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From drying rainforests to heavier downpours, Australia’s climate is changing

Professor Karoly said that, while the lineage of the forests dates back many millions of years, changes were underway in a matter of a hundred years, far faster than species could adapt.

Similarly rapid changes were underway in the oceans around Australia although their remoteness from most people’s experiences meant they were not well known.

The Tasman Sea is warming at four times the global average, placing at risk giant kelp forests off the Tasmanian coast.

The Tasman Sea is warming at four times the global average, placing at risk giant kelp forests off the Tasmanian coast.Credit:Craig Sanderson

The Tasman Sea, for instance, is warming four times faster than the global average in part because the East Australian Current is strengthening and dragging tropical water much further south. Key ecosystems, such as the giant kelp forests off Tasmania, are at risk from more frequent heatwaves.

“A marine heatwave [in the Tasman Sea] similar in intensity to those in 2015–16 and 2017–18 is currently expected to occur approximately once every 20 years,” the report said. “Under [a global] low-emissions scenario, it is expected to occur once every 15 years by the end of the century, and under the high-emissions scenario, a marine heatwave is projected to occur almost every year.”

Thunderstorms were another area of interest, including how the number of danger so-called “pyrocumulonimbus” clouds formed out of bushfire plumes.

At least 35 of them were detected during Black Summer, increasing the risk of erratic winds on unpredictable fire behaviour and ignite new blazes ahead of the fire front, the report noted.

East coast lows, another big weather event affecting coastal areas from Queensland to Victoria, were among phenomenon undergoing change. The Hub developed new ways to analyse the complex storms and found the most extreme rainfall near eastern Australia was frequently caused by such low-pressure systems combining with a front and a thunderstorm.

The researchers found short-duration events produced by thunderstorms could potentially increase in intensity by about 15 per cent per degree of global warming.

A line of storms associated with an east coast low sweeping over the Hawkesbury River north of Sydney in July 2020.

A line of storms associated with an east coast low sweeping over the Hawkesbury River north of Sydney in July 2020.Credit:Nick Moir

Andy Pitman, head of the ARC Centre of Excellence for Climate Extremes and a Hub advisor, said east coast lows were “one of the least effectively studied phenomena in Australia” even though their impacts can be huge in terms of floods, storm surges and wind damage.

“I worry about how ill-prepared we are for any climate signal for east coast lows,” he said.

At the other end of the weather spectrum was so-called flash droughts, another of the Hub’s research areas. These are triggered by lower-than-average rainfall, accompanied by abnormally high temperatures, a dry atmosphere, clear skies and more sunshine, and can be perilous for crops.

Drone vision of Lake Burrendong in the central-west region of NSW in January 2020 when water levels fell to a couple of per cent of capacity.Credit:Nick Moir

The researchers showed the sudden dry spells could be forecast, and they can happen even in winter.

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The outgoing Hub cost $23.4 million, with matching contributions from CSIRO, the Bureau of Meteorology and five universities including the University of Melbourne and the University of NSW. Its successor has been allocated federal funding of $38 million over six years.

While welcomed, “we are not investing remotely enough given the scale of the risk”, Professor Pitman said, adding the new funding was “not even one year’s salary of a top soccer player”.

Simon Marsland, a CSIRO senior scientist who will lead the new Climate Systems Hub, said how communities could adapt to the warming impacts still to come will be one priority as will efforts to work closely with Indigenous populations that are often particularly exposed to extreme weather.

Dr Marsland noted the current record-shattering heatwave in Canada, with near 50-degree temperatures recorded even at a latitude as far as 50 degrees north, were “a good reminder that climate change is here now and not something in the far future”.

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