Temperature and te distance from the sun

[gammaray]

Given that the sun is approx 93 million miles away why is it that a distance of only a 1000 miles on earth can make a big difference in the recorded temperature? For example the temperature in London currently is around 9 or 10 degrees yet Madrid is 15 degrees. Teneriffe a few hundred miles further on is 17 degrees. Temperatures in Africa during the "summer" months can reach 40 to 50 degrees yet in England 30 degress is considered sweltering. Yet in terms of distance they aren't that far apart when you consider the total distance from the sun!

[brachiopod]

Because it is not absolute distance that matters, but angle of incidence of the sun's rays.

Imagine a fixed 'circle of sun's rays' shining at rightangles to the surface (assume rays are parallel). It will create a circular area of light of area X.

Now tilt the card to simulate a land surface at a higher latitude. The same 'circle of sun's rays' now produces an elongated oval of area Y.

Since the 'circle of sun's rays' is fixed - it contains the same amount of solar energy. But in the first example, the same amount of solar energy is concentrated in an area X, whilst in the second, the energy is less concentrated over the larger area Y.

Try it with a torch shining on a piece of card.

And finally, the Earth is closest to the sun during the Northern hemisphere's winter !! So small differences in distance are insignificant.

[gammaray]

Thank you brachiopod, for a most illuminating (sorry) answer.

[brachiopod]

<groan> :o)

[Clanad]

But... but.... as brachiopod knows, the temperature in a given location on earth isn't controlled exclusively by the directness of the sunlight. The ocean currents, especially the Gulf Stream, moderates temperatures and the currents, as a whole, are largely responsible for weather phenomena. The winds aloft (above about 3,000 feet above ground level (AGL) also moderate temperatures, but are affected by the ocean currents). This, especially, explains the differing summertime temperatures in the moderate latitudes...