We've been burning fossil fuels at ever increasing rates since the dawn of the industrial revolution. Clearly a substantial amount of CO2 gas has already been introduced into the atmosphere as a result. We know the effects CO2 has on climate, although estimates and models vary, the empirical evidence is clear for a trend towards global warming. The objection posed by most skeptics now seems to be "yeah, so it will get a bit hotter, so what"? So should we stop adding CO2 now, when in fact it may still only get a bit hotter, or should we keep going until it kills us all for certain?