 Hi students, this is the model for step two, the second part of the lab. And I want you to familiarize yourself with this model before you get started. So basically what we have here are three different switches down the bottom that I'm going to explain. And we have the scenarios up here on the right side and the carbon cycle model, which is basically the same model as we used in the first part of the lab. So let me explain these switches. So what we have is the business's usual, which we talked about in the first step A2. And this is the scenario here A2 with fossil fuel burning just keeps going up and up and up and up. And in the second one, we can turn this off. We have B1, which is our best case scenario. I turn that on and then that is our drastic reduction of fossil fuel burning at around 2010, 2020 somewhere in there. It doesn't really matter when it is, but you can see it comes down significantly. Okay, so that's the two. A2 with that switch on, B1 with that switch off and this switch on. And the third model, this is what's critical is it with both of these switches off, business as usual and B1. We have the A1B model, the basically likely scenario where fossil fuel burning starts to decrease in the later part of the century. Okay, it doesn't come down to zero, but it starts to decrease 2030, 2050 somewhere in there. All right, so basically those are our three scenarios A2, B1 and A1B with both of these switches off. Okay, and finally over here we have a permafrost burning switch. This is going to show you what happens when we start burning permafrost and putting all that methane and CO2 into the atmosphere. Let's start this with this switch on, okay, with this switch off. We do not introduce that methane and CO2 into the atmosphere. All right, so let me show you what happens. Basically, it's the same controls as we had in the, it's the same graphs we had in the last part of the lab. All right, so let's run through them again really quickly. Let's do it with the A1B scenario. So we can run the A1B and you'll see temperature in one, CO2 in two. And again, if you run your cursor along here, it gives you a value in a year, calendar year and a value, which you need to be able to do to do well in this lab. pH comes down and you can see that doesn't flatten out. And this shows you some of the same things we explained in the last lab. How much of the carbon is absorbed by the air? How much is absorbed by the ocean? How much is absorbed by terrestrial biosphere? This shows you fossil fuel burning in A1B. This shows you permafrost, which we don't have on, obviously. This shows you how much is absorbed by the atmosphere? How much is absorbed by soil? How much is absorbed by land biota? And we don't have permafrost on. This shows you surface and deep ocean. This shows you how much carbon we put in from fossil fuel burning. And this, again, shows you the comparison between the real data in red, the observed data and the model that we ran here. Okay, so let me just show you a couple more things before I set you free to work on this. So what we can do again is we can run different scenarios and compare them side by side. So we can do that. This is A1B. Let's turn A2 on. So there's our A2 scenario, business as usual. Let's turn B1 on. And then that's our third one. That's our business, our B1 scenario, the best case scenario. Okay, and then finally, let me restore everything. Okay, let's run A1B. And now let me show you what happens when I turn permafrost burning on. And you can see a lot more fossil fuels or a lot more carbon ends up into the atmosphere. And you can compare curves side by side. So I think you'll have a lot of fun with this. Make sure you understand these controls before you start. And please let me know if you have any questions.