 Number five, we have a slightly different model of the climate system that's got a few new features to it. We see the initial temperature and albedo and ocean depth from before. The solar multiplier here is just something that if it's one, it's not going to change the solar input at all. If I make that greater like two or 1.5 or three or something, that's going to increase. It's going to multiply, so the constant by 1.3 in this case, I'm going to undo that here. It also has something called a CO2 multiplier that does the same thing to the CO2 concentration. So here it's set at one initially, I could make that two. And then in that case, instead of having 380 parts per million CO2, we'd have 760, so we would double it. And if I made this be 0.5, then we would cut our CO2 concentration in half. And in doing that, we're changing the greenhouse effect of the climate model. We could change the history of atmospheric CO2 using this graph here, but we're not going to work with that in number five. It also has a couple of switches down here, one for a solar cycle and one for the albedo switch. This albedo switch is the most important thing for this problem. When it's in this position, it's off, and then we have just a constant albedo that's assigned up here in this box. But if we turn that thing on by going click, like that, it suddenly knows going to make the albedo be a function of temperature. And that creates a feedback mechanism that does some interesting things that you'll kind of explore that in this problem. Let me just show you a few things here. So if we restore everything to the way it was when you first opened the model and you just run it, you see that in this page one of this graph pad, everything is just constant all the way across here. CO2, solar input and temperature are staying the same. I'm going to switch to page three of this, and this shows the temperature for the first run here. Now, if I switch the albedo switch on, I'm activating that feedback mechanism, but if I run it, it doesn't change anything at all. Now watch this, I'm going to turn that back off. I'm going to decrease the CO2 multiplier. I'm going to make it be point, something very small, point one, let's say, just change that to point one. And now I'm going to run the model and see what happens. So it gets quite a bit colder because we've taken a lot of CO2 out of that mess right here. It gets down to 8.3 at the end of 80 years. Now if I turn the albedo switch on, see what happens now. Now the temperature really drops. It drops to minus 5.6. So the difference between minus 5.6 and this, 8.3, that's the impact of the feedback mechanism. It has an effect, a cooling effect from 8.3 to minus 5.6, so something more than 13 degrees of a negative shift in temperature. For that feedback mechanism. So in this problem you're going to be assigned a CO2 multiplier value. And you'll type that in here. It'll be something like 0.25 or 0.5 or 2 or 4, something along those lines. You enter that number in there, let's say you've got 4. And then you run the model with the albedo switch off. And then you run it again with the albedo switch on and you look at the temperature difference between those two runs of the model. To get a sense of how big the albedo feedback effect is in our climate system.