Heatwaves have become more frequent and have been lasting longer across much of the planet, including Australia, over the past seven decades and the trend is accelerating as the world warms.
Researchers from the ARC Centre of Excellence for Climate Extremes based at the University of NSW said the findings emerged from the first comprehensive assessment of heatwaves down to regional levels.
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| Australia is among the parts of the world experience more frequent and longer heatwaves, and the trend is accelerating as the planet warms up. Credit: Twitter/@andrewmiskelly |
Typically a heatwave would be at least three successive days in the top 10 per cent of warmest days for that time of the year for a particular location. The cumulative or additional heat is based on counting the extra degrees above that 90th percentile threshold using the Berkeley Earth temperature dataset.
For Australia, the worst heatwave season - such as the 2009 belter across southern Australia - caused an additional 80 degrees of cumulative heat across the country, the paper found. For Russia in 2010 and the Mediterranean in 2003, their most extreme seasons involved 200 degrees of extra heat.
“Not only have we seen more and longer heatwaves worldwide over the past 70 years, but this trend has markedly accelerated,” Sarah Perkins Kirkpatrick, the paper's lead author, said.
“Cumulative heat shows a similar acceleration, increasing globally on average by 1-4.5 degrees each decade but in some places, like the Middle East, and parts of Africa and South America, the trend is up to 10 degrees a decade.”
Anthropogenic climate change caused by rising levels of greenhouse gas emissions was driving the shift in heatwaves, the paper said.
As heatwaves are getting longer, average intensity changes during hot spells are statistically insignificant for most parts of the world. The exceptions, though, include southern Australia and small parts of Africa and South America where heatwave intensity is showing a detectable rise over time, the researchers said.
Teasing out the regional variations was important because areas that were enduring longer, slightly warmer heatwaves would require different management systems for public health and energy supply than shorter, more intense events – even if cumulative intensities were similar, the paper said.
Trend changes were not globally uniform in magnitude, with the biggest shifts occurring in regions already "known to experience disproportionately more adverse effects of climate change", it stated.
“This research is just the latest piece of evidence that should act as a clarion call to policymakers that urgent action is needed now if we are to prevent the worst outcomes of global warming," Dr Perkins-Kirkpatrick said. "The time for inaction is over."
Links
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