Sydney: Southeastern Australia has suffered through a series of brutal heatwaves over the past two months, with temperatures reaching a scorching 113 degrees Fahrenheit in some parts of the state of New South Wales.
“It was nothing short of awful,” said Sarah Perkins-Kirkpatrick, of the Climate Change Research Center at the University of New South Wales, in Sydney. “In Australia, we’re used to a little bit of heat. But this was at another level.”
So Perkins-Kirkpatrick, who studies climate extremes, did what comes naturally: She looked to see whether there was a link between the heat and human-driven climate change.
Her analysis, conducted with a loose-knit group of researchers called World Weather Attribution, was made public Thursday. Their conclusion was that climate change made maximum temperatures like those seen in January and February at least 10 times more likely than a century ago, before significant greenhouse gas emissions from human activity started warming the planet.
Looked at another way, that means that the kind of soaring temperatures expected to occur in New South Wales once every 500 years on average now may occur once every 50 years. What is more, the researchers found that if climate change continued unabated, such maximum temperatures may occur on average every five years.
“In the future, a summer as hot as this past summer in NSW is likely to happen roughly once every five years,” the report said. It could make Sydney a less liveable city, one of the report’s authors, Perkins-Kirkpatrick, said.
For the overall 2016-17 summer in New South Wales, the researchers say, climate change made the hot average temperatures — which set records for the state — at least 50 times more likely than in the past.
The findings are the latest in what has become a growing field: studies that try to assess the influence of climate change on extreme weather as soon as possible. The idea is to offer scientific analyses of heatwaves, floods and other events while people are still talking about them, and to counter the spread of misinformation, intentional or not, about the impact of global warming.
Climate scientists have long said that climate change should bring an increase in extreme events like dry spells and heatwaves. Because warmth causes more evaporation and warmer air holds more moisture, climate change should also lead to more intense and frequent storms.
“I grew up in Sydney, so I’m kind of partial to it, and we are actually starting to think, well, can we live here?” she said. “To live here it’s going to take a lot more preparation that what we are used to, looking at the building codes, including things like full insulation and double-glazing. Sydney should start having these discussions now because that sort of situation is just going to occur a lot more often.”
Studies have shown that these effects are occurring on a broad scale. But the natural variability of weather makes looking at individual events more difficult.
World Weather Attribution, which is coordinated by Climate Central, a research organisation in Princeton, New Jersey, is one of a number of groups doing rapid analysis. Among other events, they have looked at flooding in Germany and France last May; high temperatures in the Arctic in November and December; and an usually strong storm that hit northern Britain in 2015.
Not all of attribution studies have found a climate-change link. In general, studies of heatwaves tend to produce the clearest signal of the influence, or not, of global warming.
Australian heatwaves have been examined in the past, most recently in several studies that showed a clear link between climate change and a period of torrid weather in 2013. David Karoly, a scientist at the University of Melbourne, was involved in one of the studies, which took more than six months to produce.
“That was considered very rapid at the time,” Karoly said.
As a member of World Weather Attribution, Karoly helped with the study of the recent heatwaves, which took about two weeks.
A big difference between the two studies is in the use of computer climate models — both of the current atmosphere with its greenhouse gas emissions and of a hypothetical atmosphere as if those emissions had never occurred and climate change was not happening.
The older study, like most attribution studies in the recent past, run the models over and over again, which can take months. The newer, rapid studies use models that have already been run, extracting data as needed.
Melbourne University’s Dr Andrew King, another author of the report, said that while Australia had experienced extremely hot days or extreme weather events in the past, the data showed the frequency and severity of those events had increased markedly in the past 20 years and would continue to increase unless drastic action was taken to reduce greenhouse gas emissions. “Yes, people would have experienced 40C days several decades ago around different parts of Australia and in Sydney but we know that these incidences of very hot days are getting more frequent and we are setting more records for heat,” he said.
— New York Times News Service