Another important influence is the pH. Increase in carbon dioxide or other acids lowers the pH of plasma and shifts the dissociation curve to the right. At high carbon dioxide concentrations more oxygen is given up at any given oxygen pressure. This effect is known as Bohr effect after the Danish scientist who first described it.
Figure: Bohr effect
Therefore, as carbon dioxide enters the blood from respiring tissues it encourages the release of more oxygen. This is an important characteristic because it allows more oxygen to be released to tissue which need it the most. More oxygen is loaded in the lungs and more unloaded at the tissues due to Bohr effect than would be the case if only diffusion along the concentration gradient was responsible.