 My name is Sarah Perkins. I'm a research fellow at the Climate Change Research Centre and my field of research is heat waves. So I look at heat waves. I currently have a research grant to analyse how they've changed, why they've changed, what drives heat waves, how those drivers interact with each other and the human contribution behind those changes as well. So heat waves, they're very complex as I'm discovering. I guess the term heat wave is quite anecdotal. You hear it in the press and you're like, oh, there's a heat wave. What does that mean? It's a bit hot. So that's what kind of got me into my research was what actually is a heat wave. What does it mean and how do we measure them? And it turns out that there are lots of ways of measuring them. It depends what you're interested in. If you're interested in human health, you might measure it differently to someone who's interested in flying foxes or fruit bats. You might include different variables like relative humidity. You might not. You might just want to look at temperature. You might want to look at nighttime temperature only. There is actually a plethora of ways. By the way, we're trying to break it down. The climate community is looking at their intensity. So how hot the hottest part of a heat wave is, the hottest day, I guess, the duration, how long the heat waves go for, the frequency, both in terms of the number of heat wave days you may get in the season and also the overall number of discrete heat wave events, the spatial extent. So how big is a singular event? What area does it cover? And their timing. So how early does a heat wave season start? I haven't looked at this myself, but also how late does a heat wave season end? So is it broadening? Is it shrinking? So there are sorts of different ways that we really look at heat waves. You can also look at the average magnitude, so just the average intensity of an event. You can do other things like combine all those indices together to get one magical heat wave index, which I don't think works very well personally. And those sorts of all those characteristics of heat waves are potentially affected differently by different physical mechanisms. And that's what we're trying to nut out. What drives heat wave intensity? Is it different to what drives heat wave timing? Does that also affect heat wave duration? If not, what drives those sorts of different things? Heat waves have occurred in the natural climate record before. I'm not going to deny that, particularly in summer, it's hot. Occasionally you'll get three or four days that line up and form a hot event. That's true. I agree with that. However, they are changing. They are increasing in their intensity, frequency duration, and also how early they occur in the season. That's what we're concerned about. If we didn't exist, yes, heat waves would still occur, but they wouldn't occur as often, and they wouldn't be occurring at higher intensity or as early. That's what we're concerned about. And there's also the argument that climate change has happened before, and greenhouse gases have been higher before than what they are now, particularly carbon dioxide, which is also true. But the reasons for them being higher were different. The reasons why there was more carbon dioxide in the atmosphere however long ago, before the industrial resolution, it was natural. It was how the Milankovitch cycles were changing, how species were changing and things were evolving. It wasn't because we were digging up coal and burning it. The reasons were different, and that's what I'm concerned about. Well, the fact that it's changing, the fact that that's directly attributable to our activities. Different locations are exhibiting different changes of different magnitudes, but generally overall, all those sorts of characteristics of heat waves are increasing. So it depends how long the observational record is. Over Australia we can look back in some locations as far back as 1910. Over the globe, really the best data set that we can use only goes back to 1950 with any sort of reliability. In terms of observed data, I have looked at heat waves in Australia, over Australia and globally as well. At the moment I have almost three PhD students looking at Australian events, but my research in terms of projections and what's changing them and the human contribution behind those changes, I'm trying to do that at a global scale as well. There's a few methods that you can use to work out the human contribution. I'm at the moment using a methodology called the fraction of attributable risk. So it's working out what fraction or what's the percentage behind a particular event in terms of its likelihood of occurring. So it's the same kind of analysis that doctors use for studying the risks of cancer in smokers versus in on smokers or cases like that. So we look at events, say the hottest year on record last year or the number of heat waves we had last year. Compare that in a model to conditions where we don't have climate change or it's just the climate as if we didn't exist and work out how often that particular event occurred in both of those cases. Then we compare them and it's just a matter of comparing two probabilities or two percentages and then you get that attributable risk factor. How much are humans contributing to the increase in heat waves? That's a good question. It's currently what I'm working on now. It depends what sort of characteristic you're looking at. So we're seeing a much larger contribution from humans in heat wave frequency. That's a detectable signal that we're already saying it's only going to get worse and even at the moment I'm actually quite surprised at how large it is. So it's around about if we look at a heat wave that occurs once every 20 years on average that event now compared to say 50 years ago or 30 years ago now occurs 16 times more often. So it's not quite once a year but almost once a year now. So that is like for an area average that's maybe safe for the entire of Australia but it is quite scary that we're seeing these already quite detectable changes. That is preliminary results so I need to look into that a bit more. The heat wave metrics I'm looking at, I have only looked at one model. I've still got a lot of work ahead of me but this model is certainly indicating that for heat wave frequency we're seeing 16 times more likely but for heat wave intensity it's a bit less. It's around about 9 or 10 times more likely. It depends what you're looking at, where you're looking at, how you're defining heat waves. I'm seeing larger signals when I look at Australia as a continent averaged. If I look at say southeast Australia so that's like Victoria and New South Wales it's a lot less because you've got a lot more natural variability or internal variability which you average out of the continental scale. So it depends if I did that globally I would get an even stronger single again. Talking about increases in risk in terms of heat waves or any other extreme event I find it helpful and I know some people find it helpful but other people tend to really struggle with probability. So perhaps the cancer analogy fails here because if you say you're twice as likely to get cancer if you smoke cigarettes you'll go goodness me that's not good. But you're twice as likely to experience this number of heat waves now. People can't, I think it's still something that's a bit more sort of looking for abstract to them. It's still not something that's in there that directly affected by you like the cigarette you're responsible for yourself getting cancer but with these heat waves it's still something or any other extreme event they're still very much removed from their everyday life. That's something I'm trying to tackle at the moment. How do you communicate? Europe actually is showing a lot of changes. So over regions where we saw the Russian heat wave, the 2003 heat wave parts of eastern Asia are showing increases. South-eastern Australia that's what we're seeing most increases in heat wave intensity. We don't have enough data unfortunately for Africa, basically all of Africa or India or the Arctic or Antarctic so I can't say what's going on there. South America we've only got a little bit of data and I'm not sure how good it is. And actually in America so the western parts of America are showing increases but there is the warming hole as it's called in the central eastern part. So that's actually in a lot of the temperature records that that area hasn't warmed as much or if at all and a lot of that's actually been put down to land cover change. So there's a reason for that but perhaps if that didn't happen then it'd be equally as warm as the continent. So if you look the models don't pick it up because they haven't incorporated that sort of land cover change into the model itself. If it is put in there has been, this is not my area of expertise but there is quite a bit of literature out there that if you do incorporate the land cover change and the hypotheses why we think it's happened the models do pick it up. But yeah if you look at something like Had Crutee, I look at Had GHC and D you can see it. So no change or maybe a slight decrease but there's physical explanations behind that. It's not that we're stuffing up. Unfortunately it's not the people who are causing the problems that will be most affected. So you know America and also the highest emitters per capita but it's the people in the developing regions that will be affected most. So Porog Kiribati is already having salt water intrusion and inundation and sea level rise and they're not putting any greenhouse gas emissions into the atmosphere. Those that are low lying, those that don't have access to things like air conditioning or good public health infrastructure, you know if you get a heat wave in those sorts of areas people get sick or the elderly generally get really sick after a heat wave if they don't have the public infrastructure to cope with that more people will unfortunately be killed. If we see higher intensity of tropical cyclones they generally occur in the tropics and we do have a lot of developing nations in the tropics. They simply don't have the infrastructure. So it's really unfortunate and really unfair that those people aren't causing the problems will be the people who will be affected the most. In any society the people who are most affected by heat waves are generally the elderly and the very sick. So it is actually somewhat difficult to attribute deaths directly to heat waves because they aggravate underlying conditions. So you might have a heart problem, maybe a problem trying to be able to cool yourself down or something like that and in a period of prolonged heat it will aggravate those sorts of problems. Perhaps that sort of illness may have killed you a little bit earlier than what you would have died of natural causes but the heat wave brings that earlier still. So the way they measure it they look at mortality data I think maybe a few days after the heat wave or for a period after the event and work out what do they normally expect at this time of year and what did they actually get and then that's what they attribute to the heat event. There's a lot of work going on at looking at flying foxes at the moment particularly in Queensland. Unfortunately they tend to literally drop out of the trees at 42 degrees Celsius so lactating mothers and their babies. I think yesterday or the other day a colony of 5,000 in Queensland, yep. And that's not the only one that's happened here in Sydney, it's happened I think further south. I know certainly of that one but that's an example of an animal that has a finite threshold. For us I'm not entirely sure what our threshold is we can adapt at least to different climates and we have the benefit of being able to walk into an air conditioned building but different animals would have their own thresholds and they may not be particularly sensitive to that threshold. Was that climate scientists getting their satellites to form a little heat bubble over the city? No that was not climate scientists trying to create a heat bubble over Brisbane. We did not create that. That did happen. I can't explain off the top of my head the meteorological events for that to happen but quite likely there was some sort of high pressure system just off the coast of Queensland. It's been really dry. I actually went up to Brisbane on Monday so I know how dry it's been there. The lack of soil moisture is a big driver of heat waves. We know that by how much we're not sure but we know it definitely affects heat waves in hot days. It affects the latent and sensible heat fluxes so generally something's wet so you've got lots of vegetation or lots of soil moisture any sort of extra energy that's put into the system so say a hot day would go into evaporating the moisture. Take the moisture out of the system and all it's got to do is in the sensible heat flux that would just simply heat up the area. So that would have contributed to Brisbane having hot days as well. So certainly there would have been some sort of high pressure system somewhere involved but no we didn't just go hey let's just fry all the world leaders and give them all the intense heat. I actually feel really sorry for them that they had to experience that day. I feel I have two minds of that because I get really annoyed when skeptics or deniers or cranks or whatever you want to call them react to certain things like oh it's winter climate change doesn't exist. It really annoys me when they do that because they're just kind of riding on any wave that they can find. I know we do the same thing like the G20 it really highlighted the issue which is good for us but then are we also being hypocrites kind of thing. Gosh responding to skeptics my reactions are varied. It depends who it is. If it's my seven year old nephew then I'll quite calmly sit down with him and explain how it works is actually if I do say so myself pretty smart so you know he can get it. If it was my 81 year old dad then sometimes I think well you're just not going to understand. I try my best to explain it but it's just the level of scientific knowledge or sometimes he was just firmly in his beliefs so it's harder. On Twitter I've occasionally taken a couple on you know especially when they start getting personal and calling me like a lobbyist or something like that and it's actually no I'm just telling you what's going on so it really does depend, it also depends on my energy level sometimes I'm quite battered down by them particularly when they get personal. Have you ever encountered the argument that climate scientists are just getting paid to... That infuriates me I must admit because science doesn't pay. Well I'm in a job shore but it doesn't pay nearly as well as I don't know having you know being a partner in a law firm or some you know economic firm. We're paid to you know we're not on the poverty line we're paid well in science but we're not on millions of year or even on hundreds of thousands a year we're not on any of that so whether A we're doing it for the money is not right and B the research grants that we get we don't see you know that's going to our science if we don't spend the money on our science and we are accountable for that we are audited for that we have to give it back to the research grant and that's fine I have no problem with that if I don't spend it it goes back into the pool for someone else to use. Yes that funds our salary but we don't touch that that goes to the university and then they pay our salary it's not like we get Christmas bonuses out of it we don't even you know that's not even an option for us so for people especially people who are in high paying jobs to come back and say to us oh you're just in it for the money that it infuriates me because I know absolutely nothing about what's going on and it's personal as well. I don't think the general public realise that we don't, well certainly somebody in my position we don't have permanent work we have to bid for these research grants to fund our work we're not doing it because we want the money or we want it you know it's a hobby we have to prove that the science is worthwhile funding that it has impact for the broader community that something good is going to come out of it and the ARC or the Australian Research Council isn't wasting their money it's not like we just get handed out money every year we have to fight tooth and nail to get that money you know there's sometimes only a 10% chance you get your project funded we can eventually argue over these proposals they're not easy to come by so it's not like yeah it's a waste of taxpayers money it's far from it that's a very difficult question to answer straight away as I spoke about earlier we can say whether or not our activities have increased the likelihood of that event an event of that magnitude can we expect, so if we have a heat wave where the highest of the average intensity was 45 degrees we can then go on and say maybe not straight away but we can at least look at our models and say well a human activity has increased the likelihood of getting that event two or three times so we're going to see that event two or three times more often than what we used to without us doing anything to the climate we can do that and those sorts of analysis are robust and we can say with a certain confidence once we've actually done the analysis but saying whether or not did climate change cause this event outright we can't answer that cause we don't know that heat wave could have occurred sure, but maybe the intensity wouldn't have been as strong or maybe it would have lasted as long but we just don't know, particularly in summer so that for example the Australian open heat wave it was summer so getting a heat wave at that time of year probably could have happened anyway but in my mind it was more the intensity that was the issue we likely would have seen it but perhaps it would have been a couple of degrees cooler using the poll of water seeds but the robust climate change science is just outright wrong so that was typical of weather in the region what happened was the jet stream just was pulled further south in that region of the world for a number of weeks and there was so the poll of water seeds this is somewhat going out of my area of research but from what I've read they're common for that region they do occur, they're cold and they do occur during winter if you go to the other side of the globe in northern hemisphere but on the other side of the Arctic they actually had warmer conditions as well so it balanced out really and if the jet stream moves down that way it has to pull from the other side of the hemisphere and yes it was cold say in terms of 30-year record some places had the coldest winters on record but not very many, a few locations at best if we saw those winters occur more and more often then I'd be a little bit concerned for that region but the coldest winter in 30 years versus the hottest summer that we keep on blitzing year in year out or if not we get very close to it it's comparing the cold records versus the warm records so in Australia I think the number of warm records we're creating that number of the cold records 5 to 1, I can't remember the exact number but that's a sign that we're warming yes sure we're occasionally going to get a cooler event particularly in winter when it's naturally cooler anyway but the fact that we're seeing our warmer events far more outnumber the cooler events that's where the problem is and people need to look a little bit further beyond news headlines to see that I have started a blog I do enjoy blogging but I guess my time management isn't very good at the moment to keep it up so it's sarahnscience.com that's also my Twitter handle it was sarahnscience and my idea was firstly just to talk about life as a climate scientist I'm reasonably I don't know if young's the right word but you know I'm in a transition from a postdoc to academia so I thought it might be a fresh perspective and what it's like to be a scientist because a lot of people including myself I used to have the perspective that they're all 60 year old men balding with big fat glasses and elbow patches on tweed jackets so I kind of wanted to move away from that and show that we're actually some of us pretty young and pretty keen in our work we don't like to always sit in our ivory towers and also practice my communication skills because I really think that we as scientists have a responsibility to communicate our work particularly it's so topical whether we like it or not it is what it is and we need to do our duties as scientists and also perhaps talk about issues that people don't necessarily have a handle on so for example the poll of water season winter what should they believe I'm sure there's other blogs out there too that may address the issue but perhaps someone might stumble along line and go okay well okay she's in the know if I read a blog about how to buy a car or some car expert then I trust their opinion on cars more than I would my mums or something I've had a couple of friends comment and say oh that's I didn't understand what that was about thank you or I didn't realize I think once I blogged about the stress of being a scientist and how you just got it you feel like all this pressure about going for grants publishing papers communicating your work blah blah blah and it can be quite tiring and I don't think they had a bit more of an appreciation of what we go through to actually do our work than just thinking that we just play around on our computers all day so I have had a bit of positive feedback I think I need to put more time into it to get it back to where it was I explained to someone yesterday who wasn't too keen on being in the media think of it as explaining it to a seven year old kid so I used the example of my nephew before and I don't actually I've never talked to him about climate science but I have him in my head well Charlie this is how it is and try and have I don't know if it comes across but have that sort of enthusiasm in my voice that you talk to a kid and use words that they don't understand like if you think about I must not use jargon I must not speak too fast I must not do this or that it becomes too much and overwhelming but I find if you're speaking to a child that just comes naturally you know that their level of knowledge is not as well as your not as good as yours in your field so that's something that I think of one tip that has been priceless for me is I only have three main points three or four main points and even if you repeat them again and again it helps it helps you to explain what you're talking about and it doesn't overload you know who you're communicating to and also know your audience speaking to a bunch of school kids is different to speaking to someone on the 730 report and you know don't be afraid the media is not actually that scary it can get a bit nerve wracking when you have a light in your face and a camera in front of you like it this is actually this is fine but when I've been in the studio before I just all of a sudden I tense up and I try not to and it is hard but it is you know not talking to children helps think of something that does make you enthusiastic and try and you know be a little bit more animated someone else here got a website together and I thought I can do that how can I make a heat wave website but it was just kind of stewing in the back of my mind I was just casually talking with a couple of people here and someone said well you know you could do this I might and it just spawned like okay well yeah we can look at all the different stations we can look at maps of current heat waves we can provide pass records and a bit of context but it just kind of it didn't come out of no way but it's just something that was slowly built on in a couple of months and all of a sudden here I was developing it but the main point behind it is for people to track heat waves over Australia the Bureau of Meteorology provides a forecast of heat waves but this kind of works a bit more retrospectively it's like a record I guess and to put the context of current heat waves in the context of past heat waves so for example the outskirts of Brisbane had a heat wave valley this week how does that compare to a heat wave they had 50 or years ago or the hottest heat wave or the longest heat wave or what have you so that's what the websites aiming to achieve and it does get more popular this time of year because this is when it's hot though we can technically have heat waves in winter too we actually had one in May last year because it was hot relative to that time of year I do have plans on developing it further and putting more interesting facts and records and things like that on the website because at the moment it only updates daily update hourly if I could and also as I said earlier I really feel like we need to communicate as climate scientists even scientists in general and the website that's the fruits of my labour I was looking at how to measure heat waves how they've changed over Australia I already had the data there, I had the methodology there it's been published in a paper but what good is that to Joe blogs down the pub he can't access that this is a tool that basically everyone can access and I think people can relate to heat waves because it is it is a weather event I analyse it from a climate perspective but it is ultimately a weather event so it's just happened oh my gosh was that heat wave really hot or how long did it last for it's something that people can certainly relate to how heat waves are measured though I do sometimes struggle in explaining that because there are different ways of calculating them and the way that's probably the best way the way that the Bureau uses isn't exactly the easiest to explain the maths behind it is really simple but if I was explaining it to my partner I think he'd vague out pretty quickly there's still a bit of difficulty there but certainly talking about their intensity frequency, duration, timing etc people can generally get a handle on that so I've been working with someone from psychology to develop the website and see whether or not people are learning more about climate change learning more about heat waves some people have said it's really useful the use of red is far too much which it is I love the colour red but it's a bit overkill I don't like the writing can you put the statistics in a different format and it has been good feedback because there's no point presenting this information if people aren't going to uptake it so that sort of feedback is absolutely invaluable to me generally the consensus is it's good and helpful but it's just the devil's in the detail in terms of tracking heat waves currently or in near real time I've certainly been able to do that and a lot more simply than I thought was possible mind you I didn't do the programming personally but actually that all I had to do was make the website, everything else was there the data was there, the tools were there I don't talk about attribution, not yet maybe because I'm currently doing that work again that's the sort of work where the devil's in the detail so I really want to make sure I've got those numbers robust all that sort of thing before I put them up there if I will do that and it's also the work that has to be published as well so I've always looked at extreme events my PhD was looking at extremes over Australia and how they're changing an older version of climate models and before I took up a job here I did my PhD here but then I went to CSIRO for two years and that's when we had really bad hot weather and I think, God how have heat waves changed how do you measure them? and even though I couldn't work on them in that case because it wasn't my job it was just ticking the back of my mind everyone talks about a heat wave but what exactly is this sort of event we don't, as far as I know we don't measure it I actually had a meeting with Lisa I think maybe at a conference one time and we both was discussing this and she goes, yeah no one's actually looked at heat waves so it kind of laid down the path for me to slowly move into that so when I took the job up here my job description was basically look at extremes over Australia do what you want kind of things oh, heat waves, I'll take that one I guess there's a natural curiosity and a natural fascination there because they are so complex we don't really understand everything about them it'll be some time before we do and they do have an impact you know everything is impacted by weather and climate particularly the extreme events and especially in Australia we're really prone to heat waves yes they have happened before so we need to be able to cope with those changes so my most interesting scientific question is finding out the human signal behind these events and not just the occurrence of the end result of the event but the physical processes behind that event so how much has humans changed soil moisture and what has made those changes occur you know what interactions in the climate system yes we've pumped greenhouse gases in the atmosphere but how has that affected all the processes which then drive soil moisture which then go into effect heat waves that's the ultimate question I will not answer that in my lifetime probably no one will we know things are changing but linking those processes up is very very difficult and complex and I don't even know if it is possible to do that entirely yeah to me at the moment though currently is working out the chain of events for heat wave manifestation so we can measure them now we know the general physical principles and mechanisms that cause heat waves how do they all link up in a seasonal climate system so how does El Nino for example affect heat waves over New South Wales and if we know the state of El Nino can we then predict something about heat waves for that season and how does that control the synoptics which then controls the event itself so to me that's what interests me presently but the big picture thing I think that's what drives most scientists is the big picture thing whether or not we get there in our own careers in a life 50 years ago but maybe back then someone's like oh gee I wish we had good observations so we could measure these extreme events properly now we have those observations we base our climate models on the physical principles we know occur in observations so the science has moved on far beyond what they would have achieved in a lifetime but they've helped contributed to those changes we're already seeing the impacts of climate change on the events we're experiencing today whether it's particularly for temperature so whether it's meaning temperature extreme temperature particularly we're already finding the detectable change due to humans so we're not talking like we were 50 years ago 40 years ago that this will be a problem it is a problem and I don't think people have the grasp on that yet and I'm concerned that by the time they do it will be too late sure we will be I'm sure we'll be able to reduce our greenhouse gas emissions to have an impact on how much the climate will change but it is already changing so we're already past some point of no return and now we have to work really hard to make sure that we don't pass that point even further