To show how handy my Excel worksheet is, here’s one I did in the last 15 minutes.
Apparently Sydney has had its warmest December minimum on record at 27.1 C. The record before that was Christmas Day, 1868 at 26.3C.
The following seven plots show this in context.
Fig. 1: The annual range in Sydney’s minima:
Extremes in minima can occur any time between October and March.
Fig. 2: The first 2 weeks of December
Plainly, a new record was set this morning, but apart from Day 340 the other days are within the normal range.
Fig. 3: 7 day mean of Tmin in this period
Extreme, but a number of previous years had warmer averages.
Fig. 4: Consecutive days above 20C Tmin.
But there have been longer periods of warm minima in the past.
Now let’s look at the same metric, but for all of December.
Fig. 5: All Decembers (including leap years).
A record for December, with 1868 in second place.
Fig. 6: 7 day mean of Tmin for Decembers
Seven day periods of warm nights are not new. The horizontal black line shows the average to this morning (20.6C) is matched or exceeded by a dozen other Decembers. (Of course this December isn’t half way through yet.) Also note what appears to be a step change about 1970.
Fig. 7: Consecutive days above 20C Tmin in December.
I doubt if 15 December will be as warm as today, but could still be over 20C.
This is weather, not global warming.