VANDERLEI ALMEIDA/AFP via Getty Images The tropics could become uninhabitable if we don’t limit global warming to less than 1.5°C, the target set in the Paris Agreement on climate change. Above this, the equatorial region, which is home to around 43 per cent of the world’s population, could see air temperatures increase beyond the limit that the human body can withstand. Yi Zhang at Princeton University in New Jersey and her colleagues used data from 22 climate models to determine how rising air temperatures in the tropics will affect wet bulb temperatures – a measure of both heat and humidity made with a thermometer covered by a wet cloth.