 This is the interface to the carbon cycle model that we'd be working within this module if we Clicked on this button here. We would see a view of what the carbon cycle Looks like that's implemented in this model. It's a complicated thing But it's a very realistic carbon cycle model that's going to allow us to explore in a pretty realistic way What will happen to atmospheric CO2 and to other aspects of the carbon cycle as we change the Burning of fossil fuels and the human effect on this particular system this carbon cycle model Here is attached to a little climate model. It's you can see the edge of it over here That's the same one that we worked at it within module three and so the carbon cycle model will will control the atmospheric CO2 concentration here and Then that will feed into the climate model here and control the greenhouse effect and then the Temperature determined by the climate model will then come back and affect different parts of the carbon cycle model here So let me show you how to work this this model If you run it just the way you First open it you'll see it calculates the the global temperature change over time So zero is is the temperature at 1880 But that's this is temperature relative to that time and then the temperature rises as we go to the year 2000 and 2100 Now these switches down in here control different histories or scenarios of fossil fuel burnings the business as usual Emissions scenarios what we ran first so when this switch is on it uses that business as usual scenario And it looks like this where the carbon emissions just go up and up and up with no change all the way to 2100 If we click this off And leave this switch off. It's going to implement a scenario in which the fossil fuel burning just levels off So after the year 2010 it just levels off like this So we hold emissions constant and we can see what happens to the the temperature and the rest of the system in that case If we turn this switch on like that it will implement this scenario here There's a very unrealistic one where after 2010 we drop quickly down to zero Fossil fuel burning for the rest of time. So this is the really dramatic case Just to see how the system will respond to that change Now you can graph different parts of the system here. We can look at the atmospheric CO2 concentration Here we can look at the ocean pH Here we can look at where the carbon goes how much of it what fraction of it stays in the the atmosphere what fraction goes into the Biosphere and what fraction goes into the oceans? This shows us the details of the fossil fuel burning history that we applied in that case And this plots both the atmospheric CO2 concentration and the fossil fuel burning history together so you can see how they compare This shows the values of carbon and all the different reservoirs in the carbon cycle model This is the cumulative amount of carbon that we've released over time. So it just gets bigger and bigger and bigger This is not the annual map of the cumulative Now this is an interesting one to look at because it goes from 1880 to 2010 so the period of time that we know something about and it plots in Red the actual observed atmospheric CO2 level and in blue the CO2 level that the model calculates And so you can see that those two are very close throughout this whole time And so that means that that our carbon cycle model coupled with the climate model is Giving us a result that matches a historical record And so we say we have a good model and we can we can essentially trust what it tells us in terms of projections off into the future