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Tracking climate change - in real time

The thermometer pushed 50 degrees C at times as Australia sweltered thought its hottest year on record in 2013. So was this the effect of human-induced climate change – or just a very hot year?

While politicians confidently gave their opinions, climate scientist David Karoly decided to dig deeper. He ran a study which concluded it was “virtually impossible” to have reached those temperatures without humanity’s greenhouse gas emissions.

“This couldn’t happen without climate change … it’s the first time that any study has been able to make such strong conclusions,” he says. That study landed on the front page of the New York Times, which described it as “perhaps the most definitive statement climate scientists have made tying a specific weather event to global warming”.

But Karoly, who has been researching climate change since 1987 and is a Professor of Atmospheric Science at the University of Melbourne’s School of Earth Sciences, is still not satisfied. He’s working on ways to inform the public about whether extreme weather events like heatwaves, floods and bushfires are linked to climate change – within days.

The process is rigorous; climate scientists do conclude that some events are not linked to climate change. Karoly cautions against “overhyping” the link.

His study on 2013 involved analysing climate model simulations and observational data. Some models show what happens in a world without human-caused climate change. Others show a world affected by climate change. The simulations were run on many models by different research groups around the world. The scientists found that without climate change, Australia’s 2013 heatwave would happen about once every 12,000 years. It would happen once every six years with climate change. The risk of a hot year like 2013 was increased at least 2000 times by climate change.

So how to do a study like that in “near-real time,” as Karoly wants? It used to take six to 12 months. “That’s not quick enough, the public’s lost interest,” he says.

His team has started working on calculations in advance, preparing data tables so analysis can happen quickly. And Karoly is working with US and UK scientists on identifying the causes of weather events within a week. That program – World Weather Attribution – starts in 2015. “What we’re trying to do is to communicate as quickly as possible in a way that is scientifically robust,” he says.

That study landed on the front page of the New York Times, which described it as “perhaps the most definitive statement climate scientists have made tying a specific weather event to global warming”.

It’s a big change for Karoly, who as a young man studied theoretical physics and applied maths and hated public speaking. He switched to weather and climate and his first research on climate change was in 1987; “I did it because I thought I was clever and young and was going to disprove that human-caused climate change was having any influence on temperatures … all scientists are sceptical.”

But he found emissions were affecting temperatures. Karoly went on to work with the UN’s climate science body, the Intergovernmental Panel on Climate Change (IPCC). He was an author of the IPCC’s 1990 and 1995 reports, a lead author in 2001 and 2007 (when the IPCC won the Nobel Peace Prize), and an editor in 2014.

He’s also engaged with climate policy, motivated by what he describes as the “apparent disconnect between policymakers and scientific evidence”. He sits on the board of the government’s Climate Change Authority and is involved in the Wentworth Group of Concerned Scientists.

He does 200 media interviews a year and was part of a University team which won a Eureka prize in 2014 for mapping 1000 years of Australia’s climate history.

Climate change is politicised and controversial in Australia. Climate sceptics have been influential and policymakers have not always acted on scientists’ advice. Karoly has been regularly criticised.

That hasn’t put him off. “I respond by trying to remain engaged, it provides me with a stimulus to say I need to do more,” he says. “I find it means that my research and my communication is even more important, because if the science was accepted, the policies were in place, I could retire.”

He’s not retiring yet. He wants to research whether forests and soils will store less carbon dioxide as the planet warms. And there’s work to do on methane clathrates, frozen methane (a potent greenhouse gas) deep in the ocean. As the oceans warm, will the ice melt and the methane enter the atmosphere?


Watch ABC Lateline’s report on the heatwave study.

Tune in to David Karoly speaking about climate change.



Professor of Atmospheric Science