The Climate Crisis Is Increasing Home Runs in Baseball

Why have the number of home runs struck at baseball games gone up since the 1980s? 

There are many possible factors, from steroids to alterations in bat and ball design to improved analytics. But one part of the answer may surprise you: climate change.

“There’s a very clear physical mechanism at play in which warmer temperatures reduce the density of air. Baseball is a game of ballistics, and a batted ball is going to fly farther on a warm day,” Dartmouth College assistant professor of geography Justin Mankin said in a press release. 

Mankin is the senior author on a unique study published in the American Meteorological Society Friday that found that more than 500 home runs since 2010 could be attributed to warmer temperatures from the burning of fossil fuels. That amounts to an extra 58 runs a year between 2010 and 2019, The Guardian pointed out. Or around one percent of recent extra runs. 

“We don’t think temperature is the dominant factor in the increase in home runs — batters are now primed to hit balls at optimal speeds and angles,” lead author and Dartmouth geography doctoral candidate Christopher Callahan said in the press release. “That said, temperature matters and we’ve identified its effect. While climate change has been a minor influence so far, this influence will substantially increase by the end of the century if we continue to emit greenhouse gases and temperatures rise.”

By 2100 under these conditions, 10 percent of home runs or more could be attributed to the climate crisis. 

The study authors looked at 100,000 major league games and 220,000 hits, and then saw which home runs occurred during warmer than average temperatures. They then compared the changes in air density to other factors that could have influenced the runs. 

Syracuse University assistant professor of geography Ethan Coffel, who was not involved with the research, told CNN that the findings were convincing. 

“The authors show that the effect of warming on home runs is less for indoor stadiums and night games, making a somewhat controlled experiment,” Coffel said. “There may have been other changes to gameplay or equipment which could have also affected trends in home runs, but one might not expect those things to differ between indoor and outdoor stadiums or night versus day games.”

These findings also hint at ways stadiums could reduce runs in the future, by either increasing night games or building domed roofs. The researchers could also predict which current stadiums would see the biggest impact because of their design and schedule. Chicago’s Wrigley Field would see the most because it is open air and rarely schedules night games. If temperatures rose to four degrees Celsius above pre-industrial levels, home runs there could increase by 15 per season. 

Of course, if we see four degrees of warming by 2100, we’ll have much larger concerns than entering an era of what Dartmouth called “climate-ball,” including the health and safety of players and fans on hotter game days. However, the study authors say focusing on how the climate crisis might alter America’s Pastime is one way to raise awareness of its effects.

“It’s important for us to recognize the potentially pervasive way that climate change has altered, or will alter, all the things we care about that are not necessarily encapsulated in heat waves or megadroughts or category 6 hurricanes,” Callahan said in the press release. “The effects of global warming will extend throughout our lives in potentially subtle ways.”