The structural evolution and transformation pathways of carbon dioxide phase IV (CO2-IV) are investigated over 13.0–76.7 GPa and 296–700 K using synchrotron X-ray diffraction, Raman spectroscopies, and first-principles calculations. CO2-IV was obtained from CO2-I by isothermal compression to 13.0 GPa at 600 K. Subsequent single-crystal diffraction performed at 14.5 GPa and 296 K confirms that CO2-IV adopts a rhombohedral R-3c structure, consistent with Datchi et al. [Phys. Rev. Lett. 103, 185701 (2009)], establishing its purely molecular character without evidence for an “intermediate bonding state”. At room temperature, deviatoric stress promotes a symmetry lowering distortion of R-3c CO2-IV at 14.6 GPa, yielding a distorted molecular configuration with triclinic P1 symmetry, denoted here as an IV’-type distortion. From 296 to 600 K, the onset pressure of this distortion increases modestly, giving rise to a positively sloped kinetic onset line in the P–T diagram. At 650 and 700 K, enhanced thermal relaxation substantially reduces the influence of deviatoric stress, and no symmetry breaking is detected before the molecular-to-nonmolecular transformation, and stabilize the R-3c structure in the molecular regime. Upon further compression, the molecular solid transforms into metastable nonmolecular states containing mixed three- and fourfold-coordinated carbon atoms. The transformation pathway is temperature dependent: at 296–600 K, amorphization proceeds from the P1-distorted form of CO2-IV to a-CO2, whereas at 650–700 K the transformation proceeds directly from R-3c CO2-IV to the more ordered metastable covalent phase VI. The onset pressure of the molecular-to-nonmolecular transformation decreases with increasing temperature. These results reveal that the high-pressure behavior of CO2 is governed by the interplay between deviatoric stress and thermal activation, which controls symmetry lowering within the molecular regime and the subsequent pathways toward amorphous and metastable covalent structures.