How much of our extreme weather is due to climate change?

This week, Phil Vine dives into the science of climate attribution. How much is climate change affecting extreme weather events? And how can this new science prepare us for the future?

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.

The cost of climate damage …

Go to this episode on rnz.co.nz for more details