[steve in DC]

One might suggest that the differential in mass might place more air molecules in closer proximity to the pendulum, but overall, the mass of air in the atmosphere has to be considered static for these purposes.

Regarding a change in proximal mass, and its discernable impact in the speed of the pendulum, I would suggest that the near transit of a heavy truck would have more significant gravitational impact than a slight change in air temperature, no matter how swiftly that change in temperature might occur.

(But I am too poorly schooled and too lazy to perform the calculations to support my statement:-)

[swilhelm73]

I would suggest that the near transit of a heavy truck would have more significant gravitational impact than a slight change in air temperature, no matter how swiftly that change in temperature might occur.

That's exactly why I have to believe that the reporter meant air resistance, not air's gravitational effect. ;)