 Melissa Hart from the University of New South Wales and my research is in the area of urban climate. My past research has been observation based, so looking at temperature observations across urban areas and trying to quantify the urban heat island magnitude. So that's temperature difference between urban areas and rural surrounds. We tend to find that urban areas are warmer than rural surrounds and it's called urban heat island because it tends to show up sort of like an island of heat if you think of a city that's not sort of too complicated geography and is just you have urban areas and then perhaps grasslands pastures surrounding it and you get this island of heat in the middle. And it's caused because we replace sort of natural landscapes, rural landscapes with lots of concrete and lots of buildings that absorb more of the energy from the sun and then they hold that energy for longer. So in the rural areas, as I said before the rural areas cool off at night they cool off quicker whereas the cities they retain that heat for much longer and then also because you have the complicated geometry within cities as I said the heat gets trapped as well within the street canyons. We also find that cities tend to have less vegetation so you don't get that cooling aspect of vegetation that you have in rural areas. Plus cities tend to release their own heat through what we call anthropogenic activities or human activities so that might be from cars if you walk down the street you can feel it if a bus goes past and the exhaust hits you in the face and you can feel the heat from that. From heat released from buildings so from air-conditioning vents and then heat released from people of ourselves. So you know when you're standing in a crowd you can feel the heat from the people around you and all of these also impact the climate within the city. The anthropogenic sources it tends to be a smaller amount. It's more sort of the changing of the land use that has the bigger impact. The work I did in Hong Kong were particularly interested in quantifying what the urban heat island magnitude was so what the temperature difference was in the city between the city and the surrounding non-urbanized areas. We're then also being interested in looking at where the hottest parts of the city are and what are the characteristics land use surface characteristics associated with the hottest parts of the city. So you know how much vegetation there is what the building density is like to see where the really hot parts are. I've been working on cities in the US in Hong Kong and now back in Australia. The work we did in the US was Portland Oregon and we found that vegetation cover was the main factor that was influencing the urban heat island magnitude within Portland. So as soon as you hit the more vegetated parts of the city the temperature difference in temperatures in the urban areas were much cooler. Particularly for that city we found that yeah particularly tree canopy cover was incredibly important and it yeah we had a significant cooling of the city in areas where you had lots of trees. Hong Kong was a little bit different because you've got these very very tall narrow street canyons and so you the influence of the buildings is much greater than the vegetation. So we found that the hottest areas tended to be those areas where you had really dense buildings. Minimal vegetation but mainly because there's no room for the vegetation. Lots of vehicles so lots of heat emissions from cars and people and such and really tall buildings as well. So buildings that basically street canyons that are tall and narrow and that are trapping heat within those street canyons so they're not being able to cool off. We're particularly interested in the impacts of urbanization on sprawl versus density. So if you were to grow a city or if you had to if you had growth within a city whether you're going to grow it externally or whether they're going to grow within the city and so there've been some studies that are done on that but there's still a lot more to be done so I have a student that's going to be doing a modelling study for Sydney. Differ's depending on city, geographic location, climate, time of day, time of year but short answer is yes it does differ. We looked at some longer term temperature trends in Hong Kong between the urban area and the rural surrounds and actually found that on some days, some hours of the days particularly found that we were getting temperature differences of up to 12 degrees Celsius which was a significant difference. They tended to be differences in minimum temperature so the early hours of the morning. It tends to have the greatest impact overnight so it tends to be more that the cities are slower at cooling down overnight than the rural areas so they stay warmer throughout the night but those temperature differences are important particularly if they, depending on the time of year but it's the minimum temperatures from a human health perspective that have the greatest impact on heat related mortality, morbidity and such so if you do get increased minimum temperatures in the city during the summer time then you've got an added burden on the urban population because if you've got a hot day that then it cools off at night the body has the chance to recover from the heat but if you've got a hot day and it stays quite warm during the night then your body doesn't have the opportunity to recover then you've got a hot day the next day and so it's that accumulated impact so within urban areas where we've got these often much warmer minimum temperatures than rural surrounds this I guess this added burden for people living in urban areas versus those in the countryside. Which parts of the population are most vulnerable to heat stress? It tends to be the elderly also those that are homeless those that living alone and then people that have underlying health health conditions as well but mostly the elderly. Well I guess the most important thing is that when you are looking at climatological records of temperature that the weather stations that are in the middle of the cities are not included but if you're looking at sort of climate change and sort of global climate change and wanting to know how greenhouse gashes are affecting their climate then temperature records from stations in the middle of the cities are usually not included it's stations that are not under any influence of urbanization because you wanted to want to just look at influences of sort of other forcings not urbanization. The data I look at is in that I'm actually interested in the urban urban measurements but those that are particularly interested in global climate change then they'll either look at the data that's from non-urban areas or homogenized data sets so Australia they're a concept data set so they'll concentrate on those sites whereas for me I like the sites that are in the urban area because I'm trying to look at yeah I want more more sites in the urban area but that's purely for looking at urbanization not looking at sort of climate global climate change. I think that needs to be understood that there's a lot of work that's done under developing these data sets that are just purely to be looking at global climate change without the impacts of urbanization and so there's papers documents galore that you can read about this where you can see that that they look at each individual site and they'll look at any outside influences and they'll discard sites which have moved in time or which I've got a significant urbanization impact on them so yeah it's it's not just taking every site in the world and looking at how the temperatures change you've worked in a couple of different countries has that influenced you in the way you approach science communication? I was in the US first but I I don't know I was a postdoc and I think I just sat in my little postdoc bubble bubble and did my research so wasn't there I did some work with high school students but beyond that not so much it wasn't till I moved on to a faculty position that I started yeah I guess communicating more in Hong Kong we worked a lot with the local government so the Hong Kong Observatory and such but beyond that I'm I'm probably not a good post a child for science communication professionally yeah it's been just yeah governments or local organizations and such one thing that I thought was interesting from my work in Hong Kong was that the Hong Kongers in general didn't have a lot of general worries about climate change it wasn't number one on their sort of environmental issues radar and I believe that came down to the fact that they have an incredibly bad air quality problem there and that that just was number one for everybody there because it's something that you see almost every day and you experience whereas climate change I guess unless you it's really difficult to experience stay you can't experience day in day out and so for Hong Kongers yeah whenever they were asked about environmental issues that greatest that worried them it was always a quality that was number one actually did an air pollution meteorology PhD first up so that was just I think I did an undergraduate degree undergraduate course sorry in air pollution meteorology that I really liked so I did my PhD in air pollution meteorology and then it was just pure chance that when I was looking for a postdoc post after finishing my PhD there was one that was advertised this was in the US that was looking at the impacts of both air quality and heat and urban heat island on urban populations so that opened up the urban urban climate sort of door for me as well have you ever had to ever had much interaction with people who reject climate science and how do you respond to it yeah always taxi drivers how many people say that I sometimes I kick myself because I get in a taxi in a taxi driver starts chatting and says so what do you do and sometimes they'll say oh climb I'm a climate scientist and then it starts and I'm like oh I did I say that way and so I actually have started lying a little bit then occasionally the other day I got in a taxi and I just said oh I work at a university and then he said what do you do at a university I said I work with graduate students but I didn't take it further because I just was tired and I should you know it's not every single taxi driver that comes at me being a climate change denialist but I guess there's a level of frustration as well just when I come across people in the general public that I guess yeah I feel that a lot of people have more trust in the media than the science than scientists and that frustrates me and and I get frustrated by the amount of time that done denialists often given within the media as well I think that yeah there's a lot the media can do what would be your advice to scientists about how to better communicate the climate science to the public honestly I think I should somebody else should be giving me this advice too because I'm sure I don't do it I know that I don't do it as well as I should so we've had a lot of talk within our center about engagement with schools there's a lot of people that do go into schools already within our center but we're talking around I guess yes seeing if we can expand that a little bit further I would have loved that as a school student I had never met a scientist but apart from my science teachers until I got to university so I would have just loved to have somebody in it come in you know from the core piece of science research and talk about it in schools I yeah I loved science at school I mean that's why I yeah carried on through university and science I loved it but honestly I didn't have the best I came from a public school with not the best science teachers unfortunately but there was something in there that kind of got me hooked but I would have loved the opportunity to have scientists come into schools what are the most interesting questions in your field of research at the moment it's that link between sort of urbanization and climate change so if you think that people within urban areas you have that I guess that double whammy added burden of you live in an urban area so it's going to be warmer but then you've got global climate change you and have a warmer climate so it's it's quantifying I guess that the the relative impact input impacts of global climate change versus urbanization because when it comes to sort of adaptation or mitigation there's a lot of things that we can do that can help both so within urban areas it's so easy you know greening cities and changing building practices and things that can help to mitigate the impacts of both human emissions of greenhouse gases have had having a significant impact on our climate and it's relatively recent just in the last 100 odd years and the changes are sort of unprecedented within that timescale and it's something we should be definitely worried about and looking at