Researchers at Dartmouth College analyzed 100,000 major league games. They found that warmer air has contributed to about an extra 50 home runs per year.
It's because when air heats up, it becomes less dense.
And baseballs go farther through thinner air, since there is less resistance to slow the ball down.
The average temperature in June, July, and August has increased by more than two degrees in the last 40 years.