Is there a chart that shows the relative warmth of the sun at different latitudes? How is this measured?

Question

Is there a chart that shows the relative warmth of the sun at different latitudes? How is this measured?

Answer 1

There is, and you'll find it in any geography textbook or atlas that shows average monthly temperatures for different places around the world.  As a rough rule of thumb, the further north a place is, the colder it will be when the sun is south of the equator, and the further south a place is, the colder it will be when the sun is north of the equator. Theoretically, the coldest temperatures should occur in the month when the sun is furthest away - either over the Tropic of Cancer or the Tropic of Capricorn.

The physical principle that determines how much of the sun's heat falls in a given square metre, and therefore, the average temperature, is the angle of incidence between any particular place and the sun.  

For example, at the equator, on midsummers day the sun is directly overhead. Therefore a square metre receives maximum heat. As the sun moves north or south relative to the equator the position where the sun is directly overhead changes until the sun reaches the tropic when it starts its return journey.  The further north the sun is, the less heat fall per square meter in areas to the south, in proportion to the angle of incidence between the curvature of the earth  and the position of the sun.  The principle operates in reverse when the sun is south of the equator.  Areas within the arctic circle receive 24hr/7 daylight when the sun is north of the equator, and no light when it is south of the equator.  Areas within the antarctic circle, receive 24hr/7 daylight when the sun is south of the equator and no light when it is north of the equator - no light equals no heat.  However, just because an area is receiving light 24/7 doesn't mean that it is basking in a six month long heatwave - because of the curvature of the earth, the sun light is spread thinly over a wide area, so the soil doesn't get that hot.  To check this, look at graphs of average monthly temperature for places on the equator, then choose other places further north or south.  If you plot the temperatures against latitude, you should find that average temperature s decrease progressively or increase progressively, depending on the place's position relative to the sun.  Have fun.