 In this next step in this project we're going to calculate the total energy demand and we'll do that simply by combining the population part of the model with the per capita energy curve here. So this shows the per capita energy in terms of exajoules of energy per billion people over the history of this model runs over about 200 years. And this is a graphical function of time that can be changed and we'll change that here in just a second. So if we run this model now let's go back here to the beginning. We'll just run this model in time and see what happens. Okay here's our our carbon emissions curve here. Here's our global temperatures. See we're getting close to keeping it below three. Now if we go backwards here here's our graph showing the global energy demand. Also the reference global energy demand. They're one and the same here because I haven't made a change to this curve here. Also shown on here is zero right now is the energy conserved. So if I go ahead and change this curve here and lower the energy demand that represents conservation of energy. So let's go ahead and do that. Make a little bit of a change here. Let's say we lower the energy demands through time like this. On this graph this line over here the edge represents the year 2200. This line over here represents the year 2010. Every little increment here represents an additional 48 years I think. Okay so we can adjust this history. So I've made some big steps in energy conservation. Let's see what happens and we'll run the model. And sure enough the global energy demand is less than this reference value here. And the difference represents energy conserved. Now this energy conserved isn't free. It comes with a cost and so later in this model you'll see that the costs that are attributed to this conservation of energy. And you can look at that if you just go back here to page five and you can see this pink line here conservation costs is very very low here. It looks like a flat line not changing. It's actually changing a little bit but it still just stays very very low. So that's a very modest cost. The other thing you can do of course in adjusting this model is to lower the population limit. So let's lower the population limit from something like 12 to something down near 9. We run the model and you see that everything gets shifted downwards. The reference curve gets shifted downwards. The actual global energy demand gets shifted downwards and the energy conserved shifts downward as well. So these two controls population limit and per capita energy are how you determine what the global energy demand is.