Baseball commentator Tim McCarver has been ridiculed for suggesting that global warming is to blame for an increase in the number of home runs hit in the major leagues. To a point he’s correct. Balls carry better in warm, humid air. The increase in global temperature does track with an increase in home runs. However, other factors are involved, including changes in athletic ability, batting and ball technology and pitching styles. One physicist argued that a two-degree rise in temperature could lead to a 1.75 percent increase in home-run odds. A climatologist argued that an increase in carbon emissions makes the atmosphere heavier, which should result in fewer home runs (Washington Post blog, April 30).