The lack of CO² is by the plants using it. Warmer temperatures make it easer for the plants to process the extra CO².

The only part light plays is you need to have HID lights, fluorescent lights don't have enough lumens for the plant to process the extra amount of CO².

You can get fresh CO² by changing out the air but you will only end up with normal amount around 300 PPM. Enhanced CO² is more like 1500 PPM extra so that raises the level to 1800 PPM to feed your plants.

So cool temperature is great but if you use enhanced CO² then you need to push the envelope and raise the temperature to around 85-88f or even into the low 90. Yes you run some risk of hermie but I have found the plants respond to enhanced CO² and do not turn hermie. It takes temperatures over 100 for extended periods to do that. It's all about the environment they live in. You can push the limit but being in control is the key.