Revealing hand behind weather

It’s a fact insurance data makes uncomfortably clear: Climate change isn’t just a problem we’ll face in the future, but one that’s hitting us hard today.

Yet, when discussing extreme weather events as they strike, meteorologists are naturally restrained in implicating its hidden hand.

That’s because few extreme events are caused by it alone.

But what if there was a way to tease out its contribution?

New Zealand scientists are set to soon make this a reality.

“Extreme weather events are at the sharp end of climate change,” Dr Greg Bodeker said.

“Every extreme event has a contribution from natural variability, as well as an anthropogenic contribution resulting from the accumulation of greenhouse gases in Earth’s atmosphere and the associated warming of the climate system.”

A new million-dollar project led by his Alexandra-based company, Bodeker Scientific, aimed to develop of scientific method that could tell us the precise difference that climate change made to an extreme event — and within just a day or two of it happening.

“For example, we want to be able to make statements such as ‘this rainfall event was 27 per cent more severe than it would have been had there been no anthropogenic climate change’ or ‘in pre-industrial times these sorts of events would have happened once every 65 years but now, because of anthropogenic climate change, are expected to happen every 35 years’.”

The work, bringing together experts from Niwa, MetService and Victoria and Canterbury universities, would build off a decade of research.

Previous approaches had mainly drawn on retrospective analyses, such as issuing statements on droughts up to a year after they’ve had ended.

Bodeker and his colleagues have set their sights on achieving this in near-real time, with a focus first on weather events marked by extreme temperature or rainfall.

As it happens, MetService uses a supercomputer to continually run weather simulations. The new project will run a similar ensemble — but with sea surface and atmospheric temperatures, along with atmospheric humidity values, modified to mimic what they would have been under preindustrial conditions.

By comparing the simulations, the team can quickly make inferences about changes in the severity of an extreme event.

After the three-year project is complete, Bodeker hopes the new capability will be built into MetService’s operations.

The project is being supported with a grant from the Ministry for Business, Innovation and Employment’s Endeavour Fund.