As major league baseball gets back underway, a new study from Dartmouth looks at how climate change is showing up in the game.
Warm air is thinner than cold air, so when it’s hot outside, a baseball can fly farther. Dartmouth researchers analyzed more than 100,000 major league games between 1962 and 2019, and found about 1% of recent home runs can be linked to global warming.
If we don’t reduce greenhouse gas emissions and global temperatures continue to rise, the researchers say that could increase to 10% of home runs by 2100.
The researchers say temperature hasn’t been the most important factor in the increase in home runs — there are other changes, like differences in the construction of bats and balls, and the adoption of technology to optimize a batter’s hits.
The study controlled for those kinds of confounding factors and looked at how much home runs increased with each degree Celsius of temperature change. Then, the researchers compared that to climate model experiments that show how much climate change has increased temperatures at ballparks around the United States.
Some ballparks — like those that have domes, to keep them insulated from temperature changes, or those that host a lot of nighttime games — had less fluctuation in home runs based on temperature changes.
Chris Callahan, a PhD candidate at Dartmouth and the lead author on the study, said it’s an example of how climate change shows up not just in extreme events, but in the daily parts of life.
“When I go to a baseball game, I'll be thinking about the ways in which there might be more home runs in that game. There also might be risks to people at the ballpark from extreme heat, for example,” he said. “So it just makes me more conscious of the ways that climate change has sort of snaked its way into every part of our lives.”
Callahan said the large volume of data available on baseball helped to make it possible to do this kind of study. But there are many aspects of daily life, which could also be shaped by climate change, that don’t have the same kind of detailed records.
“The availability of data is a reflection of privilege and institutional capacity. There are lots of places and phenomena where we don't know how climate change is going to affect them because we don't have the data,” he said. “We need to be conscious of the ways in which the questions we ask and the answers we give are shaped by what kind of data we have available to begin with.”
