.
Unfortunately, however, these changes in emissions have been too small to have a perceptible impact on climate consequences such as global temperatures, said Dr. Trewin.
“In the normal course of things, we have variations of something more or less than 20 or 30 percent in the change of CO2 levels per year just through natural variability.”
Natural variability that comes in the form of weather events such as El Niño and La Niña.
“So the kinds of changes we’ve seen in emissions, if limited to just one year, won’t really be detectable in carbon dioxide levels beyond that natural variability,” he said.
“If they were sustained longer it would be a different story.”
Barring a drastic reduction in greenhouse gas emissions, climate change is something we will have to continue to grapple with.
Can we expect more floods like this?
According to Dr. Trewin, this year’s sheer downpour in the southeast will not be enough to reverse the long-term trend of lower cool-season rainfall in South Australia.
“Maybe it weakened it a bit in the short term,” he said.
He said many of the extreme rainfall we’ve seen in recent years have occurred in the summer, when there hasn’t been a huge change in southern rainfall.
“We expect extreme rainfall to increase over time, even in areas where average rainfall is decreasing.
“How much that increase depends on how much global warming we see.
“It’s much more evident in the models, at 2°C of warming or more than at 1.5°C.”
“Floods and flood impacts are much more than just precipitation,” he clarified.
“But the precipitation component: We have pretty clear expectations with a warmer atmosphere being able to hold more moisture, other things being equal.”
Can we expect more La Ninas?
The report states that El Niño and La Niña activity in the past 50 years has been greater and more significant than in the previous 50.
But it’s unclear whether this is a long-term trend.
“But what we expect going forward is that even if there isn’t a significant change in the frequency of El Niño and La Niña, we have a fairly high level of confidence that the extreme rainfall associated with El Niño and La Niña will get stronger.” , according to Dr. Trewin.
“So heavier rains with La Niña and more droughts with El Niño.”
The other big factor in the flooding in recent years has been the triple dip, with La Niña after La Niña, after La Niña mixing to saturate soils and fill dams to overflow.
Multi La Niñas are rare, and Dr. Trewin said there was no clear evidence in the projections to suggest long-running events of consecutive years would become more or less common in the future.
“But one of the things about climate change is that sometimes unexpected things happen.
“So it’s certainly something we’ll keep an eye on.”
Perhaps the most notable difference in this State of the Climate report from previous editions is the dramatic decline in Antarctic sea ice cover in recent years.
For most satellite records, from the late 1970s through 2015, Antarctic sea ice extent was mysteriously increasing, despite rising global temperatures and declining Arctic sea ice, as one would expect .
“The sea ice levels we had around 2014/15 were as high as they have been, at any point in the satellite era,” according to Dr. Trewin.
“But we started to see Antarctic sea ice decrease from 2015 onwards. At the time of the last report it hadn’t lasted very long, but that trend has continued.
“Indeed, early 2022 saw Antarctic sea ice extent reach record lows.”
Why sea ice was increasing and why it recently reversed is an ongoing area of research.