by Henry Robertson

On June 22, 2021, the town of Lytton, British Columbia, hit 121° F (49.6° C), obliterating the old Canadian high temperature record of 113°. It was a fun fact with perhaps a shudder of alarm attached, but heat waves happen.

The natural reaction is to turn up the air conditioning (except that people in those northerly parts tend not to have it). But AC with its high demand for electric power only adds to the heat as power plants burn coal or natural gas. In the case of renewable electricity, the same fossil fuels have to be burned to build solar panels and wind turbines to generate what passes for clean green electricity. Heat-trapping carbon-dioxide turns the planet’s thermostat up while you turn yours down.

On June 26, 2018, Quriyat, Oman, at the eastern end of the Arabian Peninsula, set the world record for highest overnight low temperature: 108.7°F (42.6°C). On July 6, 2021, Death Valley set the North American record high low at 107.7°/42.1°.

If these temperatures become more common, parts of the world could become uninhabitable.

Those places won’t all be in hot, dry deserts but also in places with high humidity as well as heat like the Persian Gulf and the American southeast. Humans cannot survive prolonged exposure to a wet-bulb temperature above 35°C (95°F). Wet-bulb temperature is the reading on a thermometer covered by a wet cloth. As explained in ScienceAdvances for May 8, 2020, a human body at normal temperature of 36.8°C requires a skin temperature of 35°C to maintain a heat gradient to drain heat from the body’s core. If the dry-bulb air temperature exceeds 35°C, the body must cool itself by sweating, but if the wet-bulb temperature exceeds 35°C, “this cooling mechanism loses its effectiveness altogether.”

 According to the report, “Climate models project the first 35°C TW [wet-bulb temperature] occurrences by the mid-21^st century. However, a comprehensive evaluation of weather station data shows that some coastal subtropical locations have already reported a TW of 35°C and that extreme humid heat overall has more than doubled in frequency since 1979.” (Colin Raymond, Tom Matthews and Radley M. Horton, “The emergence of heat and humidity too severe for human tolerance.”)

In desert heat, sweating will continue at a dry-bulb temperature above 35°C, but at the risk of dehydration, and the body cannot survive an internal temperature above 42–44°C.

The extremes at Lytton and Quriyat show nature once again working at a faster schedule than science. The way to slow global heating is to keep the fossil fuels in the ground, not try to air condition ourselves out of it.

If parts of the world become unsurvivably hot, the people will move. Other climate consequences such as sea-level rise and drought can also set people in motion. Crop failures due to prolonged drought in Guatemala have already sent migrant caravans to the US border. Climate disruption is also one motivation behind African migration to Europe. Desperate groups of people colliding threatens to breed violence and destabilize nations on a hotter Earth. This is the way the world could go if we don’t kick our fossil fuel addiction.

Henry Robertson recently retired as climate and energy lawyer at Great Rivers Environmental Law Center in St. Louis.