The 4°C scenarios are devastating: the inundation of coastal cities; increasing risks for food production potentially leading to higher 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 frequency of high-intensity tropical cyclones; and irreversible loss of biodiversity, including coral reef systems. And most importantly, a 4°C world is so different from the current one that it comes with high uncertainty and new risks that threaten our ability to anticipate and plan for future adaptation needs. The lack of action on climate change not only risks putting prosperity out of reach of millions of people in the developing world, it threatens to roll back decades of sustainable development.

This report, Turn down the heat: why a 4°C warmer world must be avoided, provides a snapshot of recent scientific literature and new analyses of likely impacts and risks that would be associated with a 4°C warming within this century. It outlines a range of risks, focusing on developing countries and especially the poor. The report shows that a 4°C world would be one of unprecedented heat waves, severe drought and major floods in many regions, with serious impacts on ecosystems and associated services. However, this can be avoided with greater mitigation and adaptation efforts. Thus the level of impacts that developing countries and the rest of the world experience will be a result of government, private sector and civil society decisions and choices, including inaction, the report underlines. It also points out that, given the uncertainty of the full nature and scale of impacts, there is no certainty that adaptation to a four degrees Celsius world is possible.

Further reading:

Turn Down the Heat: Climate Extremes, Regional Impacts, and the Case for Resilience

Image credit: Asian Development Bank