Fun fact: In the 17th century, Tycho Brahe’s data allowed Kepler to deduce the elliptical orbit, but the precise timing of perihelion wasn’t nailed down until the late 1800s.

Perihelion has a significant impact on the Earth's climate. During this time, the Earth receives about 7% more solar energy than at its farthest point, aphelion. This increase in solar energy leads to several effects:

Climate change driven by human activity is about the greenhouse effect trapping heat in the atmosphere. While changes in Earth’s orbit (Milankovitch cycles) do cause ice ages over tens of thousands of years, the annual perihelion of 3.3% distance change does not drive the current global warming trend.

Earth is tilted on its axis by about 23.5 degrees. During January, the Northern Hemisphere is tilted away from the Sun. This means sunlight hits at a lower, more glancing angle, spreading the same amount of energy over a larger area and taking a longer path through the atmosphere. Days are also shorter, giving less time for the ground to warm.