The report warns that the world will heat up by 4 degrees at the end of the century if the global community fails to act on climate change. The 4°C scenarios are potentially devastating: the inundation of coastal cities; increasing risks for food production potentially leading to higher under and malnutrition rates; many dry regions becoming dryer, wet regions wetter; unprecedented heat waves in many regions, especially in the tropics; substantially exacerbated water scarcity in many regions; increased intensity of tropical cyclones; and irreversible loss of biodiversity, including coral reef systems. Climate change also has the potential to catalyze rapid shifts in ecosystems such as sudden forest loss or regional loss of
agricultural productivity resulting from desertification.