Fig 1.
Comparison between the tilt and distance effect on the seasonality of daily-averaged incoming solar radiation (insolation).
(a) Insolation resulting from the tilt effect; (b) insolation resulting from the distance effect; (c) insolation at the equator from tilt (blue line) and distance (red line); and (d) globally averaged insolation from tilt (blue line) and distance (red line). Insolation calculated using the code from Huybers and Eisenmann [10], using pre-industrial orbital parameters stated in Erb et al. [11]: e = 0.0167, obliquity = 23.439°, and longitude of perihelion = 102.932°. For calculating the insolation from tilt, eccentricity was set to zero in the calculation; and for the insolation from distance, obliquity was set to zero.