There's an obvious difference between scientists being concerned about rising CO2 levels and the likely correlation with climate, and people calling it an impending catastrophe, a planet-threatening crisis, that we must do everything to avoid. Those latter ones, I call climate hysterics.
The "grave danger" is assuming that only centralized action can remedy the situation. It leaves out the emergent action by octillions of living organisms adapting 365/24 for decades. It does so for scientific reasons (basically because there is no model for it) and ignores empirical evidence going back millenia, that shows how surprisingly adaptive the ecosphere is.