Unpredictable El Niño means summers aren’t always the same between hemispheres

Temperature records are tumbling in the northern hemisphere, and Australians and accustomed to scorching summers might receive that news with trepidation, particularly with the threat of El Niño persisting to the end of the year.

On Tuesday, the World Meteorological Organization declared the first week of July as having the planet’s hottest daily temperatures on record. Last month was also the hottest June ever recorded.

Regionally, parts of Europe, the US and mainland China have set new temperature benchmarks, with the potential for more extreme heat to come.

Climate scientists have been predicting spikes in global temperatures for years, but it appears the current records are being particularly exacerbated by El Niño, a natural climate phenomenon forced by declining trade winds across the Pacific resulting in the ocean’s warmer waters shifting towards the Americas.

Both the WMO and the US National Oceanic and Atmospheric Administration have declared El Niño.

But treating these records temperatures as a portent for a sizzling Christmas in the southern hemisphere, is, to an extent, ill-advised.

Australia’s Bureau of Meteorology remains on ‘El Niño alert’ but is yet to make a formal declaration. It’s keeping a lookout for atmospheric shifts that firm up the likelihood El Niño persists into the latter months of the year.

Ruby Lieber, a researcher at the Australian Research Council Centre for Climate Extremes based at Melbourne University explains that what’s being witnessed amid El Niño in the northern hemisphere doesn’t necessarily mean southern nations will experience likewise at the end of the year.

“We can’t forecast that far ahead, but, if the El Niño persists [to the end of the year], we know that would mean for our summer, generally, warmer than average [temperatures], especially in the southern part of the continent,” Lieber says.

“But every event is unique, so we can’t be certain what we’re going to see in response. Sometimes we’ve had really strong events, where the sea surface temperatures have been really above normal, and we haven’t seen much of an impact in Australia.”

Even though the events in the northern hemisphere in recent weeks aren’t guaranteed to be replicated below the equator later this year, El Niño years typically result in higher-than-average temperatures, so it’s not unreasonable for those living below the tropics to anticipate hotter and drier conditions.

It’s not helped by the persistent increase in average global temperatures fuelled by record levels of carbon being spewed into the atmosphere by energy, agriculture and transport industries and use. Every decade since 1980 has been hotter in terms of average air temperature at the planet’s surface.

“Human-caused climate change is increasing temperatures globally, including in the Northern Hemisphere as well as Australia, with this leading to more frequent heat extremes,” says Andrew Dowdy, a principal research scientist at the Bureau of Meteorology.

“For Australia, temperatures have increased by an average of 1.47°C since national records began in 1910, including with more frequent and more intense heat extremes. These trends are virtually certain to continue into the future for coming decades, including for more extreme hot temperatures and heatwaves in Australia.”

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