Home runs are becoming more frequent in Major League Baseball (MLB) due to climate change, a new study finds.
"There's a very clear physical mechanism at play in which warmer temperatures reduce the density of air," study co-author Justin Mankin (opens in new tab), an assistant professor of geography at Dartmouth University in New Hampshire, said in the statement. "Baseball is a game of ballistics, and a batted ball is going to fly farther on a warm day."
The team examined data from more than 100,000 MLB games played between 1962 and 2019, and 220,000 individual hits between 2015 and 2019.
Their findings, published April 7 in the journal Bulletin of the American Meteorological Society (opens in new tab), showed that between 2010 and 2019, more than 500 homers could be attributed to higher-than-average temperatures as a result of global warming, with an average of 58 additional home runs per season, according to the study.
They discovered that a reduction in air density results from higher temperatures and "was the driving force" in why homers increased on hotter days. Additionally, climate change may have contributed to approximately 1% of home runs in that time frame. However, by 2100, that number could jump to 10% compared with averages between 2010 and 2019 if greenhouse gas emissions and climate change continue at their current pace. This could result in what researchers have dubbed the "climate-ball era," according to the statement.
Under an emissions worst-case-scenario, the team estimated there would be an additional 192 home runs per year by 2050, climbing to 467 by 2100.
To counter the impact of climate change, the researchers suggest playing more games at night, when temperatures are milder, or building domes over stadiums.
The team also accounted for outside influences that could impact a dinger, such as athletes using performance drugs and ball and bat construction to determine what if any impact those factors could have on home runs.
"We asked whether there are more home runs on unseasonably warm days than on unseasonably cold days during the course of a season," lead author Christopher Callahan (opens in new tab), a doctoral candidate in geography at Dartmouth, said in the statement. "We're able to compare those days with the implicit assumption that the other factors affecting batter performance don't vary day to day or are affected if a day is unseasonably warm or cold."
He added, "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."
Jennifer Nalewicki is a Salt Lake City-based journalist whose work has been featured in The New York Times, Smithsonian Magazine, Scientific American, Popular Mechanics and more. She covers several science topics from planet Earth to paleontology and archaeology to health and culture. Prior to freelancing, Jennifer was a reporter at Interior Design Magazine, and before that she held an Editor role at Time Inc. Jennifer has a bachelor's degree in Journalism from The University of Texas at Austin.