The EarthSun distance, which is 149 million km, on average, varies throughout the year. The Earth passes each semester, alternately, at perihelion, i.e. it is at this point closer to the sun at aphelion, i.e. it is at this point than away from the sun. The difference between these two distances is determined by the eccentricity. It is a parameter or Milanković or Milanković cycles corresponding to three astronomical phenomena affecting the Earth's eccentricity, obliquity and precession. These parameters are used in the context of the astronomical theory of paleoclimate. They are partly responsible for natural climate change, whose main consequence, the glacial and interglacial periods. Describes the Earth in space, not a circle but an ellipse, which the Sun occupies one focus, but this ellipse is deformed up to a maximum eccentricity of 0.06. it is currently at 0.016 and the Earth  Sun distance varies from 3%, about 5 million km. In the solar system, planets have orbits that are all roughly in the same plane, called the ecliptic. The solar energy captured by the Earth is on average during the year of 1367 W/m2.   This energy varies from 6% between the point closest to the Sun and the furthest point, it varies between 1408 and 1326 W/m2 W/m2. Over time, the eccentricity varies substantially, so that the EarthSun distance varies between 129 and 187 million km. This eccentricity is due to the Sun and the gravitational attraction exerted by other planets. It characterizes the degree of flattening of the ellipse from a circle. It is currently very low, thereby stabilizing the climate. The attraction of the Sun imposes an elliptical motion but the gravitational pull of other planets tends to distort the ellipse slowly. This eccentricity evolves over time with a period of 412,800 years and a set of periods of about 100 000 years. There are 128 000 years during the last interglacial period, the eccentricity was close to 0.04 and the energy received by the Earth between the perihelion and aphelion ranged from approximately 16%.
NB: A high eccentricity decreases the smaller axis (perihelion) and increases the largest axis (aphelion), but does not alter the long axis.   Features of the Earth  Characteristics    Average orbital radius (1 ua)  149 597 887,5 km  Aphelion  152 097 701 km  Perihelion  147 098 074 km  Orbital Circumference  9,4×10^{8} km, or 6,283 au  Orbital eccentricity  0,016 710 22  Sidereal period of revolution  365,256 96 days  Mean orbital speed  29,783 km/s or 107 218,8 km/h  Orbital inclination  0°  Sidereal rotation period (sidereal day)  0,997 258 days or 23,93419 h  Speed of rotation (the equator)  1 674,38 km/h  Axis inclination  23,45° 

The eccentricity of the orbit of the planet would have an effect on the fluctuations of the inclination and intensity of the geomagnetic field. This was stated Toshitsugu Yamazaki and Oda Hirokuni, scientists from the Geological Survey of Japan. The Earth's magnetic field is generated by the motion of liquid metal core, the deep layers of the Earth. By studying the longterm variations of the magnetic field, the two researchers have examined the magnetic properties of a column of marine sediments, 42 meters long, made over a period of 2.25 million years. This enabled them to establish the intensity and direction of the magnetic field change with a cycle lasting 100,000 years. Eccentricity measures the deviation of the Earth's orbit from a circular orbit.   It ranges from 0 for a circular orbit at 1 in a highly elliptical orbit. But the eccentricity of Earth's orbit varies between 0 and 0.06 for every 100 000 years. Image: The eccentricity, obliquity and precession are used within the astronomical theory of paleoclimate. They are partly responsible for natural climate changes that have major consequence, the glacial and interglacial periods. © 2013 Astronoo   