Lab 5: Carbon Cycle Modeling

Hi, everybody, so this is the model that we're going to use in the first part of the lab, and I want you to really familiarize yourself with the controls before you really get started, okay? I think it's really important. And, it can be a lot of fun to experiment with this and really get used to playing with it before you start the lab. And I think if you do that, then the lab will be very straightforward.

So basically, what we have here is a carbon cycle, very complicated. This is the STELLA version of the carbon cycle here, and you can basically see all the knobs and bells and whistles with these STELLA connections. And over on this side is the ocean model that we already used in Module 3 lab. So you really don't need to understand this, of course, but it shows you how complicated it is, and we'll see later on why it's such a good model.

Ok, so the bottom line is we have three different emissions scenarios that are controlled down here by these switches, okay? We have a business as usual (BAU) switch, which is basically the worst case scenario, emission scenario A2. And you can see that is here. It goes all the way up and actually, then it drops off, but still it goes all the way up through 2100. We continue fossil fuel burning through 2100 without stopping. Okay, that's this switch. So that's with this on. And you can read about this down here. So if I turn this switch off and I leave this switch off, and I'll explain this switch in a minute, then what we do is we level off fossil fuel burning around 2010. We just level it off, okay? Which obviously didn't happen because we've gone through 2010. But it just shows you what happens if we slow down fossil fuel burning, don't completely stop it, okay? And then the third switch is what we do is if we all of a sudden drastically stop fossil fuel burning, FFB Halt. And what that shows is that around 2010, we stop. Let's see if I can move this up. But anyway, it's down here. You can see we stop fossil fuel burning at 2010. It goes down to zero. Ok, so that's basically what happens with that third switch.

So the three switches are, the three scenarios are, business as usual (BAU) with this switch on, this switch off. Both switches off, is Leveling Off at 2010. And then with this switch on, we halt fossil fuel burning (FBB) at 2010. Ok, don't worry about the land use switch for this part of the lab.

All right now, the critical thing is we can run, let's run business as usual (BAU). I want to show you one other thing. You run this model here, and let's say you want to then run another model. Let's say we'll turn it off and run the second one. You can see these two curves side by side, so you can see business as usual (BAU), and then you can see the leveling off of fossil fuel burning (FFB). And then if you want to run the third one. Excuse me, sorry about that. We're just going to turn this on. And then you see the third scenario here, 3. So, 1 - business as usual (BAU), 2 - leveling off (Leveling Off), 3 - fossil fuel burning (FFB). But what I wanted to show you also, is that if you want to then start over again and do something different, you restore everything. Okay? In general, it's a good idea between experiments to restore everything, to get everything back to back to usual, back to normal. And then why not?

One other tip that I just thought about is if for some reason the model isn't working for you and you aren't using Google Chrome. Switch to Chrome because it's the most stable. It's the most stable browser for STELLA models.

All right, so let me show you the output that we can get. So let's have business as usual (BAU). This is global temperature change, and as I said, the emissions, the fossil fuel burning stops at 2150, or so. And so you'll see this temperature decrease, which isn't really important for the lab. CO₂, you can see it rises steadily here, and then drops here. pH goes down and then rises a little bit, but you can see it's going down. This is ocean pH.

And then one other thing I wanted to show you is make sure you can read the values here. So I'm going to click on the curve and you can see it running along the curve. It shows you the values down on the bottom rung, 8.14987. And then moving down the curve, you can see the values. You can see both the year and the values. So now I'm 2040, and I'm now at 2083, my value is 7.844. And now I'm down at 2040, excuse me, 2153, at the bottom and my value is 7.55. Ok, so make sure that you can run the the cursor along the curve and read the values not only of the year, but the values of pH, temperature, CO₂, et cetera. All of these different curves you can do this, which is really, really helpful and very important for the lab. All right? So then we also have how much of the CO₂ is absorbed by the air? How much is absorbed by the ocean? How much is absorbed by the biosphere in the purple curve, number 3.

Moving along, page 5 shows you fossil fuel burning, which shuts off as I said earlier, around 2050, or so. This is both CO₂ and fossil fuel burning. Fossil fuel burning in red, CO₂, atmospheric CO₂ total, in blue, comparing those two curves. This here shows you what happens in the biosphere. It's the atmosphere in 1, the land biota in 2. How much CO₂ is absorbed by land. How much is absorbed by soil. How much is absorbed by permafrost. And then this here shows how much it's absorbed by surface ocean and deep ocean. This here shows you the gigatons of carbon from fossil fuel burning. And then finally, a comparison of the model and observations.

So this shows you in blue the model run. This is the model run that we have established with this carbon cycle. And in red, we show the observed atmospheric CO₂. This is measured in the atmosphere through twenty ten and you can see how close they are together, which shows that this model works really well. All right, so that's a good summary of what this model does. This is for the first part of the lab step one, and I will be producing another video for step two.

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 as usual (BAU), 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, and turn that on. And then that is our drastic reduction of fossil fuel burning at around 2010, 2020, somewhere in there. Doesn't really matter when it is, but you can see it comes down significantly.

Ok, 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 with both of these switches off, business as usual and B1. We have the A1B model, the basically likely, the likely scenario where fossil fuel burning starts to decrease in the later part of the century. Ok. 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. Ok. And finally, over here, we have a permafrost burning switch. This is going to this is going to show you what happens when we start burning permafrost and putting all that methane and CO₂ into the atmosphere that is with this switch on. Ok, 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 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 1, CO₂ in 2, 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 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 in 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 and read the observed data and the model that we ran here.

Ok, 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 (BAU). Let's turn B1 on. And then that's our third one. That's our business, our B1 scenario, the best case scenario. Ok, and then finally, let me restore everything. Ok, 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 the 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.