What is the 'human climate niche' and why does it matter?

New data shows 2023 is “virtually certain” to be the warmest year on record, with October’s global temperature reaching 1.7°C above pre-industrial levels.

The temperature range that has sustained human life and activity, known as “the human climate niche”, averages 11-15° C and we have been thriving in it for thousands of years.

But the climate crisis has already put more than 600 million people outside of the climate niche. This number could rise to a third of the population if the current trajectory of 2.7°C above pre-industrial temperatures is reached, warns a new report published by Nature.

Here are some of its key findings.

Today, around 9% of the population already live in areas outside of this niche, according to the report, titled Quantifying the Human Cost of Global Warming. But we’ve adapted well so far to the challenges of high and low temperatures – mainly with the help of innovations such as air conditioning, heaters and insulation, it says.

If you live in New Zealand, you’re on the low end of the level that we thrive in at 10.9°C, while Greece sits near the top, at 14.8°C, according to 10-year temperature averages.

But living beyond these ranges may lead to increased morbidity, mortality, and displacement, says the report. High temperatures also increase the likelihood of other factors such as the spread of infectious diseases and lower productivity.

India and Nigeria are the two countries facing the greatest risk of climate-induced temperature increase, according to the report, as both already show “hotspots” of exposure to extreme heat. India’s heatwave this year killed hundreds of people, while many countries in Africa continue to battle higher temperatures with fewer resources than wealthier economies.

To avoid the rapid rise in exposure to unprecedented heat – defined as having a mean annual temperature of 29 °C or higher – we must reduce emissions to slow global warming, the report’s authors say.

As temperatures rise, more areas of the planet are likely to become deserts, devoid of life, where once there were communities, animals and fertile land.

This will lead to increasing numbers of people having to migrate. It’s already happening – over 32 million people were displaced in 2022 by weather-related events such as flooding, droughts and storms. And failure to mitigate the effects of the climate crisis could even lead to mass migration, experts warn.

“By 2050, sub-Saharan Africa could see as many as 86 million internal climate migrants; East Asia and the Pacific, 49 million; South Asia, 40 million; North Africa, 19 million; Latin America, 17 million; and Eastern Europe and Central Asia, 5 million,” says the World Bank.

UN Secretary-General António Guterres announced in July that “the era of global boiling has arrived”, as large areas of the planet experienced record-high temperatures.

The only solution, he says, is to rapidly accelerate global action to reach net-zero targets by 2050.

By strengthening climate policies, we can reduce both our exposure to unprecedented heat and the number of people forced to move to cooler areas.

Every 0.3°C reduction in end-of-century warming will reduce the number of people who live outside the human climate niche by 350 million, say the authors of the report.

There are multiple ways to cut emissions, but a key enabler of success will be achieving international agreement on tripling renewable energy capacity and doubling energy efficiency measures by 2023 at COP28 in the United Arab Emirates, 30 November-12 December 2023.

Collaboration is essential to a sustainable future, as the World Economic Forum points out in its recent whitepaper Climate Governance and the Circular Economy: A Primer for Boards.

“The complexities, interdependencies and technical challenges that the [energy] transition demands require broad collaboration and partnerships across industry sectors, value chains and a variety of stakeholder groups.”