Warming is obviously a lot more complex than CO2 levels, because warming has continued to basically flatline as it has for decades now. So why are we still so concerned about CO2 emissions when the runaway effect predicted is simply not occurring?
There are simply too many natural processes in the earths climate that deal with variances in heat, most variances from other causes are vastly greater than the current minuscule levels of CO2 we see (they are historically high but factor in very little in terms of atmospheric mix).
If we're lucky, we'll get a nice 2C boost for a few hundred years out of all combined warming effects, before sliding into yet another ice age. Sadly I do not think we will be that lucky.