View Full Version : Home runs and global warming

17 May 08,, 02:18
Sabernomics » Blog Archive » April Homers (http://www.sabernomics.com/sabernomics/index.php/2008/05/april-homers/)

For the second year in a row, home runs are down in baseball. It won’t be long until someone attributes this change to improved drug testing and the response to the the Mitchell Report. Here is a graph of March/April home runs:



The average temperature for major league baseball games [in 2007], 58.2 degrees Farenheit, was over four degrees cooler than the average during the early part of the previous two seasons. This relationship seems relevant to understanding why home runs, and consequently run totals, are down this season….

Game-time temperature was a significant predictor (at the p [greater than] .001 level) of whether or not batted balls left the ballpark, but the day of the season was not statistically significant. A batted ball has a 4.0% chance of leaving the park during a game played in 70 degree conditions, but only a 3.5% chance of becoming a home run in a game played in 50 degree conditions. This relationship exists regardless of whether or not the game is being played during the first week of the season or in the middle of May.

In summary, it’s true that hitters gain an advantage in hitting home runs as the season progresses, but this advantage can be explained entirely by accounting for air temperature changes.



Over the past decade, early-season home runs and temperature have moved together. April 2008 was actually 0.3 degrees cooler than April 2007—sorry Al Gore*—and 5.12 degrees cooler than April 2006. This doesn’t mean drug testing has not affected hitting power, but we have have a decent alternative explanation for why home runs are down. So, make sure you point this out to the first person who claims drug testing is working.

17 May 08,, 07:39

17 May 08,, 21:35
I gotta get into a beer league and remind myself how fun it is to top balls on cold nights