As human population growth increased as did the total energy consumption and atmospheric carbon dioxide concentration. The increase in these quantities since the industrial revolution are outlined in the following link.
In my opinion the relationship that can be established today is between economy growth and the increase in carbon dioxide concentration. With an increase in economic growth a country needs to use more energy and for this reason an increase in carbon dioxide concentration can occur. Increase in human population do not necessarily means an increase in the use of energy if the economy does not grow in parallel.
China and India are good examples that can be used as reference in order to support this view.