How is it possible that the Earth is closest to the sun in January when is winter in the northern hemisphere?

The Earth's distance from the sun does not determine the seasons on Earth; rather, it is the tilt of the Earth's axis that causes the changing seasons. During January, the northern hemisphere is tilted away from the sun, resulting in colder temperatures and winter conditions. This tilt causes the southern hemisphere to be closer to the sun and experience summer during this time. The Earth's elliptical orbit does cause variations in its distance from the sun, but these variations are not significant enough to affect the seasons.