Climate change will affect essentially every aspect of our lives, climate researchers say, even America’s unofficial pastime, baseball. Because warmer air is less dense and exerts less drag on a batted ball, the number of home runs should in theory climb as global temperatures increase. And, sure enough, a new study shows that about 0.8% of the homers hit in Major League Baseball (MLB) since 2010 made it over the fence thanks to the extra distance global warming lent their flight. Other factors, however, from the explicit effort of players to hit more home runs to the design of the ball itself, play bigger roles in explaining why home run numbers have skyrocketed in recent decades.
“From a purely baseball point of view, this is primarily an academic result, not a result that Major League Baseball should really worry about,” says Alan Nathan, a physicist at the University of Illinois, Urbana Champaign, who was not involved in the work. Nevertheless, the study shines a light on just how pervasive the impacts of climate change will be, says Gerald Meehl, a climate scientist at the National Center for Atmospheric Research who was not involved in the work. “A lot of people are pretty serious about baseball, and this could draw their attention to this problem in ways that other things just wouldn’t.”
The idea that climate change could affect baseball isn’t new. During a game between the St. Louis Cardinals and the Milwaukee Brewers in 2012, former big-league catcher and broadcast commentator Tim McCarver wondered aloud whether climate change was driving an upward trend in home run rates across the sport. At the time, many fans and some scientists were dismissive. However, the idea resonated with Christopher Callahan, a climate scientist and baseball fan at Dartmouth College.
To find out whether rising temperatures and decreasing air density played a role in home run rates, Callahan and his colleagues delved into the copious data MLB keeps. In addition to keeping home run stats for decades, since 2015 MLB has used an automated system of cameras and computers called Statcast to track the velocity and trajectory of every ball thrown or hit in every game. “MLB is obsessed with collecting data on itself, so we have this treasure trove of numbers,” Callahan says.
The researchers tracked game-day temperatures and homers from 100,000 MLB games between 1962 and 2019 at stadiums at various elevations across the country. To control for the launch angle and speed of each batted ball–and thus the skill of both pitchers and batters in varying temperature conditions –they combed through high-speed Statcast camera footage of 220,000 individual hits between 2015 and 2019. Both analyses returned the same effect: On average, a 1°C increase in air temperature on game day correlates with nearly a 2% uptick in the number of home runs per game. Each additional degree of global warming results in an additional 95 home runs per baseball season, and more than 500 home runs since 2010 can be attributed to anthropogenic warming, the researchers report today in the Bulletin of the American Meteorological Society. “I think we’ve vindicated McCarver,” Callahan says.
However, those extra homers represent a tiny fraction of the more than 65,300 hit since 2010. They also account for only a drop in the tsunami of home runs that has inundated MLB. Over the past 4 decades, home runs have increased by 34% per game.
Most of that increase has nothing to do with climate change, says Nathan, who in 2018 chaired a committee tasked by MLB officials to explain the spiking home run rates. The biggest driving factors, the committee found, were batters attempting to hit the ball harder and higher—as statistical analysis suggests teams do better if batters always swing for the fence—and small physical differences in drag caused by variations in the ball’s stitching. “It’s hard to control that variation, and that effect on the flight of the baseball is much, much, much greater than the kind of effect you get from a 1°Celsius raise in temperature,” Nathan says.
Although the impact of climate change is small now, it is detectable and will only increase with more warming, says Justin Mankin, a climate scientist at Dartmouth College and the study’s senior author. In the future, MLB might consider scheduling more night games or playing more in covered stadiums, the authors say, especially if warming continues unchecked.
The researchers also emphasize they were only able to isolate the tiny impact of temperature on home runs because of the robust data available. The study highlights a data inequity issue in climate science, Callahan says. “There are a lot of places around the world where we are missing the effect of climate change on people and their wellbeing, because we just don’t have the data to assess the impacts.”
Source: Science Mag