According to a new study, climate change is pushing the planet’s tropical regions towards the limits of human livability, which threatens to plunge much of the world’s population into potentially lethal conditions.
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What is Happening?
- The study, published in the journal Nature Geoscience, says that if governments fail to curb global temperature rise to 1.5C above the pre-industrial era, areas in the tropic band that stretches either side of the equator risk changing into a new environment that will “hit the limit of human adaptation.”
- Humans have a core body temperature that generally stays around 37C, while our skin is cooler to allow heat to flow away from the inner body. However, if the wet-bulb temperature- a measure of air temperature and humidity- passes 35C, high skin temperature will render the body unable to cool itself, which could have deadly consequences.
- Wet-bulb temperature is measured by a thermometer that has its bulb wrapped in a wet cloth, helping to mimic the ability of humans to cool their skin by evaporating sweat.
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Yi Zhang, a Princeton University researcher and leader of the study, says, “If it is too humid our bodies can’t cool off by evaporating sweat – this is why humidity is important when we consider livability in a hot place. High body core temperatures are dangerous or even lethal.”
- The team looked at different historical data and simulations to determine how wet-bulb temperature extremes will change as the planet continues to warm; they found that these extremes in the tropics increase at around the same rate as the tropical mean temperature.
- To avoid the wet-bulb temperature exceeding 35C, global temperature rise must be kept to 1.5C.
- However, the study found that even 1C of wet-bulb temperature increase “could have adverse health impacts equivalent to that of several degrees of temperature increase.” Scientists say that the 1.5C threshold could be reached within a decade.
- Around 40% of the world’s population currently live in tropical countries, which is set to expand to half of the global population by 2050. This study was centred on latitudes found between 20 degrees north, a line that cuts through Mexico, Libya and India, to 20 degrees south, which goes through Brazil, Madagascar and northern Australia.
- Elsewhere, extreme heatwaves could push parts of the Middle East beyond human endurance and livability, with rising temperatures from climate change also posing enormous risks for parts of China and India.
- The number of potentially fatal humidity and heat events around the world doubled between 1979 and 2017, with the coming decades set to see as many as 3 billion people pushed beyond the historical range of temperature that humans have survived in over the past 6 000 years.
