Overseeing Australia’s two-yearly report card on the State of the Climate might seem like demoralising work, with the outlook heading in one direction – hotter, more extreme and more unpredictable.
But reflecting on what it’s like to compile this report, the Bureau of Meteorology’s (BOM) manager of climate monitoring Dr Karl Braganza has a surprising response.
“Certainly sobering is a word that comes up, sometimes I also think that maybe my job isn’t so difficult,” he says.
The report has a clear message – the world is sick, it’s addicted to fossil fuels and the only way to bring the temperature down is to get off them.
“I’m a bit like a doctor and I just have to say, ‘hey, this is what’s going on … You need to get to net zero as quickly as possible,'” Dr Braganza says.
“That’s a little bit like telling someone who’s got a large drinking habit or smoking habit, ‘you need to quit that as soon as possible.'”
Just like a patient with a drinking problem some of the damage is already baked in, with the report outlining that projected warming up to 2040 is largely determined by greenhouses gases that have already been emitted.
Scientists can roughly say how much the world is going to warm over the next decade, but what impact that will have on extreme weather is unpredictable.
“It means that climate change and the rate of change in particular is probably holding some surprises in terms of the impacts that it has across Australia,” Dr Braganza says.
But by kicking our habit of producing dangerous greenhouse gases as quickly as possible, the damage can start to be repaired.
“Obviously making that change is really hard. It can’t just happen overnight,” Dr Braganza says.
“It involves the economic system, the social system, the engineering systems.
“We’re grappling with how do we reduce to net zero as quickly as possible.”
There’s a predictability to reports documenting the increase in global temperatures in line with greenhouse gas emissions, making them depressing reading.
But there is one figure that has surprised scientists over the past two years, according to Dr Braganza.
“The increase in ocean temperatures has been something really significant for the climate science community,” he says.
“There are changes that are many standard deviations above the mean over the last couple of years.”
Dr Braganza says high ocean temperatures are having flow-on effects across the climate system.
“Things like record low sea ice or record high ocean temperatures is really significant for us [at the BoM] because it means that relying on past history as an analogue for what might happen in the next few months is increasingly less confident.
“The rate of setting records in the climate system both in the Australian region and globally is something that’s really significant.”
What do the numbers mean for our weather?
The State of the Climate 2024 states that Australia’s climate has warmed by 1.51 degrees since 1910, while sea surface temperatures have increased by an average of 1.08 degrees since 1900.
The report shows we are already living in a ‘new climate’ with increased frequency of extreme heat events over land and oceans, longer fire seasons, more intense heavy rainfall and sea level rise.
It also unpacks what the weather of our future will look like as warming increases.
Heat extremes
While the average temperature has increased in Australia and globally, so too has the frequency of extreme heat events.
2019 remains Australia’s warmest year on record, while eight of the nine warmest years on record have occurred since 2013.
The report warns extreme heat has caused more deaths in Australia than any other natural hazard and has major impacts on ecosystems and infrastructure.
The report found that there were fewer heat extremes from 2020 to 2023, thanks to La Niña conditions, but the numbers were still high when compared to the years prior to 2000.
“Largely, that variability is driven by rainfall,” Dr Braganza explains.
“Wet periods in Australia tend to have less extreme heat days and dry periods and drought periods tend to have more.”
But the overall trend is stark.
“The rate of change in this graph also points to how rapidly our climate system is changing,” Dr Braganza says.
“That really means that the climate of the 1980s and the 1990s is very different to the climate that we’re experiencing today.”
Shifting currents
Climate research manager at the CSIRO Dr Jaclyn Brown says warming oceans are also impacting the patterns of ocean currents.
For example, the East Australian Current now extends further south, creating an area of more rapid warming in the Tasman Sea, where the warming rate is now twice the global average.
But it’s also leading to feedback loops that scientists don’t fully understand.
“The East Australian Current is shifting further south because of changes to the winds and the winds change because of changes to the surface temperature of the ocean,” Dr Brown explains.
“There’s these feedbacks between the atmosphere and the ocean as they talk to each other.
“As one thing changes, it changes something in the other one which feeds back to the atmosphere.”
Warming of the ocean leads to more frequent and intense marine heatwaves, with devastating effects on marine ecosystems, including depleting kelp forests and seagrasses.
Hot oceans are also contributing to sea level rise, with the report stating globally mean sea levels have risen by around 22 centimetres since 1900.
“Things, when they’re warmed, expand and that’s true for water as well, Dr Brown says.
“About a third of the sea level rise that we’re seeing is purely from the oceans warming up.”
But sea level rise isn’t something you can necessarily see at your local beach, and doesn’t happen evenly around the globe.
“Why does it vary? It doesn’t just go up like a bathtub,” Dr Brown says.
“There’s a lot of other factors in what happens with sea level. One of them is the ocean currents.
“The rest of the sea level rise is due to ice melting over Antarctica and Greenland and a change in the amount of water over land.”
Extreme rainfall on one end, drought on the other
The other significant takeaway from the report is that changes to rainfall are inconsistent, with some places experiencing extreme rainfall and others drought.
In the south-west of Australia, there has been a decline of around 20 per cent of rainfall from May to July since 1970.
South-east Australia has also seen a decrease in cool season rainfall of about 9 per cent since 1994.
In contrast, the wet-season rainfall in northern Australia has increased by around 20 per cent since 1994.
“We’re seeing a shift in circulation as the planet warms,” Dr Braganza says.
“We’re getting less rain from those systems over the cooler months of the year. Conversely, over northern Australia, it’s been wetter over the last 30 years.”
“The intensity has increased by around 10 per cent or more in some regions, particularly in the north, and that’s associated with the increased moisture-holding capacity of the atmosphere.”
The fire season is also becoming longer and more intense.
“We are now starting to see fires almost every year occur in late winter and early spring, it’s also pushing later into autumn as well. ” Dr Braganza says
“2023 was one of Australia’s biggest bushfire seasons in terms of area burned, and that’s largely due to the fuel growth that we’ve seen in some of the northern parts of the continent over the years preceding last year.”
Greenhouse gas emissions
So how do we stop things from getting worse? To go back to Dr Braganza’s drinking analogy, it won’t stop warming until we stop emitting greenhouse gases.
“Our ecosystems can adapt and they’ve adapted for millions of years as climate changes,” Dr Jaclyn Brown from the CSIRO says.
“But the speed from anthropogenic [human-caused] climate change means that these changes are happening very quickly.
“And so the ecosystem can’t re-establish itself or move or regenerate somewhere else.”
The Paris Agreement, which Australia and the world have signed up to, aims to keep warming below 2 degrees Celsius and as close to 1.5 degrees as possible to prevent “dangerous anthropogenic interference with the climate system”.
Because greenhouse gases remain in the atmosphere, we’ve got a set amount we can emit before the world crosses that threshold leaders have set for themselves. But how long it takes to reach it isn’t set in stone.
It’s like having a set amount of money in the bank; how quickly you spend it determines how long it will last. The more CO2 we emit each year, the closer the date we have to stop gets.
According to Dr Brown, we’ve got about seven years if we keep emitting at current rates.
“It’s the rate of change that has slowed down. We’re seeing the same amount of greenhouse gases now coming out year by year, but that’s adding to the total,” Dr Brown says.
“At our current rate of emissions, if we keep emitting the same amount as we are at the moment, we’ll exceed our limit in seven years if we’re going to stabilise at 1.5 degrees.
“So, seven years to really do something about the amount of carbon dioxide that we’re emitting.”
If emissions start to drop now then that number could grow, but while the world may have passed peak global emissions, we’re not yet on track to reducing them.
Australia lags behind much of the world when it comes to reducing emissions, so if our summers and winters are to stay recognisable, along with the world, we need to quit fossil fuels.
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