Baseballs are flying farther with climate change, helping home runs, study says

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Warm day at the baseball park? Your chances of seeing a home run are slightly higher.

“As soon as it gets warm, the ball carries a lot better,” Washington Nationals manager Dave Martinez told The Washington Post. “I usually tell everybody, right about the middle of May, the balls will start flying out of the ballpark.”

Players, coaches, managers and baseball fans have long observed changes in performance during sunnier versus cooler conditions. Now, a new science study explores how rising global temperatures have and will affect the number of homers.

Since 2010, more than 500 home runs can be linked to warmer-than-average temperatures because of climate change, according to the study released Friday in the Bulletin of the American Meteorological Society. That number only makes up about 1 percent of home runs over that time period, suggesting that player talent, strategy, equipment, and countless other factors have more influence in dingers. Still, researchers say rising temperatures could play a bigger role in the future.

The authors found that for every 1 degree Celsius increase in average global temperature, there could be 95 more home runs across a baseball season. If temperatures were to rise to 4 degrees Celsius of warming by the end of the century, the research says climate change could account for as much as 10 percent of home runs (but in that scenario, we would also have much bigger environmental problems).

Simple physics explain that balls tend to fly farther on warmer days because the air is less dense. On warmer days, air molecules in outdoor stadiums are pushed farther apart from one another because they have more energy. The lower air density means the ball will encounter less air resistance than it would on a cooler day and can travel farther.

“The baseball carries better in warm weather than in cold weather. That’s no secret,” said Alan Nathan, a baseball physicist who was not involved in the study. But Nathan said this is an “excellent study” and is the first, to his knowledge, to comprehensively quantify how far the ball will carry under warmer temperatures.

In the grand scheme of climate change impacts, slightly more home runs isn’t a top concern, said Justin S. Mankin, the study’s senior author and a professor at Dartmouth College. The physics of a warmer world also drive much more extreme, violent weather, which will have critical human impacts. Yet he said sometimes parsing out those effects, such as deaths from excessive heat in lower-income countries, can be difficult because of a lack of data.

But a lack of data isn’t a problem in baseball. That Mankin and his colleagues could even detect an effect “just indicates all of the ways in which climate change is going to touch just about every aspect of our lives.”

“There’s a whole host of climate impacts for which we don’t have the data to make the assessment in the first place,” said Mankin, who has published studies on climate extremes such as droughts and extreme heat. “Our ability to track the impacts of global warming and maybe help inform the management of responses to it, I think, is a function of the data we have.”

The authors looked at the number of home runs and the temperatures of individual games from 1960 to 2019, applying statistical techniques to control for factors such as the construction of the baseball or the use of performance-enhancing drugs. They found that when the temperature of a game goes up by 1 degree Celsius, the number of home runs in the game increased by 1.9 percent.

Then, the authors used computer models to assess the role of climate change in those home runs. They ran simulations with and without the effects of human-induced greenhouse gas emissions, an increasingly popular technique that scientists use to study links between extreme weather events and climate change. They found that if humans had not emitted greenhouse gases, there would have been 500 fewer home runs over the past 10 years.

Climate change is not a game changer in baseball, at least so far, lead author Chris Callahan said. For instance, the well-known home run surge beginning in the 2015 season would have still occurred. Callahan, an avid baseball fan, said the increase was probably due to changes in the height of the baseball seams, advances in analytics and other factors – “all of these things would have driven increases in home runs regardless,” he said.

“Once we look into the future, these numbers start to get bigger,” said Callahan, a doctoral student at Dartmouth College. “If we keep emitting a lot of greenhouse gases, we could be looking at 3, to 5, to 10 percent more home runs than we’re seeing right now over the 21st century due to climate change.”

Nathan said he doesn’t think these results will have much of a practical effect on the game or change how a team approaches their game.

Martinez added that he doesn’t want his players “to put pressure on themselves about trying to hit home runs. Just try to hit the ball hard and the home runs will come.”

Even so, other unrelated changes could have a bigger effect on home runs. For instance, the new pitch clock, which limits the amount of time a pitcher takes before throwing the ball, could increase the number of home runs because pitchers will have less time to recover between pitches, he said. Another possibility: The new ban on infield shifts could reduce the number of home runs.

Nathan said there are ways the structure of the baseball itself could be altered to act as a counter to reduced air density brought on by warmer temperatures. For one, the bounciness of the baseball – called the coefficient of restitution – could be lowered. One way, he said, would be to increase the humid environment that baseballs are stored in before the game. That would make the ball heavier and less bouncy, so batters can’t hit it as hard.

There are more ways to adjust for the climate-induced increase in home runs, the authors said, such as moving games into the evening, when temperatures are cooler. Wrigley Field – projected to experience the most home runs with extreme warming because so many of their games are played during the day – would benefit the most from that change, Callahan said.

Other changes could be more expensive, such as building a dome over ballparks. Domed parks, such as Tropicana Field in St. Petersburg, Fla., and LoanDepot Park in Miami, are expected to experience the least change in home runs in a warming world because they are usually temperature-controlled.

“Those are political and economic choices we would have to make,” Callahan said. Whether it’s a baseball game or sea-level rise, he emphasized that climate adaptation is a “conscious choice.”