D: It looks like we have a day off in a couple weeks, Yaël. Want to go for a hike?
Y: What’s the weather going to be like, Don?
D: It’s supposed to be sunny ten days from now, but that’s all my weather app tells me.
Y: That’s as far as the best weather forecasts can accurately predict the weather these days—which is still pretty impressive compared to what meteorologists could do in the past. Today, a forecast for the next five to seven days is just as accurate as a forecast for the next day was fifty years ago.
D: So do you think we’ll get reliable forecasts for a month out in another fifty years?
Y: It doesn’t look like it. Researchers did a study where they tried to find the ultimate limit of how far out we could predict the weather, even with the most advanced supercomputers powering the weather models. Their research suggested we could add another four to five days of useful results, and probably not any more. That’s because of something called the butterfly effect. The atmosphere is full of turbulent flows— irregular flows of air that form clouds, power storms, and push around cold fronts—that build on each other and form layers. A tiny disturbance in one layer, even one as tiny as a butterfly flapping its wings, can have a domino effect, affecting the other layers and snowballing into radically different weather patterns. All that variation and uncertainty is why there’s a limit to how far out we can meaningfully predict the weather.
D: Luckily there’s no limit to hopeful guesses. I’m going to pencil that hike into my calendar.