On 2nd January 2013 Planet Earth will be at closest point to Sun in its elliptical orbit around Sun at 0.983 AU (14,70,99,586 km or Approx. 147 million km) from Sun. Astronomically this is phenomena is known as “Perihelion”.
Distance not Reason for Season:Commonly it is believed that Distance of Earth to Sun decides the season or temperature on earth. However it is not true. Actually axial tilt (approx. 23.5 Degree) of Earth on its axis while revolving around Sun regulates seasons on planet Earth with one of the Hemisphere facing away or towards Sun.
What About Perihelion? Aphelion? Earth Closest to Sun on 2nd Jan, 2013: Earth revolves around sun in a elliptical (oval shape) orbit. So at one point of time during its journey around sun it will be at closest point it can get (perihelion) and one point of time during the year it would be at farthest point (aphelion).