Scientists explain when individual weather events can be blamed on climate change
Summer in Australia has been marred by intense heatwaves and bushfires in the west, and devastating floods in the east.
And as each event occurred, a crucial question was asked: Is this a result of climate change?
It’s a question that has been growing in intensity in recent years, and with good reason.
But it’s one that can be tricky to answer.
So can climate scientists link an individual extreme weather event to climate change? And if yes, when?
Here is what the experts say.
Weather events and climate change
Up until about a decade ago, the go-to answer from climate scientists was: “You can not blame an individual extreme weather event on climate change”.
But in recent years, this stance has softened.
This is thanks to a developing field of science known as ‘extreme event attribution’, which is all about determining how much of a role human influence played on an extreme weather event.
University of NSW climate scientist Sarah Perkins-Kirkpatrick works in this field.
She said climate scientists were now able to determine whether climate change had increased an event’s likelihood and, in some cases, they could even put a number on how much.
But she said providing that answer required a study of the event.
With questions from journalists coming during, or immediately after the event, this can limit what climate scientists are able to say.
“We’re working towards that and some countries are starting to get them more quickly than others, which is what we call real-time attribution.”
Dr Perkins-Kirkpatrick said attribution studies for some events, like heat extremes, could be done relatively quickly.
But other events, like rainfall, required a more detailed analysis, something that could take months or even years to complete.
This includes the recent floods in Brisbane and New South Wales.
Evidence for climate change mounts
That being said, there are some types of events that have such a breadth of evidence linking them to climate change that scientists can make broad statements immediately.
Dr Perkins-Kirkpatrick said this was mainly extreme temperature events, such as heatwaves.
“If you pick your favourite heatwave across the world, there’s always been a (climate change) signal found, so it’s got that body of evidence,” she said.
“We might not have the specific signal for that event, but we know that it’s there.”
University of Melbourne climate scientist Andrew King added to this, offering insight into the nuances in making similar statements about events other than temperature extremes.
“It depends a lot on the location and the type of event,” he said.
“For example, if we had extreme rainfall over a few days, it would be quite hard to say what the role of climate change was.
“However, if we had an extreme rain event in the space of half an hour and it caused flash flooding, that kind of event actually has a slightly stronger climate change influence.”
In the absence of directly linking an event to climate change, Dr King said they could answer broader questions.
This included how the type of event compared to trends of climate change in that region.
“With any extreme weather events, we can say something about climate change,” he said.
“But, it might be something quite inconclusive.”
“Asking, ‘Could climate change have played a role in this event?’ or ‘Does climate change increase the likelihood of this kind of event?’, those are good questions.”
Caution not to undermine climate science
“And we don’t want to provide any fodder for that, obviously.
“So we need to be producing studies, and we need to be giving statements founded on robust analyses, and good understanding, and we don’t want to overstate the role of climate change on extreme weather.”
Dr Perkins-Kirkpatrick said there were many ways climate science could be incorporated.
“I don’t think it hurts,” she said.
“But how exactly we do that I think depends.
“We don’t always have to rely on attribution to say that climate change is happening now and we can see it happening now.”