Notice hundreds of more home runs in Major League Baseball lately? It can be traced, in part, to a warming planet, according to a study published Friday.
Over the past several Major League Baseball seasons, home runs have climbed significantly. Aaron Judge, for instance, broke records with his 62 homers for the New York Yankees last year.
But ace players haven't necessarily improved their game. In a peer-reviewed study published in the Bulletin of the American Meteorological Society, Dartmouth College researchers said they can connect at least 500 additional homers from 2010 to 2019 to Earth's human-caused climate change.
From 1998, the first season of the 30-team MLB through 2022 - not including 2020 which was cut by COVID - the number of home runs has varied each year from 4,186 in 2014 to 6,776 in 2019.
How is the climate changing America's pastime?
If current climate trends continue, researchers said, there will be 192 additional long balls per year by 2050 and 467 more per season by 2100, according to the study. Currently, however, researchers attribute only 1% of recent home runs to climate change.
"There's a very clear physical mechanism at play in which warmer temperatures reduce the density of air. Baseball is a game of ballistics, and a batted ball is going to fly farther on a warm day," said senior author Justin Mankin, an assistant professor of geography.
Last year was Earth's fifth hottest year on record, according to NASA. Researchers explain that it's no coincidence the spike in homeruns coincides with warming temperatures. Warm air is less dense than cool air. As air heats up and molecules move faster, the air expands, leaving more space between molecules, resulting in a batted ball being able to fly farther on a warmer day than it would on a cooler day thanks to less air resistance.
Lead author Christopher Callahan, a doctoral candidate in geography at Dartmouth, said the researchers considered factors including the use of performance-enhancing drugs, the construction of bats and balls, and the adoption of cameras, launch analytics, and other technology intended to optimize a batter's power and distance.
"We asked whether there are more home runs on unseasonably warm days than on unseasonably cold days during the course of a season," Callahan said. "We're able to compare those days with the implicit assumption that the other factors affecting batter performance don't vary day to day or are affected if a day is unseasonably warm or cold."
"We don't think temperature is the dominant factor in the increase in home runs — batters are now primed to hit balls at optimal speeds and angles," Callahan said. "That said, temperature matters and we've identified its effect. While climate change has been a minor influence so far, this influence will substantially increase by the end of the century if we continue to emit greenhouse gases and temperatures rise."
"It's important for us to recognize the potentially pervasive way that climate change has altered, or will alter, all the things we care about that are not necessarily encapsulated in heat waves or megadroughts or category 6 hurricanes," Callahan, an avid baseball fan, said. "The effects of global warming will extend throughout our lives in potentially subtle ways."
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