I propose the following five-level system for describing the current global ecological threat level. As with DEFCON, higher numbers represent greater safety.
GEOCON 5: Ecologically Stable
Net emissions are neutral or negative, and current concentrations are at safe levels.
(Catastrophe not predicted)
GEOCON 4: Future Ecological Risk
Current concentrations are at safe levels, but emissions are positive. Emissions must be reduced to zero in order to prevent ecological catastrophe.
(Catastrophe predicted if emissions stay above zero)
GEOCON 3: Temporary Ecological Risk
Current concentrations are at potentially unsafe levels, but emissions are sufficiently negative and concentrations are projected to return to safe levels in time to prevent ecological catastrophe.
(Catastrophe predicted if emissions rise to zero)
GEOCON 2: Imminent Ecological Danger
Current concentrations are at unsafe levels, and emissions are either positive, neutral, or insufficiently negative to recover in time. Emissions must be made sharply negative in order to avert ecological catastrophe.
(Catastrophe predicted if emissions stay at zero)
GEOCON 1: Current Ecological Catastrophe
Runaway global warming has made large areas uninhabitable.
(Catastrophe has occurred)
As of this writing (October 2015), the current concentrations are about 400 ppm. Based on my reading, the best-supported estimate of the maximum safe level seems to be 350 ppm. Global net emissions are currently positive, so this puts us at:
IMMINENT ECOLOGICAL DANGER