For a just world, limiting warming to 1.5°C will not be enough, say researchers

It will not prevent massive suffering in developing countries. Limiting global warming to 1.5°C will prevent runaway climate change, but it will not be enough, warned a consortium of 50 researchers on Wednesday May 31.

Even if the world respects the +1.5°C ceiling compared to the end of the 19th century, a threshold set by the Paris agreement, some 200 million people in poor regions will be exposed to unbearable heat, and half a billion will face the ravages of rising waters, warn these scientists in a study published in Nature (link in English).

This scenario is now considered optimistic. Greenhouse gas emissions remain at record levels, and for IPCC experts, current policies lead instead to a warming of 2.7°C by the end of the century. The Earth’s average surface temperature has already increased by almost 1.2°C since the pre-industrial era. In order to prevent large sections of humanity from being exposed to “significant damage (…), the right limit must be set at 1°C or below”and atmospheric CO2 concentration – currently at 420 parts per million (ppm) – needs to be reduced to 350 ppm, scientists say.

New “planetary boundaries” crossed

“We are in the Anthropocene, endangering the stability and resilience of the entire planet”, underlined Johan Rockström, lead author of the study, referring to a new geological epoch marked by the human footprint on the planet. Johan Rockström is one of the initiators of the concept of “planetary boundaries”, red lines not to be crossed.

In 2009, he and his colleagues identified nine such limits and three had already been crossed: greenhouse gases warming the planet, accelerating species extinctions, and excess nitrogen and phosphorus in the the environment. Since then, three other limits have been crossed: deforestation, the overexploitation of fresh water and the omnipresence of synthetic chemicals. Outdoor particulate pollution could add to that this year, and ocean acidification may not be far behind. “Nothing less than a just global transformation (…) is necessary to ensure human well-being”conclude the authors of the study.