 Welcome, Kate, or, shall I say, Seyroo, Seyroo, all right. I'm having the honor and the pleasure to introduce to you three people here for the first lecture. And Seyroo will start, she's a PhD, doing a PhD concerning environmental physics in which university. Heidelberg, all right. I notice here that for some people climate change seems to be just news that's passing by. For some others it's a little bit more fake news. Someone this morning called it even, he called for some good old global warming, I noticed. And I think we all need to reconsider solutions. Otherwise we could end up in a kind of a couple of lips. The word is to you. Please give her welcome applause. Hello, everyone. Is this working? Oh, fantastic. I was just not used to that. Okay, fantastic. Welcome to the talk about climate change. Why am I here? Last year I was at Congress and I talked to some friends about climate change. And they had a lot of questions, really basic questions and a lot of open issues. And I'm not used to that. In my surroundings, everyone is working with us. We know a lot of this. And it was not clear to me that there's a lot of need for information out there. So I proposed to do a talk. And apparently it was really, really popular. So now I'm here. And I will show you about the basics of climate change. And I will invite you to become part of the climate conspiracy with us. So what are the basics? We have two bodies in space. There's the sun. And there's a planet or a rock. And they don't have any way of interacting with each other, with each other apart from electromagnetic radiation. You can see here there's a lot of distance between the two. And the only interaction possible is light. What is light about? As you know, you can deconstruct light into its components. You can see a rainbow if you use visible light for that, as you can see here with a prisma. And if we do that for sunlight, we see that there's a large maxima in the visible part in the green to be exact. And of course that's not a coincidence. And there's also a large part that we cannot see. That's on the right, this long tail that's infrared light. You can feel as warmth. And on the short side, there's a bit of ultraviolet radiation that is harmful to the skin. So this is what arrives at the top of the atmosphere, this kind of spectra. You can see at the bottom is the wavelength, which is a parameter that gives the energy of the light. And you're going to see that a lot during this talk. On the other axis, you have the intensity of the light. So a lot, well, high values mean a lot, low values mean only a little. And this is a new spectra that's been taken on the ISS, where they have monitored this spectra for over nine years all the time to see the changes within one solar cycle. So this is a very important area of research to see how this changes. So if you've done physics before, you have probably seen this kind of form before. It's this form. It's given by Planck's law. Planck found this law in about 1900. And it gives the relationship between the temperature of the body and the radiation that comes out of it. And you can see that everybody that has a temperature higher than zero Kelvin, so nothing, emits energy. You can feel it when you touch anything. You can feel some radiation going off. And if it becomes warmer, you put something in the forge. It radiates off more energy. So this is the relationship. I put the formula at the bottom. Don't be surprised. At the same time, if you do the derivation to see where the maximum is, it's simply inverse to temperature. And as you can see here, there's a body that's very hot. It's a 2,000 Kelvin. There's a body that's only 1,500 Kelvin. And a body that is only 1,000 Kelvin. And you see that it gets less. But the maximum also shifts. So why is this interesting? Let's look at the temperatures of the sun and the temperature we have at Earth. I did this in Python. And I mistyped a little, so it's close enough. It's fine. You can see here that you can see nothing. Let me scale that up. You can see there's a 2 to the power of the minus 7 on the right side. And that means that there's a large difference in intensity between those two bodies. But what is really interesting is this part. There is almost no overlap between those two spectra. So the radiation coming off the sun and the radiation coming off the Earth, they are very, very different in energy. Why is this interesting? We can now calculate the temperature that the Earth would have if it was just like this, simple energy equilibrium. There's another parameter we need because the Planck spectrum, the thermal radiation spectrum, describes the sun fairly well, the Earth not so well. And the reason is that the Earth also reflects light. And the ratio between the incoming light and the reflected light is called albedo. And just to demonstrate this, I put an object with high albedo and an object with low albedo here. And you can see that one of them absorbs all incoming light and the other one reflects all incoming light. And so you can imagine that the person who is here with a low albedo will become very warm after some time and also start to radiate off heat. And you can imagine that the wavelengths they will radiate off if they didn't have internal energy, whatever, will be different. So Earth has an albedo of about 0.3, 30% of the radiation coming in from the sun is directly reflected off. And you can see here I put a green dot there. And I put these green dots at places where we have a chance to change parameters concerning the system. So if you see this green dot and if you don't see it, just think about what should we do to change parameters of the system to change what's going on. So here's one chance we have. Something that has high albedo on Earth is snow. Fresh snow reflects about 90% of incoming light. Something that is dark is the ocean. The ocean reflects only about 10% of incoming light. So you can imagine that if ice on the ocean goes away and open seas there, you get a change in this reflected value. At the same time, you can just paint stuff white and you will also get a change. So if we add this together, we get a temperature of minus 15 degrees on the planet. This is not true. You know this. I'm happy it's not true. And the reason is that we have an atmosphere. What does an atmosphere do? It can interact with light. There's a law here that's been found by Lambert and Baer, different people who found parts of it at different times, 17, 29, 18, 52, as you can see, and it describes how light is absorbed in a gas or in a body. I put the formula here because it's very easy and telling that there is an exponential decrease in the light and it depends on three parameters. It depends on the distance the light travels in the gas, L. It depends on the density of the gas, so how many molecules of the gas are there. It's rho and there's a parameter called sigma. It's the absorption coefficient and this is gas-dependent. It's also constant, so it doesn't change every time. It doesn't change a little with pressure and a little with temperature, but not really, and we measure this in lab. So this is a very well-researched law and you can also research this in your lab if you want or in the hackerspace or whatever. It's really easy. So what are the consequences of this? I brought you a picture of NO2, you know, the diesel scandal gas. Not very healthy, so don't breathe it in, and you can see different concentrations here. We have almost nothing up to a very high concentration and you can see that it gets darker and darker. I also put the absorption coefficient down there and I also painted with colors the wavelengths you can see. As you can see, there's a lot of absorption going on in the blue wavelength range and not a lot in the red wavelength range. And these two images are linked. If you had to guess from the plot which color the gas is or you should be able to do that now, you can say it's reddish because the red can pass through. So we have this effect in the atmosphere. We have gas that absorbs in the infrared but not in the visible. Let's run our calculation again. Now we have an atmosphere here. There's 100% of light coming in from the top. It goes down to the atmosphere. 30% as I said before is already reflected back. So this does not concern us at all unless we want to change it, but yeah. And 47% are absorbed by the ground. The ground heats up. You can feel this if you put your hand on the stone when it's sunny. And the rest is already going into the atmosphere. Now what does the gas actually do? As you can see, about 12% can make it through of the infrared light, the light with a very long wavelength range. And it can go through, but a lot of it cannot go through. It will be absorbed by the atmosphere immediately. So the lowest layer of the earth heats up. It becomes warm as well, so it starts to radiate as well. Depending on the temperature, it will radiate at different wavelength ranges and at different intensities, but it's still going to be in the absorption area. So at the wavelength the gas absorbs, it's also going to emit. I'm going to show you later. This effect also stacks to further layers. So the next layer of the atmosphere will also absorb some of the light coming from the downwards direction. It will heat up. It will start to radiate. This radiation is going all directions, so a part will go back down. And in the end, you get a mean radiation level of about 97% of the incoming sunlight going back down. So about twice the level of the sunlight that reaches the ground is coming back down from the atmosphere again. And if you run the calculation on that, you can just run the sums here, you can see that 144% of the light are actually radiated out. So the black body temperature that you get at the earth is higher than it would be without atmosphere. We get about 15 degrees Celsius. This is the real temperature we have. So this is actually a very nice effect. We call this the greenhouse effect, the natural greenhouse effect. And it's useful for life on earth because it protects us. I can show you the same thing in spectra. The top spectra shows the black body radiation of the ground. So you can see it's very smooth. You can also run the calculation on that. You get the same plot. In the next part, you get the downwards radiation. So the gas absorbs in the parts that are elevated here and absorbs and heats up and emits again. So this is coming down. This is what you can see if you measure the light coming down. And at the same time, there's a netto. So the difference between the plots is the bottom part. And you can see that there's a window where the light can go out and parts where almost nothing of the light makes it out. The plot has marked the greenhouse gases that act here. You can see that a large one is water, H2O. H2O also plays a significant role here. And CO2 is a large part. So the question is what happens if we change the concentrations of these gases? What happens, in fact, is that this part here gets broader and this part here gets smaller. So the outgoing radiation is less. So the ground heats up. It's a bit more complicated than that. Of course, if you run the calculations, you get a lot of changes in the vertical profile. But that's the basics. At the current level, we have about 0.8 watt per square meter of energy coming in that's not going out. Here's an advanced concept I just wanted to show you briefly. It's also connected to the black body temperature. At the same time, it tells you about the black body temperature of different layers of the atmosphere. You can see that in the window, you can actually see the ground. The ground has a mean temperature of 15 degrees. And you can see in the outgoing radiation here, the radiation you measure from space, you can see the photons from the ground. At the same time in the water absorption areas, which are two here, you can see that it's about minus 30 degrees. This light comes from an area where the air is minus 30 degrees. So in the stratosphere already, maybe top of whatever. At the same time, you can see that ozone comes at minus 10 degrees. That's the top of the stratosphere, so the top of the ozone layer. And we have CO2, which comes from a level of minus 55 degrees. So you can see here which height the light comes from. And at which layer the air is transparent for this wavelength ranges. I'm sorry, if this is a bit complicated, you can ask me later about details. Let's keep going with increase of gas in the atmosphere. This is the current plot. I just pulled this from the Mauna Loa Observatory page of NOAA yesterday. You can see that they have a continuous record since its 1960s to today. And their current level in September was 402 ppm, parts per million. And you can see that it's oscillating. This is due to the fact that the hemispheres have summers and winters. And the north has a lot of plants. The south doesn't have a lot of ground, so it doesn't have so many plants. And the plants respirate more in summer than in winter, so you can actually see the plant life here. Okay, so what do we do with this? We can run a very simple calculation from what I showed you before. You know everything you need to run a very simple climate model. If we increase the CO2 level twice, you can get a temperature increase of 1.2 degrees Celsius. Now, if you compare that to the increase we had already back from the past, you can see that there's a mismatch there. So what is happening is that there's a lot of feedback mechanisms. We have energy coming in. The energy can melt water, can melt ice, can change the albedo of the earth. It can generate more clouds. There's more energy. More water can be evaporated. More clouds can be generated. It changes the albedo. It changes the outgoing energy level. And the temperature gradient changes. So there's a lot of feedback mechanisms. And we come to a result of about 1.5 to 4.5 degrees Celsius from this. But you see there's an error range there. We'll talk about that later. We call this concept climate sensitivity. It just says how the climate system reacts to a doubling of the CO2 content. See you next talk. So the question is we have too much energy going in now because the sun gave us energy and it's not going out anymore because there's a barrier there now. So where did it go so far? I already told you that there's a plus of 0.8 watt per square meter coming in. But we don't have a heating that corresponds to this value. So where did the energy go? So far I talked about basic laws, basic physics laws. You can easily measure in your own lab that physics students all over the world measure every year and so far I didn't find a mistake. So now I'm going to talk about measurements that fit together with this result that we have too much energy. So where does the energy go? So far it seems to go into the ocean. About 93% of the energy so far went into the ocean. This plot shows you a few data sets that all have the same conclusion. The upper layer of the ocean, that's the top part, warms up. The lower layer, the deep ocean also warms up. That's the lower plot. So this is where the energy goes so far. Here's another place where the energy goes. It's a plot that shows the ice extent on the Arctic, on the top in an annual way and the lower part shows it dissolved for different months. And it's different data sets, different colors, different data sets and you can see they all agree it's going down. So here's another sink of energy for us. And if we add these together, there's the expansion of water due to heat. You know, things that warm up expand. And there's the expansion of water content due to ice melting. That's the lower two curves. And if you add them together, they fit very nicely to the curve that shows the measured increase in sea level. So this follows from very basic physics. This is where the energy is going. If you're not convinced by this yet, I have more plots. I'm not going to discuss these in details. There's a few plots here that correspond to air temperatures. I marked them with air. And there's a few plots that are corresponding to sea temperatures and sea ice, no, sea temperatures, sea content. And snow and ice are also there and you can see they all agree. We have two data sets in minimum and up to seven data sets here. They all agree. So the data is also there. So what we know so far. The basic physics tells us that an increase in any of the greenhouse gases will lead to an increase in temperature. There's feedback mechanisms and we don't know exactly, very, very exactly what that leads to because there's an error range on the climate sensitivity. And we see that the data shows an increase in energy uptake in the system. Where do we go from here? We have to run models. So what we do is we use these basic physics laws. We parametrize the Earth and we try to calculate the response of the system. Now, I only discussed very, very basic things here. And there's a lot more impact factors on the climate. You can talk to me later if you want to discuss this. No problem. The main ones here are aerosols. So particles in the air that shield the heat while the incoming light a little. There's clouds that can change. There's ozone and the chemistry that also is a climate gas and can also shield light. And of course the emissions of greenhouse gases and aerosols which are also not known for the future. A few more are there. So it's a complex system. We're trying to model this. But some things are still unknown. Some things might be unknowable because we're talking about a chaotic system here. It's clear, however, that we have this energy surplus and that it's going somewhere. So there will be consequences of this. Physical consequences. And physical consequences also mean that there will be consequences for people on Earth. And my colleague will now tell you more about that. So if you have any questions about the climate system and the basic physics or the data, just come talk to me. You can also read the IPCC report. It has a lot of plots. A lot of plots. And you can learn anything you want to know about the data from there also. So just check it out. Thank you. Okay. We know fairly well about the greenhouse. And well with some confidence, we can also project the temperature on average for the next coming decades. Of course that depends on how we emit further greenhouse gases. So if we continue emitting, we'll probably end up at about four additional degrees Celsius. If we really manage to mitigate a lot of our emissions, we might even manage to get below two degrees. But what does that mean? Well, one of the most well-known impacts of climate change is sea-level rise. Like Katja said, the mechanism there is not fairly simple, but at least easy to understand. Because when oceans heat up, they expand. That gives a big contribution to sea-level rise. And of course, as the temperature increases, we'll melt snow and ice. Especially in the glaciers, on Greenland and Antarctica. So knowing the temperature, we can also project quite well the mean sea-level rise that we have to expect in the coming decades until the end of the century. And we might end up at one meter sea-level rise on average, or maybe manage below that. But all these things that we said in motion there, the melting of the ice, is actually quite slow process. So even after 2000, even after we have emitted, even maybe after humanity has ceased to exist, the ice is still melting. And several additional meters of sea-level rise are expected to be there. Well, okay, sea-level rise probably affects coasts and islands. But what does the warming itself do with the economy? How does the economy react on climate change? Of course, that's a very difficult question to answer, but we can start with kind of simple observations. So this is from a fairly recent study by scientists in California who looked at the change in GDP per capita, that is kind of like the average income a person has in the country, in the last 50 decades, and tried to find the relation to the annual average temperature there. So in there they account, of course, for specific variables that the countries have, if they're poor, if they're rich, to begin with. And well, they find this kind of U-shaped relationship between those two. So, well, okay, if we know the annual average temperature, how does that affect the GDP per capita? They said, okay, let's try to extrapolate that. If we extrapolate that, they find that, well, regions that are already warm, kind of like beyond the curve, even go down in the slope when additional warming occurs, and colder countries might actually benefit because they get up the curve. But this is a fairly simple econometric model. So it just accounts for the direct impact of the temperature on to economic activity. And if you can really extrapolate that under climate change, we don't know yet. Another very important number that is discussed in climate economics is the so-called social cost of carbon. Because we might ask, well, if we emit an additional ton of CO2 or another greenhouse gas, what damages does that mean along the road? So if you think of a simple coupling of an economic and the climate model, you can say that, okay, the economy produces that leads to emissions. The emissions in the climate system lead to temperature change. And similar to the relationship I just showed you, every temperature change might come with a damage. So we put in there a simple damage function that gives us, depending on the additional temperature, additional damages on the economy. And we can run that in the model. And then we ask, well, let's put one additional ton of CO2 in there. How many damages do we get additionally along the road? In a formal way that looks actually like that. So if we emit an amount of carbon at T0, the temperature reacts. So this relationship is given by the climate model in the model. This temperature change then leads to a change in climate damages. This is given by the damage function. And then we just sum up all these damages that occur along the road due to this carbon emission and sum that up. But what is done in economics, very common in there, is discounting that. It's just basically because of the fact, if I offer you 10 euros in a year, you'll probably prefer me to offer you 10 euros for tomorrow. So you'll value these 10 euros tomorrow more than those in a year. So this de-evaluation of the future in comparison to the present is given by the social discount rate. How does it look like if you run this kind of model? Well, depending on the year and the emissions so far in the model, we'll get some damage. This is the famous model DICE. It's actually quite simple. And we are currently trying to make that more accessible for people who know Python to play around with that. We can start with the social discount rate in here, which is normally used with 1.5% in that model. So that means we kind of gray out the future in a way from the symbolic point of view. Yeah, so we care more about the damages here than here. But if you increase the social discount rate, these graying out goes more and more into the present. So we don't really actually, with 7% social discount rate, we don't really very much care about the end of the century but more about the one or two decades to come. Well, why is that important? It is very important because these kinds of models are very, very sensitive to the social discount rate. Because, well, if we don't value the damages along the road as much as the damages tomorrow, of course we'll have less damages overall and we probably don't care so much about the overall social cost of carbon. So if we stick with 1.5% social discount rate, we start with $20 per ton and up to over 100 in 2100. The peculiar thing about that is that the US government actually uses these kinds of numbers. Because in the 1980s, they established a law demanding all federal agencies to make a cost-benefit analysis of their actions. And if those involve carbon emissions in a way, they have to take into account the social cost of carbon. So it's a very political number in that way. And the Obama administration used the social discount rate which is more like 3% and came up with lots of models in average around $45 per ton. Now, the Trump administration, which has kind of a different goal, they decided to have a social discount rate of 7% and only look at damages in the US and not on the whole globe. So they come up with only a couple of dollars per ton. So in the end, this kind of discussion is still ongoing and very much comes down to an ethical question, the ethical question of how much do we de-evaluate the damages that future generations will have to cope with in comparison to the damages that we have to cope with? Okay, still, this is a very simple economic model and with a very simple climate model in there. So it totally neglects another very important kinds of impacts. And those are extreme weather events. Extreme weather events are much more difficult, of course, to model in comparison to looking at these temperature increases on average. But so the discussion, for example, for hurricanes is still going on if they get more frequent or more tense. But as Katja explained to you, due to climate change we'll have more energy in the whole earth system and so we'll probably get also more energy in the hurricanes, especially since they feed from the heat of the water under there. And as well, they need a certain temperature to exist on the ocean surface. So if the oceans warm, they might even cover a larger area. So just as an anecdote in the last hurricane season, the hurricane Ophelia reached Europe and thus really got off the charts of the grid that the US Hurricane Center uses. Well, you probably also heard about other kinds of impacts which are floods and droughts. And also here, the basic physics at least tells us that if air warms, it can hold more moisture, and so wet regions probably also get even wetter. On the other hand, hot and dry regions, warming probably also get drier. What does that mean for society? Well, indirect effects on society are displacement and migration. So just as an example in 2015, weather-related events alone displaced 15 million people across the globe. Displacing means, well, they might have to move well, to their neighbors, or they might have to move to the next village, or they might even have to move across borders. All in all, we know that these kinds of impacts and these changes in the climate system will put the societies on Earth under additional pressure. So societies that are already prone to ethnic rights, for example, or are not very stable in their political system probably are also going to experience more conflicts. But this discussion of the relationship to climate change is still ongoing, but at least we know the pressure on these societies is going to increase. Well, and we might say, okay, why do we care? Why do we care in Europe? We might be able to cope with floods because we are rich, in comparison to the rest of the world. Well, the world is increasingly interconnected economically, so supply chains of corporations nowadays cross several countries and our trade relations get stronger and stronger. So even if there is an event in Bangladesh happening, for example, we probably experience some effects of that down the road that might go from price changes but also to supply failures. So we'll also suffer from damages. This is red now. Okay, you can hear me, great. Okay, so next let's have a look at global emissions. So this is global greenhouse gases over time, the red line, and yeah, we can see that clearly they have been more or less steadily rising over the past decades. And in gray, we can see the range of projected emissions from the climate action plans of countries. So these climate action plans or nationally determined contributions short NDCs are part of the Paris Agreement process and each country individually determines what they want to do to reduce their emissions. And the range is so wide because each country makes their own plans and it's difficult to assess. So countries might rely on economic growth, for example, one country might only give out targets that they are very sure to reach, another country might have difficulties reaching it. For example, Germany is not even on track to reach their 2020 goal. And if you compare this range with the range that would be required to stay below two or even 1.5 degrees, we can clearly see that we're not even close to that. So in green and violet, you can see these ranges. So what should we do? Maybe should we start hacking the climate if you're not reducing emissions fast enough? Geoengineering is a topic that has been widely discussed in the past years and especially last months and weeks. There have been lots of articles in The New Yorker, The Economist, Wired or Der Spiegel. And also the NGOs published warning reports and of course the scientists also published many studies. So why is it important to talk about geoengineering and removing emissions from, removing carbon dioxide from the atmosphere? They're practically part of all scenarios that are used to assess our chances to stay below two degrees. So here's one stylized scenario. The red line is the emissions pathway and the brownish area shows the CO2 emissions and emissions from us the greenhouse gases. And below the zero line in blue, we see emissions that are being removed. So negative emissions. And if these negative emissions get even larger than what we emit, as you can see at the end of the century, then we might even be reducing CO2 concentrations in the atmosphere again. So how can we do that? One easy way is to simply plant lots of trees, a forestation and make sure that these trees never get cut off or burn. Another more technical approach that is part of all these scenarios or of most of the scenarios is a technology called BEX. And BEX stands for bioenergy with carbon capture and storage and it basically means producing bioenergy as we all are already doing. So planting crops or fast growing woods and then transporting these biomass to a power station, burning the fuel and capturing the carbon that is released again in the burning process and then storing this carbon in geological storage size deep underground. So this sounds like a great idea and if you think it through, it means the more electricity you produce with BEX, the more CO2 you remove from the atmosphere. So if you were driving a car that would be powered by electricity from BEX, the more you drove your car, the more CO2 you removed. But of course, such a technology doesn't come without its disadvantages. So to really make a difference, it would require huge areas of land. So in some scenarios this can be up to the size of one or two times of India. So here you see India over Europe and it's clear that having so much additional land use and farming land required would not be without problems. So there would certainly be competition with food production, so potentially rising food prices and it's not easy to produce such large amounts of bioenergy without heavy fertilizer usage and then potentially using biodiversity loss and all the problems that we already have with sustainably producing things in every culture. Another problem is that we need to move all the biomass that we need to the power stations and then we need to transport the CO2 that we captured to the sites where it can be stored so that it would require building a huge network of pipelines and it seems likely that few people want a CO2 pipeline in their backyard and also not a CO2 storage site. And in fact, now already in Germany there are in some federal states there are laws and regulations against having such sites because nobody wants them. So carbon dioxide removal like BEX is a technology that directly works or attacks the main cause of climate change so reducing carbon emissions. There exist other geo-engineering ideas that work more against the impacts that we saw. And one of these is solar radiation management and more specifically, stratospheric aerosol injection. And the idea here is to mimic what happens to a volcanic eruption and to, as we saw in the first part from Katja, to reflect back incoming sunlight so that it doesn't reach the Earth. Of course with the volcanic eruption, the reduced temperature is gone after a couple of years so we would have to artificially, using airplanes, bring small particles into the stratosphere and do this basically forever. This also points to one of the main challenges of this proposal. If you at some point would have to stop this for technological or economic or maybe a war reason, then all the global warming that would be masked and prevented by this technology would then quickly be added to the warming we got anyway and it seems certainly bad to have a fast termination shock like this than a slow, gradual temperature rise. Another problem is that who gets to decide about the optimal global temperature? It could be that in some northern countries the people would accept higher temperature and some people in low lying islands, that's not by sea level rise, they would rather want temperature rise to stop immediately. And looking at the current climate negotiations process, it seems unlikely there would be an agreement found in a short time. Another idea that was discussed in the comic book story from 1988 where I took most of these pictures from was to simply freeze water to reduce the sea level. So here, Anko Scrooge wanted to profit from a volcanic eruption and install large cooling stations at the north and south pole and then have lower temperature and freeze the water again to have wide stretches of land across the coast to build hotels there or do farming and make a profit. In this story it didn't turn out so well but in fact real scientists in the last years have looked what it would take to pump water back onto Antarctica and let it freeze there again to prevent sea level rise. Another study looked what it would take to rebuild the Arctic ice and both studies used wind power to do this. It turned out that it's quite difficult and also quite energy intensive. So for Antarctica it would require about 7 to 14% of global primary energy production to pump all this water back. So it seems all these approaches are either very expensive or potentially dangerous or both. So what should we do with these geo-engineering ideas? Certainly we should continue researching them but we should also be very careful how they are framed, who is proposing them, which billionaire might be funding them and how their advertised name can also be an indicator what's planned to do. So climate engineering is also a term widely used. Some say it should rather be intervention and as an engineer myself I would like to agree because engineering is usually quite boring and done to systems that are well understood and easy to model. The term solar radiation management was actually coined to avoid using geo-engineering which was already a loaded term. It was later tried to replace radiation with reflection but other scientists have argued that it's not management at all because we're not managing a process that we don't understand completely. It should rather be called albedo modification or even hacking. Cocktail geo-engineering is another example of a fancy name. This was given in a modeling study where two geo-engineering approaches were combined. Carbon dioxide removal is I think a pretty descriptive good name but negative emissions, well, aren't emissions always kind of negative? So let's look back at our emissions trajectory. If you want to be really sure that we can stay below two or even 1.5 degrees above pre-industrial warming, we should be reducing emissions much faster because if these technologies don't work, if we are not successful in implementing BEX, then we have a problem. So we should take more action. It's time to do something but the question is what? So in our own work we work a lot with emissions data, historical emissions and the political process and we try to make this as openly as possible because without open data we can't judge what countries are doing and whether we are on the right track. We use Jupiter notebooks and the binder project to make them as explorable and easily usable as possible. So go and check them out. Here's one example. This is the Edgar emissions dataset which gives us CO2 emissions by sectors. So for Germany we see here the power sector, transport and buildings. Buildings looks pretty much okay. So there's at least a downward trend visible so it could go further. I mean we have passive houses as a technology. Transport doesn't really look like it's making progress. So we need more electric cars and fewer cars in general. But if you look at the statistics from last month we can see that there were 300,000 newly registered cars in Germany and there were 50,000 SUVs and only 3,000 electric cars so it's really not heading into the right direction. And this is a political decision that was made. So it was Germany who prevented stricter emissions relations for cars in the European Union a couple of years ago. And the same goes for the power sector. We could be building wind power plants and solar panels much faster than we do. It's a political decision to not build this as fast as we can. Here's some data from the SMART platform which shows transport Germany. And a couple of days ago we actually met all energy or electricity demand with renewable sources and some nuclear energy. So we could have switched off signal power on this day. But it's a challenge. And if we want to reach this on less windy days we need more capacity and also storage. And building such a fully decentralized SMART grid is a very hard task but I think we have to do it. And I think at this congress and in past versions we saw great talks that describe some of the challenges. And yeah, Sven, we'll have some more. So even if we managed to go to 100% renewables well we have to think about efficiency. And I think this is also where people who are interested in hardware and software come into as these ICT technologies get more and more common and popular. But just as an example, with cryptocurrency they have a built-in inefficiency. So we kind of have to find a way to still stick to these kind of decentralized systems which are a fascinating technology. But on the other hand, find a way to get that running without an energy demand that is for Bitcoin itself in some numbers going up to the electricity consumption of Denmark. A nice example of which is more like hacking the system, hacking the social system is the divestment movement. So the idea is here to alter the monetary flows so getting investors, persuading investors not to invest into companies that are carbon intensive but to green their portfolio. Just as an example, this movement was kind of successful recently when they managed to persuade the Norwegian government to divest from the Norwegian pension fund all companies that rely on 30% coal or more. But of course, us as consumers, as individuals, we are also investors in a way with our daily decisions so we should just keep that in mind when traveling or in our diet. But as Robert said, there is not one solution to the climate problem and we probably have to think that very holistically from the individual to politics. And so we also need policy and political regulations that demand from business to get greener. And just as a last example, I think in democratic states like ours, we as citizens almost obliged to protest when we think things are going wrong. And this just as a last example, the end of the movement that now grows from year to year where people block lignite mining production that is still going on in Germany though we claim to be quite renewable already. So to sum up, 2WATT and well, we don't know everything about climate change but we know definitely enough to act. Thank you very much. Thank you, Katja, Akasai, Sven Wilner and Robert Kieske. Thank you for enlightening us about climate change and climate system and the ways to hack it. We have time for certain questions. So if you would approach a microphone. Mr. Sicks, yes, please go. Hello, I have a question. Do you make calculation what is the real emission of electric car in Germany because there are some countries in Europe when electric car in fact is coal powered car and when we compare emissions from this electric car powered by coal it's two times greater than the emission from normal gasoline cars. We don't work exactly on this but it's a very good question and I agree you need to take this into account. There's for example the electricity map.org where you can see what the current emissions are from a country where you could should load your car when it's powered with renewables. Another question, microphone number two. Thank you. There was a statement that 0.8 watts per square meter hit the earth. Could you say a little bit more about this? I can see how if you look at the whole earth together then the sun is always shining on one side so if you discount the side then it doesn't really matter where you look but doesn't it get more and less over the year so is this like a yearly average or what does 0.8 mean? It's a yearly average of course. Well you have about 350 watts per square meter coming in from the sun so you can relate it to that and most of that is going back out, right back out from the thermal emission of the earth and ideally you have an equilibrium and it's only an equilibrium over a year and an equilibrium over a day is not there and the space also is not an equilibrium normally you have a lot of emissions during the polar night there's a lot of stuff going out and at the same time there's a lot of energy coming in at the equator so this is actually a mean value, yeah of course. Good, this lady here please. Hello. So thank you for your talk. So I guess the earth has its own temperature changing cycles like we had ice age and stuff which were natural climate change occurrences so how much or do you actually know how much of that good old climate change is caused by man right now? We do have numbers for that, yes. There's one parameter that is not influenced by humanity that's the sun intensity so what's coming in and the sun has been getting a little bit brighter if you look at the components that make up this climate change there's a very nice chart in the IPCC report and you can see that there's, I have to guess but it's a few percent very few percent that is made up by that, yes but most of that is actually really due to changes in the greenhouse gas content there's some changes in land use that's also important most of it has actually been cooling the earth we have been replacing forest with farmland so that reflects off more but at the same time we have all these greenhouse gases coming out from farming so that's the main component sadly we can talk later about that if you want. Yes, I have to remind you as well that we can give feedback via the fireplong and I suggest as well we take one other question here but we're out of time we have in 15 minutes another lecture regarding climate change so we're gone please shoot. Don't hesitate, it's a, I think it's a very simple question in irony text so we, a minute ago we talked about equilibrium state but what is definitely not an equilibrium is an exponentially growing economy and so my question is do you think that the climate problem could be solved inside or along with an exponentially growing economy because I doubt it? Well, this pretty much comes down to the question if there is something like green growth so I personally believe that it's not possible with the growth that we are experienced and that we have experienced that we are currently still experiencing to really get to carbon neutral society so I think well it's most often people that are very optimistic of technology solutions that say okay we can keep our lifestyles we can keep on the way that we live and that we organize society and the economy and still get down to zero emissions I personally am not that optimistic but for example discussions about degrowth for examples or a steady-state economy are not very common in climate impact research unfortunately Mike for number seven there and they're really in the back Hi, you told about all the possibilities to reduce climate change and they all have trade-offs and costs but then you brushed on animal agriculture really quickly and I myself can't see what's what are the costs there could you please comment on that? Or do you mean like... I mean animal agriculture seems to be the odd one out in this series of things we can do because I myself can't see any cost by just stopping to farm animals Are they some I'm missing? Of course not every possible solution or a thing we can do does have to come with the costs but of course we kind of just brushed through that that pretty much comes out I think down to a societal discussion of how we want to treat animals and how our standard of living or what we're used to eat is actually how much we value that over for example climate change Is that sufficient? Okay, microphone number two the very last question All right, thank you My question is about the climate modeling so one of the least crazy skepticisms I've heard was by physicist Freeman Dyson who doubted that basically the effect of increased carbon in the atmosphere on plant growth would be sufficiently modeled and he theorized that more carbon would mean faster plant growth and regarding the feedback loops that were mentioned would be one example of a dampening feedback loop rather than a reinforcing feedback loop Yes, that's true that's one of the feedback loops and it is modeled there are papers out there that actually measure plants they put plants in a little greenhouse and put CO2 there and measure how fast they grow the part that was missing from the 97% that went into the ocean so far is supposed to be taken out probably by the biosphere, we're not sure so this is included in the model the question is how well it is included in the model these insecurities, these unknowns always create a bit of an error range so what you usually do is you put the bottom parameter in you put the top parameter in and a few in between maybe and you see what happens but yes, we're working on that it's just not enough as far as we see, it's not enough to offset the problem and there's a talk on that later I just showed it Thank you, please give us a warm applause these three structures