 Okay, so we're going to run a GCM, a very famous GCM, in fact. This is the GCM that was constructed back in the mid-1980s, which was used for a number of very famous climate modeling experiments by James Hansen and his group at the NASA Goddard Institute for Space Studies that we'll be talking about a little bit more later on in this lesson. So that model has actually been taken and put in a format that can be run on a PC, on a Mac or a PC. Of course, by modern standards, the computational requirements of climate models, written in the 1980s, are far exceeded by current-day state-of-the-art models. But because they are a couple of decades old, they can in fact be run fairly efficiently now on simple laptops and PCs, like we're going to do. Now this model is available at the website edgcm.com. I would have had students in the class download the model and run it themselves. That was possible a few years ago, unfortunately now you actually have to pay to obtain the model and so I will be doing some experiments with the model and you will be watching me do these experiments rather than actually downloading it and running it yourself. But if you felt so motivated, you could indeed download this climate model and do the very same sorts of experiments that we're doing right here on your PC or your Mac or whatever computer you have. So let's go ahead. I'm going to look at this doubled CO2 experiment. If we click here we can get some information about what that experiment is. It basically takes the CO2 concentration from 1958 and instantaneously doubles that CO2 concentration. And then we see how the climate model responds to that sudden increase in CO2. And now because of the presence of an ocean, a large ocean that has a large thermal capacity in this model, it takes quite a bit of time for the climate model to equilibrate to that increase in CO2 concentrations, in fact several decades to near a century. So this underscores the point that when we're looking at transient climate change, whether we're looking at observations or looking at the results of a climate model, we are in fact observing a system that is not in equilibrium and that might take quite a bit of time to equilibrate to whatever change enforcing is imposed. So ultimately we know that this model will warm the amount that is consistent with the sensitivity of the model in response to that CO2 doubling, but it will not achieve that equilibrium warming for several decades again to nearly a century. And so what I'm going to do now is actually continue a run of that model that I started previously. And I'm just going to click that and I should be able to run.