Climate change doubled the likelihood of the New South Wales heatwave – let’s be clear, this is not natural

The heatwave that engulfed southeastern Australia at the end of last week has seen heat records continue to tumble.

On Saturday 11 February, as New South Wales suffered through the heatwave’s peak, temperatures soared to 47℃ in Richmond, 50km northwest of Sydney, while 87 bushfires raged across the state, amid catastrophic fire conditions.

On Friday, the average maximum temperature right across NSW hit 42.4, beating the previous February record of 42.0. The new record stood for all of 24 hours before it was smashed again on Saturday, as the whole state averaged 44.0 at its peak. At this time, NSW was the hottest place on earth.

A degree or two here or there might not sound like much, but to put it in cricketing parlance, those temperature records are the equivalent of a modern-day test batsman retiring with an average of over 100 – the feat of outdoing Don Bradman’s fabled 99.94 – and would undoubtedly be front-page news.

And still the records continue to fall. Mungindi, on the border of NSW and Queensland, broke the Australian record of 50 days in a row above 35, set just four years ago at Bourke airport, with the new record now at 52 days.

Meanwhile, two days after that sweltering Saturday we woke to find the fires ignited during the heatwave still cutting a swathe of destruction, with the small town of Uarbry, east of Dunedoo, all but burned to the ground.

This heatwave is all the more noteworthy when we consider that the El Niño of 2015-16 is long gone and the conditions that ordinarily influence our weather are firmly in neutral. This means we should expect average, not sweltering, temperatures.

Since Christmas, much of eastern Australia has been in a flux of extreme temperatures. This increased frequency of heatwaves shows a strong trend in observations, which is set to continue as the human influence on the climate deepens.

It is all part of a rapid warming trend that over the past decade has seen new heat records in Australia outnumber new cold records by 12 to one. 

Let’s be clear, this is not natural. Climate scientists have long been saying that we would feel the impacts of human-caused climate change in heat records first, before noticing the upward swing in average temperatures (although that is happening too). This heatwave is simply the latest example.

What’s more, in just a few decades’ time, summer conditions like these will be felt across the whole country regularly.

Attributing the heat

The useful thing scientifically about heatwaves is that we can estimate the role that climate change plays in these individual events. This is a relatively new field known as “event attribution”, which has grown and improved significantly over the past decade.

Using the Weather@Home climate model, we looked at the role of human-induced climate change in this latest heatwave, as we have for other events previously. 

Courtesy of Guardian News & Media Ltd