As far as I understand, there are two main reasons for having lower temperatures in winter :

  1. shorter days, so the sun has less time to heat the earth
  2. smaller angle of incidence, so the energy from the sunlight is absorbed in a larger area on the ground

Which of these has a bigger effect? Does it depend on the latitude?


The smaller angle of incidence should have the greater effect, otherwise during the summer the northernmost regions (in the boreal emisphere) would be hotter than the southern ones, and, believe me, northern Scotland in August is still colder than southern Italy in March. Or think about the Poles: they have six months of summer, but are still freezingly cold

  • $\begingroup$ This is inconclusive: the poles have zero-length days in winter. $\endgroup$ – Ruslan Dec 4 '16 at 18:29
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    $\begingroup$ My point is that if irradiation time was the principal cause you would have much warmer summers in the north. $\endgroup$ – Luca Dec 4 '16 at 18:57
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    $\begingroup$ Good point. Could be interesting to see some equations. $\endgroup$ – user1583209 Dec 4 '16 at 21:21
  • $\begingroup$ The formulas for daytime length are physics.stackexchange.com/questions/28563/… and $\endgroup$ – Luca Dec 4 '16 at 22:56
  • $\begingroup$ Find all the equations at Solar Radiation Calculation.pdf - ResearchGate (you may google it) $\endgroup$ – Luca Dec 4 '16 at 23:12

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