Higher temperatures are leading to more home runs in baseball

Baseball’s heaviest-hitting sluggers have been getting some help from climate change. New research finds hundreds of Major League home runs wouldn’t have made it over the wall without hotter temperatures, which reduce air density and lessen drag.

“If you’re a fan of baseball, this has impacted you,” says Justin Mankin at Dartmouth College in New Hampshire.

Mankin and his colleagues considered data on weather and hits from more than 100,000 Major League games played outdoors between 1962 and 2019.

Using statistical methods, they isolated the effect of temperature from other variables, such as changes in training. They also analysed the trajectory of more than 220,000 balls recorded by high-speed cameras since 2015 to further isolate the effect of temperature.

They found an additional 1°C increase in the high temperature for a given day increased the number of home runs during a game by just under 2 per cent.

The researchers then used climate models to look at temperatures with and without the influence of human-caused emissions. Cooler temperatures due to aerosol emissions led to fewer home runs from the 1960s to 1995. Warming from then on increased the number of home runs, adding an average of 58 home runs a year between 2010 and 2019.

Under a very high emissions scenario, they project an additional 467 home runs a year due to hotter temperatures by 2100. Under a low-emissions scenario they project an additional 130 home runs by 2100.

“The physics is pretty much indisputable,” says Alan Nathan at the University of Illinois Urbana-Champaign. Hotter temperatures reduce air density, decreasing drag on the baseball and enabling it to fly further, he says.

Commentators had speculated this effect might have played a role in the “explosion” of home runs seen between 2015 and 2019, which had raised concern that games were becoming too boring.

However, Nathan says the change in home runs attributable to climate change is tiny compared with other factors, such as batters swinging for the fences more often, or even how subtle differences in a baseball’s stitching affect drag. “From a practical point of view of the game it’s hardly worth worrying about,” he says.

Scoreboard aside though, hotter temperatures affect players, ballpark staff and fans in other ways, says Brian McCullough at Texas A&M University. “We don’t want to see climate change affecting our sports,” he says.