Rail tracks covered in silt in the Esk Valley by flooding during Cyclone Gabrielle, 20 February. Photo: RNZ / Jimmy Ellingham
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For a long time when asked this question, climate scientists simply shook their heads.
They had been telling people that global warming was making many storms, floods, and weather events worse – but when asked: “by how much?” – they didn’t have an answer.
Then one day Oxford University physics professor, Myles Allen, experienced one of those extreme weather events.
As the River Thames flooded and threatened to pour water through his kitchen door, on the radio the Met Office was saying it was impossible to accurately link the event with climate change. He said to himself: “we need to do better than that”.
Famously, rather than search out sandbags to keep the floodwaters at bay, he sat down and wrote a journal article – making that connection between global warming and specific weather events.
And a branch of science was born: extreme event attribution studies, or climate attribution for short.
In Aotearoa, there’s a whole gang of scientists from different institutions carrying out world-leading research in this new field.
2023: the year of storms
Few in the upper North Island will forget the beginning of 2023.
The Auckland Anniversary Floods arrived at the end of January. Four people dead. Seven thousand homes damaged.
Less than two weeks later came Cyclone Gabrielle. Eleven people killed. A staggering 850,000 landslides.
After Cyclone Gabrielle, Dr Luke Harrington from the University of Waikato and an international team from the World Weather Attribution project worked round the clock on rainfall data and climate models.
They were endeavouring to find out if, and how, climate change had affected the devastating tropical cyclone.
And they broke with scientific tradition. Rather than wait and publish a paper in a year’s time, they sought to get a report out while Cyclone Gabrielle was still in the news.
"If it's 12 to 18 months after the event happened, the public doesn't really care,” says Luke.
The project team worked out that 10–15 per cent more rain fell because of global warming.
“It demonstrates that climate change isn't a future problem. It is not something that you are going to see play out in 50 years' time, it's already playing out now,” Luke says.
Clockwise from left: Damage from a slip in Auckland's Titirangi in January 2024 - a year on from the 2023 Auckland Anniversary floods; a massive slip on the cross-Coromandel Peninsula SH25A in January 2023 caused widespread disruption to traffic over many months; mud poured into Alana Pearce's Nelson home during a 2022 landslide; a retaining wall collapsed during heavy rain in Timaru in 2022. Photo: RNZ and supplied
The cost of climate damage
Alongside climate scientists, economists such as Dr Ilan Noy from Victoria University of Wellington are adding dollar values to the additional weather damage caused by climate change – another new field called impact studies.
“I think it's very important to measure that so that we can manage it better. We can assess what we need to do,” says Ilon.
He, Luke, and other colleagues, prepared a report for the New Zealand Treasury figuring out the cost of weather damage from global warming – a world first.
Over ten years climate change was responsible for NZ$720 million worth of drought and NZ$120 million in flood damage.
University of Waikato environmental science senior lecturer Dr Luke Harrington. Photo: Supplied / University of Waikato
How much do I owe?
More recently Ilon and others have figured out how much extreme weather damage has been caused by climate change, worldwide.
The total comes to US$140 billion a year. That’s US$16 million of climate damage every hour.
Dr Daithi Stone from NIWA says work is also being done on a system to analyse an individual’s greenhouse gas emissions and establish how much damage they are responsible for.
“The world works in dollars. If we translate that into dollars in your pocket, that is a translation, that helps contextualise climate,” he says.
So, will all of this interesting new data improve the way we deal with this existential threat?
Dr Lauren Vinnell, lecturer of emergency management at Massey University, warns, "If you're giving people that kind of information, you really need to also tell them what they can do about it. We don't want to just make people feel guilty, because then they will disengage.”
Pointing the finger
Professor Myles Allen, the founding father of climate attribution, also cautions against apportioning individual blame: “pointing fingers at people who have very little agency, blaming them for things they don't feel they could avoid doing, I think is very unhelpful."
He says climate change is overwhelmingly caused by four products: coal, oil, gas, and cement. Those products are made and sold by fewer than 100 companies.
“So that's where we need to focus the conversation.”
Listen to the audio to find out what climate attribution might mean for the insurance on your home and how this new science is helping weather victims take large companies to court.
Photo: Kaipara District Council / Supplied
Learn more:
- Veronika Meduna originally looked at the emerging field of climate attribution in 2015 for Our Changing World after Dunedin got soaked with two months of rain in a single day.
- And check out this episode of Our Changing World about an ambitious sediment-drilling project to discover more about the accelerated loss of ice in the small and vulnerable West Antarctic Ice Sheet.
