<P> The relative increase in solar irradiation at closest approach to the Sun (perihelion) compared to the irradiation at the furthest distance (aphelion) is slightly larger than four times the eccentricity . For Earth's current orbital eccentricity, incoming solar radiation varies by about 6.8%, while the distance from the Sun currently varies by only 3.4% (5.1 million km). Perihelion presently occurs around January 3, while aphelion is around July 4 . When the orbit is at its most eccentric, the amount of solar radiation at perihelion will be about 23% more than at aphelion . However, the Earth's eccentricity is always so small that the variation in solar irradiation is a minor factor in seasonal climate variation, compared to axial tilt and even compared to the relative ease of heating the larger land masses of the northern hemisphere . </P> <Table> Season durations <Tr> <Th> Year </Th> <Th> Northern Hemisphere </Th> <Th> Southern Hemisphere </Th> <Th> Date: GMT </Th> <Th> Season duration </Th> </Tr> <Tr> <Td> 2005 </Td> <Td> Winter solstice </Td> <Td> Summer solstice </Td> <Td> 21 December 2005 18: 35 </Td> <Td> 88.99 days </Td> </Tr> <Tr> <Td> 2006 </Td> <Td> Spring equinox </Td> <Td> Autumn equinox </Td> <Td> 20 March 2006 18: 26 </Td> <Td> 92.75 days </Td> </Tr> <Tr> <Td> 2006 </Td> <Td> Summer solstice </Td> <Td> Winter solstice </Td> <Td> 21 June 2006 12: 26 </Td> <Td> 93.65 days </Td> </Tr> <Tr> <Td> 2006 </Td> <Td> Autumn equinox </Td> <Td> Spring equinox </Td> <Td> 23 September 2006 4: 03 </Td> <Td> 89.85 days </Td> </Tr> <Tr> <Td> 2006 </Td> <Td> Winter solstice </Td> <Td> Summer solstice </Td> <Td> 22 December 2006 0: 22 </Td> <Td> 88.99 days </Td> </Tr> <Tr> <Td> 2007 </Td> <Td> Spring equinox </Td> <Td> Autumn equinox </Td> <Td> 21 March 2007 0: 07 </Td> <Td> 92.75 days </Td> </Tr> <Tr> <Td> 2007 </Td> <Td> Summer solstice </Td> <Td> Winter solstice </Td> <Td> 21 June 2007 18: 06 </Td> <Td> 93.66 days </Td> </Tr> <Tr> <Td> 2007 </Td> <Td> Autumn equinox </Td> <Td> Spring equinox </Td> <Td> 23 September 2007 9: 51 </Td> <Td> 89.85 days </Td> </Tr> <Tr> <Td> 2007 </Td> <Td> Winter solstice </Td> <Td> Summer solstice </Td> <Td> 22 December 2007 06: 08 </Td> <Td> </Td> </Tr> </Table> <Tr> <Th> Year </Th> <Th> Northern Hemisphere </Th> <Th> Southern Hemisphere </Th> <Th> Date: GMT </Th> <Th> Season duration </Th> </Tr> <Tr> <Td> 2005 </Td> <Td> Winter solstice </Td> <Td> Summer solstice </Td> <Td> 21 December 2005 18: 35 </Td> <Td> 88.99 days </Td> </Tr>

Which milankovitch cycle takes the shortest amount of time