Colour-shaded map of eastern New South Wales showing modelled near-surface air temperatures. Warm colours (yellow, orange and red) dominate inland areas and the Sydney region, while cooler greens and blues occur along the coast and across the elevated terrain of the Snowy Mountains in the south-west. Weather station locations are marked by labelled circles distributed across the map, with a dense cluster around Sydney. The Tasman Sea appears on the right in pale blue-green shades, and the map focuses solely on the geographic region without axes, title, or legend.

Slaying the monster of climate change, one reproducible result at a time

In Greek mythology, Theseus unspooled a ball of string behind himself as he ventured deeper into the dreaded labyrinth of King Minos.

After defeating the Minotaur – a terrifying beast that lived within the maze on the island of Crete – the Athenian hero used the string to retrace his steps and escape the labyrinth.

At 21st Century Weather, our scientists are only able to successfully defeat the wicked problems and computational demons of complex climate modelling thanks to modern-day heroes like Dr Chermelle Engel.

A person stands at a lectern giving a presentation in a conference venue with wood-panelled walls. They are wearing a light blue shirt and a conference lanyard and are gesturing with both hands while speaking into microphones. Behind them is a banner displaying the ACCESS and NCRIS logos, and a projection screen is partially visible to the left. The lectern bears the logo and name of The Shine Dome. Glasses of water and presentation equipment are visible in the foreground.
Dr Chermelle Engel (Credit: Harshula Jayasuriya, ACCESS-NRI)

Together with her colleagues at Australia’s climate simulator, ACCESS-NRI, Chermelle – one of the Centre’s Associate Investigators – provides each intrepid student and researcher with the vital digital string to guide themselves into the depths of highly demanding software and programs, and then return safely with results they can trust, time and time again.

“The responsibility of a scientist is to be able to defend their work, to rerun the model in five years,” Chermelle said.

“But supercomputing architecture may have changed. It’s too hard for an individual scientist to keep track of all those details.”

The Australian Community Climate and Earth System Simulator (ACCESS) is the country’s leading national climate model. Developed by the Commonwealth Scientific and Industrial Research Organisation (CSIRO), it contributes to global projections of the world’s rapidly changing climate, and allows us to understand what we can expect from our weather and climate in Australia and the surrounding region in the decades to come.

Like all of the world’s leading climate models, ACCESS is the result of years of international collaboration and incremental development. In the past, this gradual, iterative process meant that some climate models lacked the guidelines and clear steps necessary to enable new users to quickly get up to speed on their functionality. 

That’s where ACCESS-NRI comes in. Based at the Australian National University in Canberra, it’s a National Research Infrastructure team that specialises in exactly the type of rigorous software engineering necessary to make ACCESS as user-friendly as possible, for new students and experienced researchers alike.

Dr Mat Lipson, a Senior Research Fellow at 21st Century Weather, said: “If you’re a student joining the Centre who has never run a model, you rely on years of effort from ACCESS‑NRI to produce a documented, reproducible, robust way to get a model running. Their documentation and website let you get a model up within a day.

Heat map of near-surface air temperature across eastern New South Wales, Australia, titled “RNS 1km (BARRA-R2, CCI large domain)”. Colours range from cool blue (around 15°C) to hot red (above 40°C), with warmer temperatures inland and across the Sydney region, and cooler temperatures along parts of the coast and the Snowy Mountains in the south-west. Numerous weather station locations are marked with labelled circles across the map. Latitude and longitude axes frame the figure, and a colour bar on the right indicates the temperature scale. Summary statistics in the upper left compare modelled and observed temperatures, showing a small cool bias in the model.
Air temperature in the Sydney region, using the ACCESS-RAM3 model for at 1km. The circles are Bureau’s observing stations with colours matching the colour bar, so if they blend into the background, the model is performing well. (Credit: Mat Lipson, 21st Century Weather, UNSW.)

“In the past, a new student would rely on word‑of‑mouth, someone sitting nearby, often doing things in a way that wasn’t scientifically robust and varied from user to user. It could take weeks or months to get up and running. They’ve transformed that into a reproducible, standardised approach.

“If you’re a more experienced user wanting to create bespoke experiments, that’s where people like Chermelle are absolute gold. These models are incredibly complex, with different parts built over decades by the (UK) Met Office, the Bureau of Meteorology, CSIRO and university researchers.

“They’ve been passed around, developed for different purposes – operational forecasting, research, climate change, weather scales – so they’re complex beasts that don’t always make sense.

“Someone like Chermelle can immediately tell you whether your idea is possible, and if not, how difficult it would be to make it possible. And she’ll help you do it, often setting aside days or weeks to support you.

“Because she has a science background and cares about doing good science, she’s an enabler. She enables science within the Centre. It’s incredibly valuable.”

One of the major recent achievements produced by the relationship between 21st Century Weather and ACCESS-NRI is the Regional Atmosphere Model, or ACCESS-rAM3 for short.

Adapted from the UK Met Office but modified to work with data available to Australian researchers, it enables researchers here to focus on areas of particular interest to them in greater detail than ever before, without taking up huge amounts of expensive computer power.

“It’s very powerful,” Chermelle said.

“It’s a regional model, unlike (the) global models that cover the whole Earth. Global models are expensive to run. A regional model lets you cut out a smaller region and get much higher resolution – like zooming in on Google Maps. You can zoom in step by step while keeping scientific integrity. 

“People use it for exploring concepts, testing model performance, or recreating weather events in detail. Students often take a day of weather and change the scientific settings to see what happens. It’s cheap enough to run repeatedly and detailed enough to be useful.

“The model was designed for operational weather forecasting – it needs to be fast and ready for the news. But our researchers don’t have access to all the underlying things needed for that kind of work.

False-colour satellite-style map of New Zealand and southeastern Australia showing a cyclonic weather system over the ocean north-west of New Zealand's North Island. The cyclone has a distinct eye at its centre, shown in dark blue, surrounded by a ring of intense orange and red indicating the strongest activity. Broader bands of green, yellow, and blue spiral outward across the Tasman Sea. New Zealand's North and South Islands are outlined on the right and lower centre of the image, while the coastlines of Victoria and Tasmania are visible on the left. A latitude–longitude grid overlays the map.
A rAM3 simulation showing wind gusts for a cut-off cyclone forming over the Tasman Sea, January 2018. (Credit: Model runs by Dr Corey Robinson, 21st Century Weather, Model development by ACCESS-NRI)

“Gaps appear when someone wants to drive the model with Australian data. My role is to make that step seamless. They shouldn’t even know someone built that bit for them. We give them an example that works, and they can alter it in small ways.”

It’s a challenging time for climate science in Australia and across the globe. In the United States, the organisations responsible for producing some of the world’s most powerful climate models, and the research that powers them, have suffered funding reductions during the current presidency. And closer to home, CSIRO recently announced job losses within the Environment Research Unit, which is responsible for investing in and building future versions of ACCESS.

Nevertheless, the joint achievements of 21st Century Weather members and the software engineers at ACCESS-NRI continue to demonstrate the enormous value of the global climate modelling community, with the production of dynamic new tools and impactful research now a regular occurrence. 

It’s just one example of what’s possible when Centre members and Associate Investigators join forces to push the boundaries of meteorology and climate science.

“That’s why collaboration is essential – the problem is bigger than one person or one country,” Chermelle said.

“The partnership means young scientists here can push something exciting back up into the Met Office model, benefiting everyone. It’s a privilege to work on something with so many years of innovation behind it.”

This article is part of a new series focused on the working relationship between 21st Century Weather and our Associate Investigators at organisations in Australia and around the world.

In the next edition, we’ll meet Dr Tim Raupach, an Industry Scientia Senior Lecturer with the Institute for Climate Risk and Response at UNSW in Sydney, who is an expert in hailstorms and convective processes.