The temperature pathway travels through the sensory tract, specifically the spinothalamic tract which is part of the somato-sensory tract (conscious sensation). The sensory pathway is an ascendent pathway that carries information from the periphery to the brain, in this case the sensation is the heat, which is felt at the finger, the sensation then travels upwards and enters the spinal cord at the cervical level and crosses the midline to the opposite side, then continues to the brain stem and finally to the parietal lobe, areas 3, 1, 2 (primary somatosensory area) where the information is processed.
CO2 molecules can vibrate in ways that simpler nitrogen and oxygen molecules cannot, which allows CO2 molecules to capture the IR photons. Greenhouse gases and the greenhouse effect play an important role in Earth's climate.
