It’s likely that CO2 has some warming effect, but real proof of that hypothesis is tricky. You have to confirm by observation exactly how the CO2 changes the situation at different altitudes in the atmosphere and in different regions of the world. For example, CO2 is supposed to warm the upper air faster than the surface, but the measurements don’t show that happening. When the CO2 effect is eventually pinned down, it will probably turn out to be weaker and much less worrisome than predicted by the global warming theorists.