Chapter 3 explores the idea of a tipping point for understanding the possibility of catastrophic, relatively sudden, climate change. If global warming continues at the current rate, a tipping point could be reached when it is impossible to reverse climate trends. The melting of the Greenland and Antarctic ice sheets, shifts in ocean currents, deforestation, and the release of methane buried in the permafrost have the potential to accelerate the shift toward a hothouse planet.