If Global Warming Is Causing More Homeruns in MLB, It’s Also Causing More Strikeouts

Guest “Just a bit outside! ” by David Middleton

After reading Anthony’s excellent takedown of the claim that climate change is causing more homeruns in Major League Baseball, one thing really stood out: The authors of the BAMS paper didn’t know jack schist about baseball.

Here’s the abstract of the BAMS paper:

Global warming, home runs, and the future of America’s pastime

Christopher W. Callahan, Nathaniel J. Dominy, Jeremy M. DeSilva, and Justin S. Mankin

Online Publication: 07 Apr 2023
DOI: https://doi.org/10.1175/BAMS-D-22-0235.1


Home runs in baseball—fair balls hit out of the field of play—have risen since 1980, driving strategic shifts in gameplay. Myriad factors likely account for these trends, with some speculating that global warming has contributed via a reduction in ballpark air density. Here we use observations from 100,000 Major League Baseball games and 220,000 individual batted balls to show that higher temperatures substantially increase home runs. We isolate human-caused warming with climate models, finding that >500 home runs since 2010 are attributable to historical warming. Several hundred additional home runs per season are projected due to future warming. Adaptations such as building domes on stadiums or shifting day games to night games reduce temperature’s effects on America’s pastime. Our results highlight the myriad ways that a warmer planet will restructure our lives, livelihoods, and recreation, some quantifiable and easily adapted to, as shown here, many others, not.

*Corresponding author, Christopher.W.Callahan.GR@dartmouth.edu


Their claim can easily be refuted with baseball statistics.

Inside Baseball

Most of what follows deals with the intricacies of baseball and, more specifically, baseball statistics. If you are unfamiliar with the subject, and you ask nicely, I’ll try to explain the terminology in the comments section. If I tried to explain it in the main body of the post, I’d never finish writing it.

I’m fairly certain that Earl Nash isn’t a climastrologist, but he had it figured out 10 years ago.

Home/Red Sox News

Pitching Mound History–balance between pitchers and batters


By Earl Nash

Dec 13, 2013

The last time MLB made a major rule change for the Pitchers’ mound was 1969.  In 1904 the height of the mound was limited to no more than15 inches higher than the level of the baselines and pitchers were prohibited from soiling a new ball.

In reaction to the complete dominance of pitching over hitting in 1968, MLB attempted to recalibrate the balance to favor the hitters by lowering the mound 5 inches to a height of 10” inches above baseline.

This was one change that was part of a general policy to make the game more exciting for fans by increasing the number of hits and runs scored, which later led to the intrusion of the DH rule in 1976.

Media consultants told MLB that only purists enjoyed shutouts and close, low-scoring games—“pitchers’ matches”—and that the majority of fans wanted to see more scoring and more HRs.

When the Steroid Era arrived and Mark McGwire and Sammy Sosa were “chasing the Babe,” Commissioner Bud Selig promoted the race and, since it was creating more fan interest and revenues for MLB, he continued to turn a blind eye to the readily apparent used of steroids.

Prior to the Steroid Scandal in MLB, most sudden changes in the delicate balance between the pitcher and the batter was attributed to “juiced” baseballs, “corked” bats, and the height of the mound.


Red Sox News

Personally, I love a good pitchers’ duel. I once had the pleasure of seeing Roger Clemens and Nolan Ryan in an awesome pitchers’ duel at the old Arlington Stadium.

Ryan and the Rangers defeated Clemens and the Red Sox by a score of 2-1, on Rafael Palmeiro’s 2-run homer in the bottom of the 8th inning. Arlington Stadium was a small ballpark. Even though we were sitting in the right field bleachers, the sound of their fastballs popping in the catchers’ mitts was remarkable. Ryan struck out 11 Red Sox in 8 innings; while Clemens struck out 6 Rangers in 9 innings. The funny thing is that homeruns and strikeouts go together like baseball and hot dogs… Or like baseball and statistics for that matter.

The Stats

For major league baseball statistics, my go-to website is baseball-reference.com. For climate data, I relied on Wood For Trees.

The number of homeruns per team-game has been steadily increasing since Cro-Magnon Man threw out the first pitch in 1871 and this has coincided with the warming depicted in HadCRUT4 NH and most other temperature anomaly records:

Figure 1. Homeruns per Team-Game (1871-2022)

Allegedly some of the increase in homerun frequency since 1962 is the result of warmer, less dense air converting some long flyballs into homeruns. OK… ‘splain this then:

Figure 2. Strikeouts per Team-Game (1871-2022)

The number of strikeouts per team-game has also increased along with the alleged rise in temperatures; while the ratio of strikeouts to homeruns has remained relatively flat since 1920.

Figure 3. Strikeouts per Homerun (1920-2022)

Anyone who’s ever been a serious baseball fan, knows that there is a strong tendency for power hitters to strikeout more frequently than contact hitters; although this is not a universal rule.

JUN. 25, 2019, AT 3:18 PM

You Can’t Have Home Runs Without Strikeouts

Literally so. The ratio between the two hasn’t changed throughout history.

By Michael Salfino

Filed under MLB

The defining characteristics of baseball in 2019 are the home run and the strikeout. Both are at all-time highs as of Tuesday. Make no mistake, the two statistics are closely related — and have been throughout baseball history.

This season, as of Tuesday, there are 6.4 strikeouts per homer. The average in the Live Ball Era, which began in 1920, is 6.5. So when adjusting homers in relation to strikeouts, 2019 is nearly a perfectly average year, ranking 45th out of the last 100 seasons in terms of most strikeouts per homer leaguewide. And note that just four of the top 20 seasons with the fewest strikeouts per homer have occurred after the Expansion Era began in 1961: 1961 (5.51 strikeouts per home run), 2000 (5.51), 1987 (5.62) and 1999 (5.62), according to Baseball-Reference.com.


When will the feedback loop of strikeouts begetting homers end? Never, if we’re to believe the sport’s preeminent sage, Bill James, who predicted these changes many years ago. He referred to it as “the push/pull effect.” Baseball now knows that getting more strikeouts has come to define being a better pitcher. But decision-makers are well beyond the point in which they believe the best hitters strike out less. In fact, teams now seem to be acknowledging what James has long contended — “strikeout-prone hitters are slightly better.” Simply put, hitters don’t care a whit about whiffing.

“So you have upward push on the strikeout column from pitcher selection, but no downward push from batter selection,” James wrote. “The result of this is that strikeouts go up over time.” And, apparently, so do homers.

Check out our latest MLB predictions.

Michael Salfino is a freelance writer in New Jersey. His work can be found on The Athletic and the Wall Street Journal. 


The full article is well worth reading.

From what I recall, Nate Silver, the founder of FiveThirtyEight.com, and I shared the same gateway drug to statistics: Baseball, particularly Bill James and Sabermetrics.

It stands to reason, that if climate change was converting long flyballs into homeruns, it would also be converting shallow fly balls into long flyballs and we would see an increase in the number of sacrifice flyouts.

Figure 4. Sacrifice Flyouts per Team-Game (1954-2022).

Looks like climate change is very selective in how it converts flyballs into homeruns. It must only be “juicing” long flyballs.

If climate change is causing more deep flyballs to sail over the fence, then the ratio of homeruns to flyballs (HR/FB) should be increasing… Right? I could only locate HR/FB data back to 1988. This should be good enough, because that’s the year that Al Gore and James Hansen invented Gorebal Warming.

It would appear that the HR/FB ratio is not changing in a statistically meaningful manner.

Figure 5. Homeruns per Flyball (1988-2022)

The historical increase in the rate of homeruns can clearly be explained by:

  • Changes in baseball rules designed to make “the game more exciting”
  • Improvements in physical conditioning, training and equipment
  • The gradual acceptance that an increase in strikeouts is a good tradeoff for more homeruns


The claim that global warming is “juicing” MLB homeruns would appear to be…

“Just a bit outside.”
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April 14, 2023 2:20 am

“climate change is causing more homeruns”

An interesting and highly local claim. Take cricket, a game that also involves hitting a ball with a bat to get runs. Hit the ball out of the field and you get 6 runs. This game is played around the world, and guess what? That hasn’t changed one iota. No, the cricket world has an entirely different climate change bogeyman…

Many Test nations lie at particularly climate-vulnerable latitudes – Pakistan, India, Bangladesh, West Indies, Sri Lanka, South Africa – and global temperature rises are having a devastating impact.

At the sharp end are cricket’s groundstaff, out in the elements all year, the changing climate their new reality. BBC Sport spoke to three, in the UK, Australia and South Africa, about how the climate crisis is affecting the way they work and their worries for the future.

“We have to work hard to manage the grass, whereas 15 years ago the climate did it for us.”

The claim in the paper is as funny as the title of world series. And equally untrue. How are the baseball fields holding up?

Reply to  David Middleton
April 14, 2023 4:12 am

They haven’t stopped playing cricket – yet. And they won’t.

I do like the BBCs turns of phrase…. climate-vulnerable latitudes

Last edited 1 month ago by strativarius
Reply to  strativarius
April 14, 2023 4:34 am

Did they go to all natural fertilizers on cricket fields in Sri Lanka?

Reply to  Scissor
April 14, 2023 4:54 am

I heard they stopped for tea….

Reply to  strativarius
April 14, 2023 12:26 pm

We have been told that the “climate-change” warming is most severe in the Arctic, i.e., it is the most climate-vulnerable region on Earth. How is that affecting the cricket there?

Reply to  strativarius
April 14, 2023 8:37 am

An interesting and highly local claim.

Good point. Wouldn’t it also affect distance of American football passes, football (soccer) goal distances, long range target shooting, archery, etc?

Reply to  Tony_G
April 14, 2023 12:27 pm

Actually, Tom Brady found that the football worked better in colder weather.

Reply to  strativarius
April 16, 2023 7:55 am

Actually cricket has changed substantially, the introduction of shorter format games for example. The surface is much more important in cricket because the ball usually bounces before the batsman hits it.

April 14, 2023 4:49 am

When baseball players transition, does this impact their on base percentage?

Reply to  Scissor
April 14, 2023 5:04 am

What I’ve noticed is Nike wanted to pay six-time Olympic gold medallist Allyson Felix 70% less after she became a mother.

Nike will have ‘other’ problems with Dylan Mulvaney – even though he/she/it cannot get pregnant

Reply to  strativarius
April 15, 2023 6:09 pm

Like what sport it is good at?

April 14, 2023 5:14 am

Baseball is both simple and complex. Simple in theory, but complex in its execution. Such that many factors affect the results in terms of both pitching and hitting. Weather is certainly a factor in outdoor stadiums, but there are a lot of indoor stadiums now that reduce the impacts of weather. The conditions of the field – wet, dry, fast or slow infield and outfield affect things.

The dimensions of the ballpark – there have always been “hitter friendly” parks and not so friendly parks – based upon dimensions and geometry of the stands and walls, are a significant factor. The elevation of the park matters, affecting the friction imparted by the atmosphere. In addition to the distance from the wall to home plate, the height of the wall that the ball must clear also matters a lot. The pitchers mound height has been a major factor. And of course the physiques and capabilities of the players collectively. Nobody can deny that the steroid era was “juiced” by illegal steroid use by at least a few of the biggest stars of the era that led to a lot more homeruns. Plus, sports science including diet, conditioning, and general health maintenance have been on an upward climb over the past 160 years of baseball.

But just addressing the notion that warmer air makes the ball travel farther, that is true, even though the affects are negligible. The aerodynamic factors involving travel of the ball are rather complex to model.


Generally speaking, a hit baseball’s travel distance will increase approximately 0.5% for every 10 deg F change. Using an assumed 1 deg F increase in temperature over the last 60 years, that would imply a 0.05% increase in travel distance – or for a 370 ft homerun, it would increase by less than 0.2 ft, or 2.2 inches. That is way down in the noise level considering all the other factors above and more.

Last edited 1 month ago by Duane
Reply to  Duane
April 14, 2023 5:19 am

So why do other games – indeed in global locations – not do the same?

And they don’t. You just underlined the folly of the paper nicely.

Last edited 1 month ago by strativarius
Reply to  Duane
April 16, 2023 7:48 am

About one third of current MLB stadiums were built in the last 20 years so distance required for a home run might well have changed in that time too.

April 14, 2023 5:59 am

If this were a real factor, then looking at it from the pitcher’s perspective, a fast ball would slow down a little bit less in thinner air, but a curve ball would not curve as much either.

Tom Halla
April 14, 2023 6:02 am

There was also the report by Roger Pielke that HRs are unchanged in Japan, or minor leagues.

April 14, 2023 6:11 am

You are absolutely right, particularly the 3rd point: “The gradual acceptance that an increase in strikeouts is a good tradeoff for more homeruns”
The statheads are guilty of this. “Sabermetric” analysis has led to the view that 3 true outcomes are what matter – home runs, walks and strikeouts.
So players that hit home runs but strike out a lot – a precedent set by McGwire and Canseco in the modern era but which could be ascribed to Reggie Jackson. Reggie Jackson actually struck out a lot more than McGwire, for example both in absolute numbers and as a percentage of at bats but McGwire hit more home runs in absolute numbers and as a percentage of at bats.
There are also factors like changing fence distances, the existence of the Colorado Rockies as an expansion baseball team, steroids and so forth.
The usual climate change apocalypse garbage masquerading as science.

Rick C
April 14, 2023 6:13 am

Presumably the Homer ratio will go up now that the National League has instituted designated hitters. Of course “Climate Change” may be the underlying cause of Baseball rule changes. More study and funding is required to properly study this important issue.

Gunga Din
April 14, 2023 7:22 am

A side note.
In addition to holding the career Homerun record for decades, he held the career strikeout record for decades … until it was broken by Mikey Mantle!

April 14, 2023 7:23 am

That’s because increased CO2 in the air is making it harder to see the ball–according to the best Yoko Ono Science. /sarc

April 14, 2023 7:55 am

Anyone studied soccer (football) and the (lack of) impact that climate change has had?

old cocky
Reply to  Colin
April 14, 2023 4:03 pm

The additional CO2 makes the grass grow more, so the field is a little softer when they flop?

April 14, 2023 9:06 am

I seem to remember reading, years ago, that while the Babe has 60 HR’s, he also led in strikeouts.

April 14, 2023 10:29 am

I wonder how many Team Catastrophic members looked at the paper and thought, I don’t know whether the premise is true or false, but the topic sure could make us look dumb by association.

April 14, 2023 11:28 am

I would not assume the authors are serious about the claim. Such publications can be done for a variety of not mutually exclusive reasons, such as click baiting, desire to be nominated for Ig Nobel prize, ridicule the notion that global warming causes everything, or just having fun.

old cocky
Reply to  Someone
April 14, 2023 4:04 pm

What was the date of publication?

April 14, 2023 12:10 pm

‘Anything corelated with anything in anyway causes everything’ is absurd and hardly worth a comment.

Reductio Ad Absurdum works as a form of argument in this case because of foundational absurdity f the argument.

I exist in realty, the concept of God exists in reality then I must have caused God to exist. LOL!

A dog lives in my yard. I walk through the yard, the dog caused me to walk walk through the yard rather than go make dinner or go to a base ball game to watch MLB’s myriad of muscle head power hitters, hit against relief pitchers who pitch at 104 MPH.

April 15, 2023 3:16 am

Here is one almost on par with the homerun BS.

Eco-Nuts Aim to Prevent UK’s Grand National Horse Race | Newsbusters

April 15, 2023 5:57 am

It’s air density that makes the difference. Hunidiity is more important than temp. Elevation is more important than hunidity, and wind speed & direction are more important than any of those (Cf- the wind blowing out at Wrigley Field.) https://www.amazon.com/Physics-Baseball-3rd-Robert-Adair/dp/0060084367

I was a .400 hitter (but I was also a .400 fielder).

We’ve been blaming the drier all these years for all those lost socks…Could it really be the washer?

general custer
April 15, 2023 9:24 am

The baseball home run/strike out situation has nothing to do with climate. It’s a function of economics. Players who can hit long fly balls are paid more than those who can’t. Much more. Ergo they swing harder, strike out frequently but hit enough uncatchable long fly balls to drive in some runs and bring the casual fans to their feet. Yankee right fielder Aaron Judge isn’t paid $40 million annually because he hits singles and doubles. It’s because he swings hard and produces really long fly balls.

April 15, 2023 12:12 pm

Just eyeballing the graph of air density vs. temperature, a 1 deg. F rise in air temperature results in a 0.2% drop in air density at 14.7 psia. Since the aerodynamic drag force is linear with air density, a 1 deg. F rise in air temperature results in a 0.2% drop in aerodynamic drag. Since deceleration is directly proportional to the drag force, a corresponding 0.2% drop in deceleration results.

How much of a change in air temperature would be needed to see a meaningful difference?

Reply to  lanceman
April 16, 2023 7:44 am

Drag is proportional to velocity squared also so that would be a factor.

April 15, 2023 7:10 pm

Bad move “Christopher W. Callahan, Nathaniel J. Dominy, Jeremy M. DeSilva, and Justin S. Mankin”!

I can think of no sport that has so many legions of detail oriented fans.

Fantasy baseball players may never run spreadsheets for any other purpose, but they do use spreadsheets for fantasy baseball where the fantasy team performance is based upon real baseball games and performance.

Fantasy players try various formulae and statistics to gauge player strengths and weaknesses as they bid for their fantasy team makeup.

This is before mentioning all of the baseball fans who’ve memorized baseball data for each team and players going back decades.
When the local paper or news channels make an error in calculating or repeating team or player performance, droves of people correct them.

one thing really stood out: The authors of the BAMS paper didn’t know jack schist about baseball.”

That statement nails it, David!

Jim Steele
April 16, 2023 9:00 am

Baseball Imitates Climate Science Alarmism

There many stats in baseball and climate that can be cherrypicked to tell a preferred narrative. Climate alarmists have cherry picked the amount of HRs

A better measure of how air density is affecting home runs would be to see if home runs are getting longer.Or if baseball outfields are getting shorter. 4 teams shortened their outfields in the early 2000s: Tigers, Mets, Padres and Mariner . Tigers an Mets each hit 50 more home runs relative to their previous year with shorter outfields.


And despite the steroid era that delivered some long home runs, the longest home runs were hit during colder times.

Babe Ruth’s 1921 575-foot still holds the record for longest
Mickey Mantle’s 1953 564-ft is 2nd
Reggie Jackson’s 1971 539-ft is 3rd
Willie Stargell’s 1978 535-ft 4th
Adam Dunn’s 2004 535-ft 4th Tied
Dave KIngman’s 1976 530-ft 5th
Darryl Strawberry 1988 525-ft 6th
Ted Williams 1946 530-ft* (upgraded from 502 for truer distance after hitting a spectator in the head shortened original estimate) Still Fenway Parks record longest

April 16, 2023 7:24 pm

Has anyone read the actual “study” and how they got the game temperatures?
It does not appear that they were measured but were estimated from models.
I do nit see how they could get accurate temperatures for the last several years especially 2015-2019 when they claim they did a lot of the home run analysis. The temperatures have not been increasing in the last 8 years and the max temp charts show they have dropped since the 1930’s. But they solved that problem the usual way by starting in the 1960’s.

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