How life-threatening are heat waves going to be with global warming?

As climate change continues to dial up the thermostat, a future of more extreme weather looms. Already in 2020, a study detected multiple instances in which the temperature was “nearing or beyond prolonged human physiological tolerance.” This quiz might help you assess some of the risks.

The burden of heat-related death is, of course, not distributed uniformly. Extreme heat so far has been experienced mostly in South Asia, the Middle East and the coastal Southwest of North America — along Mexico’s west coast. Plus, not everybody is equally vulnerable. The very old and the very young are particularly susceptible, as are poorer people who often lack the resources to keep themselves cool during heat waves. Developing countries and countries lacking air conditioning are also particularly exposed.

In other words, preparedness and infrastructure matter. Mortality from extreme weather will depend on how extreme the weather gets — how often humans are struck by heat waves and how long they last — but also on how well people adapt to warming scenarios. To what extent will cities deploy cooling infrastructure such as air conditioning and trees for shade? How much summer outside work can be brought inside? In Japan, construction workers and police who must toil outdoors often wear air-conditioned suits. These technologies, however, are not affordable in Mexico, Nigeria or Bangladesh.

Development brought enormous progress in protecting people from natural disasters over the past few hundred years. The question is whether technology and economic growth can keep it up, despite increasingly volatile weather.

A warming world brings one, albeit slim, silver lining: fewer people are likely to die of the cold. Research finds that the death rate from cold weather has declined since the turn of the century in every region of the world. That said, the net effect of warming on temperature-related deaths will depend strongly on how well people prepare for the weather.

Ultimately, stopping the world’s warming trend will require slashing emissions of carbon dioxide and other greenhouse gases, which trap the energy coming from the sun in the earth’s ocean and atmosphere, inexorably raising the global thermostat. The average global temperature is today 2.1 degrees Fahrenheit hotter than at the turn of the 20th century. The governments of most countries are trying to stop it by eventually cutting GHG emissions to zero.

Humanity has largely learned how to protect itself from nature, crafting ecosystems around its needs. Air conditioning and indoor heating have protected increasing numbers of people from the heat and the cold. Economic development and automation have reduced demand for outside work in industries such as agriculture, reducing workers’ exposure to extreme weather.

Progress in taming nature has been far from homogeneous, though. The heat-related death rate is rising in many parts of the world, spiking over the past few years even in some of the world’s most affluent countries, such as France, Italy and Spain, which have sizable elderly populations and where air conditioning remains relatively rare. South Asia, still mostly poor and with a billion-plus population, faces an immediate emergency.

All this raises a paradoxical situation. Today, only about one-third of the world’s households have some form of air conditioning. Protecting humanity from increasing heat will require deploying a lot more in the near future. And this is going to consume a lot of energy, which will entail additional emissions of carbon dioxide, the main cause of climate change. But even if governments were to cut greenhouse gas emissions to zero today, the world would keep on heating for a while, as the gases humans have already put in the atmosphere keep trapping the sun’s energy.

This is not an excuse for inaction, but the opposite. The best approach is to drive adoption of renewables, so electricity is plentiful and green, along with investment in the infrastructure humans will need to live in a warming world.