Shortest Day

Winter Solstice

The axis around which the Earth rotates is tilted at an angle to its orbit and at the winter solstice, the sun is at its southernmost point in the sky.

The axis around which the Earth rotates is tilted at an angle.
On a winter solstice, the sun is at its southernmost point in the sky.
Near the winter solstice, the length of the day changes very slowly.
The orbit of the Earth is not circular, but an ellipse
The axis around which the Earth rotates is tilted at an angle to its orbit and at the winter solstice, the sun is at its southernmost point in the sky.

This is the shortest day of the year in northern latitudes, with London seeing only 7 hours and 50 minutes of daylight on 21st December 2005.

...the time of sunrise continues to get later after the winter solstice...However, for anyone observing the times of sunrise and sunset, it seems odd that the time of sunrise continues to get later after the winter solstice, while the time of sunset has already started to get later before the winter solstice.

In 2005, the time of sunset started getting later after December 13th and the time of sunrise doesn’t start to get earlier until the 6th January.

...the orbit of the Earth is not circular, but an ellipse...This asymmetry in the times of sunrise and sunset is due to the fact that the Sun does not cross the meridian (when it is highest in the sky) at precisely noon every day. This is because not only is the Earth's axis inclined to the plane of its orbit around the Sun, but the orbit of the Earth is not circular, but an ellipse.
Near the winter solstice, the length of the day changes very slowly, as does the Sun’s height in the sky – one of the reasons why the long winter nights seem to go on forever!

The effects of the elliptical orbit and tilt of the axis are particularly dominant...The effects of the elliptical orbit and tilt of the axis are particularly dominant at this time of the year and cause the time at which the sun crosses the meridian to change by ten minutes between the 16th December (the sun is highest in the sky at 11:59am) and 5th January (the sun is highest at 12:06pm).

It is this factor which is the more dominant at this time of year and this causes the perceived anomaly in the observed sunrise times.