Key facts:
- Baseball season is heating up. Since 1970, average temperatures during the Major League Baseball (MLB) season have warmed by 2.8°F on average across the 27 MLB cities.
- Warming seasons aren’t the only way that climate change affects players and fans of America’s pastime.
- Warmer air is less dense, helping batted baseballs fly farther. This effect is driving a measurable increase in home runs.
- A recent study found that warming caused by climate change added an average of 58 MLB home runs per year over the 2010-2019 period — about a 1% increase.
- The effect of warming on home runs could triple by the 2050s — adding 182 home runs annually in a scenario that assumes global goals to reduce planet-warming carbon pollution are met.
Baseball season is heating up
As the climate warms, baseball season is heating up — affecting players, fans, and even home runs.
Climate Central analyzed temperature trends in every Major League Baseball (MLB) city from 1970 to 2024.
All but one of the 27 MLB cities have warmed during baseball season (March 30 – Oct 1). On average, the 26 warming MLB cities have seen average temperatures rise by 2.8°F during the season.
The exception was Los Angeles, home of the Angels and Dodgers, which experienced no change in baseball season temperatures since 1970.
As average temperatures warm, extreme heat occurs more often --- putting players and fans at risk.
All 26 MLB cities in the U.S. are also experiencing an average of 13 more extremely hot days annually than they did in 1970.
Extreme heat is risky - from Little League to MLB
Sports and extreme heat can be a dangerous mix. Heat is the deadliest weather-related hazard in the U.S. And athletes are among those most at risk.
Exercising or playing sports outdoors in extreme heat can add increased stress to athletes' bodies, putting them at risk of dehydration and heat-related illness.
An intense early summer 2025 heat wave sent multiple MLB players off the field with heat exhaustion and illness.
- According to Climate Central's Climate Shift Index, the high average temperatures on those game days were made at least two times more likely by human-caused climate change at both Busch Stadium in St. Louis and Wrigley Field in Chicago.
As our climate warms, the rise in extreme heat is a growing concern among all athletes --- from professionals to student athletes heading back to practice in late summer across the U.S.
Extreme heat can also put ballpark staff and spectators at risk --- particularly during outdoor day games.
Warmer, less dense air helps baseballs fly farther
Warming seasons aren't the only way that climate change affects players and fans of America's pastime.
Warmer air is less dense and therefore exerts less drag on batted baseballs, allowing them to fly farther.
The number of home runs per game has increased since the 1980s. While many factors -- including the use of performance-enhancing drugs and changes in analytics and player training -- have likely contributed to the documented rise in home runs, science suggests that rising game day temperatures and decreasing air density over the same period are playing a measurable role.
Home runs are an exciting part of baseball, and can change the course of a game in an instant. But rising home run rates have implications beyond the scoreboard. Over the long term, more home runs can potentially affect gameplay, strategy, player acquisition, and public engagement with the sport.
Warming has caused a 1% rise in MLB home runs in recent years
A 2023 study found that warming --- through its effect on air density --- has in fact caused a significant (albeit small) increase in MLB home runs.
The study found that a 1°C (1.8°F) increase in daily high temperatures on game days in open-air stadiums leads to a 2% increase in home runs per game. This effect is slightly larger for day games played in the early afternoon and smaller for night games.
Between 2010 and 2019, human-caused warming led to an average of 58 additional home runs per year, or 577 in total. This is a statistically significant but small effect, accounting for about 1% of all home runs during the same time period.
Ongoing research is testing various explanations for the leading causes of the recent surge in home runs.
More home runs in a warmer future
Although the influence of warming on home runs to date is small, the effect is real and is expected to increase with future warming (in the absence of future gameplay changes such as more domed or night games).
The effect of warming on home runs could triple by the 2050s --- adding 182 home runs annually under projections that assume global pledged commitments to reduce planet-warming pollution are met. This represents about a 3% increase relative to the recent (2010-2019) annual average.
But many countries are failing to meet their commitments to reduce pollution. In alternate scenarios with very high levels of pollution and future warming, the MLB could see a 9% increase in home runs annually by the end of the century (2090s).
Baseball leagues could adapt to some extent by scheduling more night games or building more ballpark domes, but our warming climate will continue to add home runs to America's pastime --- potentially altering gameplay, strategy, public engagement, and the business of baseball.