NicoClimate tipping points are cycles that are triggered once the climate warms sufficiently, that further sustain climate change. A major example is permafrost melting. As the climate warms, permafrost releases methane, which in turn warms the climate further, causing the permafrost to release more methane. Should this turn into a self sustaining cycle, a tipping point has been reached.
Tipping points are one of the major reasons for the 1.5 degrees C warming limit target. Below this temperature, tipping points are unlikely, above they may be inevitable.
If a tipping point is reach, even if we stop emitting greenhouse gasses, concentrations may continue to increase, and the climate may thus continue to warm. In such a scenario, we would likely have to extract from the atmosphere a truly enormous quantity of greenhouse gasses in order to lower temperatures to a point where the tipping point cycles cease.