Baseball has been evolving ever since its inception in the mid-19th century. Most recently, rule changes have made the game more interesting for viewers. But the game is also changing due to a much less discussed factor: the Earth’s changing climate.

New changes were made in 2023 with the goal of reducing dead time during games. Some of the changes include a 15 second pitch clock with no one on base and 20 seconds with runners on. The bases were also increased in size, and infielder shifts were banned.

So far, the changes have worked. The average MLB game in 2023 is now more than 30 minutes shorter than 2022. Games clock in at just two hours and 37 minutes, the shortest average game time since 1978. However, the game is evolving in more ways than just rule changes, and these changes could have a far more drastic effect on baseball for years to come.

According to a study in the Bulletin of American Meteorological Society that looked at 60 years of baseball data and air temperatures, higher temperatures and thinner air accounted for 1 percent of home runs from 2010-2019.

While this may not sound like a huge number, you have to remember that home runs in the modern era of baseball have become one of the most important skills that a player can possess. There were 4,552 home runs hit in the 2011 regular season, compared to 6,776 home runs in 2019. So the 1 percent of home runs that are a result of climate change account for more than 500 home runs directly linked to warmer air temperatures in just a 10 year period.

To be more precise, for every degree Celsius warmer it is, there is a 1.8 percent higher chance of a home run being hit.

The idea for this study started with a comment made on the air in 2012 by baseball commentator Tim McCarver, where he said, “I think ultimately it will be proven that the air is thinner now, there have been climatic changes over the last 50 years in the world. And I think that’s one of the reasons that balls are carrying much better now than I remember. The ball that Ramirez hit out, the ball that (David) Freese hit out, I didn’t think either one was going to be a home run, and yet they made it.”

The fan reception to what McCarver said wasn’t good, but one person who did hear it was Christopher Callahan, a climate science PhD student at Dartmouth College. Callahan, a die hard Cubs fan who grew up walking distance from Wrigley Field, decided to see if what McCarver said held any actual merit. Callahan looked at numbers from more than 114,000 Major League Baseball games from the last 60 years, and looked at days where the weather was unusually warm or cold for the climate that they were being played in to try and see if there was any correlation between the weather and the amount of home runs. Callahan found pretty quickly that the answer was yes.

Justin Mankin, a climate scientist at Dartmouth who worked with Callahan, summarized the science behind the phenomen simply. “Warmer air is less dense than cold air,” he said. “This means there’s more space between the air molecules, and so the ball is going to encounter less air resistance and it’s going to fly farther.”

Another reason why the warmer weather could affect the numbers could also be due to heat stress. Pitchers need to be on the field for long periods of time in the hot sun, while hitters get long breaks between their at bats. This results in pitchers getting more fatigued in shorter amounts of time than before, and giving hitters more of an opportunity where they can take advantage of a tired pitcher.

More evidence for this phenomenon can come by looking at the different ballparks and the home run numbers at each of them. Wrigley Field, which has the most day games played out of any major league ballpark, has seen the biggest increase. Tropicana Field in Tampa, Florida, the only full time domed park in the MLB, has seen no statistically significant increase in home runs.

So, what does this mean for the future of the MLB? Well, in some possible climate change scenarios, by the year 2050 there could be nearly 200 home runs that were aided by warming temperatures, and by the year 2100 there could be upwards of 450 home runs that are a result of warmer air. This could mean that as temperatures rise, more MLB teams decide to opt for a domed stadium as a result of the temperatures and more volatile climate.

Whatever MLB teams decide to go with to combat this phenomenon, you can be sure that the trend of more home runs isn’t going away anytime soon.