The weather forecast for the upcoming weekend in most of Minnesota is sunny and warm. But does that mean Minnesotans will be in a brighter, happier mood?
Very likely, according to a large study by a team of American and Canadian researchers. The study, published recently in the journal PLOS ONE, found a strong link between certain weather conditions and people’s moods as expressed through their social media postings.
And, yes, sentiments expressed via social media have been shown to be a good proxy for people’s underlying emotional states.
“We find that how we express ourselves is shaped by the weather outside,” said Nick Obradovich, one of the study’s authors and a research scientist at the Massachusetts Institute of Technology, in a released statement. “Adverse weather conditions — hot and cold temperatures, precipitation, added humidity, and increased cloud cover — reduce the sentiment of human expressions across billions of social media posts drawn from millions of US residents.”
OK. This may seem like a “duh” finding. Of course people are happier when the weather is warm and sunny rather than cold and dreary. Well, not necessarily. As background information in this study points out, prior research on a possible connection between ambient meteorological conditions and people’s emotional states has been mixed. Some studies have found a relationship, while others have not.
Even when a potential link was found, it wasn’t always clear which specific weather conditions were the triggers for positive or negative emotions.
How the study was done
For the current study, Obradovich and his colleagues analyzed 3.5 billion social media posts — 2.4 billion from Facebook (collected from January 2009 through March 2012) and 1.1 billion from Twitter (collected from November 2013 through June 2016). The researchers included more Facebook than Twitter data in their study because Facebook is more likely to reflect the population at large, given that almost 80 percent of online adults use that social media platform.
All the posts in the study were made by people who selected United States as their country and English as their language. The posts were matched to metropolitan areas (75 in all) by the posters’ geographic location at the time of their postings.
To determine whether a social media post expressed positive or negative sentiments, the researchers relied on a commonly used “sentiment analysis tool” that makes that determination based on keywords in the post.
When the researchers compared the sentiments in the social media posts to meteorological data, they found that temperature, precipitation, humidity and cloud cover were each strongly linked with either a positive or negative sentiment.
For example, posts tended to get more positive as temperatures rose to 68 degrees Fahrenheit, but then fell as temperatures climbed above 86 degrees Fahrenheit.
Precipitation (snow and rain), humidity levels of 80 percent or higher, and high amounts of cloud cover were associated with more negative sentiments.
To gauge the size of the effect of weather on people’s moods, Obradovich and his colleagues compared it to the effect of other types of events on sentiments expressed through social media. They found, for example, that a day of below-freezing temperature in New York City has about the same effect on New Yorkers’ mood as the anniversary of 9/11.
Limitations and implications
The study has limitations, of course. Most notably, it included only people who participate in Facebook and Twitter, and therefore may not represent the broader U.S. population — or populations in other countries (with other climates).
Still, this is the largest study to date to look at the relationship between weather conditions and the sentiment of human expressions, and its findings are both intriguing and potentially important — particularly as climate change affects local weather patterns.
“Given the ubiquity of our exposure to varying weather conditions, understanding the influence they may have on our emotional states is of high importance,” Obradovich and his co-authors write in their paper. “Here we provide a window into this relationship via the measurement of expressed sentiment on social media.”
“We find substantial evidence that less ideal weather conditions relate to worsened sentiment,” they add. “To the extent that the sentiment of expressions serves as a valid proxy for underlying emotions, we find some observational evidence that the weather may functionally alter human emotional states.”
For more information: You can read the study in full on the PLOS ONE website.