 This is the interface to the carbon cycle model that you'll be working with in this module. If you click on this button here, it gives you a diagram of the carbon cycle. It's a complicated looking thing down here, but all these boxes are just places where carbon can reside, including the atmosphere here. And the amount of carbon in the atmosphere determines the CO2 concentration in the atmosphere, which then affects other parts of this. Let me point out a couple of things about this diagram. One is that there's a fossil fuels reservoir here that includes a flow called fossil fuel burning, FFB, that adds carbon to the atmosphere. And this is controlled by different kinds of emissions scenarios that, you know, dictate the amount of carbon released at each year through this process of burning fossil fuels. It also includes a reservoir for permafrost carbon. So this carbon is stored in permafrost, but if the permafrost melts, then that will be added to the atmosphere here. And that's controlled by a switch that we can either turn on or off to consider the effect of that. The CO2 concentration in this carbon cycle model then feeds into a climate model. You can see the edge of it over here. It's the same climate model that we worked with before, but so there's a connection between these two. And then this determines the global temperature change that then in turn affects the carbon cycle. So these two are linked very closely to each other. Now let's see how you operate this. This carbon cycle model will allow you to impose three different emissions scenarios on it. One is the business as usual scenario. If you click on this, you see what that scenario is, just an increasing emission of carbon over time. It begins in 1880 and then ends in 2100. So it goes into the future a bit. Here's another emission scenario, one that involves moderate reductions after some period of time here. And then finally there's a third emission scenario here. It's shown like this, more drastic reductions through time. So you can activate those three different scenarios by using these two switches here. So the way it comes right now, it will impose the business as usual BAU scenario. That's A2 here. So if I run it, it's going to impose that emission scenario on from 1880 up to 2100. You see the temperature change. And you can see the CO2 concentration and atmosphere rising up here at the very alarming levels. If you click again, it shows the pH in the oceans going down, down, down, getting more acidic. And it shows how much of the carbon stays in the atmosphere, the airborne fraction, how much goes into the oceans, and how much goes into the terrestrial reservoirs. Click again, it shows the history of fossil fuel burning in detail from that emission scenario. And then through here, this shows the permafrost melting that's turned off now so that it didn't do anything. And then this graph and the next one show just the amount of carbon in terms of gigatons in those different reservoirs over time. And this shows the total anthropogenic change, which is the cumulative effect of burning fossil fuels and having land use changes. So if we wanted to impose a different scenario, we would turn this switch off. And now we're looking at one of these reduction scenarios. If I have this switch down like that, it's going to implement the A1B scenario. And if I click this, there it goes. And then if I click this switch, it's going to impose the B1 scenario here. So if I run it, you'll see that take effect. All right, so that's how you activate those different scenarios. If I want to turn on the permafrost melting, I would hit this switch here. Now, as the temperature rises up above a certain level, once it gets above one degree, then the permafrost melting begins. So I'm going to turn that off here. And this switch here determines whether or not the carbon emissions from land use changes, including forest burning and soil disruption, is either not turned on or turned on. In this case, that's the standard scenario. So that's the essence of how this carbon cycle model works.