In this module, we're going to talk about climate mitigation. This will include an exploration of the sources of greenhouse gas emissions, the types of reduction targets that are out there, the technologies that are used to reduce emissions and the policy tools for encouraging or accelerating the use of those technologies. But before we jump into all that good stuff, I want to introduce the Chi Identity. The Chi Identity is a way of mathematically breaking down emissions into a few different driving factors. By making these factors transparent, it can help us understand the different strategies that might be employed to reduce greenhouse gas emissions. Let's do some math, starting with the top line, which isn't really math, but more of an assumption or premise. In this top line, we're saying that the goal of mitigation is to reduce emissions. I throw in the generally caveat to recognize that we could also aim to increase or enhance carbon sinks. But for the purposes of the Chi Identity, let's restrict ourselves and equate mitigation reducing emissions. Second line, most emissions come from energy, will talk about this in more depth in future lectures. Most of our emissions come from fossil fuel combustion, which is primarily used to generate heat or electricity. Globally speaking, around two-thirds of our emissions come from energy-related activities like these. The third and fourth lines. Now these two lines say the same thing. The third line is words only and the fourth is wordy fractions. They say that emissions are equal to the number of people multiplied by the energy use per person, multiplied by the emissions released per unit energy. This last line, I'll refer to as the emissions intensity. That last term, I'm sorry. Summarizing those third and fourth lines again, they say that emissions are equal to population times energy use on a per person basis. We just multiply then by the emissions intensity. The very last line on the slide breaks down the terms Just one more step further. We keep the first term, the number of people and we keep the last term, the emissions per unit energy, that emissions intensity. But we'll disaggregate that energy per person into two separate terms. The gross domestic product or the GDP per person, and the energy per GDP. With these two terms, we've introduced the concept of economic productivity or wealth. The GDP per person can be thought of as an average economic output or average wealth. The energy per GDP can be thought of as the energy intensity. It's the amount of energy you need for one unit of economic output. I've reproduced that last line up at the top of this slide. Emissions equal to number of people times the average economic output times the energy intensity times the emissions intensity. Now, this is the Chi Identity. Let's put it to work for us. Let's say we wanted to reduce emissions. According to this, we could reduce any of these four terms and achieve an emissions reduction. Let's think about that. That if we worked on each of these terms, what might that look like? The first term, population, well, we could try to stem population growth now it's the idea of reducing the number of people that are already here is, I think a little morally questionable. I don't really support that. But if we think about it in the future tense, we could work on trying to make sure our population doesn't grow quite as fast. Now, this is a good option in parts of the world maybe where populations are growing. But in a lot of the economies that actually produce the most emissions, like the United States, Europe, Japan, Australia. A lot of our populations are actually not growing very much or even shrinking. This particular strategy is probably not appropriate for those places. It may be appropriate for other places, especially if some of those energy and emissions terms are very small. Let's move on to those other terms. Let's talk about those GDP per person. Now, we could reduce our economic output, essentially shrink the national and world economy. This is in a real popular option. However, it's one we know that's empirically true when we've had recessions or for example, when we've had some of the economic shock associate with COVID, emissions have gone down, we reduce our economic activity. I don't think this is necessarily a goal to slow this down. However, there's another way we can think about this term, and it's this idea of becoming more frugal, so we can have the same quality of life, but we are doing it with less consumption. This is I think a newer way of thinking about future economic growth that maybe we don't measure success by GDP, but we come up with other metrics that would allow us to still have a good quality of life, but maybe reduce the cost from an economic standpoint. The next two terms I think is where some of the solutions may become more recognizable. Energy intensity, the energy per GDP. If we were to reduce this term, it's really about making our activities more efficient. We can still have the same amount of economic output, but we use less energy to do so. The last term is about making our activities cleaner, and making energy more clean specifically, so that we can still maybe generate the same amount of energy. We keep the denominator the same, but we reduce the emissions associated with that. Let's go one more slide and let's talk about these last term. Some examples of a more efficient use of energy or cleaner generation of energy, so efficiency, some examples are shown in these bullets. We could improve the way buildings use energy, maybe through better materials or better insulation, such that we wouldn't need to use as much energy to heat or cool. We could also get better appliances things and use less electricity like newer TV's or newer refrigerators. We can get more fuel efficient cars, so we can still drive the same distances, but we don't have to consume as much gasoline and do it. Also another thing are called combined heat and power systems. You see this in some big facilities like hospitals or maybe universities where they're basically generating their electricity in their heat in the same spot. You don't have the losses associated with electrical lines coming from the power plant. That handles that energy intensity term. Let's talk about some examples of the emissions intensity. How can we get cleaner in our economic activities or energy activities? We can switch to non-carbon fuels. We would reduce our emissions to near-zero, for all the energy that comes out of non-carbon fuels, we could switch to lower carbon fuels. We would still be producing emissions. But let's say if we switch from coal to natural gas, we'd producing much fewer emissions for the amount of energy we get out. Another thing we could do is what's called carbon capture and storage, where we essentially capture carbon dioxide when it's leaving a power plan or maybe an industrial facility where there's combustion going on. It never gets to the atmosphere. We're still realizing the benefits of that energy production, but we're really significantly reducing our emissions if not getting them all the way to zero. Those are all examples through the Chi Identity of different strategies to reduce our emissions, to mitigate climate change. That brings us to the end of this video. But hang in there for the rest of the module and we'll talk more about climate mitigation. Thanks for your attention.
