A friend of mine used to be responsible for (among other things) water temperature measurements on naval ships. Speaking loosely to make the point, they used t

A friend of mine used to be responsible for (among other things) water temperature measurements on naval ships. Speaking loosely to make the point, they used to measure temperature from the front of the ship, then inexplicably (to him, anyway) changed the procedure to sample from behind the ship (where the water was warmer from engine exhaust/water output), leading to a sudden increase in water temperatures.