Because of the orientation of the Earth with respect to the Sun, there is significantly more solar heat flux at the Equator than at the poles. There exists a temperature gradient between the Equator and the poles; however, the gradient would be much larger if there were no meridional heat transport. In order to reach the temperature gradient observed today, there needs to be a pole-ward flux of about 6 petawatts, which includes both atmospheric and oceanic heat transport (Marshal & Plumb 2008).
