Humanity’s superpower is sweating—but rising heat could be our kryptonite, and an average temperature rise of 2 degrees Celsius above preindustrial levels could bring regular, fatal heat waves to large parts of the planet, says Tom Matthews, a senior lecturer in environmental geography at King’s College London.

“We have evolved to cope with the most extreme heat and humidity the planet can throw at us,” he explains. But when our core temperature gets to about 42 degrees Celsius (around 107.5 degrees Fahrenheit), people face heat stroke and probable death as the body strains to keep cool and the heart works harder, inducing heart attacks.

Matthews cites an example from his home country, the UK. In the summer of 2022, the UK broke its high temperature record, surpassing 40 degrees Celsius (104 degrees Fahrenheit). Scientists estimate there were roughly 3,500 heat-associated deaths that summer in the UK. Across Europe, they estimate high heat caused more than 60,000 deaths.

“At 1.5 degrees Celsius of warming, the likes of Lagos, Karachi, [and] Shanghai start to experience heat waves exceeding our limit. At 2 degrees Celsius, the events increase at least 10 times more often, and if we get to 8 degrees Celsius, a large fraction of the Earth’s surface would be too hot for our physiology and would not be habitable,” he says.

Air conditioning and heat-escape rooms would help, but we might need to abandon intense outdoor work such as rice farming in hotter regions. And these solutions will need to be able to meet demand. “The infrastructure must be able to withstand the surges when everyone turns on the air conditioning, and must be able to withstand hurricanes or floods,” he says.

Our best hope in the face of inevitable rises in heat? Cooperation. “We’ve built forecasting systems that will warn us when disasters are incoming by working together at enormous scale. We must continue to do the same.”