says that 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.
. . .
The report notes, however, that a 4°C world is not inevitable and that with sustained policy action warming can still be held below 2°C, which is the goal adopted by the international community and one that already brings some serious damages and risks to the environment and human populations.