Temperatures compared to a 1951-1980 baseline since 1880 and the average home runs per team per game since 1880. (Temperature data from NASA GISS; home run data from Baseball-Reference.com )

“There have been climactic changes over the last 50 years in the world, and I think that’s one of the reasons that balls are carrying much better now than I remember,” McCarver said.

Deadspin called McCarver’s statement “one of the most insane things ever asserted by a professional broadcaster.” The blog Watts Up With That described it as “climate craziness”. WeatherBell meteorologist Joe Bastardi tweeted: “What a stone stupid comment”.

@BigJoeBastardi @markjweather McCarver now ranks up w/Danny Glover-blamed Haiti’s earthquake on Global Warming. Send him AK ice report plz

— Justin Berk (@JustinWeather) April 29, 2012

Tweet exchange between Baltimore meteorologist Justin Berk and WeatherBell’s Joe Bastardi

But data and physics are on the side of McCarver... to an extent.

We’ve blogged previously about the fact baseballs travel farther in warm, humid air. And data show the atmosphere has trended warmer and more humid over the last 120-plus years.

In 2006, the New York Times printed a piece headlined The Weather Was Fine, and the Home Runs Were Easy. Excerpt:

When Major League Baseball made the penalties for positive tests [for steroids] far stronger after last season, predictions followed that offense would decrease in 2006.

But it has gone up instead. A lot. Almost as much as the temperature and the heat index in the United States, which could very well have been responsible for most of it.

The graph I’ve displayed at the top of this post shows how home run rates (number of home runs per team per game) have closely tracked the long-term changes in global temperature. They went up until the 1950s, leveled off through the 70s, and then ramped back up before showing a pause over the last decade or so. There are minor differences with the temperature curve but the similarities are eerie.

Related: Behind the present pause in global warming

Of course, just like blaming a decrease in the number of pirates for global warming, correlation doesn’t equal causation. To be sure, the reasons for changes in home run numbers over time are difficult to unravel and complex. Bat/ball technology, evolving quality of pitching/batting, performance enhancing substances, ballpark depth and other factors have no doubt played a role.

Related: Global warming and greenhouse gases activate steroid era of our atmosphere

While the home run/temperature correlation may be mostly a coincidence, it is overly dismissive to discount weather and climate from playing any role.

As such, McCarver’s listing climate as “one of the reasons” for increasing home run totals is not all that far-fetched. Maybe Bastardi, Deadspin, Watts, Berk et al. should dial back their criticism.

Post script: Daily Climate has a good piece about global warming, home runs, and McCarver. Two interesting snippets which muddy the waters a bit...:

* Robert Adair, a retired physics professor from Yale University, gained notoriety a few years back when his book, The Physics of Baseball, gave scholarly explanations for why a curveball curves and a knuckleball wobbles. He calculated that a two-degree temperature rise will add one foot to a 400-foot home run ball, increasing home run odds by about 1.75 percent.

* [Climatologist Michael] Mann .... [said] that the carbon emissions behind climate change may even lower home runs. “If anything, anthropogenic carbon emissions and global warming should make the atmosphere slightly heavier, because we’re taking carbon that was trapped in the solid earth and releasing to the atmosphere (in the form of CO2), and a warmer atmosphere will hold more water vapor. Both CO2 and water vapor contribute (slightly) to the mass of the atmosphere.”

Additional reading:

Does cloudiness affect baseball game outcomes?

Aerodynamics of Baseball: NASA interactive simulations; specify weather conditions and see effects on hitting and pitching (great fun)

Can the wind make Strasburg’s fastball faster? (from the Capital Weather Gang)