Are wild winter temperatures a warning for southern summers?

It’s winter in the southern hemisphere, but try telling that to folks living in Chile.

The nation which lines the southwestern coastline of South America has seen double-digit temperature anomalies – or deviations from a long-term average temperature – for this time of year.

Vicuña, a small town in the Andes, saw the mercury peak at 37°C. The nearby port town La Sirena – which has an average August maximum of about 15°C – has seen week-long temperatures over 35 degrees.

It’s been a similar pattern across the rest of the country, and neighbouring ones with parts of Brazil, Bolivia and Paraguay also pushing towards 40°C. Argentina experienced its hottest first day of August in 117 years, with an Argentinian meteorological service spokesperson telling the Associated Press some regions had seen temperatures “10 to 15 degrees above what is normal for this time of year”.

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This map shows the temperature anomaly for South America against baseline measurements. Orange and red shaded regions indicate temperatures above the baseline. Around the Chile-Argentina border these are in excess of 10°C above the average. Credit: Data visualised by University of Maine/ from NCEP CFSV2 and CFSR data.

The heat sweeping South America comes amid months of heatwaves baking parts of the northern hemisphere.

“It does look really remarkable [but] it’s only just happened and it’s kind of hard to tell exactly the relative roles of climate change versus climate variability and other factors,” says Dr Andrew King, a climate science lecturer at the University of Melbourne.

“The temperatures are so unusual, so extreme, that it’s really quite likely that climate change has played a major role.”

The WMO is likely to declare July 2023 as the hottest month on record. Data mapped by the University of Maine from US National Oceanic and Atmospheric Administration (NOAA) observations shows the global air temperature almost every day in July beat the previous daily highpoint set in 2016.

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2m air temperature data until 3 August. Credit: Data visualised by University of Maine/ from NCEP CFSV2 and CFSR data.

At the same time, parts of China have seen unprecedented rainfall.

The capital Beijing set a 140-year rainfall record – 744.8 mm recorded in just under two days – which claimed 20 lives, according to news agency Reuters.

Tens of thousands of people have been evacuated because of the deluge brought by the aftermath of nearby Typhoon Doksuri. Some have suggested climate change has exacerbated the impacts of these events. In 2021, the Intergovernmental Panel on Climate Change’s updated physical science of climate change report identified heavy rain and flooding would “intensify and be more frequent” in parts of Asia, as well as see an intensification in tropical storms.

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Local residents paddle a makeshift boat as they help others in an area inundated with floodwaters near Zhuozhou, Hebei Province south of Beijing, China. Credit: Kevin Frayer/Getty Images

Despite atmospheric conditions not being developed enough for Australia’s weather bureau to declare El Niño, unusual temperatures across the nation have brought springlike conditions to the middle of winter.

They include daily highs of 21.9°C in Sydney, 19.8°C in Melbourne, 24.7°C in Adelaide, and 25.0°C in Perth.

One-day maximums at these levels aren’t unheard of – Melbourne’s maximum was the hottest for this time of year in a decade – though some are certainly the hottest for some time. Adelaide’s 24.7°C Thursday was the warmest early August day in nearly half a century.

Much of Australia’s east saw above average temperatures in July. Credit: Bureau of Meteorology.

Warmer winters might be nice, but they’re probably driven by climate change

Single-day hot events, even heatwaves in the middle of summer like those seen across Europe and the United States, are not unusual and are even expected, says King.

NOAA has also declared an El Niño. This ocean phenomenon can add degrees of warmth to what parts of the US might normally expect from a typical summer.

But some of the events below the equator are cause for concern.

“In some of these cases, with some of these temperatures, we just wouldn’t be getting them without human-caused climate change,” King says.

“It is worth saying though, in the northern hemisphere in summer, there’s always some extreme weather. We’ve seen some extreme heat waves last few years, some really bad flood events as well. Even though we’re seeing extreme events, we would expect extreme events at this time of year.

“In terms of the Australian heat, our winters are warming because of climate change, so we know that we’re more likely to see these warmer days than we used to.”

But with El Niño looking increasingly likely, and sudden spikes in winter temperatures for parts of the region, King warns the coming spring and summer are shaping up to bring some challenging heat conditions.

“We’re having quite warm conditions across much of Australia at the moment and at this time of year, I think people quite like that. People like warmer winter weather,” he says.

“But is a bit concerning, given the spring and summer ahead with a likely El Niño developing, we could see some really significant heat events.

“It’s very early to say. But I think we should be concerned about the summer that lies ahead.”

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