Antarctic sea ice extent hits record highs in latest State of the Climate report

Antarctic sea ice extent hits record highs in latest State of the Climate report

Australia continues to warm. Extreme heat days continue to become more frequent, fire weather continues to intensify, and sea levels continue to rise.

The latest semi-annual State of the Climate report, jointly released by the Bureau of Meteorology and CSIRO, showed that even the global pandemic with a slowdown in industry and transportation has not been enough to stem global warming. incessant climate.

Senior researcher at the Bureau of Meteorology Blair Trewin said COVID is impacting greenhouse gas emissions.

“Globally, at its peak, emissions were down about 6% or so. In Australia it was about 5%,” he said.

Unfortunately, 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 a bit up but still “significantly lower than they were in 2019”.

Unfortunately, these changes in emissions have been too small to have a noticeable impact on climate consequences such as global temperatures, Dr Trewin said.

Map of Aust with the key points listed: sea level rise, increased sea and land heatwaves, fewer but more intense cyclones
Climate trends continue despite the wet year.(Bureau of Meteorology/CSIRO)

“In the normal course of things, we have variations of plus or minus 20 or 30% in the change in CO2 levels per year simply by natural variability.”

Natural variability in the form of through weather events such as El Niño and La Niña.

“So the kinds of changes that we’ve seen in emissions, if confined to a single year, won’t really be detectable in carbon dioxide levels beyond that natural variability,” he said. he declares.

“If they were held longer, that would be a different story.”

So unless there is a drastic reduction in greenhouse gas emissions, climate change is a problem we will have to continue to deal with.

Can we expect more floods like this?

Dr Trewin says this year’s outright deluge in the south-east will not be enough to reverse the long-term trend towards less cool-season rainfall in southern Australia.

“That may have weakened him a bit in the short term,” he said.

He said many of the extreme rainfall events we’ve seen in recent years have occurred in the summer, while there hasn’t been a huge change in rainfall in the south.

“We expect that over time, extreme precipitation will increase, even in areas where average precipitation is decreasing.

“The magnitude of this increase depends on the magnitude of global warming we observe.

“It’s much more evident in the models, at 2C warming or more than at 1.5C.”

“Floods and flood impacts are much more than just rainfall,” he said.

“But the rainfall component of it: we have pretty clear expectations with a warmer atmosphere capable of holding more moisture, all things being equal.”

Can we expect more from La Niñas?

The report indicates that El Niño and La Niña activity over the past 50 years has been higher and greater than in the previous 50 years.

But it’s not clear if this is a long-term trend.

“But what we expect going forward is that even if there is no significant change in the frequency of El Niño and La Niña, we have a fairly high level of confidence that extreme rainfall associated with El Niño and La Niña getting stronger,” according to Dr. Trewin.

A graph showing global temperature changes over the past 70 years
La Niña generally brings cooler global temperatures, but with anthropogenic climate change, even relatively cool La Niña years are well above past temperatures.(Bureau of Meteorology/CSIRO)

“So more intense rainfall with La Niña and more drought with El Niño.”

The other major factor in flooding in recent years has been the triple dip, with La Niña after La Niña, after La Niña worsened 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-lasting consecutive events would become more or less frequent in the future.

“But one of the things about climate change is that sometimes unexpected things happen.

“So that’s definitely something we would keep an eye on.”

Antarctica melt

Perhaps the most notable difference in this State of the Climate report, compared to previous editions, is the dramatic decline in sea ice cover in Antarctica in recent years.

For most satellite records, from the late 1970s to 2015, Antarctic sea ice extent was mysteriously increasing, despite rising global temperatures and shrinking Arctic sea ice, as might be expected.

Chart showing Antarctic sea ice increase to 2015 before sharp decline, brief recovery to 2020 but further decline
Antarctic sea ice was bucking global warming trends, but has seen a steep decline in recent years. (Bureau of Meteorology/CSIRO)

“The sea ice levels we had around 2014/15 were as high as they had been at any time during the satellite era,” Dr Trewin said.

“But we started to see the Antarctic sea ice receding from 2015. At the time of the last report, this hadn’t lasted very long, but this trend has continued.

“In fact, at the start of 2022, we saw Antarctic sea ice extent reach record highs.”

Why the sea ice was rising and why it recently overturned is an area of ​​ongoing research.

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