Activists say climate change is causing increased home runs in major league baseball games, but the so-called science ignores the the actual mechanics of how baseball works.
Climate Central published a report saying 26 of the 27 MLB cities have experienced increased temperatures during baseball season from 1970 to 2024. The result, it says, is a 1% increase in home runs between 2010 and 2019.
Hot temperatures can indeed impact how baseballs fly. Warm air is less dense and reduces drag on the ball, making it fly farther. But a change in the number of home runs has far more to do with the ball than with the climate.
In the 2010s, MLB experienced a 46% increase in home runs, higher than the 44% spike from the steroid era in the 1990s, Sports Illustrated reported. That included a record-breaking spike in 2019, breaking a previous record set in 2017.
An independent study, commissioned by the MLB, found that the increase was the result of changes to the ball. The 2019 ball had lower stitches that led to reduced drag, making the ball travel farther than previous years. That change accounted for 60% of the increase in home runs, with the other 40% coming from changes in hitting strategies.
“Just to give you an idea, the change in seam height of a fraction of the thickness of a sheet of paper like this would give you a measurable effect in the change in the drag,” said Alan Nathan, professor emeritus of physics at the University of Illinois and one of the researchers of the study.
The original climate change study admitted the ball stitching had a greater impact on ball performance than increased temperatures.
“Other factors such as changes in the height of the stitches on the baseball appear to have been more important in driving recent home run trends,” the study said.
But Climate Central dismissed the MLB’s study as “ongoing research” that was simply “testing various explanations” for the increase in home runs.
This year could be the second-hottest on record behind 2024, according to climate scientist Zeke Hausfather. If the climate change home run theory is accurate, the MLB should be seeing an increase of about 58 home runs this year.
But “home runs as a percentage of fly balls hit in March, April and May are at an eight-year low” across 28 of 30 MLB stadiums, The Athletic found.
Instead of seeing less drag due to hot temperatures, the 2025 season has seen more drag on the ball. Baseballs are coming up about four feet short compared to the previous nine seasons, according to a review by The Athletic of public MLB data.
The league has identified a possible, tiny change to the ball’s seam width or height but has not made any conclusions, The Athletic said.
The increase in drag comes after MLB has altered the ball to reduce year-to-year swings in drag, the outlet reported.
“MLB bought the ball manufacturer, changed the bounciness of the inner core and installed humidors in every park,” the outlet said.
Drag became less varied in the four seasons after those changes, and the league has yet to identify the causes of this year’s increased drag.
Nathan told The Athletic that, correcting for air density, game-time temperature, and elevation, the ball traveled more than three feet farther in 2024. Still, he said there is more research to do.
“I would not take this to be the definitive word on the subject, as there is much more analysis one might do,” Nathan said.