Nah. There have been far more greenhouse gases in the atmosphere before, and there will be again. The amount of greenhouse gases in the atmosphere will mean bad things for mankind, not for the planet. The planet is amazingly resilient.
Our climate is always radically altering. Going off the top of my head, this planet seems to have 3 different phases, greenhouse which means no ice at the poles, I've heard some people suggest this was our planet's default setting, and the two stages of ice age, one of which we are currently in. The two stages of ice age are the periods when ice is in recline (what we are in now,) and a period where ice creeps across the earth, a period which is actually overdue and some scientists are starting to think it's been delayed by the buildup of greenhouse gases.