# Seasonal effect based on Earth position [duplicate]

I know that Earth rotates around the Sun in an oval route:

And I know the seasons happen, because the axis of the Earth is not vertical. I think it is 23 degree slope.

How come the distance from the sun when the earth at the closest point to the Sun has no effect and if it has effect what is it?

I can see that when it is summer on the northern hemisphere it is winter in the southern and vise versa.

Shouldn't be it is hotter time for both sides when earth is closest to sun and colder when it is furthest?

The amount of insolation (the solar irradiation a planet receives) follows the inverse-square law: half the distance to the Sun results in four times the insolation for a given surface area. However, Earth's orbital eccentricity is very low – currently just 0.0167 – which means our orbit is nearly circular, so the change in insolation is never so dramatic as a quadrupling: our perihelion is 147.1 million km and our aphelion 152.1 million km – a difference of just 5 million km – which means the Earth receives $$\left(\frac {152.1}{147.1}\right)^2$$ = 1.069 times (i.e. 6.9%) more insolation at perihelion.