I started writng this post as a throwaway post on the ridiculousness of Tim McCarver as a baseball announcer. The tie to the blog is this quote from McCarver during a Brewers-Cardinals game on why homerun rates have continued to increase over time in Major League Baseball:
"It has not been proven, but I think ultimately it will be proven that the air is thinner now, there have been climactic changes over the last 50 years in the world, and I think that's one of the reasons balls are carrying much better now than I remember."
Now McCarver is known for saying some off-the-wall things during broadcasts, but on the surface, this one seems more off-the-wall than most. That is, until I came across this graphic from the Washington Post Capital Weather Gang Blog:
Holy $#!%, global warming causes homeruns!
OK, seriously, I'm not sure which is more disingenuous, McCarver's unsubstantiated quote or the Washington Post's attempt to substantiate the quote through spurious correlation and a rigged graph. Using estimates from the graph and a quick Google search, global temperatures have risen from 56.26F in 1880 to 58.14F in 2011, or 3.3%. Homeruns per game have increased by 900% (~.1 in 1880 to ~1 in 2011). By compressing the right/homerun axis, homeruns track global temperatures. But, the same trick can be pulled with anything that has a positive trend from 1880 to 2011.
Flash: The number of cars purchased worldwide causes an increase in the number of Major League homeruns hit.
To be fair to the Washington Post's writers, they do admit to the possibility of spurious correlation:
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.
While the home run/temperature correlation may be mostly a coincidence, it is overly dismissive to discount weather and climate from playing any role.
But by their own footnoted evidence, dismissiveness may be called for:
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.
