Do different parts of the world receive different amounts of sunshine during the year? Ignore clouds, or consider only what is received either on the cloud tops or surface, whichever is available. Is it the same at the poles as at the equator? ... the northern and the southern hemispheres?
Consider two interpretations of the above: (1) number of hours per year that the sun is up, (2) the total insolation (total solar energy received per unit of area of the ground) received during the year, weaker when the sun is low near the horizon than when it is high in the sky.
(In reply to
Unscientific solution by fwaff)
There are differnet amounts of sunlight and, um, un-sunlight, during the year. While the poles receive 24 hours of sunlight during their summer and 24 hours of darkness during their winter, the period this occurs over is quite different - full sun lasts about 3 weeks, while full dark lasts more than twice that. Of course, that's got to be made up somewhere, and I can only guess that it happens (more sun than dark) between the tropic lines which mark plus and minus 23.5 degrees of latitude.
As for the second part of the question, the total energy recieved by the sun greatly diminishes with increased angle, and so therefore much less energy per unit area is received at the poles than between the tropic lines.
A final consideration is that the Earths orbit ids not circular, it is elliptical. This means that it is closer to the sun during the Southern hemisphere summer than it is during the Northern hemisphere summer. This will impact the total energy recieved as well of course (and may explain why the Southern hemisphere is, on average, warmer than the Northern?).
re: Unscientific solution
