National

Study finds 2 billion people will struggle to survive in a warming world – and these parts of Australia are most vulnerable
Source: The Conversation, Annabelle Workman, Kathryn Bowen

Two billion people, including many Australians, will find themselves living in dangerously hot places this century if global warming reaches 2.7℃, research released today reveals.

The authors calculated how many people would be left outside the "human climate niche" by 2100. The niche is defined as places with an average temperature of about 13℃, or about 27℃ in the tropics. Human population has historically peaked in these areas.

The world is on track for 2.7℃ of warming by 2100. This would push a third of people on Earth outside the human climate niche. This includes people in parts of northwest Australia such as Darwin, Broome and Port Hedland. It also includes parts of Southeast Asia, India, Africa and South America.

Limiting warming to 1.5℃ would substantially reduce the number of people exposed, including most of those affected in northwest Australia.

We were not involved in the research, which was conducted by researchers in the United Kingdom, China, Europe and United States. We are Australian experts in the health implications of global warming. Below, we discuss the broader implications of these globally significant findings. 

What is the human cost of global warming?

The research calculated the number of people outside the "human climate niche" under different demographic scenarios and levels of warming. Exposure to unprecedented heat was the main factor pushing people out of the niche.

This includes an average temperature greater than or equal to 29℃, as well as a high number of days with a maximum temperature above 40℃ or in humid places, with a wet-bulb temperature greater than 28℃. The wet-bulb temperature (as opposed to the standard dry-bulb temperature) reflects humidity and is a method used to measure heat stress. That's because it's the point at which sweating is no longer effective as a means of cooling.

The study says a wet-bulb temperature of 35 ℃ can be fatal, especially for vulnerable people, because the body can no longer cool itself.

Above the present level of about 1.2 ℃ global warming, the authors found exposure to unprecedented average temperatures increased markedly, along with increased exposure to temperature extremes.

But 2.7 ℃ of warming threatens a third of the world's population. The below map shows where in the world people will suffer the worst heat. Almost the entire area of some countries, such as Burkina Faso and Mali in West Africa, would be exposed to unprecedented heat.

Why is warming a health hazard?

 Even incremental warming increases exposure to health hazards including potentially deadly heatwaves, infectious diseases and diet-related health issues.

Let's be clear. A 1.5℃ world will result in injury and death, particularly for people in Asia and Africa. Importantly, the people most at risk will be the least capable of protecting themselves: children, the elderly and those with existing health conditions.

While populations closer to the equator are more likely to experience heat-related harm, Australians are by no means immune.

Continue reading on The Conversation