Josh Moran: 00:04 The urban heat island is really it's the best known phenomenon in urban climatology and it's focused on temperature and the basics of it are, it's warmer in cities than outside cities. Speaker 2: 00:18 You're listening to the Why & How Podcast, produced by the Ontario Agricultural College at the University of Guelph. Where we look to answer the big questions in agriculture, food, and the environment through casual conversation rooted in research. Josh Moran: 00:34 Hello everyone. Welcome back to the Why & How podcast. I'm your host Josh Moran. And today I'm joined by a friend of the show as always, Jordan Terpstra. Jordan Terpstra: 00:41 Hey Josh, how's it going today? Josh Moran: 00:43 Pretty good. Pretty good. Jordan Terpstra: 00:45 That's good. Who are we talking with today? Josh Moran: 00:46 We're talking about something that's actually super exciting today and we're actually talking to a professor, so thank you for being on Dr. Scott Krayenhoff. So maybe to start, could you give us a quick Coles notes version about what we're going to be talking about today? Scott Krayenhof: 00:59 Yeah, so the broad field I study is something called urban climatology. And basically what that means is the climate you experience when you walk down the street is different than you would experience if you were outside of the city. So cities modify their climate when conditions are sunny and clear sky conditions. Josh Moran: 01:17 Maybe since your role's a little different, we usually have on graduate students. Could you maybe tell us a bit about your position at the university? Scott Krayenhof: 01:25 Right. So yeah. A professorship typically is divided between three broad roles let's say. One that most people know as you're an instructor or a teacher, so you teach undergraduates and others you do research. So we're at the leading edge of science in our disciplines, typically as professors trying to uncover new knowledge and come up with solutions that'll help society. And the, the third role is broadly term service. The third role we do and that involves a lot of different things there involves peer review. So checking other scientists work for example or other colleagues work. It involves things like organizing conferences, service within the community within the university and keeping things running. Josh Moran: 02:09 Awesome. The backbone of the school, so to speak. Scott Krayenhof: 02:12 Yeah, you can say that. Josh Moran: 02:14 So maybe just to get into some of the background, what exactly is urban climatology? Scott Krayenhof: 02:21 So yeah, urban, I mean maybe what I'll do is I'll talk about the, the best known phenomenon with [crosstalk 00:02:29] climatology, which is called the urban heat island. And maybe that'll start to give you a flavor. So I mean climate includes a number of different things and includes things like how warm is it? What's the temperature? It includes things like how humid is it? How windy is it? Things like that. The urban heat island is really, it's the best known phenomenon with in urban climatology and it's focused on temperature. And basically the basics of it are, it's warmer in cities than outside cities during and this particularly during clear skies conditions. So clear nights and sunny days. And that's important for a number of different outcomes, let's say. So it can make people too hot. It can and cause health problems. It can lead to the need to air conditioned buildings a lot more. And so a lot more energy expenditure. It can have a variety of other effects. Josh Moran: 03:26 It seems like there's a lot of indirect effects associated with that. When you talk about things like energy expenditure, so like what, what are the average temperature increases that you see in cities in comparison to say, I don't know, rural areas in Canada? Scott Krayenhof: 03:39 Right, great question. So I mean a typical, it depends on a lot of factors. One being the size of the city, the population and all sorts of things. If you're, you know, a small city like Guelph you might only be a couple of degrees warmer than say a farmer's field outside of town on a clear sky summer night. If you're talking about a big city like Toronto or you know, maybe Edmonton or Phoenix or you know, a fairly big city like that, you can get urban heat islands that are more like four or five and in rare cases, 10, 12 degrees. [crosstalk 00:04:11] So, and you, you know, you can notice this on your thermometer for example, like most cars nowadays have, they tell you the temperature on the dashboard, right? And if you drive between Guelph and Toronto, you'll notice when you go through the lower density, greener areas like less, more rural areas, effectively it's cooler typically on a warm summer night than it is as you approach Toronto for example. Josh Moran: 04:36 And what's, and what's actually increasing this temperature is [inaudible 00:04:40] or off these buildings or what's the idea with that? Scott Krayenhof: 04:43 A lot of different things that cause the urban heat island and I would say there's somewhere between five and seven different sort of mechanisms that we look into. They all are going to have bigger or smaller impacts depending where we are. So if we're in Vancouver versus Edmonton versus Phoenix versus New York versus Montreal, different causes are going to play a different role or different magnitude of role. So the big causes typically are we've removed vegetation in cities. There's still some vegetation, but compared to a rural area, like you can think of a forest or a farmer's field where it's vegetated or soil or vegetation everywhere in a city we have a lot of asphalt, we have a lot of concrete. We have buildings, we have a lot of other manmade materials, and these materials are particularly good at soaking up heat from the sun during the day and releasing it in the evening and night. So evenings and nights tend to be warmer. Scott Krayenhof: 05:42 There's a number of other factors. So the removal of vegetation, essentially the change of materials. So these manmade materials, the fact that you have buildings, adds, I'm trying to think how, explain this in a accessible way, one way to put it would be, especially in the evening and night, the sky is cold. And so that's how rural areas cool. They release heat to the sky through something called infrared radiation. Now if you think of being in a city, you have buildings all around you, especially in a denser part of the city, that means you can see less of the sky because the buildings are blocking the sky and the buildings are a lot warmer than the sky. So they're kind of trapping the heat in there, not allowing that infrared radiation to escape. So that's another big factor. And I would say another significant factor is that buildings can slow down the wind and wind typically is going to whisk heat away from the city. Yeah, that's quite a few factors and they're all interacting too. Josh Moran: 06:46 Oh, that's interesting. That idea of heat absorption. I think about it like if I was wearing a black shirt in the sun, you know it's obviously going to be warmer, but overnight I find that interesting as well that that heat that's been retained by these are actually causing greater temperatures overnight, so it doesn't actually really level off in the same way as a rural area. Is that correct? Scott Krayenhof: 07:06 I'm not sure if this is quite getting at your question, but cities are particularly warmer in the evening and nighttime, whereas the highest temperature is a unique experience in the city or in a rural area is typically in the afternoon. So there's a different timing. So it's adding heat at a time of day when usually it's a bit cooler. Josh Moran: 07:25 Interesting. And you briefly talked about earlier on some of the implications of these increased temperatures. You talked about more use of air conditioning and so on and so forth, but I'm kind of curious as to what the actual implications would be for things like urban wildlife. Is there is there connections there? Scott Krayenhof: 07:45 Well certainly you know, that's not really my area of expertise, but I can speak a little bit to it. So for example, urban gardeners, so people have gardens in their backyard, they're going to typically have warmer temperatures. So the frost is going to come later in the, in the fall. The growing season is going to start maybe a couple of weeks earlier in the spring. So they're going to have a longer growing season for example that compared to just outside the city. So that's one impact and no doubt this impacts all the other, you know, flora and fauna and the city [crosstalk 00:08:19] and yeah, I mean certainly trees are impacted, you know, leaf out for example is going to, the timing is going to be different. Yeah. It's not really my area of [crosstalk 00:08:30] expertise, Josh Moran: 08:31 So I'm curious for a bit more of the, like the background information. So how long has this type of research actually been happening? Scott Krayenhof: 08:38 This is really interesting you ask this because I'm just reading a paper by a colleague of mine who wrote about the history of the discipline. And so measurements of, you know, temperature in cities have been happening for two or three hundred years, now the first real methodological innovations where people really started to get systematic and really tried to understand the phenomenon are probably more like a hundred years ago. So people have been studying this for a long time and in particular temperatures. So that urban heat island that's been studied for a long time. Josh Moran: 09:12 Interesting. Scott Krayenhof: 09:13 Yeah. Josh Moran: 09:14 I would have definitely thought it was. I wouldn't think it would have been that long. I guess. I don't know, just because cities are getting larger now, it's becoming more urban. I thought maybe it was [a] Jordan Terpstra: 09:25 And it definitely becomes an important issue as we do become a more urban based population. Right. So I think it's very interesting. Scott Krayenhof: 09:32 Yeah. So I think one point to add in there is if you go back several decades or a century or two, cities were actually quite dirty places, quite polluted. And so people were quite interested in how do we, like what's causing this, how do we improve the environment of cities and of course temperatures only one factor. Other factors are, you know, coal burning and all sorts of things. But so that, you know, there was this interest even a long time ago and there was intelligent people working on this. They didn't have all the same technology that we have now. You know, advanced instruments and models that we have now [crosstalk 00:10:07] . But there was intelligent people thinking about, Hey, why are cities the way they are and why are they uncomfortable, why are they unhealthy and how can we make them better? Which is still what we're working on. And we've made a lot of progress in some respects. Josh Moran: 10:19 Would you get sort of like pocket climates when you do have this urban heat Island, like more precipitation in these areas are greater levels of humidity I'd imagine are associated with that as well. Is that something you see? Scott Krayenhof: 10:29 You know that's a relatively newer part of the field. I think it really kicked off in the 70s they looked at this, there's kind of a two way effect here. So one is do hotter cities, generate more clouds and precipitation or not. And there's some evidence that they do, they generate more like convective thunderstorm type precipitation and that's reasonably well established. Although I would stay there still a lot of work to do there to understand that. And the other piece of it is how does precipitation affect the urban heat island? Right? So cities that get more rain, how does that change their urban heat Island? Josh Moran: 11:12 And you'd talk about things like, but there'd be an association with higher greenhouse gas emissions with these urban heat islands as well with new talk about energy expenditures and so on. Scott Krayenhof: 11:22 Well yeah, I think it's probably quite complex, but one sort of obvious point that relates to urban heat or there've been heat island is if cities are warmer, especially in a hot climate. So it's already hot climate. So a lot of the buildings are going to have air conditioning. And then you make it even hotter because of just the way the city is built, those air conditioners are going to have to work even harder. And what an air conditioner does is it essentially takes heat from inside a building and puts it out into the space between the buildings and in doing so it uses some energy and the heat, the waste heat from that use of energy and use of electricity effectively also goes out. Josh Moran: 12:00 Like a fuel to a fire. Scott Krayenhof: 12:01 Yeah. So we're heating up the external environment, which makes it, you know, the gradient or the difference between the temperature inside and outside even bigger. Scott Krayenhof: 12:10 So the air conditioner has to work even harder, which is of course all producing greenhouse gases. Well, depending on the fuel source that's powering electricity. Josh Moran: 12:19 And so you mentioned the variability between city to city. Do you specialize in one city or do you do your research in various cities? Scott Krayenhof: 12:28 That's a great question. So there's different ways we scientists approach their discipline. In my field, I would say there's broadly three ways that we approach trying to understand the climate. Of a city. One would be direct observation where we take things like thermometers and go out into a city and measure what's the temperature and how does it vary between neighborhoods. Another one is scale modeling where we build mini cities and try and make them as similar to real size cities as possible in some ways and understand how those many cities modify the climate. Scott Krayenhof: 13:03 Now that's not done that often, but it's a very interesting way of going about it. The third way, well there's, there's even more ways, but let's just stick with these for now. The third way I would say is numerical modeling, computer modeling, and that's what I really specialize in. Now obviously if you're going out into a city with our thermometer, you're measuring a specific city and typically people who do that will measure in a few cities, you know, a handful of cities and maybe do some comparisons between them. These kinds of measurement campaigns where you take a whole range of sophisticated instruments into a city and measure the climate. You know, how does it vary as you go up towards the building roofs and higher and how's it vary across the city? It's quite an expensive undertaking and complicated undertaking. So you can't do every city, you know, in the country or the world. Scott Krayenhof: 13:52 Whereas with numerical modeling, it's a bit, what we're trying to do with numerical modeling is we're trying to come up with general principles that work in any city. So it's not, you know, the heat Island, urban heat island is going to be different between different cities. But let's say there's five interacting mechanisms or causes that caused the heat island. And the fact that the magnitude or the size of the heat Island is different in two cities comes from a different mix of those factors. And so what we're trying to do with computer models, we're trying to actually represent those mechanisms or those factors as accurately as we can so that we can go to any city in the world and predict how hot is the heat Island, Josh Moran: 14:35 Does this higher temperature in these cities or this altered climate affect surrounding areas as well. Or is there like a radius that other neighborhoods say just outside of the city experience due to these situations in cities? Scott Krayenhof: 14:52 That's a great question. Yeah, so of course when we think about climate, we think about a few different things. We think about air temperature, we can think of humidity, we can have a wind, we could think about radiation, radiation being the infrared radiation I was talking about earlier or sun, like are you in the shade or are you in the sun? You know, those are two different microclimates. You can be under the tree or beside the tree and you're experiencing a very different climate. So air temperature and humidity mixed with the atmosphere, they mix with the air. So that means they vary more slowly and they can also be the impacts of the city go into the air and the air of course can move downwind to the city. And so the answer to your question is yes. So cities are going to tend to be warmer and drier areas downwind to the city are going to tend to receive some of that effect. Scott Krayenhof: 15:45 So they're, they're going to tend to be influenced by that warmer drier air coming from the city. Josh Moran: 15:49 How far will that reach new? Think about? Scott Krayenhof: 15:52 It's going to depend on conditions. And this is still a developing area of research, I would say. And not a hundred percent understood, but I would guess and you know, well just to say that within the city this is happening, air from this hotter neighborhood is being transferred down to this cooler neighborhood. Downwind air from this city park, which is cooler, has being transferred is cooling the neighborhood downwind of it. So this is happening at all sorts of scales within the city and then also between the city and the downwind area. But yeah, I mean I would, I would say probably on the scale of tens of kilometers, so 10, 20, 30 a hundred kilometers. Josh Moran: 16:28 Interesting. And to kind of build off that question, and I'm sure you see that similar to in cities that are beside water as well, right? Scott Krayenhof: 16:35 Absolutely. So there's, I mean there's a well known atmospheric phenomenon called the seabreeze or the Lake breeze. Toronto has, it has a Lake breeze, right, where you essentially have a temperature difference between the land and the water. And that creates a pressure difference, which creates a wind essentially a wind that travels in land during the day. And so areas of Toronto right next to the water are necessarily going to have a heat island during the day. Not that they necessarily would anyways, but they're going to have a cooling breeze off the Lake during the summer. Josh Moran: 17:08 And as this becomes a more prevalent issue or more studied issue, what, what sort of, what sort of ways are cities combating this? What, what sort of things are you guys proposing? Scott Krayenhof: 17:18 Yeah, so this is, this is a great topic and a lot of people talk about urban heat island mitigation. Scott Krayenhof: 17:25 Meaning how do we reduce the urban heat island? How do we make a cooler? I prefer to talk about urban heat mitigation. So how do we make a cooler in the city if that's what we want? Cause it actually, you know, you can, if you think about it, Moscow in the winter it's very cold and it has an urban heat island that's beneficial. You want that. You don't want to mitigate that. Whereas a, you know, you could have a city say close to the equator that doesn't have a urban heat island. You still want to make a cooler. You still, so I think we're just trying to mitigate heat. We're trying to reduce temperatures in cities when, when it's too hot, when it's too hot for people, too hot for buildings, things like that. So there's a number of ways you can go about this. And this is a somewhat well-researched area. Scott Krayenhof: 18:14 Typically it's easier to mitigate heat during the day, so make it cooler in the day than at night. And this is another reason why I think it's better just to talk about cooling down cities rather than mitigating the urban heat island. Cause the urban heat island is more, it's stronger in evening and night and it's harder to cool down the evening and night by in terms of changing how we build and design cities. So essentially what we want to do, if we want to cool down a city during the day, what's warming it up? Ultimately it's the sun. That's the sort of base level driver of urban warming. So what we want to do is want to either bounce some of that solar radiation from the sun straight back up into space. And one way to do that is to change our surfaces. So change our roof top surfaces, maybe even our road surfaces, but roofs are a good one. Josh Moran: 19:08 Something that's reflective? Scott Krayenhof: 19:09 Something that's very reflective. Josh Moran: 19:10 This might be a really stupid question, but say would that interfere with air, air, travel and airspace and stuff like that if you are reflecting all this light back? Scott Krayenhof: 19:18 Yeah. Well that's a great question and I'm actually not sure of the answer that you know, we think about that in terms of, cause there's also a cool pavements or reflective payments, right? You can put those on roads, which seems like a great idea until you try and drive down a road that's really reflective or walk down a road, you know, you can't see anything cause it's beaming so much sun at you. So yeah, so that's, that's a consideration for sure. There's, this has been adopted on rooftops quite a bit. I would say cool pavements are reflective. Pavements have not been adopted as much. But in practice if you fly over, you know a lot of cities in California or Arizona you'll see a lot of quite reflective rooftops. Scott Krayenhof: 20:00 So, so that's, that's one way you can cool down cities during the day. The other is trying to reintroduce vegetation. So add more street trees, add more trees and backyards add green roofs. Anything that adds more vegetation and therefore water. Cause the thing, the way that vegetation deals with this sun that's coming down, solar radiation from the sun that's coming down and warming the city is it essentially converts instead of all of that sign being absorbed by say a roof or by a road. And most of it being converted into heat in the air that you can feel and that warms the air temperature. Some of that heat hits the vegetation, the vegetation through evapotranspiration converts that into water vapor, which takes a lot of that energy so that energy doesn't go into warming the air. It goes into essentially making the atmosphere more humid. Josh Moran: 20:51 So these plants are releasing a misted form of misted water basically. Right. And that's what's... Scott Krayenhof: 20:57 Yeah, yeah, like humidity, humidity. Yeah. Josh Moran: 20:59 Interesting. This is a lot better thought out than what my idea would have been when should be to send Jordan and I to all the cities because we're super cool. Jordan Terpstra: 21:09 Yeah, that's very coordinated. Josh Moran: 21:11 This might be another silly question, but we're talking about temperature and I'm thinking about like just how this affects my day to day. So when I look and check at the temperature for Guelph for the day and I'm planning on what I'm going to wear and things like that. So where are those temperatures being taken and how does this heat island effect actually affect the temperature that we are expecting in our city? Scott Krayenhof: 21:31 So those are mostly going to be relating to the airport. So what's the climate at the airport, which can be quite different than in the city. And you know, in a place like Guelph that's not going to be a huge difference cause it's not a huge city. But in a big city it could be different. Now there's another layer to this, which is really when you check the weather you're, what are you checking? Air temperature. Is it going to rain? I mean maybe is it windy. Yeah, maybe is it humid. Yeah. But when you walk down the street, what you actually experienced depends on more than those things. I mean it does depend on the air temperature does depend on the humidity, which you know, a hot, humid day in the summer is not always pleasant. A wind depends on wind. A windy day in the winter, it's not always pleasant. A windy day in the summer might be pleasant. Right. It also depends on things like are you in the shade or not? Scott Krayenhof: 22:29 Are you, so one way to better design a city to keep people cool would be provide shade options. You know, if there's walkways that they people need to walk on, are they in shade for or is at least one side of the street in shade for particular hot part of the day, for example. Another thing is just that the temperatures of the surfaces, so when you're walking, if you're walking, you know, across a parking lot that is covered with asphalt and it's pretty hot in the middle of the day versus if you're walking across a sports field, it's covered in grass, it's the same day, the parking lot and the sports field. It could be right beside each other and there'll be very different, different temperatures, natural surfaces of the grass versus the asphalt. And what that means is you're going to experience a very different amount of heat coming off of those surfaces and in the form of infrared radiation. Scott Krayenhof: 23:25 And so that can actually make a big difference in terms of how hot or cool you feel in the city. So there's, you know, we've been talking about the urban heat island, we've been talking about how do we cool down the urban heat island. That's all air temperature. That's all. That's one part of what makes you hot or cool, but there's many other factors such as wind and humidity, which you already know about. And are you in the shade or not? But then also, are you standing on a hot surface or not? Are you standing beside a building that's in the sun that's beaming heat at you? Or are you standing beside and building this in the shade? Or does it shaded by a tree? Josh Moran: 23:58 And so when it comes to some of these solutions that you're talking about, is it, do they tend to be more proactive or reactive or a combination. Scott Krayenhof: 24:08 In terms of how they're actually applied? Josh Moran: 24:09 Well, I guess just like when like designing cities and things like that. I'm sure when a lot of cities were designed, they weren't thinking about this stuff. So yeah. Do you find that when they are trying to combat some of these issues, is that more of like, okay, we're building this new space so then that's, well, we'll take these into consideration, or is that okay, let's go back to all the other spaces? Scott Krayenhof: 24:29 That's a good question. I mean, I think you're right that these climate impacts of building cities are unintended. You know, we didn't build cities to warm them up. Like we didn't purposely try and create cities as warmer. And the thing is, if you look back throughout history, cities were often designed to make their outdoor and indoor climate comfortable, especially before the era of fossil fuels. But like before the 1950s cities were actually designed in a climate sensitive way. Scott Krayenhof: 25:00 And we've gotten away from that because we have fossil fuels, we can afford to heat and cool our buildings, although less than less and less with climate change, you know, can we really afford to do that anymore? So, you know, of course cities are still expanding. So when we're building new neighborhoods, in some cases that's taking into account like how do we actually build this neighborhood? So it's, you know, more walkable, it's going to be more comfortable given the climate, things like that. But the thing is, you know, a lot of cities are, are built already and we're not going to tear down all those buildings and build new ones just to have a better climate in the city that would be prohibitively expensive. So often what people think about is how do we modify the existing design and the ways you can do that are things like adding trees, right? Scott Krayenhof: 25:47 Redesigning the street, using new different paving materials. Cause streets need to be repaved frequently anyways in most cases, using different rooftop materials such as the reflective roofs or green roofs because roofs need to be reused or sorry, replaced, you know, every 30 years or so. So, but tearing down whole building because it's too tall or something like that or you know, too close to this other building is generally less feasible and you don't see that. Josh Moran: 26:20 And could things like even just putting a plant on your balcony make a difference in terms of helping out with this situation or no? Or is that something that's kind of very minimum? Scott Krayenhof: 26:29 Good question. I've never, I never thought about that. I, you know, I, the question would be if everyone in the city does that, would that make a difference? Just you putting a plant out, it probably won't do much. I can answer that one. If everyone in city a plant out, probably not a big difference. Yeah. And you know, part of that is one of the reasons trees are pretty effective is not just their impact on air temperature. It's also the fact that they provide shade. So when we're talking about the greater range, the greater range of effects they have on the climate, not just air temperature but on, you know, shading and, and other factors. So. Josh Moran: 27:10 The trees are also nice in a way when you think about that aesthetic appeal and playing into that. So there's a lot of benefits to actually adding this green infrastructure in your cities, I would think anyways. Scott Krayenhof: 27:21 Yeah. Yeah. And there's, and believe me, it's, it's a big topic of conversation amongst and research amongst academics. So, and hopefully planners and I think to a degree it is in cities. Yeah. Josh Moran: 27:33 Very cool. So speaking of academics, what originally actually drew you to this research area? What started you in this? Scott Krayenhof: 27:41 Yeah, you know I, I was, let's see, when was this? This was, I was somewhere in my undergrad, second or third year and a professor approached me and asked me if I wanted to work for him that summer. I think I'd worked for him the previous summer and he had a project that had really, it really drew me in and the, the project was essentially using computer modeling to give a number, put a number on if on the following, if every second rooftop in Toronto had a green roof, was converted to a green roof, how much cooler would it be in Toronto on a typical summer day? That was a question I was asked and I worked on that for two summers and we didn't really have the computer modeling tools back then. This was like 15 years ago and we did our best and we got, we got some somewhat of an answer and now we have, we have much better tools and we can answer that better. That question much better. Josh Moran: 28:44 Was your degree in environmental sciences? Scott Krayenhof: 28:45 No. No. So I'm currently in the environmental science's department here, but my degree was in atmospheric science, so meteorology. Josh Moran: 28:52 Okay. Yeah. And I liked the, I love the idea of green roofs when you think about it, cause you're not, you're not filling space that could be used for things like property and so on, but you're actually helping contribute to the solution as well. It's a really, it seems like a really good solution if it can make an impact. Right? Scott Krayenhof: 29:12 Yeah. You know, when people can garden on them and, and all sorts of things. The, the trick with green roofs from a climate perspective, which is what I know about is they really only work as well. They only really only work well if they have enough water. So in a climate like, well for Toronto, they're actually likely to function reasonably well because in the summer when it's hot us and we want cooling, we actually get quite a bit of rain it might rain, you know, every week at least. Usually, I think, and by conversely, if you're in Vancouver, which is where I, I'm closer to where I'm from, they have very dry summers, even though the rainforest and it's wet most of the year, they're pretty dry summers. So a green roof, there's that. The vegetation might, the soil, my dry out with vegetation might die. And then your green roof is essentially just a bunch of dry dirt, which actually isn't. Scott Krayenhof: 30:03 Yeah, there you go. Turns into a Brown roof and it's not actually going to help that much from a climate perspective. Josh Moran: 30:10 So what, what would an ideal city look like? And we'll use Toronto as a reference, say that population and what, what could we do to make Toronto the perfect climate happy city. Scott Krayenhof: 30:21 That's a, that's a great question. You know, that's an easier question to answer in a city that is not next to a big body of water. Scott Krayenhof: 30:30 Okay. But... Josh Moran: 30:32 Say there's no body of water, then we can.. Scott Krayenhof: 30:34 Say there's no body of water. Well, I mean in general, you know, in this kind of climate, I think an important, I mean in almost any city that can support it, that has enough water to support it, you want more vegetation. So things like green roofs and street trees, you basically want the impervious surfaces to be less exposed to the sun or removed. Scott Krayenhof: 30:56 So in the case of, you know, greener, if you're removing the impervious surface, in the case of planting trees above a, say a parking lot or above a road, you're shading the impervious surface that would otherwise receive the sun and convert that into heat. So those would be two things, adding more vegetation. And I think strategically adding high like reflective surfaces the tricky thing becomes, you know, so far I've talked about essentially the summertime case. Like how do we cool down hot cities. But of course any change you make is still there in winter. And do you want to be cooling down a city in winter like Toronto? No, you don't. Then it's further complicated by things like, okay, but in the winter the roofs are covered by snow, right? So if you make a change the roof, it doesn't actually matter. It doesn't actually affect because the snow is dominating the climate effect of that roof in winter. Scott Krayenhof: 31:54 It's actually becomes quite a complex question and then you add in the Lake next to it and things like that. What we do is we run fairly complex computer models to try and answer some of these questions. The other thing would be, you know, we're starting to move towards more sustainable transportation options. I mean, this isn't really my field, but if you remove the amount of road and highway that's going to help move people by, by rail, for example, much more things like that. Yeah. You know, we typically don't answer a question like what would be the ideal because it's so far from what's attainable at this point. But that's, that's a great question to think about. Josh Moran: 32:36 That's one thing I didn't even consider that you, you brought up like the seasonality aspect of it. How Canada has these, these winters. Do you ever look at you, so you look at that as well. Do you, what sort of effect do you see in those? Scott Krayenhof: 32:48 Yeah. So, well I can, I can talk about Chicago, which isn't that dissimilar from Toronto. Cause I did a study in Chicago. What we did is we looked at increasing the reflectivity of the roofs in Chicago in certain neighborhoods in Chicago. And what you see is they cause a nice cooling during the summer. That's great. And we assumed depending, we assume different lengths of the winter season where the risks were snow covered, therefore are when the roofs are snow covered. Our increase in reflectivity makes no difference. But what we actually found is the shoulder seasons. So we're talking mid, mid or late fall, early or mid spring. Those periods are still cold enough that we're, we want a hotter environment and so adding, there's no snow. And so we're cooling the environment in the city when we don't want to cool it. Scott Krayenhof: 33:41 And what we found is that effect was about as big as the cool. Like that negative effect was about as big as the positive effect of cooling you got in the summer. So for a climate like this, just sticking up a reflective roof may not be the way to go and or it may have little impact in sort of a net energy sense now. I mean there's, there's different outcomes. You can look at it. That was mainly looking at heating versus air conditioning. You know, we're increasing the amount of heating you have to do in the shorter seasons, lowering their conditioning during the summer. But if we then look at, okay, in 1995 Chicago had a serious heat wave, hundreds of people died from the heat. If they'd had all of these reflective roofs, that period that he waved would have been maybe a degree or two cooler and maybe only 50 people would die instead of 500 or a thousand. Scott Krayenhof: 34:37 So, you know, there's different outcomes that can tradeoffs. Yeah, there's different outcomes you can look at. Josh Moran: 34:41 Yeah, for sure. Digging a note of the time, we are running a little bit low. So it's always a shame. Always a shame, right Jordan? Absolutely. But so I might leave you off with a few questions if that's okay with you. Scott Krayenhof: 34:52 Absolutely. Josh Moran: 34:53 So first of all ask you if anyone's interested in this sort of realm of research, what advice would you have for them? Scott Krayenhof: 35:01 That's, that's a great question. I think it depends a bit whether they really want to be deep in the science of it or if they're more interested in the applications. If they really want to go into the science, then I would say learn your math and physics and maybe even an atmospheric science program. If you're more interested in the sort of applications then yeah, maybe something like geography or planning, urban planning, urban design, landscape architecture, that kind of thing. Scott Krayenhof: 35:30 Which I know less well. I mean I took the math, physics option route. Yeah, I think, I think, yeah, really. I mean, so what I'm talking about today is an application, right? It's like an application of the atmosphere and what modifies the atmosphere in a city. And to really get to something like that, you need to start off with some of the fundamentals like, so to be able to do what I do, I've started off by learning a lot of the fundamental math and physics of the situation and then about the atmosphere, the physics of the atmosphere. So yeah, that would be my, Josh Moran: 36:04 The people that we always have on. And I, and I could say this about every guest we've had so far, it always amazes me and it kind of, Oh again, I get taken aback a bit cause I can only imagine how rewarding it is to be presenting research that is so practical in terms of what you can do in the long run. So super neat. So we'll also ask you if there's anything exciting going on in life right now that you want to share with the audience. Scott Krayenhof: 36:28 You know, I'm, I'm really enjoying working with the grad students I have. And what we're, what we're looking at is we're taking a model I developed a very fairly simple model of all of the energy exchanges in a city and we're putting a little pedestrian in this model and we're moving the pedestrian around and we're doing things like adding trees and we're changing the size of the buildings. We're changing the paving materials where, so we're actually getting and trying to get at a question that is related to one you asked earlier, which is if we want to design an ideal city street, not an ideal city, but an ideal city street for a person to be most comfortable, say on a hot summer day to walk down that street, what does that street look like? Incorporating all of these factors and where do you put the trees and where do you put these different asphalts or different pavements and, and things like that. So yeah, that's, that's been really rewarding and got some great students working on that. Josh Moran: 37:27 Awesome. Scott Krayenhof: 37:27 And we're also, we're also actually looking at if you know, climate change proceeds as we think it look, if it looks like it is, and let's say 30 years from now cities are going to be a bit hotter. How do we design that same street for those conditions? So we're starting to think about how do we design not only for present conditions but for future conditions. Josh Moran: 37:52 Yeah, it's super exciting cause it's something that you, when you, when you talk about the research you realize, Oh yeah it is. I do notice that now when I'm in the city it's a little bit more, it's a little bit warmer, it's a little bit more this and that. So it actually kind of have a bit of a reasoning behind that is super duper cool. Scott Krayenhof: 38:07 Yeah. And you know, some of the stuff you can actually, I mean obviously everyone can feel the difference being under a tree versus not under a tree on a hot day. But you can also feel some of these other effects. Like if you just take the Palm of your hand and you, it's a hot, it's the middle of a hot day. Say it's 2:00 PM hot sunny day, we don't have many left in the season, but it might be a couple more and you walk out over asphalt and you just put your hand facing down maybe a couple feet above and just feel how hard that feels. That's the infrared largely coming off of that and you do the same over grass, you'll notice a difference. And so you can just notice that there's all of these factors that are affecting your actual thermal experience or how warm or cool you feel. Josh Moran: 38:47 Yeah. Scott Krayenhof: 38:48 And you can actually feel them with your hands. Awesome. Josh Moran: 38:52 And I guess our last question for you would be if you have any shout outs you'd like to give. Scott Krayenhof: 38:57 Yeah. My grad students has been a great create. I've only been here a year and a half or so. It's been a great experience with my grad students, my department school of environmental sciences, a university of Guelph has been a great place to work, a lot of great colleagues doing really interesting work. You know, I've had a lot of great mentors over the years in my field in the field of urban climatology, which is a really neat field. It's a tight knit group of a few hundred people worldwide and we get together every year and a half for these international conferences. And yeah, just a really great group of people doing, doing pioneering work and yeah, some really great mentors. Yeah, I've had some really great mentors, so shout out to them and, and my department here at Guelph. Good place to be. Josh Moran: 39:44 Very cool. Well thanks again for being on. It's been an absolute pleasure and I again, this, I can't get over how great an opportunity this podcast is cause it's a bunch of stuff that I probably have no business learning, but I get the opportunity to, and it's people like you that they make this university a great place. So thank you so much for being on. Scott Krayenhof: 40:03 It's been a pleasure. Thanks both. Perfect. Thank you. Take care. Until next time. Speaker 2: 40:08 The Why & How podcast is published by the Ontario agricultural college of the university of Guelph, and it's produced by Stephanie Craig and Jordan Terpstra recording and editing done by Jacob HighSeq and Kyle Richie. The host is me, Josh Moran. Funding for this episode was provided by the W.S. Young Memorial communications grant to the OAC alumni foundation.