 For problem number four, we're going to see what happens to the climate model in response to a brief change in the solar constant. We're going to increase the solar constant for a little bit and see how the model reacts. But before doing that, we're going to try to set the model up to begin with in such a way that it represents something like our Earth. So we're going to change the emissivity first to 0.6147. That's an emissivity value that kind of represents the strength of our greenhouse. We're going to change the initial temperature of our planet to 15 and we'll leave the other things the same. Then we're going to go to the solar constant here and click on that. And right here in the middle of this graph, I'm going to position the cursor right here and click one little tick mark up there. So I've made a graph now of the solar constant so that it's steady at 1370. Then it bumps up to 1372 here for a little bit and then it drops back down like that for 1370 for the rest of the time. You hit OK. And now we're ready to run the model to see what happens. So it's evaluating it and we're about to see the results here. So we see in magenta now the temperature of our climate model is staying constant at 15 up until the point where the solar constant starts to increase. And then as it increases, the planetary temperature increases to 15.05. It peaks there. And notice that that peak occurs at 16.6 years, 16.7 years, something like that. That's about 1.7 years after the peak in the solar constant value. So that's what we call a lag time, a difference in time between the peak of some kind of forcing like the solar constant and the response, which is the planetary's temperature. So it peaks about 1.7, 1.8 years later. And then it drops back down. It doesn't quite get back down to 15 after we have restored the solar constant to 1370 because the system takes a while to sort of settle down again. And that's a function of the kind of thermal mass of the climate system, which is related to the ocean temperature. And so what we're going to do in this question is to change the ocean depth from its default value of 100 to different values by simply typing in a different value here. So there's 200 and then running the model and comparing the response of the model to this kind of control version here that we're looking at in this little video. So you might want to, in fact, you should take note of the maximum temperature rise of the model following this spike in the solar constant and the timing of that as well.