On Jan. 4 at 8:00 a.m. EST (12:00 GMT), Earth reached its perihelion for 2014. The perihelion of a planet's orbit occurs when the planet is at its least distance from its star during a particular orbital cycle.
At the perihelion point, Earth was roughly 147,098,291 kilometers (0.983 AU) away from the Sun. This is a 3.345 percent difference compared to the aphelion which occurred on July 5 at at 11:00 a.m. EDT (15:00 GMT), when Earth was 152,097,426 kilometers (1.017 AU) away from the Sun. This results in a 6.912 percent greater amount of radiant heat that reaches the Earth at perihelion than at aphelion.
The perihelion date varies between Jan. 1 and Jan. 5, while the aphelion date varies between July 2 and July 6.
The times of the perihelion and aphelion clearly show that Earth's seasons are primarily dependent on the tilt of the Earth's rotational axis, not its distance from the Sun. While there is a significant difference in radiant heat, the incident angle of sunlight upon the planet is far more significant. Another important factor is the larger land area in the Northern Hemisphere compared to the larger ocean area in the Southern Hemisphere, leading the Northern Hemisphere to warm more easily.