Distance between the earth and sun.

We are closest to the Sun about January 3, and this is close to the coldest time of year in the Northern Hemisphere. Clearly, the distance is not a big effect. Why not?

The difference between the distance of the Earth from the Sun in the summer and the distance between the two in the winter is not very large - it amounts to less than 2% of the average distance from the Earth to the Sun.

In contrast, the area effect gives rise to a factor of two difference in the heating of a horizontal surface between summer and winter, and there are five more sunlight hours at the summer solstice than at the winter solstice.