Public Lecture - Understanding Climate Change

[00:00:00] Speaker 1: Welcome, everybody, to this virtual seminar. I'm Tim Bonebrake. I'm an associate professor in the School of Biological Sciences here at Hong Kong U, and also the associate dean of teaching and learning in the faculty of science. It's my distinct pleasure to introduce Dr. Jed Kaplan to you today. Dr. Kaplan is an associate professor in the department of our sciences, where he joined in 2019 after having spent time as a research fellow at the Max Planck Institute, Oxford University, and the University of Augsburg, among others. He received his PhD in plant ecology at Lund University and a BA in geography from Dartmouth. In his career, he's published over 120 articles on climate change-related topics and currently serves as the editor-in-chief of the journal Global and Planetary Change. Dr. Kaplan's research and perspective is unique in its range and breadth. I mentioned his PhD and his bachelor's in these different subjects, and I think that makes him very uniquely positioned for these the important advances and synthetic insights that he's made in in terms of climate change research. He's been involved in previous iterations of the IPCC, the Intergovernmental Panel on Climate Change, and so we're very fortunate to have him here today where he'll give some of his perspectives and insights on the most recent IPCC report. So please join me in welcoming Dr. Kaplan. We'll be discussing today understanding climate change, reviewing the past, [00:01:42] Speaker 2: and mapping out future implications. Okay, very good. So welcome, welcome everyone to this to this faculty of science lecture and I appreciate everyone joining. I'm going to talk today about climate change and as I was preparing this talk I realized that climate change is just such a massive topic that there is absolutely no way that in 40 minutes I could even scratch the surface in many respects on everything about climate change. And the hardest part about making this presentation, about preparing this presentation, was really thinking about what I could show you and what I could talk to you about. So I'm going to give you a kind of, I hope not too superficial view on climate change and in particular I'm going to try to show you a few things that you for sure haven't seen before because these are results that come directly out of my lab. You're going to see some really new and fresh off the presses science and we're going to talk a little bit about climate change in Hong Kong specifically which you don't necessarily hear too much about these these days. So I think that will that will be something fun, not just thinking about climate change globally, but also thinking about exactly how climate change might affect us during the next few decades. Before I launch into it, I need to recognize that a lot of what I'm going to show to you today is not my own work, but also work that was prepared by members of my team, including my former postdoc Alexander Koch and my undergraduate student who I'm supervising in her final year project, Yi Wang Ying, and you're going to be seeing some of their results and we'll also of course be seeing some synthesis of the science of climate change that's been done by the intergovernmental panel on climate change. And also thank you to the faculty of science for organizing this lecture. So just jumping into it, what are we going to talk about today? Well, we'll talk about what's the latest on climate change and you're coming to this talk at a good time because there are actually some exciting new syntheses that have been done and I think we know more and more about climate change than ever before. And so I think it's worth it to sort of get a picture, a very brief view of the state of the art, talk a little bit about why climate change is happening, as I mentioned what climate change will mean for Hong Kong, and then I'd like to leave you not on a pessimistic note, but rather as much as possible on a note of optimism with some discussion and some presentation of what we can do about climate change. Climate change is occurring. There's absolutely no debate that the earth is warmer than it was 10 years ago, 30 years ago, 50 years ago, or 100 years ago. And it's also very clear that that warming of the planet is caused by people. We are seeing, as noted in this headline quote from the intergovernmental and panel climate change, widespread and rapid changes in the atmosphere, ocean, and cryosphere, and perhaps some of you are old enough or astute enough to actually have noticed some of these climate changes yourself. This quote comes from, I mentioned the intergovernmental panel on climate change which is an interesting organization. It's a group of scientists, mostly volunteers, that are coordinated by a really small secretariat that was established by the United Nations and is supported by nearly 200 different political bodies by countries and regions. The intergovernmental panel on climate change. The intergovernmental panel on climate change synthesizes the state of the literature on climate change. And they do that on a regular sort of rolling process of roughly five years. They prepare major assessment reports with other reports in between. As I mentioned, you're coming to this talk at a good time because the intergovernmental panel on climate change just released their latest report, or they're in the process of releasing an entire series of reports that are part of the sixth assessment. The physical science, the science, the science, the science behind climate change report was published last August. A working group two report on climate change impacts was just published a few weeks ago and you might have seen the headlines in the news. And a third report about what to do about it is forthcoming this spring and then towards the end of this year there'll be a synthesis report. The six assessment reports are absolutely enormous scientific undertakings. Hundreds of researchers from around the world get together and review the literature. Thousands and thousands of articles. Just imagine how much reading there is to do. And they write down the extract and write down the salient points that come from each of those papers. They give you a synthesis of what's going on with climate change so that you and I don't need to read thousands or even tens of thousands of papers. And that process is very rigorous. When you see a statement like the one I put up a few slides ago about climate change being unequivocal, this is not just coming out of thin air. This is the result of this enormous synthesis of information along with a very rigorous review process where external parties, people who are not involved in actually writing the report, look at the statements and they say, well, I'm not sure you can make that statement. I'm not sure that assertion is correct, so on and so on. And all of those review comments have to be addressed and responded to in a series of drafts that come out before this final report is published. Once the report is published, it's completely free and open. And it's not just the paper itself, it's not just a book, but there's actually enormous amounts of data. And if anyone's interested at the end of this talk, I can point you towards a really fantastic website where you can go through and explore the actual data and results that are behind the IPCC report. They're all free and open access to everyone. So what's in this IPCC report? Well, first of all, as I already mentioned, human influence has warmed the climate at a rate that is unprecedented in at least the last two millennium. So I'm going to track this figure below because it's kind of a lot going on here, and I think we should take it one panel at a time. So start with the left panel. Evidence for climate change is what I would say. So what we can see here in this plot is the observed record of global temperatures for which we have sort of weather station observations going back about 150, 160 years. There are some weather stations that go back farther, but there are not very many. So before that, it becomes very difficult to sort of understand to sort of have a direct record of climate. And so to understand the context of the recent warming, we have to use climate reconstructions to go further back in time. What we can see from these reconstructions is that least over the last 2000 years, there's never been a time on Earth that was as warm as it is today. In fact, Earth's temperature today is not only warmer than at any time during the last 2000 years, but it is warmer than at any time during the last 100,000 years. This warming is truly unprecedented, not only in its magnitude, the amount of warming compared to the long term trend in climate, but also in terms of the rate of change. So you see how quickly the planet has been warming over the last 170 years. We can put that in a little bit of a different timescale just to have another way of thinking about these data. This is changes in surface temperatures. And what we see here on the right is the present day. Okay, and you see that rapid warming that's occurred over the last 60 or 70 years and in fact the rate of warming has increased even more just in the last decade. Compare that to the historical era of 1000 CE up to about 1850. And you see that we've completely kind of gone out of the envelope of normal climate variability. So that graph is a little bit variable. The temperature line wiggles up and down. But now temperatures have completely exited from the sort of envelope of natural variability. You have to go much farther back in time. Maybe in some parts of the world, there were places that were as warm today as they as warm in the past as they are today. Generally speaking, during the entire era of the development and evolution of human civilizations, temperature has never been as warm as it is today. So there is this warming. We know what's happening. You and I, those of us who've lived on this planet for more than a few decades can probably actually even come up with a personal story or two themselves of how they've experienced climate change. climate change, global warming. But what is actually causing this warming to occur? This is where we start to get a little bit more into the realm of what had in the past been the subject of debate, although now is becoming increasingly clear that there is no other explanation for what's causing the warming than human activities. [00:12:43] Speaker ?: We know that. [00:12:44] Speaker 2: We know that. We know that in part because, as I mentioned, global temperatures have completely exited from the realm of natural variability. We are now in uncharted waters in a time when Earth's climate is warmer than it has been at any time during the last hundred thousand years. And we know that it was caused by people because we can use climate models and climate models. I'll talk a little bit more about them later on in the presentation. Climate models are computer programs. And computer programs by themselves have uncertainties and they have various issues about them. We can use lots of different computer programs used to simulate climate generated by lots of different scientists all around the world. And one of the one of the most important kind of experiments that we can make are experiments where we change the forcings or the boundary conditions, the conditions that influence climate. And what we can show in these kind of simulations is that the only way to explain the observed climate change that's occurred over the last few decades, at least. We need to include human forcing as amongst amongst the variables that drive the climate. Okay, so here we have the observed record of climate, and we have in this orange area with the brown line the simulated climate when we include human and natural variability. But if we only include the natural cycles, things that influence climate like variations in the strength of the sun or volcanic eruptions, we cannot explain this recent warming which we've experienced particularly over the last couple of decades. So climate change is caused by people. What exactly is it that people do that cause the climate to change? Well, let's have a look again we've got a complicated figure here the IPCC likes to make these complicated figures and I prefer to unpack that for you a little bit more. So let's see here, we have observed warming over the period 2010 to 2019 so this is just the last the previous decade. compared to the mean over the last 50 years of the 19th century 1850 to 1900 and what we can see from instrumental records is that the earth is about one degree warmer in that decade compared to that late or the second half of the 19th century average. Now what caused that to change. [00:15:31] Speaker ?: Now what caused that to change. [00:15:32] Speaker 2: Now what caused that to change. A few things caused that to change. The main thing that caused that to change were increases in the concentrations of greenhouse gases in the atmosphere. And those greenhouse gases in the atmosphere are basically caused by human driven emissions of human by human driven emissions, and those emissions come from law in large part combustion of fossil fuels, although, although also through land use change. There are other human activities that actually caused the planet to cool interestingly, and they're responsible for about almost half to half a degree of cooling. A lot of that is related to deforestation which makes the earth surface brighter and sort of reflects more solar radiation back to space and also changes in the. In the emissions of aerosols that reflect solar radiation back to space. So actually earth, if it was only greenhouse gases that people were emitting and not doing anything else, earth would actually be even warmer would be something like one and a half degrees warmer relative to the 19th century. And here are those natural forcings which are really on average in the last decade compared to the 19th century have no effect they have no long term trend. So we can unpack this part a little bit more and see what exactly is going on with those greenhouse gas and aerosol emissions. Well, the main source of warming is carbon dioxide. methane, methane, which comes from rice production and livestock from industrial processes and natural gas production and. And landfills. Is about almost half as it's more than half as important as carbon dioxide other greenhouse gases like nitrous oxide and halogenated gases are also important contributors to warming. And, and, and VOCs which can volatile organic compounds which come from vehicle emissions in many cases and also other industrial processes. On the other hand, the main pollutants that we emit to the atmosphere that cause. poor air quality and smog like sulfur dioxide and nitrogen oxides actually lead to localized cooling of the atmosphere. So we have some issues here if we just clean up our air without addressing the emissions of greenhouse gases in particular methane and carbon dioxide, then the earth could be even warmer than it is today. There are a bunch of other factors here out in the right hand side which are less important, but they still do play a role, particularly when we start thinking about taking actions to mitigate or to stop future climate change from occurring. There is a question will I share the slides and I was going to just mention that I will share this presentation with the audience after the afterwards. So what is actually the outcome of this climate change is not just a single line of global temperature. But climate change, and this is one of the things that's really new in the latest IPCC report. is an assessment, not only of the sort of global trend in climate, but actually an assessment of the regional differences in climate change, how climate change is changing in different places. And you can look at these maps, these are these are kind of stylized world maps, if you want. So here's this is Asia over here on the right hand side. Australia down in the bottom Africa, South America and North America and so on. And you can see that almost everywhere in the world is getting hotter. It's less clear when we think about rainfall, some parts of the world seem to be getting wetter, particularly in terms of heavy precipitation others. Not really very clear how they're changing. And there doesn't seem to be anywhere in the world where we're getting less heavy precipitation, interestingly, but on the other hand, there are parts of the world where drought is definitely becoming more important. And so if you look at these orange or yellow hexagons here in the Mediterranean and parts of East Asia and parts of Australia and Western North America, we have unequivocal signs that drought is becoming more and more frequent. We also have more sort of more sort of interest, let's say localized signals that climate change is occurring, including changes in the timing of the cherry blossoms in Kyoto or the great harvest in France. All of these signals unequivocally point to the idea that Earth is getting warmer nearly everywhere. So that's the current state of climate change in literally in five minutes. And I'm just scratching the surface, but I really want to get on to talk about the future. A lot of what action individuals and governments and corporations decide to take about climate change depends on what we think might happen in the future. And climate scientists, in order to assess what might happen in the future, create scenarios. And with those scenarios, they use models to make projections. And so here's just this is this, again, a kind of a complicated slide, but just focus on the left hand side here. Here are five scenario trajectories of what future carbon dioxide emissions to the atmosphere could be like, depending on how the Earth evolves politically, economically and technologically and so on. Okay, and we use these scenarios and we combine those or we use them as a boundary condition as an entry to a climate model and a climate model is a computer program that is a mathematical representation of Earth's climate. So I'd be very happy to spend more time going over this with anyone who's interested later on, but suffice to say for now, trust me that we can use those scenarios to make projections of what Earth's climate might be like in the future under different scenarios of greenhouse gas emissions. And on the basis of that, we can have outputs like this projected changes in extremes are larger in frequency and intensity with every additional increment of global warming. So taking those scenarios of climate change of emissions, what we can do is sort of say what would happen if Earth's climate is 1.5 degrees warmer than the 19th century average or 2 degrees warmer or 4 degrees warmer. And we can look at things like the frequency of extreme temperatures that occur once every 10 years on average in a climate without human influence. And what we can see is that those hot events become much more frequent under a climate, let's say of 2 degrees and even more frequent under 4 degrees. And not only do they become more frequent, but they become more intense, 2.6 degrees hotter, 5.1 degrees hotter. These are the reasons why we try to, why we try to come up with targets like we've got to limit future warming to a certain level like 2 degrees C because, because humanity thinks, yeah, heat events that are 10 times more likely to occur and 5.1 degrees hotter are starting to start to be very difficult for society to deal with. We can look at similar kind of statistics for heavy precipitation and drought, and it's the same basic story. Both heavy precipitation and drought will become more frequent in the future under any global warming scenario. And the way they get worse, the more intense the scenario is. So I'd like to bring this back to Hong Kong a little bit because we don't often hear a lot discussed about climate change in Hong Kong particularly. And one of the things, of course, that's a major influence on our local climate are tropical cyclones. And you're probably all interested in whether or not we'll have more tropical cyclones in the future. Climate models suggest, the latest climate models suggest, that we may actually have fewer tropical cyclones in the South China Sea and surrounding areas. But those tropical cyclones that we do have will be more intense. And rising sea levels caused by an overall warmer climate will increase the impact of those tropical cyclones. So tropical cyclones are definitely a risk for the future, even if we have fewer of them. We'll definitely see a warmer climate, particularly in wintertime. Under a 2 degrees C global warming, Hong Kong will have a 1.7 degrees C warmer winter. And under a 3 degrees C global warming, Hong Kong will have a 3 degrees warmer winter. These are not insignificant warm changes in climate. These are changes that you will notice. We'll also have a drier climate, particularly under these warmer, drier winters, particularly under these scenarios of higher warming. Like under 3 degrees C warming, we could see a reduction in precipitation of almost 10%. And of course, as everyone here has experienced in Hong Kong the last few summers, we're going to have hotter and hotter temperatures in summer. Under a 2 degrees C global warming, we'll have 14 days more per year that are over 35 degrees C. Two weeks and under 3 degrees warming, we'll have almost a month of days where the maximum temperature is over 35 degrees. These start to be difficult for people to deal with. We also might see more wildfires in Hong Kong. And today, Hong Kong does have wildfires. They're common with about 5% of the territory of Hong Kong burns per year. And I'm showing you now some results of work that I've been doing with my student, Yu Wang, and with the rest of my group to try to understand wildfires in Hong Kong. Major hill fires have broken out nearly all of the natural landscapes of Hong Kong in recent years. And those burned landscapes store less carbon. So if we're trying to mitigate our local carbon emissions through our landscape, then this is a problem. Erosion and landslides also occur after fire. These are also challenges that we have. And when I started out on this research, we realized that virtually nothing is known about how projected future climate change could affect wildfires in Hong Kong. But last spring, a year ago, we had a flavor of what the future of our climate might be like. Not only did we have the warmest March and April, we had exceptionally warm weather in March and April, we had the warmest spring on record. We also had almost the driest springtime on record. Our climate here in Hong Kong was almost like what you might find if you went to Vietnam, Cambodia, parts of Northern Thailand. The hot, dry springtime, and the hot, dry springtime could leave us with more wildfires. So let's talk specifically about how climate change might happen in Hong Kong. Here are three trajectories. Minimum temperature in blue. Average temperature in green. And maximum temperature in red. For Hong Kong, under different future scenarios of climate change. And we extract these from the different climate models simulations. We have about a dozen climate models that we can get these kind of data from. And these are exactly, these are not global temperature changes anymore. This is exactly what's happening over Hong Kong. Okay? And so what we can see are in every, nearly every scenario, in every scenario, there's warming up to about 2060 or so. And then only in the sort of most optimistic scenarios does the climate tend to, does the climate stabilize or the temperature stabilize after that. In other scenarios, climate warming keeps on going right through to the end of the century. And in some cases, that climate warming is really substantial. We're talking about two or three degrees warmer in the maximum temperatures over compared to the, compared to year 2000. And so we're using these kind of climate data to assess fire danger in the future. And so Yi Wang has done some great work taking equations that synthesize meteorological variables, including temperature, humidity, and the number of days since the last rain. And those can be calculated into a fire danger index like the one you see on the previous slide. This is a picture from me. This is a picture from Australia. And we're using the same fire danger index system that they use in Australia. You can calculate it using a kind of pocket wheel like this, or you can also make these calculations on the computer. And that's what you're going to see. So we'll start with forests. There are two different ways to make the calculations actually, one for forest and one for grassland. Thinking about forests specifically, what we can see here, and these panels are number of days with the forest fire danger index in different categories. So this would be moderate, high, very high, and extreme. And the thing to notice on all of these plots, which go from 1971 up to 2100, is it doesn't matter on which graph you are, or which scenario you use, fire danger, fire season will become longer in the future. The chance of large wildfires that have a big impact on Hong Kong's landscape will only increase in the next century. We can do a similar thing for grasslands, like these grasslands you can see from the top of Sunset Peak. And the trend is similar. So grassland, also in grasslands, fire danger will increase over time. This never levels out. And in all future scenarios, as I mentioned, the fire season, the length of the fire season increases, as does the number of days with greater fire danger. We're going to see more and more weather conditions when we could have severe fires. And this could have very big impacts on the natural landscapes of Hong Kong that many of us really enjoy, and that are wonderful reserves of biodiversity and that we rely on as cultural and water resources. So just to summarize a little bit. Climate change is not just a global phenomenon. It's not just happening in the Arctic or the Antarctic or in other parts of the world. Climate change is going to affect us here in Hong Kong. Tropical cyclones might become less frequent, but the ones that do come will be more powerful, and the impact will be exacerbated by sea level rise. We are going to see warmer climate all year round, especially in winter, and a higher frequency of very hot days in summer, as we've experienced during the last few years. We'll also see an increased length and severity of our fire season, particularly in the autumn and winter when we have windy and dry conditions, we have the chances for having catastrophic fire. And so if we want to protect our country parks and preserve biodiversity and water resources we have to be thinking about how do we mitigate climate change. [00:32:56] Speaker 3: The good news is. It's possible. We can stop global warming. [00:33:06] Speaker 2: Don't be depressed. As is written here in this other quote from the Intergovernmental Panel on Climate Change, we can limit and even reduce carbon dioxide emissions to net zero, along with reducing other greenhouse gases. These will have great effects. We can stop global warming. We can also improve air quality. And so how do we do that? How are we going to reduce and ultimately bring down to zero our greenhouse gas emissions? Well, first of all, it's worth thinking about where our greenhouse gas emissions come from. About three quarters of global greenhouse gas emissions come from energy production. Of that energy production, about a third is industry, about a third is transport, about a third is buildings. There's a bit more, there's a bit of, that cannot be allocated at least at global level. Here in Hong Kong, we don't have that much heavy industry, of course, but we do use a lot of energy for other things. And so we can think about how to reduce the greenhouse gas emissions that come from our local energy system. There are also, of course, greenhouse gas emissions from agriculture, forestry, and other forms of land use. So agriculture leads to losses of carbon from soils. Deforestation leads to losses of carbon from trees that were there before. We emit greenhouse gases in particular methane, especially methane from waste. And there are some greenhouse gas emissions from industry, in particular, cement and chemical production. You'll have more time to browse this slide at your leisure after my talk. The important thing to keep in mind here is that we need to limit our greenhouse gas emissions. And in order to meet a global warming target of, say, 1.5 or 2 degrees C over the 19th century, warmer than the 19th century average, there's only a certain amount of carbon dioxide that we can afford as society to keep emitting. We've already emitted so much carbon, 2,560 gigatons of CO2 between 1750 and 2019. That's gotten us up to this one degree of warming that we see now relative to the 19th century mean. That only gives us a little bit of emissions left, depending on which target we choose. So the light band is, the yellow color is the 1.5 degrees C target, and the red color is the 2 degrees C target. That only gives us a little bit left. In fact, very little left if we want to meet a 1.5 degree target. So little that many would suggest that this is not possible. And the current sort of international negotiations to limit climate change, like the Paris Agreement, sort of point us towards a 2 degrees C target as being all we can aim for. Nevertheless, what that means is that we can only emit less than half of the carbon that's already been emitted during the last 150 years. We don't have much left, especially with the much time or budget left in global carbon emissions, in particular because of the growth of the global economy. So, you know, you have to imagine that this cumulative emissions over the last 250 years is not linear, of course, but most of it occurred during the last few decades. [00:37:07] Speaker 3: So where are we with this? Well, current commitments [00:37:16] Speaker 2: by countries and industries to limit carbon dioxide emissions don't get us onto one of these 1.5 or 2 degrees C targets. We're much more like up here on the SSP245 target, which is maybe going to lead us to a 3 to 4 degrees C warming. A lot more needs to be done to drive down atmospheric greenhouse gas emissions. This is just another way of basically looking at the same thing. So here are our emissions that were actually recorded up to 2020, and here are the different trajectories. So we're on, I said we're on the 2-4, on the 2-4-5 track, which I think gets us to somewhere between 3 and 4 degrees C of warming at the end of the century. But don't despair. There actually are a lot of things that can be done to limit carbon dioxide emissions or greenhouse gas emissions in general. And there's a great resource from an NGO called Project Drawdown that's really started to synthesize all of these different potential actions that we could take. But just to summarize them, there are three major things we need to do to reduce emissions. We need to reduce sources. We need to support sinks. And we need to improve societies. Let's look at these in a little bit more detail. So reducing sources. We can reduce emissions from electricity production. That can gain us something between 160 and 390 gigatons of carbon emissions per year. We can address food waste and diets. One of the easiest things we can potentially do that can also save huge amounts of carbon emissions. We can help get rid of greenhouse warming, refrigerants and industry, and that can reduce a lot. Then there are others, transport, buildings, and so on. We can support sinks by shifting our agricultural practices and improving degraded land, protecting and restoring ecosystems. All of these contribute. And finally, we can improve society through better health and education, which will also ultimately lead to fewer greenhouse gas emissions when people think about what they are, what they're doing to the planet, and they're better able to make decisions about their individual lifestyles and livelihoods that lead to fewer greenhouse gas emissions. You can learn more all about taking action by looking at the Project Drawdown website and their printed material. It's a fantastic resource for all of this. I just want to take the last few minutes to highlight some research that we recently did about how we could address greenhouse gas emissions reductions. And I mentioned before that one of the potential strategies is to support sinks, in particular, using or improving ecosystems, restoring ecosystems, and using degraded land. And so this is something I've personally been looking at in a study that was recently published by me and my colleague Alex Koch. We looked at restoration in the tropical forest area. And what we wanted to do there was try to say, if we make, if society makes big investments into restoring tropical forests, will it actually succeed? Or will climate change eventually wipe out all of the gains through restoring those tropical forests? And so we did some experiments where we looked at the total pasture area of the tropics. And we put some fraction of that pasture area back into forest. And we said, what would happen under different scenarios of future climate change? And would the carbon that's stored in those restored tropical forest lands actually last until the end of the century or where those forests, those restored forests maybe die back because of drought or fire, for example? And what we could show was actually quite good news. It doesn't really matter how bad the future climate ends up being. Any investment we make in restoring tropical forest land today will last and store carbon until the end of the century. And not only did we calculate that climate would not necessarily threaten the future of tropical forest restoration, but we could also figure out where the best place on Earth would be to actually invest in, to make that investment. And so you can see some parts of the world in these blue colors, for example, in the Congo Basin or parts of Indonesia and New Guinea or the Philippines and northwest of South America are really good places for restoring carbon because land is relatively cheap and the climate won't change so much that it threatens it. There are other parts of the world where land is very expensive, here in southern China, for example, where the economic decision is a little bit tougher. But nevertheless, as I wrote, as I mentioned already, the success of tropical forest restoration is not threatened by future climate change impacts and therefore it is one of those very potentially promising options for drawing down CO2 from the atmosphere. We shouldn't wait. We should start today with that. Thank you so much for your attention. I'm going to leave you with a little summary of what we talked about today. It feels like time just flew by. Climate change and its impacts are already being felt today and I think that probably many of you have felt them personally. The change in climate that we've experienced during the last few decades will only continue. It will only continue until we manage to stop emitting greenhouse gases to the atmosphere one way or another. But those climate change impacts are largely reversible. We can go back to a future which has a good climate, a climate that we are used to living in if we can reduce greenhouse gas emissions and we have the tools to do that. So my charge to you audience would be to find out how you can take action and try to raise awareness to your friends and family and colleagues and fellow students. There are great ways and I'd be very happy to share with any of you at any time in the future. Please reach out to me and I can help point you in the direction of some of these actions that can be done. So with that, I'm basically out of time and I'm very happy to take any questions that you might have and I'll stick around for a little while and thank you again for your attention. I've got one question. Okay, so there was one question about will I share the presentation? The answer is yes, I will. There is a question. Why is water vapor, a strong greenhouse gas, not included in the last graph contribution to global warming? Okay, water vapor is not considered, the global water cycle is by itself a closed cycle. So indeed, under hotter planet, we could have more evaporation of water from the Earth's surface which then traps more heat which has a positive feedback. But generally speaking, we cannot control the amount of water vapor which goes into the atmosphere. And we also cannot, I don't want to say this, it has, water vapor has a very fast, the water vapor has a very fast response. So there have been suggestions or let's say hypotheses that hotter and hotter temperatures, how hot would Earth's temperature have to get before we had to kind of run away water vapor feedback? Much hotter than we'd ever get under any of the worst possible global warming scenarios that we have developed. So you don't need to, you do not need to worry about water vapor as being a greenhouse gas that we need to control. If we can control the anthropogenic greenhouse gases, then we can, then we can control, then we can change Earth's climate because the water vapor will simply respond passively to the changes and the other drivers of Earth's climate. Okay. I've got a few other questions here. I wonder if you agree that climate change being underestimated in Hong Kong, the actual degree, the importance people and government attached to it. Well, I would say that, yeah, now with these new scenarios that we have with the latest generation of climate, future climate scenarios, I think that there has been a very big focus in Hong Kong on things like typhoon and sea level rise as being difficult issues that we're going to have to deal with under future climate. I think there has been less emphasis on things like heat and wildfire and perhaps drought under some of the more severe future climate scenarios. And so I do think that is something that we need to raise more awareness, all of us, in our communities and with government as far as possible that climate change is a major issue for Hong Kong. Apart from the usual textbook answers like the five R's and eating less meat, is there anything more individual, especially students, can do on a daily basis? I do think that you shouldn't underestimate the power of raising awareness. You need to, as a student, you can really beat the drum to your fellow students, to your family and to your friends and you can explain to them what can be done as individuals and what can be done collectively as a society in order to address climate change as an issue. Can you explain in detail about the 3D grid model or provide some sources I can read more on it? Yes. So I cannot explain in the next 10 minutes how climate models work. That is, should take one of my classes. Then we could, we could spend a whole semester learning about how climate models work. But yes, please, if, if, Helene, if you send me an email, then I'd be very happy to share some, to share some references with you that go into a little bit more detail about how climate models work. You have mentioned about wildfire and how global warming, but you have mentioned about wildfire, but will and, will and how global warming will worsen the situation? Yes. So I think it's very clear that with wildfire in Hong Kong, climate change in Hong Kong is going to make the fire season longer and more severe. So that is, that is a local effect. So we will have more, we will have much higher risk of big wildfires in the future than we have now. Since Hong Kong is heavily dependent on non-renewables for energy demand, what is the future path for sustainable energy future in Hong Kong? I'm not a, I'm obviously not a politician. I am also not in government. I do know that the issues are discussed. Hong Kong does have a commitment like many other countries, like most other countries, to reach carbon neutrality by 2050. That is to say that we will not emit any more carbon dioxide from our, from our, we will not emit any more carbon dioxide through our energy production, but we've got sort of a 30-year time window to get there. There are people working on it. Civic Exchange is an NGO in Hong Kong and Hong Kong 2050 is now who are spending a lot of energy and of great enthusiastic people thinking about how do we actually achieve this 2050, these 2050 carbon neutral target. And so I think that there are, there are some efforts underway in Hong Kong to try to, to try to facilitate or let's say catalyze our reductions in emissions. Why is the government not planting more trees in the urban areas? Betty, I'm sorry, but I do not know the answer to that question, but thank you. That's a very, that's an interesting question. There are a lot of reasons to plant more trees in urban areas and they're, those also have to do with noise and air quality and, and also carbon and so on. And I, I can, if you, if you email me, I can try to connect you with some people that might be able to, might be able to give you more details on that. Someone asked if I want to study environmental issues, is there a way you can start in university? Yes, we have a wonderful environmental science degree here at HKU. We also have degrees on earth system science and ecology and all of those environmental sciences available both at the bachelor and the master level. So please have a look at our programs. We'd be very happy to have you, have you as a student in our, in our degree programs. Let's see. Any other questions right now? I'm very happy to, oh, here's another one. Could you describe the most affected areas and least affected areas in the world? Okay, so when we're thinking about climate change, yes, indeed. Although I, although I mentioned several times, I tried to bring this back to Hong Kong. Hong Kong is actually not one of the parts of the world where climate change is actually happening fastest or with the greatest magnitude. For that, you need to go to the Arctic. And in the Arctic, climate change is really happening much faster and with much greater amplitude than anywhere else on earth. And that has to do with the number of different feedbacks in the climate system, particularly related to snow and to sea ice, which mean that with less snow and ice during summer, the earth and near the poles absorbs much more solar radiation than is reflected back to space. And because of that, the Arctic is warming very, very fast. The least affected parts of the world, although the whole world is being affected by climate change, and those of you who have been keen news observers might have seen just this week the news about how temperatures in Antarctica were 40 degrees above the normal for this time of year. But nevertheless, generally speaking, one of the areas least affected by climate change is the circum-Antarctic area, so the Southern Ocean and parts of Antarctica, particularly, not the Antarctic Peninsula, but particularly parts of Antarctica that are further towards the center of the continent. So, yeah, so climate change is really happening in the high latitudes of the Northern Hemisphere as the place where it's really having the largest impact. And, you know, you might want to go somewhere where climate change is not happening that much or as much, you might have to pay a visit to Antarctica. [00:54:03] Speaker 3: Let's see. Go ahead and present a question here. Thank you for this presentation. Yes. Okay. [00:54:16] Speaker 2: Alice, thank you for your comment, your question. And I, this is a great, this is a great question. And I think what we can do is I can point you towards some actions that also children, so school children can actually, there are lots of resources and materials out there for school children to help make them feel empowered. And I think that this is something where we can pull together some resources for you and perhaps for your school that I know there's some really engaged people who are leading the way to try to help young people feel more empowered about what they can do about climate change. And as I said, there are individual things you can do and a lot of what young people can do is about raising awareness. And that doesn't necessarily have to be protesting. Okay. We don't all have to be Greta Thunberg and standing outside with a sign or going on strike. But there are lots of other ways to raise awareness with family and friends to get people [00:55:17] Speaker ?: to get people [00:55:17] Speaker 2: thinking about how climate change is affecting them and how their actions affect climate change consumption behavior and so on. And I do, I can really point you to the project, some of the project drawdown materials to get some better, some more concrete ideas about what are the different mechanisms or levers that we have as individuals and as society towards reducing our greenhouse gas emissions. I've got another question here. I've heard that climate change predictions for modeling may differ from each other. Are there any contradicting predictions? Yes, so this is a really good, this is a really good question. Whenever I, when I showed you results about future climate change, I showed you ensembles of many, so averages of many, many different climate models. And it's true that sometimes the sign of the response, particularly when it comes to things like rainfall, like precipitation, are, a lot harder to quantify than things like temperature. So let's say all the models agree that the Earth is going to get warmer, but there's a lot of disagreement between models. And if we have a look at this slide, for example, when it comes to precipitation change. So, all right, so here's warmer winters. What we see here, this is from, this is from the IPCC Climate Atlas. This is actually a fantastic tool that anybody can go on, go to the web, and they can basically browse around in a web-based interface all of the climate model output that comes out that was synthesized in the IPCC process. And one thing that you see here, down in the bottom left, sorry, go over here, down the bottom left, there's this little legend here, and I didn't have time to mention it in my presentation, but now since you asked, OK, so you can see here robust signal basically means all the models agree that this is going to happen. So everywhere on this map where there's no crosshatching, where there's no hatching of one way or the other, basically all the models agree that this is going to happen. And so with temperature, it seems pretty clear, all the models agree that it's going to happen. But when you look at something like precipitation, that area which has no crosshatching becomes much smaller. OK, and that means that there is disagreement between the different models. And so some models maybe say there will be drier winters in Hong Kong or in Southern and Eastern Asia and other models say it will actually get wetter or they say there will be no change. And so there are there are definitely some conflicting results in some of these that come from some of these model outputs. And so I think it is important to keep that in mind. And I guess although I may have sounded very confident in a lot of my presentation for the sake of time, I do feel like at some it is important to acknowledge these uncertainties. Similarly when we look at the hot summers you also see crosshatching in some places although it's much less than we see for the rainfall estimates. So this is actually kind of an interesting result here. So what you can very clearly see is that all the models agree it's going to be hotter in winter and we're going to have more hot days in summer. But the models don't all agree about whether or not it will actually be wetter and drier at least when we think about our neighborhood of southern China. This just a bit to the west of us particularly in this three degree scenario there we have a larger area that's sort of unequivocally drier where all of the models suggest that it's going to be drier. Let's see are there any other questions? I'm happy to hang around to take a few more questions if there are. If not then I think yes the host has sent my email address to everyone in the to everyone in the chat so please go ahead and feel free to follow up with me anytime if you have if you have further questions if there's anything that I can I can ask to you and yes I will also I will put this presentation on my website and then also a few a few other links to resources both globally like Project Drawdown and the IPCC and locally so to some of the NGOs like Hong Kong 2050 is now and Civic Exchange who are working on the working specifically on climate change topics for Hong Kong actually since no one else is asking any more questions and I will just I'll just go I can go into a little bit more on to Tim's question there where do differences and predictions from different models usually originate from some of it is the actual yes underlying assumptions so it's actually equations that are used and some of it is the model resolution so it's how in how much detail does the model represent the Earth's surface and some of it is indeed related to uncertainties and initial conditions so how good are our measurements of weather conditions around the world and so on and so and so all of those three major major differences so differences there are different ways to actually you can use different equations to model the Earth system as well so that that is there are certain things that are in the climate models that are based on basic physical principles and there are other things in climate models that are based on that are based on approximations or what we call parameterizations and when you when we make approximations there are different ways to make those approximations in a computer program and so the different models may have different parameterizations for example of the way they represent clouds which is a very which is very very important in climate modeling and so that's why the different models produce different results okay well I'm getting I'm getting some thank yous and I thank you all for coming and thank you for participating and for your great questions and like I said please reach out to me anytime and I'm happy to keep the conversation going and all the best [01:02:24] Speaker 3: to all of you