Episode 29 – Interview with climate scientist Professor David Karoly (Part 1)

This week it was our absolute honour to speak with Professor David Karoly, world-renowned climate scientist and climate science communicator. David is an honorary Professor at the University of Melbourne having retired in February 2022 from CSIRO in Australia, where he was a Chief Research Scientist in the CSIRO Climate Science Centre. He is an internationally recognised expert on climate change and climate variability.

Professor Karoly was the Leader of the Earth Systems and Climate Change Hub in the Australian Government’s National Environmental Science Program, based in CSIRO, from 2018 until the Hub closed at the end of June 2021.

He was a member of the National Climate Science Advisory Committee during 2018-19. During 2012-2017, he was a member of the Climate Change Authority, which provides advice to the Australian government on responding to climate change, including targets for reducing greenhouse gas emissions.

He was involved in the Assessment Reports of the Intergovernmental Panel on Climate Change in 2001, 2007, 2014 and 2021 in several different roles. He is also a member of the Wentworth Group of Concerned Scientists. He was elected as a Fellow of the Australian Academy of Science in 2019. He was awarded the 2015 Royal Society of Victoria Medal for Scientific Excellence in Earth Sciences. From 2007 to February 2018, David Karoly was Professor of Atmospheric Science at the University of Melbourne and in the A.R.C. Centre of Excellence for Climate System Science.

We had such a fascinating and wide-ranging conversation with David that we’ve split our conversation across two episodes. Stay tuned for Part 2 next Tuesday!

You can learn more about David here:


Jen (00:00:00)
Hello and welcome to Let’s Talk SciComm, a podcast by the University of Melbourne Science Communication Teaching Team. I’m Associate Professor Jen Martin and my wonderful co-host is Dr Michael Wheeler and we believe that science isn’t finished until it’s communicated.

Jen (00:01:05)
Hello everybody and very warm welcome to another episode of Let’s Talk SciComm.
I’m Jen and as always, I’m joined by my wonderful friend Michael. Hello Michael.

Michael (00:01:20)
Hey Jen, it’s great to be here as always and I’m very pumped for today’s episode.

Jen (00:01:26)
Well, I’m pretty excited Michael, because I’m very very thrilled to introduce you and all of our listeners to today’s guest. Although I’m pretty confident that most of our listeners will have heard of him before.
Because today, we are incredibly lucky to be joined by one of the most well-known and well-respected climate scientists in Australia. And of course, all around the world. Welcome, Professor David Karoly.

David (00:01:54)
Oh well, Jen and Michael, it’s a pleasure to be on this program and you know, really happy to be involved because you know, I’m passionate about science communication in general and also about climate literacy.
And it’s only through effective science communication that we can improve the climate literacy of all the audiences in Australia and around the world.

Jen (00:02:17)
One-hundred percent. You are speaking our language, David. So before we start picking your brains, I feel like we do need to set the stage for anyone who isn’t familiar with your absolutely stellar career. Now, you recently retired after an incredible 45 years. And of course we can’t wait to explore at least some components of that in a moment.
But I do just want to give our listeners a sense of the impact of your career. And I think a fitting way to do that is to talk about your retirement symposium, which we gather absolutely went off. So first of all, the fact that you had a retirement symposium where 300 odd people attended or tuned in, that’s a pretty clear indication that you might be someone pretty important, I reckon.

David (00:03:00)
Look, whether I’m important or not, I consider myself just an ordinary person, as a scientist who’s had a long career in climate science. And sort of learnt that if I want to be effective as a climate scientist, or as any scientist, I’ve gotta learn how to communicate the science well. You mentioned 300 odd people. I don’t think the people were odd, I think they were normal people.
And I try to be careful about language a lot of the time. And that’s one example of where words in a certain place mean very different things. And I’ve being very conscious of that when I get involved in science communication, is that a word out of place can change the context or change the framing.
But look, back to the retirement symposium, I have been aware in terms of a whole range of if you like – retirement events, that it can be like a wake that you hold for someone after they’ve passed away as a celebration. But I didn’t want to wait till I passed away ’cause I doubt that I could listen to it then.
I reckon it’s much more important to do the celebration of someone’s life when they retire. So I organised it myself. I had 13 speakers plus myself, 10 minutes each. It was great. Everyone I asked to speak spoke straight away and it was a fantastic celebration. I probably should have got a swollen head but, but I didn’t because I still had to worry about giving the last talk.
And the last talk was fun because what I didn’t talk about was any of the science that I had done, but more about what I had learned from my career about coping with if you like the positive things and there were plenty of those, but also the negative things. And coping with the negative things in one’s career can be really important and I think is critically important in thinking about how you know you, you get over the the troughs in one’s career. And I have what many people in the retirement session described as a positive attitude to almost everything and a smiling face. And as you can see now, I’m smiling now.

Jen (00:05:21)
Well look David, we are certainly going to come to that because we do obviously want to talk about some of the many challenges that you faced as well as your optimism. But I do just want to say congratulations on what an incredible event in celebrating your career. And I absolutely stand corrected. I, I certainly do not believe that the people there were odd, but I think the fact that you did have speakers from all around the world covering different aspects of your career from a nervous math undergraduate [to] one of Australia’s most vocal and influential climate scientists.
And I want our listeners to know that over that time you’ve contributed to almost every area of weather and climate science. I know you’ve authored more than 250 publications. You’ve supported 46 students, both Masters and PhD students. You’ve helped bring more than 82 million dollars of funding to Australian climate change research. And you’re also part of the really revered group of IPCC authors who shared the Nobel Peace Prize with Al Gore in 2007.
So that’s you know, we want to talk about all of those things today. And most importantly for the context of our listeners is that you’re credited with really bringing climate science into public and political conversation. And your past student and our wonderful colleague, Dr Linden Ashcroft, who listeners of this podcast have heard from a number of times described you as indefatigable and noted it that we read her piece about you and she said it would be understandable that your impressive accolades would make people feel intimidated.
But instead we quote Linden: she said, “But such is the irrepressible magic of David Karoly. He is just as present and himself whether he’s giving testimony for a case, whether he’s on Q&A, whether he’s speaking at a sustainable Film Festival in Tatong, with a population of 287 people, or just chatting to you at a tram stop.” So what a, what a celebration. And I think, David, we would like to go back quite early in your career to start our conversation. Tell us about your motivation for getting into maths in the first place.

David (00:07:24)
Well, I was what I thought was a perfectly you know, normal sort of student. I went to a government-funded school, didn’t have an opportunity to go to a private school, didn’t want to go to a private school. It was close. I could walk to school. But what I liked at school and what I found easy at school was the science subjects, but particularly maths and physics. And I always like that stuff.
But at about the same time, sort of middle of secondary school, I got an invitation or had bunch of friends and one of them was involved in the Boy Scouts. And I used to go out camping and hiking and doing sort of things with the Boy Scouts. They got me interested in outdoor activities. And I loved that. I love going to the beach. My parents encouraged me both to go sailing and to go get involved in the Boy Scouts, but we also used to go on, on holidays to various interesting places, national parks. So lots of memories of being interested in the environment from when I was very young.
Finished high school and went to the closest university. Decided to go to Monash University, ’cause it was the new university in Melbourne at the time. Having shifted from being the I guess it was the site for a mental institution or a mental hospital prior to it becoming a university. Some people would argue that universities and mental hospitals aren’t that different, but I disagree with that perspective.

Jen (00:08:58)
It’s all about language, remember?

David (00:09:00)
Ah, yes indeed, all about language. So I went to the university because I was interested in science, because Melbourne was the staid older university but Monash was the new one. Admittedly, I’m talking about 1973 when I started and that’s a long time ago. But I had a wonderful opportunity there to study you know, sort of maths and physics, standard sorts of majors. But also to join the Monash Bushwalking Club, which allowed me to get away with friends from the bushwalking club out into regional Victoria.
And I did everything possible to get involved in trips to the Bush as much as I could. And that meant bushwalking, cross country, skiing, rock climbing, caving, canoeing, what else? Oh, I might [have] continued with some of the sailing as well. So all of these sorts of activities. But what I couldn’t quite work out was how I was going to fit my maths and physics into helping me with my interests in outdoor activities.
And it was actually on one of the bushwalking trips when I was on the bluff near Mount Buller in sort of central northern, well, the Alpine area in Victoria. And there were clouds forming at the edge of a very steep cliff, which is what the bluff is, has on it. And the air as it was rising was forming clouds right on the edge of this cliff as I looked over. And I thought Gee, that’s really interesting. I wonder how that’s working.
And of course at the time I suddenly realised that there was a sort of research group within applied mathematics that was offering undergraduate courses and honours courses in an honours programs in what is called geophysical fluid dynamics. The fluid dynamics of the ocean and the atmosphere.
And I ended up shifting from third year applied maths, computing and physics to doing a final year, my honours year in geophysical fluid dynamics or in meteorology, and it was essentially a complete shift. What I realised was understanding the atmosphere and the ocean, or the fluid dynamics of these was a great use of math and physics. But it was also a topic that my mother could understand, that I could relate to the average person in the street.
Having finished my honours degree, I shifted to doing… well applying for a scholarship to do graduate study overseas in the United Kingdom, and I was lucky enough to be funded by the Shell Oil Company to do postgraduate studies at the University of Reading. And I was very very lucky to go and study with Brian Hoskins, who actually was a speaker at the Retirement Symposium. But now he’s Sir Brian Hoskins, knighted for his contributions to understanding of meteorology and climate within the United Kingdom. And I was his second PhD student. He was really young and I was lucky that he took me on and took me on a project that essentially opened a lot of doors for me.

Michael (00:12:18)
So David, I’m just curious about how your personality plays into all of this because you know, obviously it’s a big step to go overseas, but you’ve been described as an introvert, a shy guy. You don’t necessarily have to talk to a lot of people or communicate a lot if you’re just focusing on maths and theoretical stuff.
But you, what you’re talking about there is kind of a shift to then practical applications of maths where you can explain it to you know, people like your mother. And then making a, a you know, an overseas trip. So is this the start of maybe shy David coming out of his shell a little bit?

David (00:12:53)
Look, it might be if one looked in hindsight. Although when I went overseas I was still, if you like, very much what I think was a shy, somewhat introverted nerdy guy. And you know… But in some sense, I was willing to take risks, willing to do things that I thought would get me into interesting places. And so what I was trying to do then was not so much communicate the science, just meet different people, explore different places and to use the opportunities to broaden my interests and things like that.
It was much later I think that I realised that the communication of the science was what was critically important, not just for me to make friends, but certainly what I was even then doing. And again, it’s perhaps in hindsight that I’d never lived away from home till I went to the United Kingdom. But that was great opportunity because what I wanted to do was to learn as much as I could about effectively England.
I had an all expenses paid, 3-year educational opportunity; and holiday opportunity to spend three years in England. And the channel was really easy to get a ferry across or a plane across. And so I visited. I don’t know how many times I crossed the channel, but it was a lot of times. Every holiday was going to you know, Europe or something like that. And I have to admit, and I’m not sure we’ve talked about this before, but I met my wife, who was another English young lady, on a skiing trip in Italy while I was a graduate student.

Jen (00:14:43)
What a lovely place to meet.

Michael (00:14:44)

David (00:14:45)
Well, yes. And we are still married and have recently celebrated our 40th wedding anniversary.

Michael (00:14:50)
Oh, congratulations. You, you must have impressed her with your skiing skills then, David.

David (00:14:55)
No, I think it was picking her up when she fell over from the snow. And I was always there to pick her up whenever she fell over.
About 20 years ago, I went back to the 50th anniversary of the meteorology department at the University of Reading. Some of the people who knew me and had taught me as a graduate student, a few people said to me, “You’re not the same communicator that we knew as a graduate student”. Because as a graduate student I was petrified of giving public talks so I could not sleep the day before I had to give a public talk. But I still stumbled over almost all of it and was worried.
And it was completely different 20 years later when I went back. And, and it was learning the skills and having practiced to allow science communication to be a more normal part. My PhD supervisors basically, and in my first job in Australia encouraged me just to write good science papers. That was all that was important, right? More science papers. Don’t worry about the communication of them except in the papers.

Jen (00:16:05)
I mean, I think that’s still a message that people are told today. And that’s one of the reasons why we’re so passionate about what we do in helping scientists and science students to develop their skills. ‘Cause often it’s not actually rocket science, it’s just practice. It’s just having having these kind of cycles of well, I’m going to practice and I’m going to get some feedback and I’m going to try again.
And obviously you’re reflecting on decades of the practice that you’ve, that you’ve done to get to the point that now you’re such a skilled and confident public speaker. But, but David, obviously we’re really keen today to chat with you about your experiences of communicating with nonscientific audiences.
But I do… before we get there, I do want to reflect on the fact that you’ve done some incredibly important communication within the scientific community in most notably your involvement in the IPCC reports and particularly thinking about the 4th report.
So just for listeners who aren’t familiar or feel like they should know what these are because they hear them on the news all the time but aren’t quite sure, can you just describe for us please, what the IPCC reports are and the importance of them in our increasing understanding of climate change science?

David (00:17:11)
Yeah. So this could be a one hour presentation or a…

Jen (00:17:15)
No, you don’t get an hour, sorry.

David (00:17:16)
Yeah no, exactly. And I, I will give the, a little longer than the elevator pitch, but of the order of the one-minute overview, because I think it is really important. The Intergovernmental Panel on Climate Change was set up in 1988 because of concerns of governments all around the world about the potential impacts of climate change.
But the science of climate change was still somewhat uncertain. And it was critically important that it was the governments who initiated this, and it was set up through the United Nations and the World Meteorological Organisation. And the Intergovernmental Panel on Climate Change, it’s not a bunch of scientists, it’s a bunch of representatives, one representative per country from each of the more than 180 members of the United Nations and the members of the World Meteorological Organisation.
And so effectively it’s run under UN processes. And what it does is it commissions reports or assessments. And it’s critically important to understand that these assessments are required to be policy-relevant in terms of the broad interests of climate and climate variability and climate change. But they’re required to be policy neutral. They never have any recommendations.
And so it’s tough for a scientist or anyone who’s trying to write a report and see action on what they consider to be critically important issues to write a report which is an assessment. And an assessment is quite different from a review. But that assessment process is aiming to provide an update on the, all the peer reviewed published scientific literature in the topic that they’re covering, in this case — climate change science, climate change impacts, adaptation and vulnerability, and also solutions to climate change. And consider all the peer reviewed journal publications, not just in one topic, but an enormous range of topics. The reports are voluminously long.
The first one was in 1990. Second one in 1995. Third one in 2001. That was the first one that I was really involved in as a coordinating lead author, as a chapter lead author or coordinating lead author, one of the two leads. The 4th assessment report was in 2007. And you’ll notice the time between them’s getting a little bit further apart, from 5 years to 6 years to 7 years. The most recent one was released in 2021 and 22, which is the 6th assessment report just released last year. I’ve been involved in some way in fact, in all of them. Initially is just what’s called a contributing author. The first one I was a coordinating lead author was in 2001.
And look, they are an amazingly difficult, time-consuming and valuable report. Because they are comprehensive. They are reviewed multiple times by experts in a much more comprehensive review process than any scientific journal paper that gets published. They’re reviewed twice by experts and twice by governments. And every single review comment has to be answered in writing, and that answer and the comments are made public. And it’s a really interesting process. The reason that it’s robust is because it’s done in an open way. Anyone can nominate to be an author. Anyone can be selected. They usually need support from the governments. And in addition, the reviews can be done by anyone who has published at least one peer-reviewed journal paper in the topic of relevance.

Michael (00:21:15)
So David, you mentioned being involved in a couple of those reports there. And the one in 2007 that won the Nobel Peace Prize with Al Gore. I mean, I think that’s pretty incredible.
I’m just curious to know, why were the authors of that particular report including yourself awarded the Nobel Peace Prize?

David (00:21:30)
Because they were nominated. And you know, in many awards what is required is a nomination of the award winner or candidate for the award and things like that. I think there had been recognition that climate change was a growingly important issue and the strength of the conclusions about the role of human activity and human caused emissions of greenhouse gases and their role in climate change were getting stronger and stronger in each of the assessment reports.
And the conclusions in the 2007 report was basically essentially that there is no doubt that climate change is happening. The phrase that was used was climate change is “unequivocal“. Observed warming of the global climate system is unequivocal. There’s no doubt in that.
The cause then was it was more, was very likely that human caused emissions of greenhouse gases have been the major cause of global warming over the previous 50 years. Again, those are very strong conclusions compared with the assessment in the forced report, which basically was along the lines of the climate system is warming, but we can’t actually unravel the causes and we can’t link human related emissions of greenhouse gases to the observed warming, but it’s likely that global warming will continue in the future due to human -caused emissions of greenhouse gases. That’s a much more how would I say, ambiguous and airy-fairy conclusion than the other ones, particularly in 2007.
So I think the reason for the success of the nomination in 2007 was the growing importance within the scientific arenas and the peer-reviewed journals, as well as in governments that concerns about climate change. But it’s also important to understand that one of the things that the IPCC has to do is to have consensus in all its conclusions and all its reports from every single government present.
And the approval of whatever statement is reached in the summaries for policymakers, the short summaries that are released from all the scientists that are present at the final plenary meeting. So to get any document approved by you know, the 140 countries present at the approval meeting unanimously often requires that it’s somewhat watered down or weaker than some…

Jen (00:23:59)

David (00:24:00)
And I know it’s… Not tentative because the conclusions are high confidence. But it might be high confidence about something that may not be the latest scientific conclusions in a peer-reviewed journal paper.
Often… Well, first of all the journals papers. You need multiple journal papers to get a conclusion reached in an IPCC assessment because the support of multiple studies is required to demonstrate – if you like – convincing evidence to all the governments that this is actually true.

Jen (00:24:34)
So David, I think it’s fascinating that you know, at the same time as the science is becoming more and more understood and and I guess more solid in in terms of what you’ve just described. But you’ve also said earlier that you’ve come from a background where your PhD supervisors were really encouraging you, saying you know, that the key thing here is to be publishing the papers.
Yet obviously we know that you’ve invested so much time and energy over the years in communicating with, with the public. And I’d love to hear your thinking on what brought you to that idea. How did you justify the time? How do you explain to people why you were doing that?
And I sort of can’t help but imagine a alternative timeline where you stayed in mathematics. And would you have become such a public communicator had you stayed in mathematics? Or was it because of the urgency of the climate change science and that you wanted people to know about it?

David (00:25:22)
Yeah. So it’s the latter. I mean, having got involved in climate science… When I first got if you like analysing observational data and trying to understand the links between human-caused emissions of greenhouse gases, I came in, way back in 1986 with what I thought was a very clever idea which would disprove that human caused emissions of greenhouse gases were the dominant factor.
Scientists are trained to be sceptical. And I was already at that time somewhat sceptical. When greenhouse gases are increased, temperatures are expected to cool in the stratosphere and warm in the lower atmosphere. And I had this clever idea that if greenhouse gases and carbon dioxide are increasing, we should look for this fingerprint of warming in the lower atmosphere and cooling in the stratosphere.
And I started to look at it because I had a graduate student who’d been looking at temperatures in the lower atmosphere in what are called the weather balloons, and they get temperatures not all the way up to 50 kilometres, but temperatures up to about heights of 20 kilometres in the lower part of the stratosphere. And what he found was yes, there was warming in the upper atmosphere. But what he was seeing was cooling the stratosphere. And I thought well, we should look at this more in the observations. We should look at all the weather balloon long term records in the data from 1963 when weather balloons started to be used around the southern hemisphere.
And unfortunately, my theory that it wasn’t greenhouse gases was thrown out or had to be thrown out in the observational data. Because everywhere he looked, when we looked at this fingerprint of warming in the lower atmosphere, cooling in the stratosphere, it was verified not in every station; but when we combined them all together, it was 99% confident that the trends in temperatures in the southern hemisphere where we looked at all the weather balloon sites were due to the increases in greenhouse gases.
Couldn’t be due to increases in sunlight from the sun, couldn’t be due to natural variability. I had to change my mind, I had to change my view. And so a conference paper that I’d originally planned to talk about this, which was a very sceptical, how would I say, of this newfangled theory, I changed. The evidence was convincing.
And since I found this convincing evidence that increases in greenhouse gases were so important in the warming of the climate system, I suddenly realised that communication of this science and the urgency of the problem, because we knew that the increases in greenhouse gases were going to continue as we used fossil fuels to power the global economy.

Michael (00:28:15)
That’s an important realisation, David. So you’re actually saying you started off as a climate change sceptic, but then you were convinced by the data and you actually had to change your mind. And then you went about trying to convince others of the data. And I suppose there we get into the realm of all of the important communication work that you’ve done.
And I think this might actually be a good point to wrap up Part 1 of the conversation, because we’d love to focus on all of that important communication work in Part 2, the intersection between science communication and politics, also your engagement with climate change deniers.
And then we’d love to also get some advice from you to others who might be communicating science in the public sphere. So all of that to come in Part 2. So to our listeners, we will see you all next week with Part 2 of our conversation with Professor David Karoly.

Michael (00:29:30)
Thanks for listening and thanks also to our wonderful production team, Stephanie Wong and Steven Tang for making these episodes happen behind the scenes. And thanks also to you, our listeners for your support.
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