Each degree of warming above present levels corresponds to roughly 1bn people falling outside of ‘climate niche’
Steven Bernard, Dan Clark and Sam Joiner November 1 2021
Map animation showing human climate niche, the suitability of for habitation. In 2020, 0.8% of the earth’s surface had a mean annual temperature (MAT) of 29C or more, and was home to 29m people. By 2070, 19% of the earth’s surface will have an MAT of at least 29C, affecting up to 3bn people
Up to 3bn out of the projected world population of about 9bn could be exposed to temperatures on a par with the hottest parts of the Sahara by 2070, according to research by scientists from China, US and Europe.
However, rapid reductions in greenhouse gas emissions could halve the number of people exposed to such hot conditions. “The good news is that these impacts can be greatly reduced if humanity succeeds in curbing global warming,” said study co-author Tim Lenton, climate specialist and director of the Global Systems Institute at Exeter university.
The report highlights how the majority of humans live in a very narrow mean annual temperature band of 11C-15C (52F-59F). Researchers noted that despite all innovations and migrations, people had mostly lived in these climate conditions for several thousand years.
“This strikingly constant climate niche likely represents fundamental constraints on what humans need to survive and thrive,” said Professor Marten Scheffer of Wageningen University, who co-ordinated the research with his Chinese colleague Chi Xu, of Nanjing University.
Global warming has resulted in a 1.1C rise in temperatures since pre-industrial times, according to scientists. This is expected to reach 1.5C within 20 years, even in the best-case scenario of deep cuts in greenhouse gas emissions.
“Each degree of warming above present levels corresponds to roughly 1bn people falling outside of the climate niche,” Lenton noted.
At present, only 0.8 per cent of the global land surface experiences mean annual temperatures greater than 29C (84.2F).
If emissions continue to rise, this could spread to 19 per cent of the planet’s land area by 2070, under the worst-case scenario set out by the Intergovernmental Panel on Climate Change, the UN scientific body.
What are the scenarios?
Three different climate scenarios and three population projections are set down by the IPCC in its landmark report assessing climate change (see table below).
To visualise how liveable the earth will be in 2070 under these scenarios, the Financial Times has paired the population projections with each climate model and mapped them across six continents.