Global warming is 'juicing home runs' in Major League Baseball, Dartmouth study finds

Climate change is making major league sluggers into even hotter hitters, sending an extra 50 or so home runs a year over the fences, a new study found.

Hotter, thinner air that allows balls to fly farther contributed a tiny bit to a surge in home runs since 2010, according to a statistical analysis by New Hampshire's Dartmouth College scientists published in Friday's Bulletin of the American Meteorological Society. They analyzed 100,000 major league games and more than 200,000 balls put into play in the last few years along with weather conditions, stadiums and other factors.

"Global warming is juicing home runs in Major League Baseball," said study co-author Justin Mankin, a Dartmouth climate scientist.

It's basic physics.

When air heats up, molecules move faster and away from each other, making the air less dense. Baseballs launched off a bat go farther through thinner air because there's less resistance to slow the ball. Just a little bit farther can mean the difference between a homer and a flyout, said Alan Nathan, a University of Illinois physicist who wasn't part of the Dartmouth study.

Nathan, one of a group of scientists who has consulted with Major League Baseball on the increase in homers, did his own simple calculation, based purely on known physics of ballistics and air density as it changes with temperature, and said he got the same result as the Dartmouth researchers.

Both Nathan and the Dartmouth team found a 1.8-per-cent increase in home run likelihood with each degree Celsius the air warms. Total yearly average of warming-aided homers is only one per cent of all home runs hit, the Dartmouth researchers calculated.

Non-climate factors contribute even more to the barrage of balls flying out of the park,