In The Deluge (Simon & Schuster, Jan.), Markley spins an elaborate yarn involving future responses to global warming.

Did you set limits on your imagination of how the climate crisis will affect the next few decades?

The terrifying thing has been that plot points I was concocting in 2012 have already become headlines in 2020, ’21, and ’22. I tried to be reasonable about what temperature a London heat wave could produce, but nope, sorry, go back and edit that number up. Everything had to at least approach the realm of plausibility, even if it might be a maximalist version of an event. My fear is I probably restrained myself too much in terms of the most frightening scenarios we will live through.

Why choose fiction to explore the subject?

Here is my truly arrogant answer that will embarrass me but is still the truth: every artist who has ever pursued a career with passion and commitment believes their art has the power to change everything. That’s why we all do it. I read no shortage of nonfiction climate change books. I watched no shortage of earnest environmental documentaries. Many of them I don’t even remember because you read about potential catastrophe, and sure, it sounds like a bummer, but it leaves no lasting emotional impact. The point of narrative, of art, is that it can reorient us emotionally. If done well, it can make vivid what is abstract. Given the enormity of the task ahead of everyone alive on this planet, we desperately need that reorientation.

This is a door-stopper. Did you consider a shorter version?

Nope, not even for a moment. If you look at the story burning inside of you and say, “I’m not sure that’ll be marketable,” or “I don’t think it would sell as much as this other idea,” then that story is not really burning inside of you. I wrote this novel the exact way it was in my head, because I couldn’t do it any other way. I wrote about 400–500 pages of the first draft, without a contract, or any idea that any agent or publisher would ever want it. If the writing is compelling, and the storytelling is fascinating, there is no page count a reader won’t tackle.

You also have written for the TV show Only Murders in the Building, which has a radically different tone. Which writing has been easier for you?

This is odd to say, but in some ways working in a TV writers room can be more difficult, simply because 95% of the job is not actually writing, but spitballing. For someone like me, with such a specificity of vision and the certainty of a mad cultist about whatever idea I happen to have, that’s occasionally frustrating.