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Why the title?  It all started with a chance meeting, and the opportunity to help a stranger and a response that left me feeling the need to write about it.

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Article: 20131221 (Sat, 21-Dec-2013, 19:59)

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The minute of the solstice, December 2013

@SatScenes 2013-12-21: The return starts now

Location: The northern hemisphere (specifically, Chessington, Surrey)

As of right this minute the days start getting longer again, although things still get colder for now.

Here follows a gross over-simplification, back of the fag packet explanation for the apparent discrepancy.  Although the planet as a whole receives a constant flux of light and heat from the sun (notwithstanding the small aberrations in solar output), to stay in balance it has to then radiate that energy back into the much colder vacuum of space (in line with the basic laws of thermodynamics), otherwise there would be a net increase in average surface temperature over time as the absorbed energy increased.  (Oh, wait...  Errm, let's just ignore that complication for the moment, and blissfully pretend the planet is in a steady state.)

Getting back on track - we experience seasons because the surface location actually receiving the most direct heat varies as a result of the Earth's approximately 23 degree tilt with respect to the plane of its orbit around the sun.  In the summer hemisphere there is a net local imbalance with marginally more heat arriving to heat the land, sea and air, which has to be offset by the exact opposite imbalance in the winter hemisphere.  (The planet as a whole being in - err-hem - steady state.)  So, although the sun is now headed in our direction from 23 degrees south of the equator, until it comes closer to crossing over (in March) the northern hemisphere still loses more heat than it gains, and hence the weather in January in particular commonly being colder still than in December.

Clearly, as I already said, this is a gross over-simplification, which ignores weather and sea currents (most significantly the Gulf Stream) as movers of warmth around the globe, but these factors only have local impact (such as keeping the British Isles a lot warmer than mere latitude alone would suggest) and don't change the predominant feature - the seasonal change in sunlight.