Climate change over the next 50 years could lead to 3.5 billion people living in temperatures higher than the climate “niche” in which most humans have historically lived, a new paper says.
Most people across the world currently live in areas with an average annual temperature of 11-15C, with a secondary concentration corresponding with the Indian monsoon region living in 20-25C, the paper says. Given this has been the case for the past 6,000 years, it adds, such conditions are probably an important factor for human thriving.
Temperatures in many highly populated regions would likely far exceed these optimum ranges in a high-emissions scenario where little is done to tackle climate change, the study says. It finds that by 2070, 3.5 billion people – around 30% of the projected global population – would live in places with an average annual temperature above 29C, which would cover 19% of the world’s land.
At present, just 20 million people (0.3% of the world’s population) live in places with average temperatures above 29C, says Chi Xu, an ecologist from Nanjing University in China and lead author of the paper, which is published in the journal Proceedings of the National Academies of Sciences. Only 0.8% of the global land surface currently has these high temperatures, mostly in the Sahara, the paper says.
The study indicates that India would be the most impacted country, with 1.2 billion people living in temperatures above 29C in 2070 without migration. Nigeria would also be heavily affected, with around 500 million people living above the threshold, with hundreds of millions in Pakistan and Indonesia also experiencing these high temperature conditions.
In this high-emissions scenario, many regions would likely see both migration and changes to where farming occurs, the paper says.
The research makes it clear that we need to begin planning for climate-driven displacement, says Alex Randell from the UK-based Climate and Migration Coalition, who was not involved in the paper. “For many people, moving will be their only option for coping with climate change,” he says. “We need to start planning for this now so that it can happen in an organised and dignified way.”
Displacement does not necessarily mean people will move countries, says Robert McLeman, professor of geography and environmental studies at Wilfrid Laurier University in Canada, and also uninvolved in the study.
“We already know that most climate-related migration tends to be internal relocations of people within countries,” he says. “If we did end up in a situation where we have large numbers of people living in extremely hot places within the next 50 years or so, the majority of the migration will likely be relocations within those areas. It won’t be internationally, especially over long distances.”
This would likely consist of two main movements of people, he says. Firstly, poor people or smallholder farmers who are more vulnerable than large farms to extreme heat damaging their crops would be pushed out of rural areas. Secondly, richer people would move out of city cores and into the suburbs to escape the heat-island effect.
Namrata Ginoya, an expert on climate resilience at World Resources Institute (WRI) India, says policymakers should be planning for expansion of cities and basic services therein. “They also need to plan for revival of rural livelihoods, the supplier of food and raw materials, which will suffer due to scarcity of labour,” she says.
Even if most displacement occurs internally, international migration is also likely to be part of the picture on a warmer planet – something that will also affect countries not experiencing direct displacement due to heat themselves, says Xu.
“Social instability and migration triggered by climate change would have profound impacts worldwide,” he says, adding that the more global warming the world sees, the larger the chance it will trigger massive migration.
It is crucial that countries develop constructive policies on international migration, says McLeman. He points out that many countries projected to have populations living under high temperatures in 2070 are also likely to have young populations. Conversely, many of the less impacted countries – such as China, the US, Canada and much of Europe – are set to have older populations, and will need more young people to be workers and taxpayers.
“There’s a lot of evidence that migration when it’s well managed, when it’s safe, when it addresses labour market needs in the destination country and where you have the ability to remit money home: everybody wins in that kind of situation,” says McLeman.
But populations will not simply move directly along with the shifting climate. Many other factors affect decisions to migrate, and adaptation measures could go a long way to addressing some of the challenges people experience.
“As the new evidence shows, climate impacts will play an increasingly significant role in people’s decisions to move or stay,” says Randell. “But other factors like a community’s ability to adapt, existing infrastructure and wealth will shape whether or not they move.”
Ginoya says local adaptation must remain the focus in coming years, and the backbone to its success is basic development – access to healthcare, education and basic amenities such as clean water, sanitation, roads and electricity.
Investment is also needed in adaptation measures that build on local knowledge, she adds. Large-scale landscape restoration projects that benefit crop farmers, pastoralists and forest dwellers as well as conservation of seeds and local agricultural and water-conservation practices are “game-changers” for a country like India, she says.
Another key adaptation measure will be the rise of cooling systems such as air conditioning, says McLeman, although this creates its own set of challenges to ensure renewable power sources. Global energy use from air conditioners is expected to triple by 2050 as demand soars in hotter developing countries.
Of course, another important action to reduce the need for adaptation is to cut emissions to begin with, and thus avoid the scenario set out in the study. “We are not doing enough,” says Ginoya. “It is important to know the price of inaction.”
Randell also emphasises that some people are already relocating due to climate change impacts. “This isn’t just a future scenario,” he says. “We should be learning as much as we can from the people who are already migrating due to climate impacts to help us plan for the future.”