- In the next 50 years, a third of the world’s population could be living in areas as hot as the hottest parts of the Sahara now.
- Humans have adapted to live in a narrow band of environmental and climatic fluctuations, but temperature rises threaten this.
- Health, food security and economic growth would face huge challenges outside the temperature ranges we currently inhabit.
By 2070, one-third of people could be living in conditions that are outside humanity’s comfort zone. That’s the conclusion of a group of scientists from the US, China and Europe who have analysed rising global temperatures and compared them to average climatic conditions over the last 6,000 years.
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Their research warns that unless decisive action is taken to reverse the damage done by greenhouse gases, billions of people could be living in what are “unliveable” circumstances.
Climate change-related rapid temperature rise combined with population growth means that about 30% of the world’s projected population will live in places with an average temperature above 29°C in the next 50 years, according to the paper published in Proceedings of the National Academy of Sciences. Less than 1% of the Earth's land surface - mostly in the hottest parts of the Sahara desert - currently experiences this climate. But by 2070, almost a fifth of the planet’s land area will reach these temperatures, the researchers say.
For more than 6,000 years, the human race has learned to live within a relatively narrow band of environmental and climatic fluctuations. The mean annual temperature over that period has been around 13ºC. And the crops, livestock and irrigation that are the bedrock of the planet’s food production system were developed, discovered and designed within those constraints.
These, and other critical systems, cannot be expected to function normally outside the environmental niche they grew up in, the researchers warn. In their recently published paper, 'Future of the human climate niche', they explain: “All species have an environmental niche, and despite technological advances, humans are unlikely to be an exception”.
As temperatures continue to rise, these human-friendly conditions could become scarce in many parts of the world. The worst effects of this change will be felt by some of the world’s poorest people and poorest countries.
“Global warming will affect ecosystems as well as human health, livelihoods, food security, water supply, and economic growth in many ways,” the researchers warn.
Most people currently live in areas where the average temperature is 11-15°C. A smaller number live in regions with a mean of around 20-25°C. If greenhouse gases emissions increase unchecked by 2070 the average person will be living in temperatures 7.5°C hotter than preindustrial times, the study authors predict. This is because population growth is expected to be the greatest in already-hot places, and although the projected global temperature rise in this scenario is just over 3°C, land will warm much faster than oceans.
While North America, Europe and large parts of Asia will be the least hit by the change, much of Africa, South America and Australasia will face challenging conditions. Some of the effects of extreme weather – droughts and floods, failed crops and famine, pestilence and disease could become the norm. That may trigger a series of secondary pressures and problems.
A growing problem
The world’s population is expected to grow to around 10.9 billion by the end of this century. According to the authors, 3.5 billion people will by then be living in parts of the world where the mean annual temperature will be around 29°C, which is far outside the climatic envelope of human development.
In the World Economic Forum Global Risk Report 2020, “climate change and related environmental issues” dominate concerns for our world in the long-term.
According to the charity Oxfam, over the last decade, more than 20 million people a year have been pushed out of their homes by climate-fuelled disasters. As living conditions become more hostile, and food production is disrupted, there is an increased likelihood of mass migration, placing increased pressure on the host countries migrants move to and through.
“People prefer not to migrate. Also there is scope for local adaptation in part of the world within limits, but in the Global South this will require boosting human development rapidly,” Professor Marten Scheffer of Wageningen University, who coordinated the research, says in an article for the University of Exeter.
He added: "This study underscores why a holistic approach to tackling climate change that includes adapting to its impacts, addressing social issues, building governance, and empowering development as well as compassionate legal pathways for those whose homes are affected, is crucial to ensuring a world in which all humans can live with dignity.”