As coastal properties have been eaten up by the sea, and rainfall records smashed, people have inevitably started asking whether the savage storm that lashed Sydney over the weekend was exacerbated by climate change.
At this stage it’s impossible to draw a causative link between global warming and the dramatic storm system, but a number of climate change-related factors may have contributed to the severity of the tempest.
Dr Karl Braganza is the Manager of Climate Monitoring at the Bureau of Meteorology, and he said that there is research to show these type of storm systems are likely to become more intense but less frequent in the future.
The storms that lashed Australia’s east coast, and in particular Sydney, were what’s known as an “east coast low”. There are typically more than 20 of them each year. As a result the natural variability, particularly in terms of rainfall, makes it difficult to pinpoint what role climate change may have played.
Dr Braganza said that these storm systems are influenced by normal climactic variations, ocean temperatures, and that possible links to climate change occur over and above that.
Climate Change has been making its presence felt over recent months, as Australia sweltered through its warmest Autumn on record. The unseasonably high temperatures have driven a mass coral bleaching event across large sections of the Great Barrier Reef.
Dr Braganza said the same ocean temperatures, which have been “trending to record highs”, may have played a part in the weekend’s storm. “We know that must have some influence on the strength of the east coast low,” Dr Braganza said.
“Straight off the bat you would say increased ocean temperatures provide a little more fuel for these storms.”
At this stage, we just don’t know how much, and any research to determine the contribution of heightened ocean temperatures would likely be months in the making.
Its role in the storm system may be uncertain, but the angry ocean certainly made itself felt as waves of up to eight metres pounded the coast around Sydney. On the city’s northern fringe, properties at Collaroy were badly damaged by the surging sea.
The Sydney Morning Herald reports that between 10 and 15 metres of coastline, and a number of peoples’ backyards, were swallowed up by the waves. Dr Braganza said that rising sea levels will exacerbate these kinds of affects.
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“[That’s] one aspect of these storms that is getting worse over time, and can be expected to worsen significantly into the future,” he said. “We know that [coastal erosion from storm surges]is progressively becoming more damaging because the sea level is rising.”
Oceanographer Dr John Hunter said “obviously the storms would have been there anyway…[but]what the sea level rise has done is just to add an extra 10 or 20 centimetres on top of it,” meaning that storm surges are coming off a higher base.
When the erosion occurs on a sandy beach, like the one at Collaroy, Dr Hunter said “what happens is you tend to get the storm eroding the beach, and before the next storm the beach won’t fully recover, so you’ll never get back completely to where you were”.
“Then the next storm that comes along will eat it back a little bit more,” he said. “Sea level rise is going one way, and that can have only have one affect basically, and it’s always bad,” Dr Hunter said.
Last week the Climate Institute released research which suggested that property owners face an $88 billion damage bill from coastal erosion, and called for the issue to be fully incorporated into the process of major banks and insurers.
There is strident debate about how much sea levels will rise in coming decades.
In March, renowned climate scientist Dr James Hansen published a paper which argued that accepted figures may be far too conservative, and we could face several metres of sea level rise over the coming century.
For most people on Australia’s east coast, however, the torrential rain was the most noteworthy aspect of this weekend’s remarkable storm. Because of the extreme variability in rainfall brought on by east coast lows, it’s hard to say whether climate change contributed to the severity of the deluge.
We do know that since carbon emissions really took off around the mid-twentieth century, the amount of water vapour in the atmosphere has climbed by roughly seven per cent. “We know that as climate change progresses you’ll get more intense rainfall out of these [east coast low]systems,” Dr Braganza said.
Earlier this year a team of researchers at the University of New South Wales published a paper which found that rainfall events are becoming more intense, but also more centralised around the eye of the storm. One of the authors of that study, Professor Ashish Sharma, said that “Australian research shows climate change is causing shorter, more concentrated, and more intense storms”.
“Researchers from the University of New South Wales analysed the data from 1300 rain gauges and 1700 temperature stations across Australia,” Prof Sharma said, “and found that flooding from more concentrated storms was up to 60 per cent more likely due to climate change”.
Much of Australia’s east coast has seen flash flooding as a result of this weekend’s torrential downpours, with homes and businesses in Sydney threatened in places like Picton and Camden. The east coast low is now moving south, and Tasmania and Victoria are bracing for flash floods, with experts warning that Launceston may be facing its worse flooding in 90 years.
The wild weather has reportedly claimed three lives so far.
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