Heat waves and home runs: Study links climate change to big bats

From 2010 to 2019, warmer temperatures led to an additional 58 home runs per year on average, according to an analysis by Dartmouth College.
Philadelphia Phillies' Kyle Schwarber hitting a home run.
Posted at 5:45 PM, Apr 10, 2023

Hotter weather is leading to even hotter batters, according to a new study.

From 2010 to 2019, more than 500 MLB home runs can be linked to warmer temperatures, according to a statistical analysis published by Dartmouth College scientists in the Bulletin of the American Meteorological Society.

Authors of the study analyzed over 100,000 Major League Baseball games since 1962 and found that an increase of one degree Celsius led to a 1.9% increase in home runs hit. There were also more home runs during games that were played in the early afternoon when temperatures are highest.

Why? It's simple physics.

"All else being equal, warmer air is less dense, and a batted ball will carry farther," the study says. "The well-documented rise in home runs has coincided with a long-term increase in gametime temperatures at baseball stadiums and a resulting decrease in air density during games."

The scientists used advanced tracking data from the Statcast system that's installed in all MLB stadiums, and were able to hold the skill of the pitcher and hitter constant. They then compared each ball leaving the bat at the same angle and speed on cold days versus warm days and found as temperatures increase, so does the probability of home runs.

"Between 2010 and 2019, global warming led to an additional 58 home runs per year on average," the authors noted.

They also ran 1,000 computer simulations to estimate how many extra home runs we can expect if the earth continues to warm. In a worst-case warming scenario, there could be about 192 extra homers by 2050 and more than 450 by the year 2100. A more moderate scenario for global warming predicted about 155 extra homers by 2050 and around 255 by the end of the century.

While this is music to the ears of guys like Aaron Judge and Mike Trout, it could prove costly for pitchers who were probably hoping that warmer weather came with more strikeouts.

Here are the projections of how climate change could impact your home-town ball club:

Christopher W. Callahan, Nathaniel J. Dominy, Jeremy M. DeSilva, and Justin S. Mankin

While climate change could be a potential contributor to home run trends, the scientists said other factors also play a role, such as construction of the baseball, increased analytics and better technology and training. As for games that are played in domes, the scientists found that temperature had a small and insignificant effect. They also couldn't find any significant effect from wind, due to little data on wind speed and direction in parks. 

"While changes in technology and player skill will undoubtedly shape the projections we show here, our results highlight that MLB will need to contend with climate change’s influence on baseball performance," the scientists said. "Steadily rising home runs may alter the incentives for player acquisition, offensive and defensive strategy, and public perception and engagement with the game, with consequences for the business of baseball and its on-field play."

Dartmouth doctoral student Christopher Callahan authored the paper alongside Nathaniel Dominy, a professor of anthropology, Jeremy DeSilva, the head of the anthropology department, and Justin Mankin, an assistant professor who studies climate variability and the human risks associated with global warming. 

The authors received no funding or endorsements from the MLB or any affiliated organization.

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