Australia Set For An Increase In The Frequency, Intensity And Duration Of Heatwaves Due To Climate Change

09/02/2016 3:12 PM AEDT | Updated 15/07/2016 12:51 PM AEST
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The latest research from the Bureau of Meteorology has revealed that the five-year period between 2011 and 2015 was the world’s hottest on record.

Australia in particular saw more than its fair share of extreme weather during this time, with unprecedented rainfalls in the southeast of the country during 2012 and ongoing droughts in both Queensland and New South Wales.

But have these events been the direct consequences of human induced climate change?

According to Dr Andrew King, Climate Extremes Research Fellow at the University of Melbourne, the answer isn't that straightforward.

“In general we find that with extreme rainfall it is harder to attribute it to climate change,” he said at the Australian Science Media Centre briefing on Tuesday.

“Changes in rainfall are a secondary effect of climate change as opposed to changes in temperatures which is a primary response.

"For Australian extreme rainfall events we find that the effect of natural variability, in this case La Niña, trumps any influence from human induced climate change.”

King did go on to emphasise the clear correlation between climate change and rising temperatures.

“If we’re to look at the probability of very high temperatures like those seen in 2013, they have increased by a factor of about 35 due to climate change,” he said.

Such increases in temperature have led to an increase in heatwaves in Australia which will continue to intensify and last longer, according to Dr Sarah Perkins-Kirkpatrick, Research Fellow at the Climate Change Research Centre, University of New South Wales.

“Over the last 50 years, we have seen a marked increase particularly in the frequency of heatwaves, we’re also starting to see increases in their intensity particularly in the southern half of the continent,” she said at the Australian Science Media Centre briefing on Tuesday.

In particular, both Sydney and Melbourne have seen a marked change of when the heatwave season begins while Canberra has seen a doubling in the number of heatwaves each season.

“Depending on where you are, the way heatwaves have been changing is quite different,” Perkins-Kirkpatrick said.

“For example, Sydney has seen a very marked change in when heatwaves start to occur in the heatwave season, starting almost three weeks earlier on average.”

Such changes to the frequency and intensity of heatwaves have been attributed to the rise in the average increase in the global temperature, which is 0.05 degrees less than the average increase seen by Australia.

“We’ve seen globally an average increase of temperature of 0.85 degrees but Australia has seen an increase of 0.9,” she said.

“Generally people think that you can’t even detect that on a day to day basis and really ‘who cares about a one degree increase’ but this small change in the average temperature can really have a large influence in extreme events like heatwaves.”

“We are also starting to see more record hot weather -- this is weather that we have never ever seen.”

Surprisingly a heatwave was recorded during the build-up to winter in May 2014, with temperatures averaging between 25-26 degrees Celsius across most of the country.

“That particular event was 25 times more likely due to climate change,” Perkins-Kirkpatrick said.

“Globally we are seeing the cooler parts of the year warm faster than the typically warmer parts of the year, such as summer.”

“Those really rare heatwaves that we might have only seen once every twenty years, for example, might occur now once every two years, so expect to see them more often -- it doesn’t mean necessarily that they will be occurring every single day but they certainly will be occurring a lot more often than they used to had climate change not occurred.”

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