We’re in for another long, cold, snowy winter in New Hampshire this year – at least according to the Old Farmer’s Almanac and publications like it.
But what do scientists make of these kinds of predictions?
Erich Osterberg is an assistant professor of earth sciences at Dartmouth College, and he says the Almanac’s winter outlook makes for better entertainment than it does actual forecasting. (The editor of Old Farmer's Almanac, Janice Stillman, responded to criticisms of the Almanac's forecast in a Dartmouth Now piece featuring Osterberg.) He joined Weekend Edition with more.
Old Farmer's Almanac claims to be accurate about 80 percent of the time. How accurate would you rate that claim - if that's even a question we can ask?
I think nobody really knows how they assess that accuracy. I think it depends on which forecast you're looking at; the almanacs will do a forecast for an individual location like New Hampshire for a specific week. You can look at this week's forecast that was put out last year - this week they were calling for cool and rainy conditions. I think we're all pretty happy that forecast didn't turn out right! I think it would be really interesting to do a rigorous analysis of how accurate the forecasts are.
How far out can we really forecast weather conditions in a given area?
It's usually just not possible to forecast the weather more than maybe a week or two in advance, with any sort of accuracy. The one exception to that general rule is actually in years like this year, when we have an El Niño event forming in the Pacific Ocean. This winter, I think we can actually make some forecast predictions for the winter in New England. El Niño events in the past, especially big ones like the one we think we're seeing this winter, tend to be associated with less snowfall than average. With that in mind, we might actually expect a little bit less snowfall than average coming up this winter.
The Almanac says its secret formula began with its founder, Robert B. Thomas, in the 18th century, and is in part based on solar science, sunspots. What do we know about solar activity and its relation to Earth's weather activity?
We actually know quite a bit about that. Sunspots we know do affect the climate, especially over large regions of the globe. We know that there's a very persistent sunspot cycle that lasts about 11 years, and we can see some evidence of that cycle in the climate records we look at from around the world. But in terms of the actual weather on a week-to-week basis, we don't see any relationship between sunspots and the weather. What's a little more challenging is that sunspots themselves are very difficult to predict, more than a few months in the future. That makes using sunspots as a weather predictor for a particular area a little difficult to do.
I was reading several articles that said the forecasting technologies we use now can help us see short-term weather to a degree we couldn't see even a few decades ago. And yet, we have a kind of urge to return to the traditional forecast we get from an almanac.
The weather forecasting abilities we have now are truly amazing. The fact that we can actually predict the weather even five days out in advance, with quite a bit of accuracy, is remarkable. That's all due to the latest technology with computers and our understanding of how the climate system works.
But like I say, there is something fun about going back to the almanac and thinking that we can predict these things months in advance. Usually we just can't. The weather has too many variables, and those variables are often random. Even when we know exactly what those variables are, some of them just cannot be predicted.