Pounding rain arriving on the heels of an unseasonably wet summer has displaced thousands of people and inundated hundreds of kilometres of Australia’s southeast coast. Scientists say the answer on whether climate change is the culprit…is complicated.
“Life-threatening floods have washed away homes and businesses with a deluge of rain inundating hundreds of kilometres of the New South Wales coast,” writes The Guardian. “The floods come a little over a year after the same areas were ablaze from unprecedented bushfires fuelled by global heating that burned entire towns and killed billions of animals.”
That has left many asking if the flooding is “another display of force from the long arm of the climate crisis.”
The answer, according to experts interviewed by The Guardian, is “complex and nuanced.” Blair Trewin, a climate scientist with Australia’s Bureau of Meteorology, noted that while the high daily rainfall totals registered earlier this month are not unusual in themselves, they would typically be localized, not spread across a large swath of territory.
Trewin added that while the present La Niña weather pattern is “generally associated with wetter-than-average conditions,” those conditions usually pertain more to inland areas of New South Wales, rather than the coast.
These subtle caveats come alongside some undisputed physics: “A warmer atmosphere can hold more moisture—about 7% for each degree of warming,” The Guardian writes, citing Steve Sherwood, deputy director of the Climate Change Research Centre at the University of New South Wales.
“So we know that something like 5% to 10% of the rain we are getting now is from global warming and the rest would have happened anyway,” he said.
At 2°C further warming, Australia could see downpours exceeding today’s worst by anywhere from 11 to 30%.
Even so, climate attribution scholars remain cautious about asserting human influence on rainfall patterns “because of all the different factors that can influence the systems that deliver rain,” The Guardian writes. For example, while a 2010/11 study of floods in Australia’s northeast was able to pinpoint warming oceans as the primary cause of increased rainfall, a southeast study conducted a year later “failed to detect any human influence.”
Describing weather systems as filled with “noisy” complexity, Michael Grose, a climate projections scientist at the Canberra-based Commonwealth Scientific and Industrial Research Organization (CSIRO), said the climate crisis could be increasing the frequency with which heavy rain systems make their presence felt in Australia, but the pattern is “trickier to get at.”
Coverage of the flooding in The New York Times, however, reveals that some climate experts are willing to go a bit further out on the attribution limb.
“There’s good scientific evidence to say extreme rain is becoming more extreme due to global warming,” said Andy Pitman, director of the ARC Center of Excellence for Climate Extremes at the University of New South Wales.
Remaining resolutely disinclined to make any such connection at all is Australia’s notoriously coal-friendly government. The Times reports Prime Minister Scott Morrison called the flood simply “another testing time for our country” in a recent radio interview.