Have been watching this TV series, and was surprised that the nearest we come in the earths orbit to the sun is in mid December.and its the earths tilt away at this time that gives us our winter and cold weather. I was always under the impression that we were nearest to the sun in June. So its not the distance from the sun but the tilt the opposite way in the northern hemisphere that gives us our summers.
The difference between Perihelion and aphelion is negligible, the proximity to the sun has no noticible effect on temperature variations throughout the year. The tilt is what concentrates or spreads the energy causing the seasons. I though that was Primary school stuff.
Oh I don't think they taught that sort of thing in school, at least not in my day. But a general interest in things scientific meant I picked it up somewhere along the way.
As I understand it there is a longer distance through the atmosphere when you are tilted away, and thus less heat gets to the surface.