How does hemoglobin's affinity for oxygen change with varying concentrations of carbon dioxide?

Carbon dioxide concentration has no effect on hemoglobin's affinity for oxygen.

Increased carbon dioxide decreases hemoglobin's affinity for oxygen, facilitating oxygen release in tissues.

Decreased carbon dioxide decreases hemoglobin's affinity for oxygen, enhancing oxygen uptake in the lungs.

Increased carbon dioxide increases hemoglobin's affinity for oxygen, inhibiting oxygen release.