A new study identifies the influence of climate change in the greater number of home runs in major league baseball in recent years. The researchers found that more than 500 home runs since 2010 can be attributed to warmer, thinner air caused by global warming, and that rising temperatures could account for 10% or more of home runs by 2100 if greenhouse gas emissions continue unabated. The researchers examined how the average number of home runs per year could rise for each major league ballpark with every 1-degree Celsius increase in the global average temperature.
Home runs are exhilarating – those lofting moments when everyone looks skyward, baseball players and fans alike, anxiously awaiting the outcome: run or out, win or loss, elation or despair.
Over the past several Major League Baseball seasons, home run numbers have climbed dramatically, including Aaron Judge’s record-breaking 62 homers for the New York Yankees in 2022.
Our new study, published April 7, 2023, offers solid evidence for another cause – rising global temperatures.
What we learned from 100,000 baseball games
The physics tell a simple and compelling story: Warm air is less dense than cool air. As air heats up and molecules move faster, the air expands, leaving more space between molecules. As a result, a batted ball should fly farther on a warmer day than it would on a cooler day owing to less air resistance.
This simple physical link has prompted speculation from the media about the connection between climate change and home runs.
But while scientists like Alan Nathan have shown that balls go farther in higher temperatures, no formal scientific investigation had been performed to prove that global warming is helping fuel baseball’s home run spree – until now.
Inourstudy, published in the Bulletin of the American Meteorological Society in collaboration with anthropologists (and baseball fans) Nathaniel J. Dominy and Jeremy M. DeSilva, we used data from over 100,000 Major League Baseball games and 200,000 individual batted balls, alongside observed game day temperatures, to show that warming temperatures have, in fact, increased the number of home runs.
The San Diego Padres’ Ha-Seong Kim celebrates a game-ending home run on April 3, 2023. AP Photo/Gregory Bull
So, what about everything else that drives home runs?
We can’t run a controlled experiment where we replay each pitch cast since the 1960s and vary only the temperature to assess its effect on home runs. But we can use the trove of data on home runs and temperature to statistically estimate its effect. Whether a game is hotter or cooler than average is not likely to be related to other factors driving home runs, like ball construction, steroid abuse, game analytics or elevation differences among ballparks. This fact allows us to statistically isolate the role of temperature.
To verify our game-level model, we use data from high-speed cameras that ballparks have had since 2015. The cameras provide the launch angle and launch velocity of each hit – 200,000 of them were included in our study. This means we can compare a ball coming off a bat at the same angle and velocity on a warm day and a cool day – near-perfect experimental conditions.
The high-speed camera model nearly exactly replicated the effect of temperature on home runs that we estimated with the game-level data. With this observed relationship between game day temperatures and home runs in hand, we were able to use experiments from climate models to estimate how many home runs have occurred because of climate change so far.
We found that more than 500 home runs since 2010 could be directly linked to reduced air densities driven by human-caused global warming.
More homers in a warming future
We can use the same approach to make estimates about home runs in the future.
For example, if the world continues to pump out greenhouse gas emissions at a high rate, the temperature will continue to climb, and that could soon yield several hundred additional home runs per year. It could add up to several thousand home runs cumulatively over the 21st century.
Increase in average number of home runs per year for each U.S. major league ballpark with every 1-degree Celsius (1.8 F) increase in global average temperature. Domed parks control the temperature on the field, so warming is less of a factor. Christopher W. Callahan, CC BY
Teams have ways to counter the heat. They can shift day games to be played at night, for example, or build domes over ballparks. In Denver, where the air is less dense because of its higher elevation, the Rockies started storing game balls in a humidor in 2002 to make them “mushier,” increasing their weight and giving pitchers more of a sporting chance.
It’s not all high-fives
More home runs might sound exciting, but that boost in homers is also a visible sign of the much larger problems facing sports and people worldwide as the planet warms.
The alarm bells were ringing long before David West’s death last May, but when the pitcher passed away it was almost like a final straw.
He was the sixth former Philadelphia Phillies player to die from brain cancer, and the discussion went national.
Dr. Marc Siegel told “Fox and Friends” shortly after West’s death that an investigation needed to be done.
“It’s a cluster, and it needs to be examined,” he said. “The amount of incidents of deadly brain cancer are about three out of 100,000. This is three or four times that or more.”
At the heart of the piece was the turf field that was used at Veterans Stadium. The Inquirer found pieces of the old turf, which were sold as souvenirs, and purchased them online. The newspaper then had those pieces of turf tested by two different labs.
And they found something sinister in the fake grass which they say was produced by Monsanto.
March Madness means 68 teams vying to become champion, Cinderella runs for a few underdogs and big business for the NCAA, which earns 85% of its annual operating budget during the men’s basketball tournament.
But all of that comes at a tremendous cost: An estimated 463 million pounds (210 million kilograms) of carbon dioxide equivalent emissions are released into the atmosphere during the three-week event. That’s similar to all the emissions of a large university – such as 2019 champion University of Virginia – for an entire year.
A colleague, Alex Cooper, and I came up with this figure based on data for the 2019 NCAA Tournament.
Past research on the carbon footprint of sporting events has primarily focused on one-city events, such as the Football Association Challenge Cup in the U.K. and centralized events like the Olympics. Little prior research has sought to determine the environmental impact of a large-scale sporting event like the NCAA’s men’s basketball tournament.
In addition, when sports organizers do calculate and report emissions for their events, they typically only report what happens at their facility during the event. They don’t consider the environmental impact, for example, of travel to and from the event.
So, we wanted to know, what’s the carbon tally for a huge and popular event like March Madness?
For our peer-reviewed study, which was published in October 2021 in the Journal of Cleaner Production, we aimed to estimate the carbon emissions for all the activities that go into running a massive basketball tournament that takes place in multiple cities across the country in a short span of time. While our estimates are based on 2019, we believe that tournament-generated emissions are comparable to other years, including 2023.
We looked beyond facilities to consider team and fan flight and automobile travel, facility operations, food consumption, waste generation and lodging for everyone based on each team’s progression through the 2019 tournament. We used attendance estimates to determine the impact of hotel stays, fan and team airand automobile travel, waste generation, food consumption and sport facility operations to form our carbon emission model.
Based on our model, we found that this resulted in 463 million pounds of CO2 equivalent emissions. That’s about 1,100 pounds (499 kilograms) for every player, coach and fan who attends. That amount is the same as driving over 1,200 miles (1,930 kilometers) in a typical sedan.
The biggest source of emissions by far was, as you might expect, fan and team travel, which accounted for about 79.95% of the total. The next-largest was hotel stays at 6.83%, followed by food at 6.37%, stadium operations at 5.9% and general waste at 0.95%.
What surprised us most was that the category of travel as a share of the total was lower than in previous studies that analyzed the carbon footprint of sporting events. But that was primarily because, unlike in those other studies, we considered many other aspects of the event, such as lodging, food and waste.
Ways to mitigate impact
So what can the organizers of March Madness – or any tournament, really – do to reduce the carbon footprint?
Since travel makes up so much of that footprint, targeting emissions from long-distance travel, such as flights, may be one of the most effective ways to lower the event’s overall impact, as other researchers have noted.
While travel can’t be completely eliminated for a tournament like the NCAA’s, organizers could consider more regional placements to reduce the distances fans and teams must travel. For example, in 2019, Mississippi State, Liberty, Virginia Tech, Saint Louis and Wisconsin all traveled to San Jose, California. The idea would be for more games to take place regionally to decrease travel distances. This would not only reduce carbon emissions but could also increase profits by making it easier for more fans to attend.
And when evaluating host cities and sites, the NCAA could consider local policies that encourage sustainable hotel operations. For example, during the 2019 tournament, California host sites had more energy-efficient hotel operations, thus reducing the second-highest contributor to overall emissions. The same could be said about selecting arenas and sport facilities that are energy efficient.
March Madness brings tremendous value and enjoyment to college basketball fans throughout the country. While its carbon footprint can never be eliminated, there are ways to reduce its overlooked environmental cost.
Brian P. McCullough, Associate Professor of Sport Management and Director, Center for Sport Management and Education and the Laboratory for Sustainability in Sport, Texas A&M University
As fans flock back to large venues, many are seeing new or updated waste initiatives. Operators are experimenting with different collection systems, reusable cups, reverse vending machines and more.
The large number of balls lost annually means microplastics are being introduced into waterways at an alarming rate, according to the Danish Golf Union.
As fall progresses and the cold Midwest winter approaches, boating might not be top-of-mind. But here’s something to look forward to when the weather is favorable: a new “carbon-free shared recreational boating service” in Saugatuck, Michigan.
Last year, the founders launched startup Lilypadafter toying around with the concept for years. Users rent six-person, low-speed watercraft that operate on solar power, with lithium-ion phosphate batteries for reserve power. The idea is to give more people easy, affordable access to Michigan’s waterways while reducing traditional watersports’ carbon impact.
Sports venue operators interested in running their spaces more sustainably have long been left mostly on their own in figuring out how to do so.
Oak View Group wants to change that with the launch of GOAL (Green Operations and Advanced Leadership), a membership platform that will help venues operate in more environmentally friendly ways by accessing Amazon Web Services (AWS)-powered software that includes a tactical roadmap, a library of resources like vetted vendors lists, progress tracking tools and the free exchange of knowledge and experience among GOAL member venues. OVG partnered with the Atlanta Hawks and State Farm Arena, Fenway Sports Group, and green building architect Jason McLennan, all of whom have equity in GOAL, to get the initiative off the ground.
North Carolina State University Extension has developed a fact sheet to provide professional turf managers with management strategies that preserve and protect water resources. It includes best management practices for:
At least 50 high school football players in the U.S. have died from heat stroke in the past 25 years. And high school athletes in other sports are not immune from the risks – female cross-country athletes are twice as likely to suffer from heat-related illnesses as athletes in any other high school sport.
We study sport ecology and legal aspects of sport. With summer temperatures rising, we believe many youth sports leagues and school districts will need to aggressively update their practice rules and heat policies to keep their players safe. We suggest particular attention be paid to low-income, minority neighborhoods and regions that can get excessively hot.
Heat risks in youth sports
Each year, summer marks the return of discussions of just how severe the sweltering heat is. Nine of the 10 hottest years on record globally have been since 2012, and this year’s late-spring and early-summer heat waves were previews for what forecasters warned would be a brutal summer of 2022.
Yet many interscholastic and preparatory sport summer camps have kids running hard through the summer months, sometimes on days that reach triple-digit temperatures.
In a period of rapid climate change, ensuring heat risks remain preventable is critical.
Recognizing the warning signs can be especially challenging for children and teens. Young people are still learning how to communicate their feelings and experiences, and that can be more difficult in sport environments that promote toughness and perseverance. Ultimately, young athletes must trust adults to protect them.
Evidence suggests the prevalence of exertional heat stroke among high school athletes is largely due to young athletes’ not acclimatizing, or physically adjusting to the heat, particularly in the first few weeks of practice. Although heat policies related to temperature and hydration exist at the high school level, they aren’t always enforced. And they may need to be improved to reflect the warming climate given the rate of heat illness.
Adults’ responsibility to keep children safe in sport settings becomes blurry as the growth in legal challenges related to heat illness demonstrates a disconnect between adults’ duty of care and athletes’ well-being. Negligence is a common claim associated with these lawsuits. Allegations of child endangerment or wrongful death can lead to civil or criminal legal disputes. But can reactive legal action prevent these heat injuries in the long run?
The fact that heat injuries are preventable is often why legal cases alleging negligence and wrongful death are successful. Still, heat stress, heat exhaustion, heatstroke and sunstroke are not uncommon in sports. Medical researchers have described heat illness among athletes as one of the most prominent pieces of evidence of climate change’s hazards and effect on sport.
Climate injustice for young athletes
Extreme heat can also enhance existing injustices and inequities.
For athletes, the consequences of extreme heat can further complicate environmental and climate injustice. For instance, racial minorities and those in lower socioeconomic brackets have greater chances of living in the warmest areas, including urban heat islands, where heat trapped by pavement and buildings can make temperatures several degrees hotter than the city average.
The heat index is a combination of heat and humidity. Heat-related hospitalizations begin rising at lower heat index values in normally cooler parts of the country. Climate Central, CC BY-ND
At the same time, efforts are underway to diversify the sport landscape and provide equitable access to sport and recreation for all people. A vicious cycle spins between social justice – efforts to diversify sports – and environmental and climate justice, in which the most vulnerable communities face the greatest climate harm and health risks but are underresourced and ill-equipped to adapt to the changing climate.
Moving forward
Sports leagues and athletes have taken a stand on many social issues, but they are often reactive when implementing and advocating for change.
The heat-related deaths of collegiate and NFL football players, notably Minnesota Vikings player Korey Stringer, have drawn some attention to the risks. Tokyo 2020 Olympians and FIFA World Cup organizers have cited the need for regulatory changes because of the effects of extreme heat on athlete health. But it’s often only after a tragedy that improvements are made to protect young athletes from heat illness.
The sport sector can make immediate practical and policy-related adaptations to extreme heat to protect children. These include modifying practice schedules, increasing the number of water breaks, revising athletic heat policies to reflect climate change, and implementing procedures to ensure compliance by coaches and athletic administrators.
Texas A&M students Ariana Taylor and Ashwin Mathew in the DeBakey Executive Research Leadership Program contributed to this article.
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