In the Global Warming chapter of the Doomsday Book, the heating that planet is and will experience cannot be ignored. Unless humanity changes course quickly and decisively, the consequences are dire. This article discusses one of the more starling near-term effects, where parts of planet earth become inaccessible to humans who are not in an air conditioned vehicle or suit. The heat and humidity are simply too high for a human to survive.

The emergence of heat and humidity too severe for human tolerance

Humans’ ability to efficiently shed heat has enabled us to range over every continent, but a wet-bulb temperature (TW) of 35°C marks our upper physiological limit, and much lower values have serious health and productivity impacts. Climate models project the first 35°C TW occurrences by the mid-21st 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. Recent exceedances of 35°C in global maximum sea surface temperature provide further support for the validity of these dangerously high TW values. We find the most extreme humid heat is highly localized in both space and time and is correspondingly substantially underestimated in reanalysis products. Our findings thus underscore the serious challenge posed by humid heat that is more intense than previously reported and increasingly severe.

What areas will first be affected?

• South Asia
• the coastal Middle East
• coastal southwest North America
• eastern coastal India
• Pakistan and northwestern India
• the shores of the Red Sea
• Gulf of California
• southern Gulf of Mexico
• (parts of Bangladesh)

See the Global Warming chapter for details.