Pickle #1 - Wet Bulb Temperature

Combinations of increased heat and humidity will render portions of the Earth uninhabitable. In fact, I have visited two places already in this situation: Daharan, Saudi Arabia, and Monterrey, Mexico. In both places, prolonged work outside was impossible.

Even heat-adapted people cannot carry out normal outdoor activities past a wet-bulb temperature of 32 °C (90 °F), equivalent to a heat index of 55 °C (130 °F)². The human body can't tolerate wet bulb temperatures that cross 35°C¹.

In other words, humans can no longer live when the peak wet bulb temperature reaches 35c. The chart below is in Fahrenheit, but the black zone is clear. I particularly note the wicked combination of humidity and temperature. As I write, humidity is 87% in Vancouver. Dangerous heat would be at just 80 degrees F. That's what we called a "heat dome" recently.