# Climate and weather without obliquity and eccentricity?

Obliquity is the most important factor of seasons. Without axial tilt, eccentricity causes small temperature variations. What would climate and weather on Earth look like, if Earth doesn't have any axial tilt, but also hasn't eccentricity?

• The eccentricity of Earth orbit is much too small to produce noticeable temperature variations. $e = \sqrt {1 - \frac {b^2}{a^2}} = 0.017$, therefore $\frac{b^2}{a^2} = 1 - 0.017^2 = 0.9997$, hence $b = 0.99986 a$; this means that the amount of solar energy reaching Earth varies by about 0.03% between perihelion and aphelion. For comparison, solar irradiance varies by about 0.1% during a solar cycle. – AlexP Mar 11 at 17:35