WHAT funny names these weather people have! Two of them in the news recently, for example, are Jeppe Dyre and Coerte Voorhies, from Denmark and the US respectively. Their achievement has been to provide an explanation as to why the average temperature of the world should be a little higher at full moon than it is at other times of the lunar cycle.
This temperature anomaly was discovered some time ago by another scientist, Robert Balling, when processing data made available from satellites. His finding that the average temperature of the earth rises and falls over a range of 0.02 of a degree Celsius as the moon waxes and wanes caused a flurry of meteorological excitement, since weather people have traditionally scorned any suggestion that the moon might have any influence on our weather.
Now that evidence to the contrary had been provided, weather heads were scratched around the world in search of explanations. Enter Dyre and Coerte Voorhies.
The answer lies in the way the earth and moon perform a pas de dewy in space. The gravity that holds the moon in thrall on its almost circular journey around the earth also exerts an attractive force on the earth itself, tending to disturb it from its own solar orbit. Rather than thinking of the moon as revolving around the earth, we should more properly regard both bodies as orbiting around their joint centre of mass.
Now the earth is very much greater than the moon, so this centre of mass is in fact very close to the centre of the earth - but does not coincide with it exactly. The end result is a little like that of a man swinging a small child in a circle at arms length: although the man may try to pirouette on the one spot, most of his body will in fact describe a small circle as he continually re positions his centre of mass to balance the centrifugal force of the whirling infant.
In the case of the earthmoon combination, we find that as the two bodies spin around in space together, the earth moves slightly closer to the sun at full moon - when the moon is on the other side of the earth from the sun - and slightly further away when the system has sprung through 180 degrees to the new moon phase.
The difference is a mere 9,000 miles - a tiny fraction of the 90 million miles that we are distant from the sun - but enough nonetheless to account for some at least of the observed increase in temperature - when the moon is full.