Rising temperatures will push billions of people outside the climate niche, an ideal condition where humans have thrived for thousands of years, exposing them to deadly extreme heat and extreme precipitation.
A study published in Nature Sustainability attempted to quantify the human cost of climate change. The authors say climate change’s costs are often measured in monetary terms.
However, the study focuses on human costs or the direct human suffering that climate change could inflict when people live in unbearably hot and humid climates.
The authors project that the world is on track for a 2.7°C warming towards the end of the century, far from the Paris Agreement goal to limit global warming to 1.5°C. Even fully implementing all 2030 nationally determined contributions, long-term pledges and net zero targets, nearly 2°C global warming is expected later this century.
The climate niche refers to the set of temperature and precipitation conditions where a species can occur. The study found that most people lived in places with mean annual temperatures (MAT) between 13°C and 25°C. Conditions outside this niche will be too hot, cold, and dry and are linked to higher mortality rates, lower food production and economic development, impaired learning, increased conflict and infectious disease spread.
People who will be pushed out of the climate niche would likely consider migrating to cooler places, and the people moving out will be in the billions.
A 2.7 °C warming, as the research indicates, will likely result in a five-fold increase in the number of people worldwide that will be exposed to unprecedented heat. This also means that 2 billion people will experience an average annual temperature above 29°C by 2030, temperatures that only a few communities have lived in the past. The study calls for climate justice to highlight the vital need to address the social injustices brought by climate change.
The study reveals the number of populations exposed to 2.7 °C global warming.
Assuming a future world of 9.5 billion, India will have the largest exposed population at around 600 million, but the number will reduce 6-fold to 90 million at 1.5°C global warming. Nigeria will have the second largest population exposed at 300 million under, but this reduces seven times to 40 million at 1.5 °C global warming.
Indonesia’s exposure will decrease 20-fold, from 100 million to 5 million at 1.5 °C global warming. With 80 million exposed, the Philippines and Pakistan will have large reductions at 1.5 °C global warming.
Land-area exposure per country
“The fraction of land area exposed approaches 100% for several countries under 2.7 °C global warming. Brazil has the greatest absolute land area exposed under 2.7 °C global warming, despite almost no area being exposed at 1.5 °C, and Australia and India also experience massive increases in absolute area exposed. (If the future population reaches 11.1 billion, countries’ ranking by population exposure remains similar, although the numbers exposed increase.)
Those most exposed under 2.7 °C global warming come from nations today above the median poverty rate and below the median per capita emissions.”
Overall, the result of the study shows the massive potential human cost and the great inequity of climate change, which makes the discussions and actions on loss and damage and the implementation of climate adaptation and mitigation critical and urgent.
Lenton, T.M., Xu, C., Abrams, J.F. et al. (2023, May 23). Quantifying the human cost of global warming. Nature Sustainability (2023). Retrieved from https://doi.org/10.1038/s41893-023-01132-6