From rising sea levels to extreme weather events, there is unequivocal evidence that Earth is warming at an unprecedented rate. According to NASA, Earth’s average surface temperature in 2023 was the warmest since recordkeeping began in 1880. Looking at the planet as a whole, we’re around 1.36°C higher, and in July, the hottest day in recent history was recorded. But one of the problems with news reports around climate change is that the numbers aren’t specific enough. Countries issue blanket heatstroke warnings, but measuring how temperature changes affect someone’s health isn’t always clear. We’re told that it’s getting hotter (and are encouraged to drink water or avoid doing exercise), but are we really all at risk, or are some people more likely to suffer?

“There isn’t really a way of tracking actual numbers,” says Professor Matthew Chersich, from Wits Planetary Health Research, a new unit at the university specialising in climate change. Chersich is also the director of the Heat and Health African Transdisciplinary Center (HE2AT Center), a research project funded by the National Institute of Health (NIH), which is developing data science solutions in partnership with IBM. “It’s not like Covid-19 or HIV, where we can say that there were X million affected; the numbers and measurements are pretty poor,” says Chersich. “The indicators and the way we understand vulnerability and burden are still quite primitive.”