Climate crisis compresses human climate niche: 1.4 billion at risk in 2030

With current policies, up to 1/3 of humanity will be out of the human climate niche in 2090

(sustainabilityenvironment.com) – Forced to live in conditions in which many communities can withstand, with average temperatures above 29 degrees. The alternative is to migrate. It is the destiny that awaits a third of humanity by the end of the century, while the climate crisis makes the global mercury column rise and narrows the climate niche of man, that is, the areas where temperature and humidity conditions are suitable to sustain human life.

Up to 4 billion people outside the human climate niche in 2090

This process is already underway and will become much more visible quickly. In a future emissive scenario compatible with the current trajectory, which leads us to +2.7°C by 2100, already in 2030, that is in less than 7 years, the contraction of the climatic niche of man will leave out 14% ( 3%) of humanity, that is from 1 to 1.4 billion people. By 2090 these numbers will more than double to reach 29% ( 5%) or 2.2-3.2 billion people.

This scenario, however, takes into account only temperature changes. If we also include in the equation the demographic curve, which for this scenario predicts a peak of 9.5 billion in 2070 and then declining to 9 billion at the end of the century, the numbers increase. And we get to 25% ( 2%) of humanity left outside the climatic niche of man by 2030 (1.8-2.2 billion people), and then rise again to 40% ( 4%) that is 3.3-4.1 billion people by 2090.

Alternative scenarios for future of the human climate niche

These are the numbers proposed by a study published in Nature Sustainability and coordinated by the universities of Exeter and Nanjing, where the authors cross the future climate trajectories with the evolution of areas where life for man remains possible. In fact, the definition used in the study of man’s climate niche is wide and does not mean that it is totally impossible to live outside those regions. But these are still extreme conditions, to which many populations are not accustomed and could therefore decide to move elsewhere. These niches are defined both by physiological factors and by cultural factors.

“Exposure outside the niche could lead to increased morbidity, mortality, adaptation on site or displacement (migration elsewhere),” the authors write. “High temperatures have been linked to increased mortality, decreased labour productivity, reduced cognitive performance, impaired learning, negative pregnancy outcomes, a decrease in crop yield potential, an increase in conflict, hatred, migration and the spread of infectious diseases”.

How does the ecological niche of man change in other emissive and socio-economic development scenarios? The “Fossil Fuel Fuelled Development” path (i.e., SSP5-8.5) exposes the majority of the population to unprecedented temperatures or to moving away from the niche due to climate change alone. But it is the “Regional Rivalries” path (the SSP3-7.0) that exposes the majority of the population out of the niche for a combination of climate change and demographic changes. Instead, keeping the temperature around 1.5 ºC, the current target, would reduce by 5 times the number of people destined to be outside the climate niche.