Mood and Setting
As you've probably noticed already, a lot of my exercises aren't just about building a realistic world. They're about building a world that you can tell a story in. After all, world-building is fun, but if you're doing these exercises, you're probably not interested in spending 2000 hours worldbuilding without any practical application to your story, right?
So, pull out your list of climates from Saturday and look them over. You should have a bunch of climates, maybe even places, and a word or two describing how you feel when you're there.
Well, it's time to make your first real decision about your novel. What kind of mood do you want it to have? See, we're going to set your novel in the kind of climate that contributes to its overall mood and theme.
The mood of a novel is how it feels to read it. High fantasy is traditionally set in a climate similar to Europe or England, thanks to the father of heroic fantasy, J.R.R. Tolkein himself. However, it doesn't have to be that way, and you can capture a completely different feeling in a Middle Eastern desert setting or a Russia-like tundra.
For theme, you can adapt your setting to what's actually happening in the novel, what kind of message your novel has to tell. For example, if you want everyone in the novel to be in a constant state of uncertainty, maybe you should set them in a seismically active volcanic region (I type this just 77 miles away from Mt. St. Helen, which apparently is due to erupt any hour now). Or perhaps you want your story to feel very "escapist." Nothing says "escape" like a tropical island with balmy days, mid-afternoon storms, lush green plants, and a climate that doesn't vary seasonally but can bring up some exciting stormy weather.
If you already know "I want to write something dark and gothic" and you look at your climate list and there's "dark" or "gothic," you're there. You've got your predominant climate, and everything else after this is going to be figuring out how to build a world around that mood and climate.
If you are thinking right now "I have no idea what kind of mood I want-- this mortaine person is crazy to think I know that this far in advance," then the below exercise is YOURS; it'll take 10 minutes and you'll have made a strong first decision about your novel. And don't feel bad if you don't know what kind of novel you're going to write-- nobody really does until they write it.
Read over your list from Day 1 and then turn to a blank piece of paper. Close your eyes and think about what kind of feeling you like to have when you write or read. Write down four words that fit into that feeling: two adjectives, a verb, and a noun. Now return to the page with your list of climates and emotions. Do any of them match up? If they do, you have your climate. If not, try to find closest-match words.
If you spend 10 solid minutes thinking about this and still can't decide, pick two climates that express moods you like. You can make up your mind later, and you can even build your world with both climates containing equally probable sites for your story.