into balance. That the ocean currents on a large scale look right. You get a jet stream, the temperature, the planets about right and so on. And then you say, okay, I'll take this arbitrary point in time as the starting point. Let me now start applying human influences. Let's say over the last 250 years as we have observed them and watch how the climate changes. And of course, there is some arbitrariness and importance as to exactly when you choose that starting point. And so what people do is take many different starting points and just average the results together. And of course, the results can differ wildly depending upon how you start them. The last thing that needs to be done is to tune the model. The subgrid parametrizations all have parameters in them. How much does the albedo or the forest change when there's snow on it, for example, or exactly how much water vapor is transported upward in convection in the warm equator from the sea surface, things of that sort. And we don't (42/57)
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